Dissertations / Theses on the topic 'Heat recovery'

Industrial drying operations are highly energy intensive, usually utilising a primary energy source to provide the necessary heat for the production of a wide range of materials. The use of hot air as the heat and mass transfer medium leads to a resultant loss of energy through the venting of humid exhaust streams. An absorption heat transformer pilot plant was designed and constructed to investigate the potential of recovering this waste heat. Using a two stage cycle, simulated dryer exhaust streams were successfully dehumidified and reheated. The first stage of the transformer employed a direct contact process which used a concentrated absorbent solution, in this case aqueous lithium bromide solution, to reduce the humidity of the gas stream. This stage was followed by an indirect contact process using a novel absorption column to reheat the 'dry' gas. It was found that, based on initial water vapour partial pressures of around 0.2 bar, exit partial pressures as low as 0.04 bar were achievable. Temperature lifts of 50 - 70°C were possible in the reheat column, while the maximum exit gas temperature achieved was 160°C. In conjunction with the experimental studies, a computer simulation program was also written. Results of the model show that the absorption process was extremely rapid, occurring within the first 5 cm (6%) of the absorption column. A good comparison between the experimental and computer results was achieved. A preliminary design of an industrial heat transformer was also proposed following an industrial case study of a spray drying operation.

High grade energy, which is primarily derived from hydrocarbon fuels, is in short supply; therefore alternative energy sources such as renewable and recycled energy sources are gaining significant attention. Pyro-metallurgical processes are large consumers of energy. They in return generate large quantities of waste heat which goes un-recovered. The overall theme of this research is to capture, concentrate and convert some of this waste heat to a valuable form. The main objective is to characterize and develop heat pipe technology (some of which originated at McGill) to capture and concentrate low grade heat. Heat pipe employs boiling as the means to concentrate the energy contained in the waste heat and transfers it as higher quality energy. The distinct design features of this device (separate return line and flow modifiers in the evaporator) maximize its heat extraction capacity. During the testing the main limitations within the heat pipe were identified. Different test phases were designed throughout which the configuration of the system was modified to overcome these limitations and to increase the amount of extracted heat.
L'énergie d'haut grade de nos jours est produite principalement à base de combustion d'hydrocarbure et les réserves de cette énergie deviennent de plus en plus rare, mais certaines énergies alternatives connues gagnent des forces parmi les marchés incluant les sources d'énergie renouvelables et recyclées. Les usines pyrométallurgiques sont des consommateurs significatifs d'énergie d'haut grade. Ces procédés industriels relâches un montant important de chaleurs (perte) à l'environnement sans aucune récupération. Le but du projet est de concentrer, capturer et convertir cette chaleur résiduelle de basse qualité en énergie valable. Par contre, l'objectif principal du projet comme tel est de développer et de perfectionner un caloduc capable d'extraire cette chaleur parvenant des gaz effluents. Le point d'ébullition d'une substance (vapeur) est utilisé comme moyen de concentrer l'énergie contenu dans les effluents avec la technologie des caloducs. Pour maximiser les gains énergétiques, la conception de ce caloduc en particulier utilise des canaux de retour indépendant ainsi qu'un modificateur de débit dans l'évaporateur, lui permettant d'extraire un niveau supérieur de chaleur. Pendant les essais lors du projet, les éléments limitants des systèmes de caloducs ont été identifiés. Les configurations du système ont été ajustées et modifiés dans la phase expérimentale d'essai pour surmonter ces limitations et maximiser l'extraction de chaleur.

SammanfattningI ett tidigare projekt, utfört under våren 2010, modellerades och simulerades en ånggenerator i GT-SUITE för att analysera och jämföra dess resultat med de faktiska motormätningarna. Projektet utfördes på Kungliga Tekniska Högskolan i Stockholm, på uppdrag av företaget som introducerat idén, Ranotor. Konceptet gick ut på att ersätta EGR-kylaren i en lastbilsmotor och med hjälp av Rankine cykeln försöka öka motorns verkningsgrad. Ånggeneratorn består av 48 mikro tuber, som alla innehåller vatten med högt tryck, vattnet värms upp av de varma avgaserna som letts in i ånggeneratorn. Detta gör att vattnet förångas och leds sedan för att driva en expander för att avlasta motorn.Huvudfokus i detta examensarbete har varit att modellera, studera och analysera ånggeneratorns prestanda i simuleringsprogrammet GT-SUITE. För att kunna göra detta måste ånggeneratorn, även kallad HRSG (Heat Recovery Steam Generator), modelleras från grunden med specifikationer från tillverkaren. En elementarmodell byggdes inledningsvis upp för att belysa beteendet av flödet inuti mikro tuberna och vilka parametrar som påverkar resultatet av simuleringarna. Senare gjordes även en komplett identisk modell av den verkliga ånggeneratorn. Modellen användes i ESC-cykeln och även för transienta körningar, där all indata är samlad från motormätningar på den verkliga ånggenerator, monterad på en DS1301, 6-cylinder 12 liter Scania diesel motor. För att kunna förbättra simuleringen av den kompletta modellen, gjordes en nedskalad modell som bara innehöll två tuber. Denna modell har samma dimensioner och egenskaper med den kompletta modellen, men fördelen med denna tvåtubs modell är den förkortade simuleringstiden.Inlopps parametrar såsom, vattenflöde, ångtryck, avgasflöde och avgastemperaturen togs från verkliga motormätningar. Samtliga parametrar varierar med tiden; detta gör det möjligt att göra en direkt jämförelse mellan den verkliga ånggeneratorn och den modellerade. Ångans och avgasernas temperatur samt tryckfallet över ångpannan är huvudparametrar som har jämförts med de verkliga mätningarna. Testkörningen är baserad på ESC-cykeln, European Stationary Cycle, som innehåller tolv lastpunkter och en tomgångspunkt. Jämförelser mellan den kompletta modellen och de faktiska provkörningarna visade följande: i det bästa fallet avviker ångans temperatur ~5% motsvarande 10°C. För det sämsta fallet är temperatur skillnaden ~20%, ca 40°C, övriga lastpunkter visar en felmarginal mellan 5-10% motsvarande 10-35°C. Tryckfallet över ångpannan visar en större felmarginal, vilket beror på mätningar under testkörningar där vissa filter var igen satta, därav uppmättes tryckfallet i vissa fall upp till 20 bar. I bästa fallet skiljer det ~1 % mellan simulering och verklighet, vilket är nästan identiskt, medan det i det sämsta falletskiljer uppemot 70 % som motsvarar 10 bar, övriga lastpunkter ligger i intervallet 10-15 % felmarginal, motsvarande 1-4 bar.Två tubs modellen beter sig som den kompletta modellen; avvikelsen mellan dessa modeller är 1-5% ~5-15°C i de flesta fallen, där skillnaden för det mesta liknar mätningarna. Värmeöverföringen, Reynolds tal, ångans effekt studeras i tvåtubs modellen. Analys av modellen visar att ~40-55 % av värmeöverföringen sker i fasomvandlingen, vilket var förvånande mycket och Reynolds tal ökar med ~450 % i denna region, från 1500 till ~6500, vilket tyder på en flödesövergångs fas. Ångans effekt varierar mellan 5-23 kW beroende på lastpunkt.Den slutliga modellen ger tillfredställande resultat och anses vara tillräckligt bra för vidare analys.
AbstractIn a previous project, made in the spring of 2010, a steam generator was modelled and simulated in GT-SUITE, in order to analyze and compare with engine measurements. This was made at the Royal Institute of Technology in Stockholm, on behalf of the company that introduced this idea, Ranotor. The concept was to replace the EGR-cooler in a heavy duty engine and with help of the Rankine cycle, try to improve its efficiency. The steam generator consists of 48 micro tubes, all containing high pressured water, which in turn is heated by the warm exhausts that are led into the steam generator. This causes the water in the tubes to evaporate which propels an expander that will unload the engine.The main focus of this thesis is to model, study and analyze the performance of the steam generator built in the simulation program GT-SUITE. The steam generator, called Heat Recovery Steam Generator (HRSG), is modelled from scratch with the specifications of the manufacturer. An elementary model was initially made to highlight the behaviour of the flow inside the micro tubes and what parameters affect the outcome of the simulations. Finally a complete identical model was made of the actual steam generator. The model was used in an ESC-cycle and also for a transient cycle, where all the input data is gathered on engine measurements of the actual HRSG, mounted on a DS1301, 6-cylinder 12 litre Scania diesel engine. In order to improve the simulation of the complete model a downsized model, only containing two tubes, was made. This model has the same dimensions and properties as the complete model but the advantage of this double-tube model is the shortened simulation time.The inlet parameters to the model such as water mass flow, steam pressure, exhaust mass flow and exhaust temperature were taken from actual engine measurements. All the parameters vary due to time; this makes a comparison possible between the real steam generator and the modelled one. Steam temperature, exhaust temperature and pressure drop along the HRSG are the main parameters from the simulations that are compared to the actual measurements. The engine measurements are made based on the ESC-cycle, European Stationary Cycle, which contains twelve load points and one idle point. During comparison between the complete model and the engine measurements following is observed, in the best case the steam temperature differs ~ 5 %, equalling 10°C. In the worst case the temperature difference is ~20 %, which is approximately 40°C, the rest of the load points shows a margin of error between 5-10 % equalling 10-35 °C. Pressure drop along the HRSG is less accurate;this is due to an error during the measurement where some filters where clogged. Disparity in pressure drop is ~1% in best case, which is almost identical and ~70% in worst case, corresponding to approximately 10 bar, where rest of the load points shows a margin of error between 10-15% equalling 1-4 bar.The double-tube model behaves like the complete model; the difference between the models is 1-5 % in most cases ~5-15°C, where the difference is mostly closer to the measurements. Heat transfer, Reynolds number and steam power are taken and studied from the double tube model. Analyses of the models reviles that ~40-55 % of the heat transfer is in the transition phase, which is surprisingly much and Reynolds number increases by ~450% in the same region, from 1500 to ~6500 which indicates a flow transition phase. Steam power varies between 5-23 kW depending on load point.The final model shows satisfying result and therefore assumed to be good enough for further analyse.

The aim of this thesis is to study and explain the purpose and the function of drain water heat exchangers. The thesis goes over theory behind heat transfer and heat exchangers and presents the general solutions of domestic drain water heat recovery systems. Systems gone over in detail are the different general shower drain water heat recovery systems. Another part of the thesis is a case study of an actual shower drain water heat recovery system of a Finnish household. The purpose of the case study is to study the actual temperature increase of cold water in a drain water heat recovery unit and efficiency of such heat exchanger. An alternate goal is to study the difference in efficiency values and temperature gains between two heat exchangers of the same model, where the other has been used significantly more than the other. In other words, another target is to study the fouling effect. The calculations are done using real measurement data. The most important findings are that utilizing a shower drain heat recovery unit provides real energy savings in the long run, and that there is a significant difference of efficiency between a dirty and a clean heat exchanger. Drain water heat recovery systems provided as high as 15 °C increase in the temperature of cold water. A clean heat exchanger boasts an impressive 50.4% efficiency, whereas the dirtier heat exchanger provides a 36.1% efficiency. The results can be further used to calculate the energy savings of the household on a yearly basis. Furthermore, the results show that domestic drain water heat recovery could potentially make a significant difference in national energy usage if implemented nationwide.

Hot water plays an import role in modem life. The consumption of hot water represents a significant part of the nation's energy consumption. One way of reducing the energy consumption involved, and hence the cost of that energy, is to reclaim heat from the waste warm water that is discharged to the sewer each day. The potential for economic waste water heat recovery depends on both the quantity available and whether the quality fits the requirement of the heating load. To recover heat from waste water in residential and commercial buildings is hard to achieve in quality because of its low temperature range. Nevertheless, efforts to recycle this waste energy could result in significant energy savings. The objective of this research was to develop a multiple panel thermosyphon heat exchanger for a waste water heat recovery system. The advantage of the system proposed in this work is that it not only provides useful energy transfer during simultaneous flow of cold supply and warm drain water but also has the ability to store recovered energy at the bottom of a hot water storage tank for later use. While this concept is not new, the design of the heat exchanger proposed for the present study is significantly different from those used previously. Component experiments were carried out to determine the performance characteristics of a single thermosyphon panel. By changing the inclination angle of the single panel heat exchanger and varying its working condition, it was found that the inclination angle of 10° could be identified as the minimum inclination angle at which good performance was still obtained. The close values of the overall heat transfer coefficients between top surface of the panel insulated and both top and bottom surfaces of the panel uninsulated shows that the overall heat transfer coefficient of the single panel was dominated by the bottom surface of the panel. Even if in a worst case the top surface of the panel might be possibly covered by the deposits from the waste water, it would not affect much on the heat transfer performance of the panel. Measurements of hot water usage and waste water temperature and flow rates were obtained for a potential application of the proposed exchanger (the dishwasher for the kitchen in the University Halls of Residence). A model of a multi-panel thermosyphon heat exchanger was also developed to predict the energy savings that would be expected if such a heat exchanger was used in this situation. The result indicated that an overall electricity of 7500 kWh could be saved annually from the dishwasher system by employing a four-panel thermosyphon heat exchanger.

The residential and service sector amounts to approximately 40 percent of Sweden’s entire energy demand. In which 90 percent of that is used by households and non-residential buildings. All in all about 80 TWh are used for heating and the provision of hot water in households and non-residential buildings. Since heating has always been such a large part of the energy consumption for buildings in Sweden, it is only natural that there have been several improvements along the way. There’s a new facility just installed last year in the building Pennfäktaren 11, a horizontal wastewater heat recovery heat exchanger. This thesis study will be focused on creating a TRNSYS model of a waste water heat exchanger, where the crucial parameters such as water flow rate, temperature, and more can be used as inputs to assess the technical performance of the heat exchanger. The model developed in TRNSYS can simulate the performance of a single heat exchanger unit, with a few input parameters needed. The model was developed by using measurement data from the facility in Stockholm to get realistic results depending on time and actual measurements. From the measured data, there were a few parameters that needed to be calculated, first off the mass flow rate of the waste water flow, this was done by an energy balance over the heat exchanger. Following the mass flow rate the cold water set point had to be determined, so that the heat recovered was not larger than the heat that could be utilized by the building. Since data was available from a single site, there was not much else to do than accept the data as true, there were some data points that had to be sorted out however, such as negative flow rates and flow rates much higher than should be possible. The finished model uses all the data from the measurements as well as the calculated values, it provided heat transfer rate along with the outgoing temperatures of both waste water and the preheated water. The first reference scenario provided 25,3 MWh of recovered energy, but the best scenario with an increased waste water temperature as well as increased flow rate it could provide a total of 47,2 MWh, almost twice the original value. To conclude the model seems to simulate a waste water heat exchanger well and returns feasible data. It should be possible to use the model to see if a building is a good “candidate” to install a waste water heat exchanger in.
Byggnads och servicesektorn står för cirka 40 procent av Sveriges energibehov. Av de 40 procenten består 90% av energibehov ifrån hushåll och kontorsbyggnader. Totalt sett 80 TWh används för uppvärmning av byggnader samt varmvatten. Då uppvärmning alltid varit en stor del av energibehovet i Sverige är det naturligt att det skett en rad förbättringar på vägen. Det finns en ny anläggning på Pennfäktaren 11 i Stockholm, en horisontell värmeväxlare för avloppsvatten. Den här uppsatsen fokuserar på att skapa en modell i TRNSYS av en värmeväxlare där parametrar som vattenflöde, temperatur, och mer kan användas för att bedöma den tekniska aspekten av en installation av värmeväxlare i en byggnad. Modellen kan simulera prestandan av en ensam värmeväxlare, med endast ett fåtal parametrar som behövs. Modellen baseras på mätdata ifrån anläggningen på Pennfäktaren, denna mätdata har sedan använts för att beräkna först massflödet av avloppsvatten men också för att bestämma hur mycket värme som är möjligt att återvinna utan att överskrida det byggnaden faktiskt kan använda. Då det bara finns data ifrån en källa fick den anses som korrekt, dock gjordes en del ändringar där data helt enkelt var omöjligt, t.ex. negativa avloppsflöden och flödesmängder så höga att de inte ska kunna vara möjliga. Den färdiga modellen använder mätdata tillsammans med de beräknade värdena. Detta används för att genom modellen beräkna temperaturvärden för utgående vatten och avlopp samt den totala mängden återvunnen värme. I referensscenariot kunde totalt 25,3 MWh värme återvinnas men det bästa scenariot med ökad avloppstemperatur och avloppsflöde kunde närmare 47,2 MWh återvinnas, nästan det dubbla från referensvärdet. För att sammanfatta ger modellens simulationer rimliga värden för värmeväxlaren. Det bör därför vara fullt möjligt att använda modellen för att bedöma ett hus rimlighet till en värmeväxlarinstallation.

The trend towards improving building airtightness to save energy has increased the incidence of poor indoor air quality and associated problems, such as condensation on windows, mould, rot and fungus on window frames. Mechanical ventilation/heat recovery systems, combined with heat pumps, offer a means of significantly improving indoor air quality, as well as providing energy efficient heating and cooling required in buildings. This thesis is concerned with the development of a novel mechanical ventilation heat recovery/heat pump system for the domestic market. Several prototypes have been developed to provide mechanical ventilation with heat recovery. These systems utilise an annular array of revolving heat pipes which simultaneously transfer heat and impel air. The devices, therefore, act as fans as well as heat exchangers. The heat pipes have wire finned extended surfaces to enhance the heat transfer and fan effect. The systems use environmentally friendly refrigerants with no ozone depletion potential and very low global warming potential. A hybrid system was developed which incorporated a heat pump to provide winter heating and summer cooling. Tests were carried out on different prototype designs. The type of tinning, the working fluid charge and the number and geometry of heat pipes was varied. The prototypes provide up to 1000m3/hr airflow, have a maximum static pressure of 220Pa and have heat exchanger efficiencies of up to 65%. At an operating supply rate of 200m3/hr and static pressure 100Pa, the best performing prototype has a heat exchanger efficiency of 53%. The heat pump system used the hydrocarbon isobutane as the refrigerant. Heating COPs of up to 5 were measured. Typically the system can heat air from 0°C to 26°C at 200m3/hr with a whole system COP of 2. The contribution to knowledge from this research work is the development of a novel MVHR system and a novel MVHR heat pump system and the establishment of the performances of these systems.

This study investigates the change in thermal resistance due to fouling in drain water pipes. As insulation of houses and energy efficiency of appliances improve, the importance of Drain Water Heat Recovery (DWHR) is growing steadily. In older houses, the relative heat loss through drain water is smaller than in newly built houses, but should still be considered. For example, 17 % of the total heat loss in Swedish multi-family houses built before 1940 was transported with the drain water (Ekelin et al., 2006). The average temperature of drain blackwater is between 23 °C and 26 °C (Seybold & Brunk, 2013), and a part of its heat can be recovered in DWHR systems. This allows cold incoming water to houses and buildings to be pre-heated by drain water before it is heated in the heat pump. Depending on the system, 30 % to 75 % of the heat from drain water can be recovered (Zaloum et al., 2007b). A threat to heat exchanger performance is that additional materials, so called fouling, accumulate on the surfaces of the heat exchangers and increases its thermal resistance. This resistance can be described by a fouling resistance and can be very costly due to losses in heat transfer and required cleaning. To quantify the fouling resistance, experiments were conducted in a climate chamber on Brinellvägen 66, using a pipe that had been installed for 3 years in the sewage system from the men’s toilet on Brinellvägen 64B. The installed pipe was compared with a pipe from the same manufacturer with the same dimensions. The pipes were sealed and filled with water at about 20 °C. Thermocouples were used to measure the decrease in water temperature over time in both pipes. Based on these measurements, the difference in thermal resistance was found, using curve fitting and the Lumped Capacitance Method. The fouling resistance was quantified by comparing the thermal resistances of the test pipe with and without fouling. The main findings were firstly that fouling significantly increases the thermal resistance of aluminium pipes. Secondly, corrosion causes a significant decrease in the pipes’ thermal resistance. The combination of these effects led to a decrease of 14 % in thermal resistance in the examined system after three years compared to the time of installation. The decrease in thermal resistance due to corrosion in the test pipe was 44 % compared to the time of installation. Furthermore, the thermal resistance of the test pipe decreased by 51 % when it was cleaned from the fouling. The fouling resistance of the 0.81 mm fouling layer was found to be 0.03068 m2K/W.
Denna studie undersöker den ökade termiska resistansen i avloppsrör på grund av beläggningar. Idag lägg stor vikt vid bra isolering och energieffektiv utrustning i nybyggda hus, vilket även sätter press på värmeåtervinning av avloppsvatten. Värmeåtervinningen av avloppsvatten är mindre viktig i äldre hus, då den relativa värmeförlusten av avloppsvatten är lägre än i nybyggda hus, men bör likväl tas i akt vid utvärderingen av värmeanvändning. I ett svenskt flerfamiljshus byggt före 1940 stod värmeförlusten på grund av varmt avloppsvatten för 17 % av den totala värmeförlusten (Ekelin et al., 2006). Den genomsnittliga temperaturen för svartvatten ligger på 23 °C till 26 °C (Seybold & Brunk, 2013), varav delar av värmen kan återvinnas i värmeväxlare. Detta bidrar till att det kalla ingående vattnet till värmepumpen förvärms av värmen från avloppsvattnet. Beroende på system och material kan 30 % till 75 % av värmen från avloppsvatten återvinnas (Zaloum et al., 2007b). Ett hot mot prestandan av värmeväxlare är att beläggning formas på de värmeöverförande ytorna i värmeväxlaren. Detta bidrar till en ökad termisk resistans och kan vara mycket kostsam på grund av minskning av värmeöverföring och nödvändig rengöring av anordningen. För att undersöka omfattningen av den ökade termiska resistansen utfördes en rad experiment i en klimatkammare på Brinellvägen 66. En jämförande metod användes där ett aluminiumrör, som tidigare installerats i avloppssystemet från herrarnas toalett i korridoren på Brinellvägen 64B, jämfördes med ett identiskt rör av samma tillverkare. Rören var tätade och fyllda med 20-gradigt kranvatten. Termoelement användes för att, över tid, mäta minskningen av vattentemperaturen i rören. Temperaturskillnaden användes för att beskriva skillnaden i termisk resistans genom att utföra kurvanpassning och tillämpa Lumped Capacitance Method. Skillnaden i termisk resistans mellan de båda rören antogs vara lika med beläggningens motstånd för värmeöverföring. Två huvudsakliga resultat kom av studien. Det första var att beläggning bidrar till ökad termisk resistans av aluminiumrör. Den andra var att korrosion tillsammans med andra externa faktorer orsakar en märkbar minskning av rörens termiska resistans. Totalt sett orsakade beläggningen tillsammans med korrosion en minskning av 14 % av den termiska resistansen i provröret, jämfört med den termiska resistansen vid installationstillfället. Vidare låg minskningen i termisk resistans på grund av korrosion i teströret på 44 % jämfört med den termiska resistansen vid installationstillfället och den genomsnittliga termiska resistansen av det rengjorda teströret låg på 51 % lägre än den genomsnittliga resistansen av teströret innan rengöring. Den beräknade resistansen för ett 0.81 mm tjockt lager av beläggning var 0.03068 m2K/W.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, September, 2020
Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 25-26).
Environmental concerns and economic incentives have created a push for a reduction in emissions and an increase in efficiency. The U.S. Department of Energy estimates that 20 to 50% of the energy consumed in manufacturing processes is lost in some form to waste heat. The purpose of this study is to review the waste heat recovery technologies currently available in both commercial and research applications to determine how thermoacoustics may serve a role in furthering the use of waste heat recovery units. A literary review of the most common waste heat recovery units was compiled to determine the advantages and disadvantages of the different technologies by comparing components and their governing processes. An existing model of a thermoacoustic converter (TAC) was reviewed and a conceptual analysis written to suggest improvements for future experimental designs.
by Alex Aguilar.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Dr. Yogendra Joshi; Committee Member: Dr. S. Mostafa Ghiaasiaan; Committee Member: Dr. Sheldon Jeter. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The energy used by building sector accounts for approximately 40% of the total energy usage. In residential buildings, 30-60% of this energy is used for space heating which is mainly wasted by transmission heat losses. A share of 20-30% is lost by the discarded residential wastewater and the rest is devoted to ventilation heat loss.   The main objective of this work was to evaluate the thermal potential of residential wastewater for improving the performance of mechanical ventilation with heat recovery (MVHR) systems during the coldest periods of year. The recovered heat from wastewater was used to preheat the incoming cold outdoor air to the MVHR in order to avoid frost formation on the heat exchanger surface.   Dynamic simulations using TRNSYS were used to evaluate the performance of the suggested air preheating systems as well as the impact of air preheating on the entire system. Temperature control systems were suggested based on the identified frost thresholds in order to optimally use the limited thermal capacity of wastewater and maintain high temperature efficiency of MVHR. Two configurations of air preheating systems with temperature stratified and unstratified tanks were designed and compared. A life cycle cost analysis further investigated the cost effectiveness of the studied systems.   The results obtained by this research work indicated that residential wastewater had the sufficient thermal potential to reduce the defrosting need of MVHR systems (equipped with a plate heat exchanger) in central Swedish cities to 25%. For colder regions in northern Sweden, the defrosting time was decreased by 50%. The temperature control systems could assure MVHR temperature efficiencies of more than 80% for most of the heating season while frosting period was minimized. LCC analysis revealed that wastewater air preheating systems equipped with temperature stratified and unstratified storage tanks could pay off their costs in 17 and 8 years, respectively.

QC 20190830

High amounts of heat energy are today deposited into the urban wastewater system. The current society-wide development for energy efficiency has so far barely touched upon the area of wastewater heat conservation, which is why the share of total energy consumption from water use is increasing. Through this master thesis a case study was performed, assessing in particular the heat recovery potential from untreated wastewater in the common sewer line upstream from a wastewater treatment plant (Käppalaverket) for supply onto the local district heating network (Norrenergi) by the use of a heat pump solution. The current wastewater treatment process is using temperature dependant biological treatment for denitrifying the wastewater before it is disposed to the Baltic Sea, which poses limitations on upstream heat extraction. The purpose of the study was to assess the heat recovery potential and possibilities when using untreated wastewater compared to what is done traditionally using treated wastewater after the treatment plant. Furthermore a technological review was done over the area of heat recovery from untreated wastewater and also an evaluation of potential equipment and technology suppliers. Hydraulic modelling and thermodynamic simulations of the wastewater system were performed. Results showed that during a majority of the year approximately 4 MW of heat could be extracted while staying within conservative limits in regards to a minimum influent temperature as well as a maximum upstream temperature decrease. During wet season however, no or very limited heat could be recovered as the influent temperatures are already in a rather sensitive range in regards to the biological treatment process. At this level, through analysis of available equipment for heat recovery from untreated wastewater, a maximum heat amount of approximately 18 GWh per year could be supplied to the district heating network. Furthermore, it was found that reducing the amount of supplementary water in the system would be highly beneficial, both regarding HR potential but also for the treatment process in the plant. Also, if extensive HR performed by water consumers would occur, the model shows that this would probably have a negative effect on downstream temperature and the treatment process. Through this study it was concluded that even though the theoretically available heat in the system is very large, the practical heat recovery potential is very limited under current conditions. The strongest reason is the limitation posed by the temperature requirements of the influent wastewater. If also cooling is considered, the heat recovery prospects might be better due to the lower net energy extraction from the wastewater. Regarding the economic feasibility of an installation for heat recovery from untreated wastewater, the assessment made in this project showed that it may actually be comparable to projects using other types of waste heat. The results and conclusions from this study should not be considered as a green light, or as motivation, for performing any upstream heat recovery installations. Such projects must be done in consensus with local authorities and especially the wastewater treatment plant in question. Further analyses in this area is considered essential before exploring it further, such as assessing the transient behaviour of the surrounding rock walls when heat is recovered upstream. The model used in this study also needs confirmation through actual temperature measurements within the system, which do not exist at the moment. Furthermore, a complete life cycle analysis should be carried out for the entire urban water system, which should find an optimal way of where to use and to recover the energy.
Stora mängder värme sköljs idag ner i avloppsnätet. Den pågående samhällsbreda utvecklingen för energieffektivisering har så här långt knappt rört vid området för spillvatten, varför andelen av den totala energikonsumtionen från vattenanvändning ökar. Inom detta examensarbete har en fallstudie genomförts där värmeåtervinning från orenat avloppsvatten längs avloppsnätets samlingsledning uppströms från Käppalaverkets reningsverk har utretts. Detta med hjälp av en värmepump för att förse Norrenergis fjärrvärmenät. Den nuvarande vattenreningsprocessen baseras på temperaturberoende biologisk rening för att denitrifiera spillvattnet innan det släpps ut i Östersjön, vilket sätter begränsningar på uppströms värmeuttag. Studien syftade till att utreda potentialen och möjligheterna för att använda orenat avloppsvatten jämfört med att som traditionellt använda redan renat avloppsvatten efter reningsverket.Därtill utfördes en teknikinventering över området samt en utvärdering av potentiella teknik- och utrustningsleverantörer. Hydraulisk modellering och termodynamiska simuleringar av avloppssystemet utfördes. Resultaten visade att under en majoritet av året så kan ungefär 4 MW värme extraheras från det orenade vattnet inom konservativa gränser i förhållande till tillåten minsta inloppstemperatur till reningsverket samt en maximal uppströms temperatursänkning. Under vintern dock så kan väldigt lite, eller till och med ingen, värme återvinnas på grund av att inloppstemperaturen till reningsverket redanbefinner sig inom ett relativt kritiskt område i förhållande till den biologiska reningsprocessen. På denna nivå så kan uppskattningsvis maximalt 18 GWh per år förses till fjärrvärmenätet. Det fanns också att en reduktion av mängden tillskottsvatten skulle vara väldigt gynnsamt, både för värmeåtervinnings skull men även för själva reningsprocessen. Därtill, om utbredd uppströms värmeåtervinning hos konsumenterna skulle tillåtas, så visar modellen att detta skulle ha en negativ påverkan på nedströms reningsprocess. Genom denna studie dras slutsatsen att trots att den teoretiskt tillgängliga värmen är stor i systemet så är de praktiska möjligheterna väldigt begränsade under nuvarande förhållanden. Den starkaste orsaken till detta är begränsningen som utgörs av temperaturkravet som reningsprocessen har. Om även kyla anses möjligt så ökar även möjligheterna för värmeåtervinning på grund av den lägre netto effekten från värmeåtervinning som sker. Då den ekonomiska genomförbarheten analyserades fanns att en installation med värmeåtervinning från orenat avloppsvatten faktiskt är jämförbar med andra spillvärmeprojekt. Det är viktigt att poängtera att resultat och slutsatser i denna studie inte bör anses som någon form av grönt ljus, eller som motivering, för att genomföra någon sorts uppströms installationer för värmeåtervinning. Projekt av sådan natur bör genomföras i samförstånd med lokala myndigheter, och i förlängningen även med avloppsreningsverket i fråga. Fortsatta analyser inom detta område betraktas som absolut nödvändiga före man exploaterar detta område vidare. Sådana studier är till exempel att analysera det transienta beteendet hos den omgivande bergväggen i avloppsnätet då värme börjar återvinnas uppströms. Modellen i denna studie behöver också vidare bekräftelse genom faktiska temperaturmätningar i avloppssystemet, vilka idag ej existerar. Vidare bör en fullständig livscykelanalys över hela det urbana vattensystemet göras, var man bör finna ett optimerat sätt att använda samt återta energin.

Thesis (MScIng)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: As the demand for less expensive energy is increasing world-wide, energy conservation is becoming a more-and-more important economic consideration. In light of this, means to recover energy from waste fluid streams is also becoming more-and-more important. An efficient and cost effective means of conserving energy is to recover heat from a low temperature waste fluid stream and use this heat to preheat another process stream. Heat pipe heat exchangers (HPHEs) are devices capable of cost effectively salvaging wasted energy in this way. HPHEs are liquid-coupled indirect transfer type heat exchangers except that the HPHE employs heat pipes or thermosyphons as the major heat transfer mechanism from the high temperature to the low-temperature fluid. The primary advantage of using a HPHE is that it does not require an external pump to circulate the coupling fluid. The hot and cold streams can also be completely isolated preventing cross-contamination of the fluids. In addition, the HPHE has no moving parts. In this thesis, the development of a range of air-to-air HPHEs is investigated. Such an investigation involved the theoretical modelling of HPHEs such that a demonstration unit could be designed, installed in a practical industrial application and then evaluated by considering various financial aspects such as initial costs, running costs and energy savings. To develop the HPHE theoretical model, inside heat transfer coefficients for the evaporator and condenser sections of thermosyphons were investigated with R134a and Butane as two separate working fluids. The experiments on the thermosyphons were undertaken at vertical and at an inclination angle of 45° to the horizontal. Different diameters were considered and evaporator to condenser length ratios kept constant. The results showed that R134a provided for larger heat transfer rates than the Butane operated thermosyphons for similar temperature differences despite the fact that the latent heat of vaporization for Butane is higher than that of R134a. As an example, a R134a charged thermosyphon yielded heat transfer rates in the region of 1160 W whilst the same thermosyphon charged with Butane yielded heat transfer rates in the region of 730 W at 23 °C . Results also showed that higher heat transfer rates were possible when the thermosyphons operated at 45°. Typically, for a thermosyphon with a diameter of 31.9 mm and an evaporator to condenser length ratio of 0.24, an increase in the heat transfer rate of 24 % could be achieved. Theoretical inside heat transfer coefficients were also formulated which were found to correlate reasonably well with most proposed correlations. However, an understanding of the detailed two-phase flow and heat transfer behaviour of the working fluid inside thermosyphons is difficult to model. Correlations proposing this behaviour were formulated and include the use of R134a and Butane as the working fluids. The correlations were formulated from thermosyphons of diameters of 14.99 mm, 17.272 mm, 22.225 mm and 31.9 mm. The evaporator to condenser length ratio for the 31.9 mm diameter thermosyphon was 0.24 whilst the other thermosyphons had ratios of 1. The heat fluxes ranged from 1800-43500 W/m2. The following theoretical inside heat transfer coefficients were proposed for vertical and inclined operations (READ CORRECT FORMULA IN FULL TEXT ABSTRACT) φ = 90° ei h = 3.4516x105Ja−0.855Ku1.344 φ = 45° ei h = 1.4796x105Ja−0.993Ku1.3 φ = 90° l l l ci l l v h x k g 1/ 3 2.05 2 4.61561 109Re 0.364 ν ρ ρ ρ − ⎡ ⎡ ⎛ ⎞⎤ ⎤ = ⎢ ⎢ ⎜ ⎟⎥ ⎥ ⎢ ⎢ ⎜ − ⎟⎥ ⎥ ⎣ ⎣ ⎝ ⎠⎦ ⎦ φ = 45° l l l ci l l v h x k g 1/ 3 1.916 2 3.7233 10 5Re 0.136 ν ρ ρ ρ − ⎡ ⎡ ⎛ ⎞⎤ ⎤ = ⎢ ⎢ ⎜ ⎟⎥ ⎥ ⎢ ⎢ ⎜ − ⎟⎥ ⎥ ⎣ ⎣ ⎝ ⎠⎦ ⎦ The theoretically modelled demonstration HPHE was installed into an existing air drier system. Heat recoveries of approximately 8.8 kW could be recovered for the hot waste stream with a hot air mass flow rate of 0.55 kg/s at an inlet temperature of 51.64 °C and outlet temperature of 35.9 °C in an environment of 20 °C. Based on this recovery, energy savings of 32.18 % could be achieved and a payback period for the HPHE was calculated in the region of 3.3 years. It is recommended that not withstanding the accuracies of roughly 25 % achieved by the theoretically predicted correlations to that of the experimental work, performance parameters such as the liquid fill charge ratios, the evaporator to condenser length ratios and the orientation angles should be further investigated.
AFRIKAANSE OPSOMMING: As gevolg van die groeiende aanvraag na goedkoper energie, word die behoud van energie ‘n al hoe belangriker ekonomiese oorweging. Dus word die maniere om energie te herwin van afval-vloeierstrome al hoe meer intensief ondersoek. Een effektiewe manier om energie te herwin, is om die lae-temperatuur-afval-vloeierstroom (wat sou verlore gaan) se hitte te gebruik om ‘n ander vloeierstroom mee te verhit. Hier dien dit dan as voorverhitting van die ander, kouer, vloeierstroom. Hittepyp hitteruilers (HPHR’s) is laekoste toestelle wat gebruik kan word vir hierdie doel. ‘n HPHR is ‘n vloeistof-gekoppelde indirekte-oordrag hitteruiler, behalwe vir die feit dat dié hitteruiler gebruik maak van hittepype (of hittebuise) wat die grootste deel van sy hitteoordragsmeganisme uitmaak. Die primêre voordele van ‘n HPHR is dat dit geen bewegende dele het nie, die koue- en warmstrome totaal geïsoleer bly van mekaar en geen eksterne pomp benodig word om die werkvloeier mee te sirkuleer nie. In hierdie tesis word ‘n ondersoek gedoen oor die ontwikkeling van ‘n bestek van lug-totlug HPHR’s. Hierdie ondersoek het die teoretiese modellering van so ‘n HPHR geverg, sodat ‘n demonstrasie eenheid ontwerp kon word. Hierdie demonstrasie eenheid is geïnstalleer in ‘n praktiese industriële toepassing waar dit geïvalueer is deur na aspekte soos finansiële voordele en energie-besparings te kyk. Om die teoretiese HPHR model te kon ontwikkel, moes daar gekyk word na die binnehitteoordragskoëffisiënte van die verdamper- en kondensordeursneë, asook R134a en Butaan as onderskeie werksvloeiers. Die eksperimente met die hittebuise is gedoen in die vertikale en 45° (gemeet vanaf die horisontaal) posisies. Verskillende diameters is ook ondersoek, maar met die verdamper- en kondensor-lengteverhouding wat konstant gehou is. Die resultate wys dat R134a as werksvloeier in die hittebuise voorsiening maak vir groter hitteoordragstempo’s in vergelyking met Butaan as werksvloeier by min of meer dieselfde temperatuur verskil – dít ten spyte van die feit dat Butaan ‘n hoër latente-hittetydens- verdampings eienskap het. As voorbeeld gee ‘n R134a-gelaaide hittebuis ‘n hitteoordragstempo van omtrent 1160 W terwyl dieselfde hittebuis wat met Butaan gelaai is, slegs ongeveer 730 W lewer by 23 °C. Die resultate wys ook duidelik dat hoër hitteoordragstempo’s verkry word indien die hittebuis bedryf word teen ‘n hoek van 45°. ‘n Tipiese toename in hitteoordragstempo is ongeveer 24 % vir ‘n hittebuis met ‘n diameter van 31.9 mm en ‘n verdamper- tot kondensor-lengteverhouding van 0.24. Teoretiese binne-hitteoordragskoëffisiënte is ook geformuleer. Dié waardes stem redelik goed ooreen met die meeste voorgestelde korrelasies. Nieteenstaande die feit dat gedetailleerde twee-fase-vloei en die hitteoordragsgedrag van die werksvloeier binne hittebuise nog nie goed deur die wetenskaplike wêreld verstaan word nie. Korrelasies wat hierdie gedrag voorstel is geformuleer en sluit weereens die gebruik van R134a en Butaan as werksvloeiers in. Die korrelasies is geformuleer vanaf hittebuise met diameters van onderskeidelik 14.99 mm, 17.272 mm, 22.225 mm en 31.9 mm. Die verdamper- tot kondensor-lengteverhoudings vir die 31.9 mm deursnit hittebuis was 0.24 terwyl die ander hittebuise ‘n verhouding van 1 gehad het. Die hitte-vloede het gewissel van 1800-45300 W/m2. Die volgende teoretiese geformuleerde binne-hitteoordragskoëffisiënte word voorgestel vir beide vertikale sowel as nie-vertikale toepassing (LEES KORREKTE FORMULE IN VOLTEKS OPSOMMING) φ = 90° ei h = 3.4516x105Ja−0.855Ku1.344 φ = 45° ei h = 1.4796x105Ja−0.993Ku1.3 φ = 90° l l l ci l l v h x k g 1/ 3 2.05 2 4.61561 109Re 0.364 ν ρ ρ ρ − ⎡ ⎡ ⎛ ⎞⎤ ⎤ = ⎢ ⎢ ⎜ ⎟⎥ ⎥ ⎢ ⎢ ⎜ − ⎟⎥ ⎥ ⎣ ⎣ ⎝ ⎠⎦ ⎦ φ = 45° l l l ci l l v h x k g 1/ 3 1.916 2 3.7233 10 5Re 0.136 ν ρ ρ ρ − ⎡ ⎡ ⎛ ⎞⎤ ⎤ = ⎢ ⎢ ⎜ ⎟⎥ ⎥ ⎢ ⎢ ⎜ − ⎟⎥ ⎥ ⎣ ⎣ ⎝ ⎠⎦ ⎦ Die wiskundig-gemodelleerde demostrasie HPHR is geïnstalleer binne ‘n bestaande lugdroër-sisteem. Drywing van om en by 8.8 kW kon herwin word vanaf die warm-afvalvloeierstroom met ‘n massa vloei van 0.55 kg/s teen ‘n inlaattemperatuur van 51.64 °C en ‘n uitlaattemperatuur van 35.9 °C binne ‘n omgewing van 20 °C. Na aanleiding van hierdie herwinning, kan energiebesparings van tot 32.18 % verkry word. Die HPHR se installasiekoste kan binne ‘n berekende tydperk van ongeveer 3.3 jaar gedelg word deur hierdie besparing. Verdamper- tot kondensator-lengteverhouding, vloeistofvulverhouding en die oriëntasiehoek vereis verdere ondersoek, aangesien daar slegs ‘n akkuraatheid van 25 % verkry is tussen teoretiese voorspellings en praktiese metings.

One of the major challenges of this decade is developing more sustainable energy systems that contribute to environmental concern, especially climate change mitigation. Extending the operating conditions of the heat pump technology to higher temperatures will allow decarbonising the industrial sector from two slopes: recovering heat from waste heat sources that currently is being rejected to the ambient and produce heat at the required industrial thermal levels that become useful for the industrial processes. Both challenges will make possible reduce the equivalent CO2 emissions of the industrial sector and operate at high temperatures that conventional heat pumps. This thesis deals with the development of high temperature heat pumps through a comprehensive theoretical and experimental analysis to overcome different technology challenge: architecture, refrigerants, experimental prototype, advanced applications and system integration, providing new knowledge that represents a step forward in high temperature heat pump technology.
Uno de los mayores desafíos de esta década recae en el desarrollo de sistemas energéticos más sostenibles que contribuyan a la preocupación medioambiental, especialmente la mitigación del cambio climático. Extender las condiciones de funcionamiento de la tecnología de bomba de calor a temperaturas más elevadas permitirá descarbonizar el sector industrial desde dos vertientes: recuperando calor de fuentes de calor residual, actualmente disipado al ambiente y producir calor a los niveles térmicos requeridos, útiles para los procesos industriales, reduciendo así las emisiones de CO2 equivalentes del sector industrial y contribuyendo al desarrollo sostenible. Esta tesis pretende abordar el desarrollo de bombas de calor de alta temperatura a través de un análisis teórico y experimental, para abordar diferentes desafíos tecnológicos: arquitectura, refrigerantes, prototipo experimental, aplicaciones avanzadas e integración de sistemas, generando nuevos conocimientos que representan un paso adelante en la tecnología de bombas de calor de alta temperatura.
Programa de Doctorat en Tecnologies Industrials i Materials

Includes bibliographical references.
A case study was thus carried out at an applicable local industry (brewery) to assess the feasibility of implementing the heat pump for waste heat recovery. Through analysis, the focus was narrowed down from a site wide audit, to a departmental breakdown and then eventually to a specific process; the wort boiler. Three different alternatives were investigated and the performance and economic viability compared; a simple waste heat recovery solution involving a vapour condenser (vq, a mechanical vapour recompression (MVR) heat pump and a thermal vapour recompression (TVR) heat pump. It was found that the MVR system yielded the greatest energy savings, followed by the VC and then the TVR system. All three systems had positive rates of return, with the VC and TVR systems being tied for first place.

Portable electronic devices have made a profound impact on our society and economy due to their widespread use for computation, communications, and entertainment. The performance and autonomy of these devices can be greatly improved if their operation can be powered using energy that is harvested from the ambient environment. As a step towards that goal, this thesis explored the feasibility of developing miniaturized Stirling engines for harvesting waste heat. A mesoscale (palmtop-size) gamma-type Stirling engine, with a total volume of about 165 cubic centimeters, was manufactured using conventional machining techniques. The engine was able to sustain steady-state operation at relatively low temperature differentials (between 20 degrees Celsius and 100 degrees Celsius) and generated a few millijoules of mechanical energy at frequencies ranging from 200 to 500 revolutions per minute. Subsequently, the gamma-type engine was transformed into a Ringbom engine; and its operation was compared with the predictions of an analytical model available in the literature. The experience gained from these studies provides some guidelines for further miniaturization of Stirling engines using microfabrication technologies.
Les appareils électroniques portatifs ont définitivement laissé un impact sur notre société et économie par leur utilisation fréquente pour le calcul, les communications et le divertissement. La performance et l'autonomie de ces appareils peuvent s'améliorer grandement si leur exploitation fonctionne en utilisant l'énergie récoltée de l'environnement. Pour s'orienter vers ce but, cette thèse a exploré si le développement d'un moteur Stirling fonctionnant sur l'énergie résiduelle était faisable. Un moteur Stirling de configuration 'gamma', de la grandeur d'une paume de main, avec un volume d'environ 165 centimètres cubes, a été fabriqué en utilisant des techniques conventionnelles d'usinage. Ce moteur a été capable de soutenir l'opération constante et stable à des différences en température relativement basses (entre 20 degrés Celsius et 100 degrés Celsius). De plus, il a produit quelques milli-Joules d'énergie mécanique à des fréquences entre 200 et 500 révolutions par minute. Par la suite, le moteur Stirling de configuration 'gamma' a été transformé en un moteur Ringbom. Par après, l'opération de ce moteur a été comparée à des prédictions basées sur un modèle analytique disponible dans la littérature. Les informations recueillies durant cette étude ont fourni certaines directives pour la miniaturisation éventuelle d'un moteur Stirling en utilisant des techniques de microfabrication.

The work presented in this thesis will explore the development of novel heat recovery systems coupled with low carbon technologies, and its integration to become one device with multifunction (building integrated heat recovery/cooling/air dehumidifier. In the first part of this thesis, an experimental performance of an individual heat recovery unit using Micro Heat and Mass Cycle Core (MHM3C) made of fibre papers with cross flow arrangement has been carried out. The unit was tested in an environmental control chamber to investigate the effects of various parameters on the performance of heat/energy recovery unit. The results showed that as the airflow rate and temperature change increase, the efficiency decreases whilst recovered energy increases. Integrating heat recovery system in energy-efficient system represents significant progress for building applications. As part of the research, the integration of heat recovery using a cross-flow fixed-plate with wind-catcher and cellulose fibre papers of evaporative cooling units have allowed part of the energy to be recovered with the efficiency of heat recovery unit ranged from 50 to 70%, cooling efficiency ranged from 31 to 54%. In another case, the integration of heat recovery system with building part so called building integrated heat recovery (BIHR) was explored using polycarbonate plate with counter-flow arrangement. It introduces a new approach to MVHR system, an established technology that uses a modified insulation panel, linking the inside and outside of a building, to recover heat while extracting waste air and supplying fresh air. In this configuration it is not only acts a heat recovery, but also as a contribution to building thermal insulation. From the experiments conducted, it was found that through an energy balance on the structure, the efficiency of BIHR prototype was found to be 50 to 61.1 % depending on the airflow rate. This efficiency increases to the highest value of 83.3% in a full-scale measurement on a real building in Ashford, Kent as the area of heat transfer surface increases. The increasing of heat surface area again proved a better performance in terms of efficiency as the results on another full scale measurement on a real house in Hastings, Sussex showed to be 86.2 to 91.7%. With the aiming to have a high performance system, a new improvement design of BIHR' corrugated polycarbonate channels with four airstreams has significant advantages over the previous prototype BIHR with two airstreams. The recovered heat is increased by more than 50%. With the issue of thermal comfort in hot region area and problems with conventional air conditioning system, a study of BIHR system with fibre wick structure for different hot (summer) air conditions using different working fluids was carried out. For the first case, water was used to give a direct evaporative cooling effect which is suitable to evaluate the system performance under hot and dry climatic conditions and the second case, potassium formate (HCOOK) solution was used as liquid desiccant for dehumidification under hot and humid climate conditions. By supplying the water over the fibre wick structure, with a constant airflow rate of 0.0157m3/s, the efficiency increased with increasing intake air temperature. The efficiency ranged from 20 to 42.4% corresponding to the minimum and maximum of intake air temperature of 25°C and 38.2°C, respectively. With the variation of airflow rate, the efficiency of the system was found to be 53.2 to 60%. In second case, the HCOOK solution with concentration of 68.6% has been selected as the desiccant and for a defined airflow rate of 0.0157m3/s, heat recovery efficiency of about 54%, a lower desiccant temperature of 20°C, with higher intake air temperature and relative humidity produces a better dehumidification performance with a good moisture absorption capacity. Therefore, this system is expected to be used efficiently in hot and humid regions. The research is novel in the following ways: • The development of multifunction device in one system; building integrated, heat recovery, cooling, desiccant dehumidification. • The design and development of BIHR is an advanced technology of building thermal insulation and heat recovery. The novel BIHR -fibre wick cooling/dehumidification system has the potential to compete with conventional air conditioning systems under conditions involving high temperature and high moisture load.

The global air temperature has increased by 0.74± 0.18 °C since 1905 and scientists have shown that CO2 accounts for 55 percentages of the greenhouse gases. Global atmospheric CO2 has been sharply increased since 1751, however the trend has slowed down in last fifty years in the Western Europe. UK and EU countries have singed the Kyoto agreement to reduce their greenhouse gas emissions by a collective average of 12.5% below their 1990 levels by 2020. In the EU, 40% of CO2 emission comes from the residential energy consumption, in which the HVAC system accounts for 50%, lighting accounts for 15% and appliances 10%. Hence, reducing the fossil-fuel consumption in residential energy by utilizing renewable energy is an effective method to achieve the Kyoto target. However, in the UK renewable energy only accounts for 2% of the total energy consumption in 2005. A novel heat recovery/desiccant cooling system is driven by the solar collector and cooling tower to achieve low energy cooling with low CO2 emission. This system is novel in the following ways: • Uses cheap fibre materials as the air-to-air heat exchanger, dehumidifier and regenerator core • Heat/mass fibre exchanger saves both sensible and latent heat from the exhaust air • The dehumidifier core with hexagonal surface could be integrated with windcowls/catchers draught • Utilises low electrical energy and therefore low CO2 is released to the environment The cooling system consists of three main parts: heat/mass transfer exchanger, desiccant dehumidifier and regenerator. The fibre exchanger, dehumidifier and regenerator cores are the key parts of the technology. Owing to its proper pore size and porosity, fibre is selected out as the exchanger membrane to execute the heat/mass transfer process. Although the fibre is soft and difficult to keep the shape for long term running, its low price makes its frequent replacement feasible, which can counteract its disadvantages. A counter-flow air-to-air heat /mass exchanger was investigated and simulation and experimental results indicated that the fibre membranes soaked by desiccant solution showed the best heat and mass recovery effectiveness at about 89.59% and 78.09%, respectively. LiCl solution was selected as the working fluid in the dehumidifier and regenerator due to its advisable absorption capacity and low regeneration temperature. Numerical simulations and experimental testing were carried out to work out the optimal dehumidifier/regenerator structure, size and running conditions. Furthermore, the simulation results proved that the cooling tower was capable to service the required low temperature cooling water and the solar collector had the ability to offer the heating energy no lower than the regeneration temperature 60℃. The coefficient-of-performance of this novel heat recovery/desiccant cooling system is proved to be as high as 13.0, with a cooling capacity of 5.6kW when the system is powered by renewable energy. This case is under the pre-set conditions that the environment air temperature is 36℃ and relative humidity is 50% (cities such as Hong Kong, Taiwan, Spain and Thailand, etc). Hence, this system is very useful for a hot/humid climate with plenty of solar energy. The theoretical modelling consisted of four numerical models is proved by experiments to predict the performance of the system within acceptable errors. Economic analysis based on a case (200m2 working office in London) indicated that the novel heat recovery/desiccant cooling system could save 5134kWh energy as well as prevent 3123kg CO2 emission per year compared to the traditional HVAC system. Due to the flexible nature of the fibre, the capital and maintenance cost of the novel cooling system is higher than the traditional HVAC system, but its running cost are much lower than the latter. Hence, the novel heat recovery/desiccant cooling system is cost effective and environment friendly technology.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.
Includes bibliographical references.
Novel methods to convert waste metabolic heat into useful and useable amounts of electricity were studied. Thermoelectric, magneto hydrodynamic, and piezo-electric energy conversions at the desired scope were evaluated to understand their role and utility in the efficient conversion of waste body heat. The piezo-electric generator holds the most promise for the efficient conversion of waste body heat into electricity. In the future, this same device could be easily extended into a combustion based power plant. An experimental apparatus investigating the use of magneto hydrodynamics was designed, built, and tested. A room temperature liquid inetal was propelled through a magneto hydrodynamic channel of 4 inches by 0.1875 inches at a rate of 10 mL/s. A 2 T induction field was applied within the channel. However, the results of the analysis did not find the magneto hydrodynamic device to be an effective electric generator at the scale tested.
by Jonathan S. Gibbons and Stephen V. Samouhos.
S.B.

Mestrado em Sistemas Energéticos Sustentáveis
Este trabalho tem como objetivo principal constituir um contributo para a sistematização e análise das diferentes opções disponíveis para a recuperação de calor residual na indústria cerâmica, através do desenvolvimento e aplicação de uma metodologia para a incorporação eficiente de tecnologias de recuperação de calor residual. Com base na revisão da literatura, a metodologia proposta fornece bases para a identificação e caracterização das fontes de calor residual presentes na indústria cerâmica, bem como apresenta a revisão e análise de aplicabilidade das tecnologias de recuperação de calor mais comuns e inerentes a este sector. A demonstração e aplicação da metodologia proposta foi desenvolvida no âmbito de um estágio extracurricular numa unidade fabril portuguesa do setor cerâmico - TopCer - integrado no programa Galp 202020@UA. O estudo de caso desenvolvido revelou a importância da recuperação de calor como uma das ferramentas para a melhoria da eficiência energética no sector cerâmico no sentido de obter uma vantagem competitiva. A revisão bibliográfica sobre recuperação de calor demonstrou que esta área do conhecimento tem apresentado um crescimento significativo em termos de número de publicações quase duplicando em número de 2011 para 2012, o que ilustra o crescente interesse da comunidades científica e tecnológica por este tema. A metodologia proposta tendo o setor da indústria cerâmica como ponto de partida, é suficientemente robusta para poder ser facilmente adaptada a outras indústrias que procuram soluções de poupança de energia através da valorização de calor residual.
This work aims to be a contribution to the systematization and analysis of the different options available for waste heat recovery in the ceramic industry, through the development and application of a methodology for incorporating efficient technologies in waste heat recovery in the industrial process. Based on a review of the literature, the proposed methodology provides the bases for the identification and characterization of waste heat sources in the ceramics industry, and presents a review and analysis of the applicability of the available technologies for heat recovery, most common and inherent in this sector. The demonstration and application of the proposed methodology was developed at a Portuguese ceramic manufacturing unit – TopCer – as part of an extracurricular internship under Galp 202020@UA program. The undertaken case study revealed the importance of heat recovery as a tool for improving energy efficiency in the ceramic sector in order to gain competitive advantage. The literature review on the waste heat recovery has demonstrated that this area has suffered a significant increase in terms of number of publications in 2012, illustrating the growing interest of scientific communities and practitioners in the heat recovery problems. The elaborated methodology for waste heat recovery incorporation is a rather robust instrument and, therefore, it can be easily tailored to other industries looking for energy saving solutions though consideration of waste heat recovery options.

This report aims to investigate how fluid-based heat-recovery systems for ventilation can be optimized. A high proportion of existing systems operate at lower efficiency than possible, and thus do not reach their full potential in terms of energy savings. The aim of this report has been to find out why, to identify which parameters affect the efficiency of such systems, and to develop a general methodology for optimization. As a method for execution, a literature study and field experiments were chosen. The results from the literature study showed that dimensioned efficiency, fluid flow in the circuit and degree of contamination of the system were important parameters that greatly affected performance. The field experiments largely confirmed this, but also showed that an implementation of the theoretically optimal fluid flow is not always beneficial to the performance, but higher flow should always be considered. The results also indicated a correlation between the fluid flow and the convective heat-transfer coefficient (U-value) in the heat exchangers. A methodology for optimization is presented in the discussion section. As a suggestion for further research, two possible directions are proposed - the potential of cleaning and the effect of the fluid flow.
Den här rapporten har syftat till att utreda hur vätskekopplade värmeåtervinningssystem för ventilation kan optimeras. En hög andel befintliga system fungerar med lägre verkningsgrad än vad som är möjligt, och uppnår därmed inte sin fulla potential vad gäller energibesparing. Målet med den här rapporten har varit att ta reda på varför, att identifiera vilka parametrar som påverkar dylika systems verkningsgrad, och att ta fram en generell metodik för optimering. Som metod för utförande gjordes först en litteraturstudie och senare fältexperiment som utgick ifrån vad litteraturstudien indikerade. Resultatet från litteraturstudien visade att dimensionerad verkningsgrad, vätskeflödet i kretsen och försmutsningsgrad av systemet var viktiga parametrar som påverkade prestandan i hög grad. Fältexperimenten bekräftade detta till stor del, men visade också att en implementering av det teoretiskt optimala vätskeflödet inte alltid är till gagn för prestandan, utan högre flöde borde alltid övervägas. Resultaten indikerade också en korrelation mellan vätskeflödet och det konvektiva övergångstalet (U-värdet) i värmeväxlarna. En metodik för optimering presenteras i diskussionsavsnittet. Som förslag på vidare forskning föreslås två möjliga inriktningar – rengöringens potential samt vätskeflödets inverkan.

This project was performed to evaluate if waste heat from hotel kitchens is enough to heat outdoor swimming pools in southern Europe or if it can be used as a compliment to another heat source. Another aim was to analyze the simulations and calculations of the pools and the heat recovery system. Then estimate how much annual costs would be reduced when using the exhaust air in the heat recovery system, in comparison with the original heating system. If the project showed positive results the purpose was to select a waste heat recovery system that can integrate with Ozonetech’s ozone generator, keep a high temperature in the pool and reduce emissions of greenhouse gas by using waste heat. Ozonetech would also conduct a pilot study in Stockholm and eventually develop their own product. A simulation model of three different outdoor pool sizes were conducted. The models were constructed and meshed in COMSOL Multiphysics. Average weather conditions for Malaga, Spain, were implemented in the model. The models were simulated by integrating each physical phenomenon in COMSOL, by using the Multiphysics interface. This created convection, emitted radiation and evaporation as thermal heat losses from the pool models. The pools were simulated to determine heating demand, heating period and required inlet temperature to make up for thermal heat losses. A mathematical model of the thermal heat losses and gains were conducted to easily receive a result for the heat demand each month of the year. A mathematical model of the possible heat recovery from hotel kitchens were performed to determine heat recovery for various kitchen sizes. By knowing the heat demand and possible heat recovery from different kitchens, a heat exchanger was selected. The heat exchanger was selected based on literature review, requirements and discussions with manufacturers. A life cycle cost analysis and calculated payback time compared original heating systems with new heat recovery system. A sensitivity analysis using Gauss error propagation concluded the project. The simulations showed that all investigated outdoor pools require additional heat during the night, due to extensive heating periods. Since the kitchen is only active during the day, the pool requires an additional heat source during the night. This conclude that the new heat exchanger only can replace the original heating system during the day. The mathematical model of the heat transfer from the kitchen determined that the maximum heat capacity approximately is 350 kW ± 10.5 kW. The waste heat can only be used to heat small and medium sized pools, since the heat loss is too great for a large pool. Selected air to water heat exchanger that meets the requirements is an air cooler with finned tubes from Alfa Laval. The fins and the coil should be treated to form an e-coat. After calculating the life cycle cost it was determined not profitable to replace a heat pump for a small pool, since the life cycle cost was greater for the new heating system. However, it is profitable to replace an electric heater with the new heat exchanger together with three of the smallest ozone generators during the day, for a small pool. Costs will be reduced by 44 600 – 202 000 kr ± 5%. Payback time will be 2.4 – 3.2 years ± 9%. It is also profitable to replace a water to water heat exchanger heated with either electricity or oil, during the day, with the new heat exchanger combined with either of the ozone generators for a small pool. Costs will be reduced by 310 000 – 698 000 kr ± 5%. Payback time will be 1.8 – 2.5 years ± 9%. It is profitable to replace all original heating systems during the day with the new heat exchanger combined with either of the ozone generators for medium sized pools. Costs will be reduced by 689 000 – 12 600 000 kr ± 5%. Payback time will be 2.2 – 22 months ± 7%.

Composting is an increasingly popular method of municipal and residential waste management. Uniform composting is necessary to obtain a consistent product and to ensure the destruction of pathogens. It requires that a homogeneous temperature be maintained throughout the compost. To accomplish this, a compost vessel with a heat redistribution system (HRS) was designed, constructed and tested. This system was composed of a heat exchanger, plastic tubing and a copper coil filled with water. The system moved heat from the warmer center of the compost bed to the cooler areas at the outside and bottom of the bed without external inputs of energy. Once composting began, the temperature of the water inside the heat exchanger increased and buoyancy effects caused the water to flow through the copper tubing, distributing the core heat throughout the compost. Heat was also redistributed by conduction along the copper tubing. The HRS can be used in applications requiring assurance of uniform composting conditions and a high-quality product. Previously obtained test data suggested that the HRS system accomplished its goal, but high amounts of heat loss occurred through the four-inch exhaust vent. An air heat exchanger (AES) was added to reduce heat loss from the top aeration vent. A total of twelve experiments were run: four with the HRS, four with the AES and four controls. The vessels were fitted with thermocouples at 33, 54 and 84 cm from the bottom. The HRS vessels demonstrated higher temperatures during the first 10 days of the experiment (p<0.001).
Le compostage est une méthode de plus en plus populaire pour la gestion municipale et résidentielle des déchets. Le compostage uniforme est nécessaire pour obtenir un produit homogène de haute qualité et assurer la destruction des agents pathogènes. Il est donc essentiel de maintenir une température uniforme dans tout le compost. Pour mieux y parvenir, un récipient de compost équipé d'un système de redistribution de la chaleur (HRS) a été conçu, construit et vérifié. Ce système est composé d'un échangeur de chaleur, un tube en plastique, et une bobine de cuivre rempli d'eau. La digestion bactérienne des matières organiques cause une augmentation de la température de l'eau à l'intérieur du HRS et provoque un effet de flottabilité qui enchaîne un déplacement d'eau à l'intérieur du tube de cuivre, distribuant la chaleur du centre le plus chaud du compost vers les zones plus froides et ce, sans apport d'énergie externe. La chaleur est également redistribuée par conduction le long du tube de cuivre. Les résultats obtenus suggèrent que le HRS atteint son objectif, mais des pertes de chaleur ont été découvertes à la sortie d'air de 4 ̎. Un échangeur de chaleur à air (AES) a été ajouté pour réduire la perte de chaleur. Un total de douze expériences ont été effectuées : quatre avec le HRS, quatre avec l'AES et quatre contrôles. Les vaisseaux été équipés de thermocouples placés à 33, 54 et 84 cm du sol. Les vaisseaux équipés du HRS ont démontré des températures plus élevées au cours des 10 premiers jours de l'expérience (p < 0,001).

Wastewater released from showers, sinks, and washers contains a considerable amount of wasteheat that can be recovered by using a heat exchanger. Conventional metal heat exchangers for wastewater heat recovery have common problems of corrosion, fouling and clogging, which makes it necessary to develop a new type of heat exchanger for such low-grade thermalenergy recovery applications. This study deals with a novel patented polymer heat exchanger (WO2020049233A1) made of soft polyurethane tubes that are capable of oscillation once subjected to external forces. Laboratory tests coupled with theoretical analyses show a stable global heat transfer coefficient of 100-110 W/m2·K, in between the ideal parallel flow and crossflow heat exchangers. The theoretical calculations indicate that the performance of polymer heat exchanger can achieve 62-92% of the performance of titanium, aluminium, and copperheat exchangers with the same dimensions and working conditions. It further reveals that the performance of the soft heat exchanger can be enhanced by 30% when it is under oscillation. In addition, the results of thermal resistance study show that the total thermal resistance issignificantly higher in the model of parallel flow than in crossflow. Moreover, in the parallel flow, the external convective thermal resistance appears to be the dominant one instead of heat conduction through the wall material.
Avloppsvatten som rinner ut från duschar, diskhoar och tvättmaskiner innehåller en betydande mängd spillvärme som kan återvinnas med hjälp av en värmeväxlare. Konventionella metallvärmeväxlare för värmeåtervinning av avloppsvatten har vanliga problem med korrosion, förorening och förstoppning, vilket gör det nödvändigt att utveckla en ny typ av värmeväxlare för applikationer med låg värmeåtervinning. Denna studie behandlar en ny patenterad polymervärmeväxlare (WO2020049233A1) tillverkad av mjuka polyuretanrör som tål vibrationer som ett resultat av yttre krafter. Laboratorietester tillsammans med teoretiska analyser visar en stabil global värmeöverföringskoefficient på 100-110 W/m2·K, mellan det ideala parallella flödet och tvärflödesvärmeväxlarna. De teoretiska beräkningarna indikerar att en prestanda hos polymervärmeväxlare kan uppnå 62-92% av prestanda för titan-, aluminiumoch kopparvärmeväxlare med samma dimensioner och arbetsförhållanden. Det visar sig att den mjuka värmeväxlarens prestanda kan förbättras med 30% när den vibrerar. Dessutom visar resultaten från studien med termisk resistens att det totala värmemotståndet är betydligt högre i modellen för parallellt flöde jämfört med tvärflöde. I det parallella flödet verkar dessutom det externa konvektiva värmemotståndet vara det dominerande i stället för värmeledning genom väggmaterialet.

This research focuses on the waste heat recovery (WHR) from low and medium grade heat sources, and its conversion into mechanical rotations and electrical energy using organic Rankine cycle (ORC), in automotive and industrial applications. The research outcomes include: (1) development of subcomponent models including a novel fuzzy based evaporator model of the supercritical ORC-WHR system using thermodynamic and numerical methods in MATLAB/Simulink, (2) overall ORC-WHR integration and complete system simulation to improve thermal and heat recovery efficiency in steady state and dynamic conditions, (3) investigation of the system performance with respect to stationary and mobile heat sources, (4) transient response analysis and dynamic simulation of the ORC-WHR system with respect to low and medium grade heat sources, (5) development of appropriate control strategies for the high thermal inertia and slow response ORC-WHR system, (6) development of a novel control algorithm to improve control performance of conventional controllers in WHR systems, (7) control system simulation to improve the operational performance, continuity, and safety of the system under steady and transient heat input conditions.

Numerous of energy saving measures have been carried out in the Swedishhousing stock since the energy crisis in the 70’s. Additionally, there have been manylow-energy housing projects. However, so far few of these have been followed up aftersome years in operation concerning the energy use. That the energy use stays on a lowlevel is important from a sustainable perspective. The objectives of this study are find a system capable of reduce energy demandand minimize the environmental impact, make the minimum investment with themaximum results and maintain the actual infrastructure of the building. This report looks into the potential for saving energy and money with greywastewater. This potential depends on both the quantity available and whether thequality fits the requirement of the heating load. To recover heat from waste water inresidential buildings is hard to achieve in quality because of its low temperature range.Nevertheless, efforts to recycle this waste energy could result in significant energysavings. To implement this system the method used is to gather all the information aboutthis system, compare all the options available and calculate how much energy can besaved and how much time is the payback. The building studied is on Maskinisten Brynäs in Gävle with 23 apartments onfive different floors and a total living area of 400 m2 in each floor. In the case building used in this report the 60% of the total water used is hotwater. Installing a heat recovery system can be saved up to 23% of the energy used forheating water. This energy can be used for the preheating of the hot water. In this report is given two different solutions to save energy with this systems,the first one is to use a heat exchanger only in the drain of the showers saving up to7.045 MWh or using a centralized heat exchanger saving up to 23.16 MWh. After analysing the results the best option is to use the centralized heatexchanger system, it can be saved more energy and the total investment is lower thanusing a heat exchanger in each shower.

Increasing fuel prices, higher demands on "greener" transports and tougher international emission regulations puts requirements on companies in the automotive industry in improving their vehicle fuel efficiency. On a typical heavy duty Scania truck around 30% of the total fuel energy is wasted through the exhaust system in terms of heat dissipated to the environment. Hence, several investigations and experiments are conducted trying to find ways to utilize this wasted heat in what is called a waste heat recovery (WHR) system. At Scania several techniques within the field of WHR are explored to find the profits that could be made. This report will cover a WHR-system based on thermoelectricity, where several new thermoelectric (TE) materials will be investigated to explore their performance. A reference material which is built into modules will be mounted in the exhaust gas stream on a truck to allow for measurements in a dyno cell. To analyze new materials a Simulink model of the WHR-system is established and validated using the dyno cell measurements. By adjusting the model to other thermoelectric material properties and data, the performance of new TE materials can be investigated and compared with today’s reference material. From the results of the simulations it was found that most of the investigated TE materials do not show any increased performance compared to the reference material in operating points of daily truck driving. This is due to dominance of relatively low exhaust gas temperatures in average, while most advantages in new high performing TE-materials are seen in higher temperature regions. Still, there are candidates that will be of high interest in the future if nanotechnology manufacturing process is enhanced. By using nanostructures, a quantum well based BiTe material would be capable of recovering 5-6 times more net heat power compared to the reference BiTe material. Another material group that could be of interest are TAGS which in terms of daily driving will increase the power output with pending values between 40-80 %. It is clear that for a diesel truck application, materials with high ZT-values in the lower temperature region (100-350°C) must be developed, and with focus put on exhibiting low thermal conductivity for a wide temperature span.

Exploitation of waste heat could achieve economic and environmental benefits, while at the same time increase energy efficiency in process sites. Diverse commercialised technologies exist to recover useful energy from waste heat. In addition, there are multiple on-site and offsite end-uses of recovered energy. The challenge is to find the optimal mix of technologies and end-uses of recovered energy taking into account the quantity and quality of waste heat sources, interactions with interconnected systems and constraints on capital investment. Explicit models for waste heat recovery technologies that are easily embedded within appropriate process synthesis frameworks are proposed in this work. A novel screening tool is also proposed to guide selection of technology options. The screening tool considers the deviation of the actual performance from the ideal performance of technologies, where the actual performance takes into account irreversibilities due to finite temperature heat transfer. Results from applying the screening tool show that better temperature matching between heat sources and technologies reduces the energy quality degradation during the conversion process. A ranking criterion is also proposed to evaluate end-uses of recovered energy. Applying the ranking criterion shows the use to which energy recovered from waste heat is put determines the economics and potential to reduce CO2 emissions when waste heat recovery is integrated in process sites. This thesis also proposes a novel methodological framework based on graphical and optimization techniques to integrate waste heat recovery into existing process sites. The graphical techniques are shown to provide useful insights into the features of a good solution and assess the potential in industrial waste heat prior to detailed design. The optimization model allows systematic selection and combination of waste heat source streams, selection of technology options, technology working fluids, and exploitation of interactions with interconnected systems. The optimization problem is formulated as a Mixed Integer Linear Program, solved using the branch-and-bound algorithm. The objective is to maximize the economic potential considering capital investment, maintenance costs and operating costs of the selected waste heat recovery technologies. The methodology is applied to industrial case studies. Results indicate that combining waste heat recovery options yield additional increases in efficiency, reductions in CO2 emissions and costs. The case study also demonstrates that significant benefits from waste heat utilization can be achieved when interactions with interconnected systems are considered simultaneously. The thesis shows that the methodology has potential to identify, screen, select and combine waste heat recovery options for process sites. Results suggest that recovery of waste heat can improve the energy security of process sites and global energy security through the conservation of fuel and reduction in CO2 emissions and costs. The methodological framework can inform integration of waste heat recovery in the process industries and formulation of public policies on industrial waste heat utilization.

Global issues of greenhouse gas emissions, security of supply and decreasing fossil fuel resources calls for increased use of renewable energy and energy efficiency measures for existing technology. In the domestic sector, main energy consumption occurs due to space heating and hot water which is mostly provided by gas or oil boiler via hydronic central heating system in the UK. In order to diversify fossil fuel usage, reduce emissions and security supply, implementation of efficient technology (e.g. heat pump) along with renewable technology is vital. The heat pump is an efficient technology based on the vapour compression cycle, mostly driven by electric motors where it provides heat at high temperature by consuming energy from low temperature sources such as air, ground or water. Electric heat pumps (EHPs) have good potential to displace existing gas boiler system to meet domestic heating demand. However, conventional hydronic systems operate with high flow temperatures where EHP's performance drops as temperature lift increases. In addition, if vast deployment of EHPs occurs then it could create issues for the electricity distribution network. Also, until the major portion of electricity is generated by renewable sources, EHP's operating at high temperatures will not give significant benefit in terms of C02 savings compared gas boiler heating. The aim of the presented work is to develop an engine driven heat pump system. This will meet the designed domestic heat demand at high flow temperatures suitable for conventional wet radiator systems. It will also use the waste heat recovered from the engine. The developed engine driven heat pump (ENHP) should also help in diversification of fossil fuel usage in domestic sector, emission reduction and thermal comfort improvement. Liquid biofuels or gas engine concepts will be possible at a later date. The diesel engine was used with modifications to take advantage of coolant and exhaust heat recovery. The engine was coupled with a reciprocating open compressor as a drive source. A water-to-water heat pump was developed for testing purposes. Diesel engine heat pump (DEHP) performance was tested at three different engine speeds and four different water flow temperatures for given evaporation temperature conditions. DEHP test results showed a strong influence of engine speed and condensing temperature on overall total heat output and heat recovery. Test results showed that heat recovery from the engine contributes about 31 % in total heat output. DEHP test results at various conditions gave primary energy ratio in a range of 0.93 to 2 showing better performance compared to conventional gas boiler. Speed variation of the DEHP system showed that it has the potential to match domestic heating demand ( at 70-73 0 C) between -4.5°c to 9°C air/water temperature by varying engine speed, hence reduction in on/off cycling. In terms of flow temperature requirements for retrofit application, the DEHP test results showed that it can provide flow temperatures in the range of 70°C to 73°C which is in a similar range of gas boiler flow temperature range in a typical household. In addition, DEHP system can provide water flow rate in a range of 5 to 20 lImin which is suitable to meet typical space heating and/or DHW flow rate demand. Another common issue was noise associated with the DEHP system and this was also reduced by acoustic insulation around the engine-compressor assembly showing potential for domestic installation where noise and vibration could be achieved in a similar range to conventional heating system. Overall, DEHP test results showed potential as a transition retrofit technology with possible use of renewable energy sources (e.g. biofuel) with integration of thermal/electrical energy storage to meet heating and electricity demand locally.

Detta projekt är inriktat på spillvärmepotentialer inom järn och stålindustrin. Högtemperaturvärme-pumpar för medelvarma temperaturkällor har modellerats. SSABs stålverk i Oxelusund har använts som exempel. Järn- och stålindustrin i Sverige är storkonsument av energi, tillsammans med pappers och massaindustrin. Det finns också en stor potential för spillvärmeåtervinning i stålindustrin. Det görs redan i Luleå t ex [1]. Järn och stålindustrins produktionsmetoder och spillvärmeåtervinning, speciellt i USA och Sverige har studerats genom en litteraturstudie. Dagens metoder och potentialer för spillvärmeåtervinning inom järn och stålindustrin i Sverige studerades speciellt. SSABs anläggning i Oxelösund, har i decennier planerat inte bara att värma Oxelösunds stad som idag, utan också expandera till näraliggande Nyköping bara 12 km bort [2]. Typiskt är den maximala framledningstemperaturen till Nyköpings fjärrvärmenät 110 °C den kallaste dagen. En spillvärme-värmepump når normalt inte upp till så höga temperaturer. Dock räcker 80 °C maximal framledningstemperatur från värmepumpen för att nyttiggöra spillvärmekällan kontinuerligt. Även en lägre temperatur som 75 °C skulle sannolikt räcka. Bara några få fjärrvärme-värmeväxlare i några hus skulle behöva bytas för att denna lägre temperatur skulle räcka till. De överskjutande graderna mellan 80 °C (75 °C) och 110 °C kan tas med värme från t ex existerande biobränslepannor lokalt i Nyköping. Att använda värmepumpar i detta sammanhang är inte självskrivet. Generellt är värmeflödena från ett stålverk så högtempererade att ingen värmpump behövs. Om man försöker komma åt dessa högtemperaturflöden i en gammal anläggning kan det bli väldigt dyrt och störa produktionen. Därför koncentrerades studien på medeltemperaturkällor (30 °C till 40 °C) och användande av högtemperaturvärmepumpar. Sådan värme dumpas nu med kyltorn. På så sätt kan 50 % av Nyköpings värmebehov tillgodoses med lätt tillgänglig spillvärme. Om man antar en värmefaktor på cirka 5, och lägger till värmepumpens förbrukade elektricitet blir det 62 % av Nyköpings fjärrvärmebehov. Oxelösundanläggningen är bara ett exempel och studien fokuseras på högtemperaturs-industriella värmepumpar HITIHP för sådana här och liknande användningar. Lämpliga komponenter och köldmedia har undersökts och generella konstruktionsprinciper av HITIHP föreslås. En litteraturstudie för att finna de bästa HITIHP-köldmedierna har gjorts. En tvåstegs högtemperaturvärmepump, som använder den tillgängliga värmekällans kapacitet och temperaturer tillsammans med fjärrvärmenätets krav, har modellerats och simulerats. Simuleringen har huvudsakligen gjorts med programmet EES. R245fa har t ex visat sig vara lämpligt som köldmedium i det andra steget av en högtemperaturvärmepump. Med R245fa kan till och med högre temperaturer än 90 °C uppnås till fjärrvärmesystemet. Tidigare skulle R134a ha använts i en sådan här applikation, men R245fa har t e lägre GWP (Global Warming Potential omkring 1000 istället för omkring 1300)[3]. Många olika köldmedia har simulerats i lågtemperatursteget av värmepumpen som initialt antogs vara en skruvkompressor-kaskad-värmepump. En större värmpump med två turbokompressorsteg och flashtank har också simulerats. Den gav också tillfredställande resultat. I det senare fallet studerades både R1234ZE(z) och R245fa som gav goda resultat men R1234ZE(z) ger mycket lägre GWP. Alla värmefaktorer (COP, energibehov, kondensortryck och tryckförhållanden (hög-/lågtryck) jämfördes. R245fa-R245fa och R600a-R245fa studerades noga i tvåstegs-kaskad-systemet med skruvkompressor. Dessa kombinationer gav bäst resultat. R717-R245fa var också bra men hade andra begränsningar. I tvåstegssystem med turbokompressorer och flashtank visade sig visade sig R1234ZE(z) ge gen bästa värmefaktorn. Man hade naturligtvis inte heller något temperaturfall i någon värmeväxlare mellan de två stegen. Om SSABs spillvärme av någon anledning inte skulle vara tillgängligt kan en sådan värmpump istället använda havsvatten som värmekälla. Begränsningen av koldioxidutsläppen är mycket svåra att beräkna. Detta kommer att bero mer på politisk övertygelse än på lättbevisade fakta. En mycket grov beräkning av kostnaden har också gjorts. Uppskattningsvis kommer projektet att kosta mellan 420 och 450 MSEK. Kostnadsuppskattningen inkluderar värmepumpen och en 12 km lång förbindelse till Nyköping. Kostnaden för värme levererad till Nyköping, kommer att variera mellan 0,2 kr/kWh och 0,65 kr/kWh när elpriset varieras mellan 0,5 och 2 SEK/kWh. Den högre värmkostnaden 0,65 kr/kWh beror också på att östersjövatten – inte spillvärme används som värmekälla. Värme från ett kyltorn kan återvinnas med en högtemperaturvärmepump. Den kan levereras från Oxelösund till Nyköping. De ekonomiska detaljerna har bar studerats översiktligt. Faktorer som om renovering den gamla pannan i Nyköping eller SSABs kyltorn kunde senareläggas, skulle kunna förbättra intresset för projektet. Ett spillvärmerör mellan Oxelösund och Nyköping har studerats sedan mitten av 70-talet av t ex Lars-Åke Cronholm [4]. Kan det vara dags nu?
This project was focused on waste heat potentials in the iron and steel industry. High temperature industrial heat pumps (HTIHP) for medium temperature, waste heat recovery were modelled. The SSAB iron and steel plant in Oxelösund was used as an example. The iron and steel industry in Sweden is a large energy consumer, together with the pulp and paper industry. There is also a large potential for waste heat recovery in the steel industry. This is already done in for instance Luleå [1]. Iron and steel production methods and waste heat recovery in the world, especially in the US and Sweden, have been reviewed in a literature study. Current methods and potentials of waste heat recovery in the iron and steel industry of Sweden were especially reviewed. The SSAB iron and steel plant in Oxelösund has been planning for decades, not only to heat the city of Oxelösund as today, but also to expand to the nearby city of Nyköping 12 km away [2]. Typically the maximum temperature entering the district heating network of Nyköping would be 110 °C on the coldest day. The heat pump output from a waste heat recovery plant generally does not have to reach such a high temperature. However, 80 °C maximum forward temperature would surely be enough to use recovered heat all the time. Even a lower temperature like 75 °C would probably be sufficient – as only a few heat exchangers in individual houses then would have to be changed, to accept that lower temperature. The extra degrees between 80 °C (75 °C) and 110 °C can be taken with heat from e.g. existing biofuel furnaces locally in Nyköping. Using heat pumps in this context is not self-evident. Generally the heat flows from a steel plant are available at such high temperatures that no heat pump ideally is needed. However collecting the heat at those high temperatures, in an old plant, can get very expensive and interfere with the processes. Therefore the study is focusing on medium temperature (30 – 40 °C) waste heat potentials implementing High Temperature Industrial Heat Pumps (HTIHP). The heat is now being rejected by a cooling tower. That way, easily available waste heat, can cover 50% of the total need from Nyköping. Assuming a COP of around 5 and adding the electricity needed to run the heat pump, the total will result in totally 62% of the energy need for Nyköping. The Oxelösund Plant is just an example and the study is really focusing on HITIHP for this and similar purposes. Appropriate components and refrigerants have been evaluated and the general layouts of proper HITIHP types are suggested. A literature study on the best choice of refrigerant in the high temperature heat pump has been done. A two stage high temperature heat pump has been modeled and simulated using the available heat sink capacity and temperature, together with the demanded temperatures in the district heating network. The simulation has mainly been performed using the EES software. R245fa is e.g. a good candidate as refrigerant in a second stage (high temperature stage) of a two stage cascade heat pump. With R245fa even higher temperatures than 90°C to the district heating can be achieved. Earlier, R134a would be used in this application but R245fa has e.g. a lower GWP (around 1000 instead of around 1300) [3]. Many different refrigerants have been simulated in the first of two stages of a smaller screw compressor driven cascade heat pump. Also a two stage turbo compressor throttling heat pump, using a flash tank, has been simulated, showing a good performance. In the latter case both, refrigerants R1234ze(z) and R245fa have good characteristics but R1234ze(z) has a much lower GWP. All COPs, compressor energy consumptions, condenser pressures, pressure ratios were compared. R245fa-R245fa and R600-R245fa were studied in the two stage cascade systems. They came out with the best results. R717-R245fa also showed a very good performance, but had other limitations. In two stage flash tank systems, R1234ze(z) had the best performance (COP) and no temperature loss between the two stages (like in the cascade systems). If SSAB Oxelösund’s blast furnace and cooling tower water would not be available, the turbo heat pump can produce the demanded heat, using sea water as heat source instead. The CO2 emission reduction is very hard to calculate. That will be more of a political conviction problem. A very rough cost estimation of the projects investment cost is also done. It will cost between 420 and 450 MSEK. This cost estimation includes a heat pump and 12 km pipe to Nyköping. The cost of heat delivered in Nyköping will vary between 0,2 and 0,65 SEK/kWh when the cost of electricity is varied between 0,5 and 2 SEK/kWh (include taxes). In that price the capital costs for the heat pump and pipe is included. The high cost level 0, 65 SEK/kWh assumes that sea water is used as heat source. A cooling towers waste heat can be recovered, using a high temperature heat pump. This heat can thus be delivered from Oxelösund to Nyköping. The economic viability of this idea is only superficially covered. Factors like if the old furnace in Nyköping needs upgrading, which could be postponed, could possibly tip the project into go. Maitenance cost, of the existing cooling tower, is another such factor, initiating the project. A waste heat pipe between Oxelösund and Nyköping has been studied at least since the middle of the 1970:s by e.g. Lars Åke Cronholm [4]. Could it be the right time now?

Thesis (M.S. in Mechanical Engineering and M.S. in Astronautical Engineering) Naval Postgraduate School, December 1995.
"December 1995." Thesis advisor(s): Ashok Gopinath, Oscar Biblarz. Bibliography: p. 61. Also available online.

Heating, ventilation and air-conditioning (HVAC) systems are widely distributed over the world due to their capacity to adjust some local climate parameters, like temperature, relative humidity, cleanliness and distribution of the air until the desired levels verified in a hypothetical ideal climate. A review of buildings’ energy usage in developed countries shows that in the present this energy service is responsible for a portion of about 20% of the final energy usage on them, increasing up to 50% in hot-humid countries. In order to decrease this value, more and more different heat recovery systems have been developed and implemented over the last decades. Nowadays it is mandatory to install one of these units when the design conditions are above the limit values to avoid such components, what is possible to verify mostly in non-residential buildings. Each one of those units has its own performance and working characteristics that turns it more indicated to make part of a certain ventilation system in particular. Air-to-air energy recovery ventilation is based on the heat recovery transfer (latent and/or sensible) from the flow at high temperature to the flow at lower temperature, pre-warming the outdoor supply air (in the case of the winter). Therefore, it is important to understand in which concept those units have to be used and more important than that, how they work, helping to visualize their final effect on the HVAC system. The major aims of this study were to investigate the actual performance of the heat recovery units for LB20 and LB21 in building 99 at the University of Gävle and make some suggestions that could enhance their actual efficiency. Furthermore, the energy transfer rates associated to the heat recovery units were calculated in order to understand the impact of such components in the overall HVAC system as also the possible financial opportunity by making small improvements in the same units. To assess the system, values of temperature and flow (among others) were collected in the air stream and in the ethylene-glycol solution that works as heat transfer medium between air streams and is  enclosed in pipes that make part of the actual run-around heat recovery units. After some calculations, it was obtained that for the coldest day of measurements, the sensible effectiveness was 42% in LB20 and 47% in LB21, changing to 44% and 43% in the warmer day, respectively. The actual heat transfer representing the savings in the supply air stream is higher on the coldest day, with values of 46 kW in LB20 and 84 kW in LB21, justifying the existence of the heat recovery units even if those ones imply the use of hydraulic pumps to ensure the loop. The low values of efficiency have shown that both heat recovery units are working below the desired performance similarly to the pumps that make part of the same units.  This fact, together with the degradation of the units that is possible to observe in the local, indicates that a complete cleaning (followed by a change of the heat transfer medium) of the heat recovery units and a new adjustment of pumps and valves for the further changes, are necessary. By doing this, it is expected to see the year average sensible effectiveness increase to close to 45% in both units which will lead to a potential economic saving of around 41 000 SEK per year.

Internal combustion engines produce much excess heat that is vented to the atmosphere through the exhaust fluid. Use of solid-state thermoelectric (TE) energy conversion technology is a promising technique to recapture some of the energy lost. The TE effect, discovered in 1821 by Thomas Seebeck, is essentially the solid-state conversion of a temperature gradient into an electric potential. The scope of this work was the design, testing and evaluation of a novel and robust TE generator that is amendable to use in a vast array of convective thermal processes. Seebeck testing of TE elements was combined with thermal/hydraulic and thermoelectric modeling to develop the design of a working prototype system. A proof-of-concept small-scale prototype (SSP) TE generator was built to evaluate concepts intended for the construction of a fully-functional field demonstration prototype (FDP). The SSP was used to evaluate electrical contact integrity, thermal characteristics, various TE materials and the feasibility of using compression-based TE contacts. The SSP featured 9 P/N TE pairs and has thus far produced a maximum open-circuit voltage of 380mV and a maximum electrical power of 1.47W. Knowledge gained from the SSP construction and testing was utilized in the design and fabrication of the FDP. A liquid-cooled Honda ES6500 6.0kW genset was procured to provide a test-bed for the FDP. The primary goal was to power the electric radiator fan with the heat energy contained in its exhaust, thus decreasing the genset's fuel consumption rate. The FDP contained 256 P/N pairs and thus far has produced an open-circuit voltage of 5.5VDC and a maximum power of 8.49W. Replacing the stock muffler reduced fuel consumption by 11.6% whereas removing the fan load reduced it an additional 1.64%. Through the recovery and conversion of wasted thermal energy, the genset's fuel consumption rate was successfully lowered, therefore validating the benefits of secondary TE power systems. The radiator fan of the Honda ES6500 consumes approximately 1% of the overall power output of the genset. Radiator fans in larger gensets can draw as much as 12-16% of their peak output. By recuperating waste heat, substantially higher fuel savings could be achieved.

This thesis describes research carried out by the author between 1986 and 1990 at the Department of Chemical Engineering, University of Edinburgh, under the supervision of Dr Colin Pritchard. The aim of the research was to devise and evaluate a novel compression heat pump cycle as a potential technology for the utilisation of work and heat from environmental sources in industrial applications. The principal requirement of such a heat pump is that it can accept time-varying inputs of work and heat whilst supplying a controlled heat load at constant delivery temperature to an external load. This requires a cycle with the ability to 'self-regulate' its capacity to match external variations in either energy input or energy takeoff. The use of a nonazeotropic mixture as working fluid offers the potential to vary the composition of circulating fluid in a heat pump cycle, thereby varying the capacity, and this was chosen as the basis for research. The prediction of thermodynamic properties of halogenated hydrocarbon refrigerants is reviewed with special emphasis on: acquisition of sufficient data for preliminary plant design from minimum information, and on the prediction of binary vapour-liquidequilibrium data (VLE) in the absence of experimental measurement. The Cubic Chain-Of-Rotators (CCOR) equation of state is assessed as a route to these properties; it is shown that this equation offers improved liquid-phase property prediction compared to other cubic equations of state. The CCOR equation is also shown (by comparison with experimental measurements from the literature) to predict binary VLE to the same degree of accuracy as the Redlick-Kwong-Soave, Lee-Kesler and Carnahan-Starling-DeSantis equations in the absence of any parameter optimisation. Procedures are described for the optimisation of the CCOR equations's performance as a predictor of both pure-fluid and mixture properties by the fitting of empirical parameters to experimental data. It is demonstrated that this optimisation procedure allows quantitative description of the liquid phase of pure fluids and of mixtures.

Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente, perfil Engenharia Sanitária
This thesis was carried as a collaboration of Delft University of Technology (TU Delft) and the companies Waternet and KWR. The main project aims to study the possibility of thermal energy recovery from wastewater, reducing the carbon dioxide (CO2) emissions linked to the energy sector. The present work is based on a previous computational model that was developed to simulate heat recovery from wastewater for constant flow rate and temperature of water. The first goal is to simulate a wastewater discharge. In order to achieve this, a Gaussian function was added to the boundary conditions for water flow rate and water temperature. As a second goal, this work aims to assess the significance of the terms present in the water heat balance and air heat balance equations. Binary coefficients were added in each term of both equations and then all the combinations were computed. The unsteady situation successfully simulated a main discharge and numerical predictions for water temperature and flow rate are presented. The deviations associated with the modified cases for the two equations suggest that the heat flux pipe to water (!!") and heat flux pipe to air (!!") terms are crucial for water and air heat balance predictions,respectively. In order to smooth extra oscillations, the time step (dt) was reduced and a smaller relative size of oscillations was obtained. This work concludes with a section of future developments in order to improve the results obtained. Despite of the fact that the current state of these routines does not allow us to accurately assess heat exchanges in pipes, promising results were obtained, proving that numerical modelling of heat recovery will contribute greatly to the development of the main project.

The purpose of this study was to assess the performance of a novel heat recovery device for integration with a passive ventilation system. Current heat recovery devices are not suitable for integration with passive ventilation systems due to the high pressure drop experienced by airstreams across the devices. This would result in low ventilation supply rates required for good indoor air quality. The device could be also reconfigured to dehumidify an incoming airstream, lowering the relative humidity of the air. These modifications would improve the air quality and reduce energy demand on mechanical ventilation systems. The novel heat recovery device was designed and constructed using 3D printing techniques and tested experimentally using different inlet conditions for two counter-current airstreams. Numerical analysis using Computational Fluid Dynamics (CFD) calculated solutions for air velocity, gauge air pressure, air temperature and relative humidity before and after the heat recovery device using the same geometry as the printed prototype. The experimental testing of prototypes of the heat recovery device validated these characteristics. The results from the experiments and CFD analysis showed that the novel design of the heat recovery device achieved the three primary objectives of the project. The pressure drop measured across the heat recovery device was between 10.02-10.31Pa, significantly lower 150Pa experienced in standard devices. The resultant air velocity suggested that an air supply rate of 140.86 litres per second was possible, high enough to provide ventilation to a room with 17 occupants. The device was capable of increasing the temperature of the incoming airstream by up to 0.68°C when the temperature of the outgoing airstream was 40°C. Finally, the relative humidity of an incoming airstream with 100% relative humidity was reduced by up to 67.01%, at regeneration temperatures between 25-40°C, significantly lower than current temperatures of 120°C.

Low-grade heat, either in the form of waste heat or natural heat, represents an extremely promising source of renewable energy. A cost-effective method for recovering the low-grade heat will have a transformative impact on the overall energy scenario. Efficiency of heat engines deteriorates with decrease in hot-side temperature, making low-grade heat recovery complex and economically unviable using the current state-of-the-art technologies, such as Organic Rankine cycle, Kalina cycle and Stirling engine. In this thesis, a fundamental breakthrough is achieved in low-grade thermal energy harvesting using thermomagnetic and thermoelectric effects. This thesis systematically investigates two different mechanisms: thermomagnetic effect and thermoelectric effect to generate electricity from the low-grade heat sources available near ambient temperature to 200�[BULLET]C. Using thermomagnetic effect, we demonstrate a novel ultra-low thermal gradient energy recovery mechanism, termed as PoWER (Power from Waste Energy Recovery), with ambient acting as the heat sink. PoWER devices do not require an external heat sink, bulky fins or thermal fluid circulation and generate electricity on the order of 100s μW/cm3 from heat sources at temperatures as low as 24�[BULLET]C (i.e. just 2�[BULLET]C above the ambient) to 50�[BULLET]C. For the high temperature range of 50-200�[BULLET]C, we developed the unique low fill fraction thermoelectric generators that exhibit a much better performance than the commercial modules when operated under realistic conditions such as constant heat flux boundary condition and high thermally resistive environment. These advancements in thermal energy harvesting and waste heat recovery technology will have a transformative impact on renewable energy generation and in reducing global warming.
PHD

UK energy prices have doubled over the last decade, which has driven the UK Iron and Steel Industry to invest in energy efficient technologies. However, even with these relatively high prices the industry still finds it difficult to build a business case to justify waste heat recovery projects. The Steel Industry has large quantities of waste heat and there are technologies readily available for its capture, but often the issue has been finding a cost effective ‘end use’. Individual schemes incorporating both capturing and an ‘end use’ for the waste heat often incur high capital costs with resulting long payback times. This thesis defines the development and modelling of a strategy and methodology for the utilisation of waste heat recovery in a UK based Steelworks. The methodology involves the utilisation of the existing steam distribution circuit to link the possible waste heat schemes together with a single ‘end user’ thus limiting the capital requirement for each subsequent project. The thesis defines the development of a numerical model that is initially verified through extensive comparison to actual plant data from a series of pre-defined operational scenarios. The model is used to predict the pressure and temperature effects on the steam distribution system as the waste heat recovery boilers from various areas of the case study steelworks are connected up to it. The developed strategy stimulated significant capital investment for the CSSW and has generated over 100,000 MWh and is therefore saving over £7m and 50,000 tonnes of indirect CO2 emissions per annum. The thesis discusses and recommends further research and modelling for low, medium and high grade waste heat as well as the potential of a partial de-centralisation of the steam system. The output of the thesis is referenced by the DECC as an example of waste heat recovery in UK industry.

Ice rinks are the largest energy consumers in terms of public buildings due to their simultaneous need of cooling, heating, ventilation, and lighting for different parts of the building which means that these facilities also have a lot of potential for energy saving. Due to the size of the cooling unit in an ice rink the refrigerant charge can become quite high, which potentially has a big impact on the environment. CO2 refrigeration units could cover all these challenges that are linked to ice rink operation. CO2 as a refrigerant has a very low impact on the environment and at the same time it could provide enough energy to cover the heating demands of an ice rink. CO2-based systems should operate in trans-critical mode which affects the performance of the refrigeration system, but by using the released heat that otherwise would be rejected to the ambience the total energy consumption becomes lower. The process of heat recovery is therefore vital for an efficient system. The refrigeration unit can produce enough energy to cover all the heating demands of an ice rink, but only when the heat recovery is controlled properly. The energy recovery method is very important, but it should also be tailored in order to cover all demands. This is because all the subsystems, i.e. demands, have different temperature and load requirements. The energy could be recovered in one or two stages from the refrigeration system. However, hardware is not enough in order to achieve proper operation, the system should also operate in the best conditions (discharge pressure and subcooling) in order to be efficient. The more proper operation, the less energy consumption.  This energy recovery method could also be used as subcooling in climates where the ambient temperature is very high, making CO2 a very efficient solution. Regular refrigerants are still often used in warm countries despite their high environmental impact. A refrigeration system using natural refrigerants and more specific CO2 does not have constraints, however. The only limitation is the wrong operation.
Isrinkar är de största energikonsumenterna när det gäller offentliga byggnader på grund av deras ständiga behov av nedkylning, uppvärmning, ventilation och belysning. Detta innebär också att anläggningarna har en stor potential att effektivisera sin energibesparing. Isrinkar konsumerar stora mängder kylmedel på grund av deras storlekar, vilket potentiellt har en stor negativ inverkan på miljön. CO2 kylenheter skulle kunna klara av alla dessa utmaningar som är kopplade till isrinkens drift. Att använda CO2 som en kylarvätska har en ytterst liten inverkan på miljön och kan dessutom bidra med tillräckligt mycket energi för att täcka uppvärmningsbehovet för en isrink. CO2 baserade system bör köras i ett transkritiskt läge vilket påverkar kylsystemets prestanda, men genom att återanvända den utsläppta värmen som annars skulle gå förlorad till omgivningen så blir den totala energiförbrukningen lägre. Värmeåtervinningsprocessen  är därför avgörande för ett effektivt energisystem. Kylaggregatet kan producera tillräckligt med energi för att täcka alla värmebehov för en isrink, men endast när värmeåtervinningen behärskas ordentligt. Energiåtervinningsmetoden är också väldigt viktig, men den bör skräddarsys för att täcka alla krav. Detta beror på att alla delsystem, dvs krav, har olika temperatur- och belastningskrav. Energin kan återvinnas i ett eller två stadier från kylsystemet. Tyvärr så räcker dock inte hårdvaran till för att uppnå en önskad drift, men systemet bör även fungera under de bästa förutsättningarna (utloppstryck och underkylning) för att vara effektiv. Ju bättre drift, desto mindre är energiförbrukningen. Denna energiåtervinningsmetod kan också användas som underkylning i varma klimat vilket gör CO2 till en mycket effektiv lösning. Vanliga typer av kylmedel används fortfarande ofta i varma länder trots att deras negativa miljöpåverkan. Ett kylsystem med ett naturligt kylmedel som till exempel koldioxid har emellertid inga begränsningar. Den enda begränsningen är den felaktiga hanteringen av driften.

The great need for cooling combined with Mexico's large availability of low enthalpy energy from non conventional energy resources such as geothermal energy, solar heat and waste heat from industrial processes, makes it very attractive to utilize these resources for cooling using heat driven absorption systems. The main purpose of the work described in this thesis is to obtain experimental and theoretical data on heat driven absorption cooling systems for the design of large scale systems. Thermodynamic design data have been theoretically derived for heat driven absorption heat pumps and heat transformers using the working pairs ammonia-water and ammonia-lithium nitrate for cooling, heating and simultaneous heating and cooling. The interaction between the operating parameters has been illustrated graphically. A computer model of the steady state thermodynamics of a heat driven ammonia-water system and an ammonia-lithium nitrate system has been developed. A comparison of both systems is made by assessing the effect of operating temperatures and heat exchanger effectiveness on the coefficient of performance for cooling and the heat transfer rates within the system. An experimental study on the performance of the absorber of an absorption cooling system operating on water-lithium bromide has been made. The experimental study of the adiabatic absorber was concerned with the determination of the effect of the evaporator heat load and the absorber reflux on the performance of the absorber. An experimental study of the operating characteristics of an experimental. absorption cooler using water-lithium bromide-lithium iodide and waterlithium bromide-zinc bromide as ternary systems has been made in order to achieve higher coefficients of performance and a lower risk of crystallization. Experimental studies with a small heat driven absorption cooling system operating on ammonia-water using a falling film generator were made. Low generator temperatures were achieved which will'enable the use of non focussing solar collectors as a heat source for the system. An ammonia-water absorption cooler operating on low enthalpy geothermal energy was installed and operated at two geothermal fields. The system was used to cool a small cold storage facility below freezing temperatures. The experimental and theoretical results on absorption cooling systems will provide a basis for the design of heat pump systems for industrial and commercial applications.

The study looks at heat recovery of a refrigeration system in a supermarket where the heat was supplied to apartments in the same building. Such a system requires cooperation between the supermarket owner and the property owner, with both having different motives. By gaining understanding of each other's needs and obligations, cooperation can become easier to achieve, with a result that is more optimal for both actors. Heat recovery for use within the supermarkets has existed for a long time, though supplying the heat to other actors is not as common. Using CO2 as refrigerant is becoming more popular in supermarket refrigeration systems, which allows for achieving higher temperatures in recovered heat, enabling use in radiator systems or for preheating domestic hot water. In lack of other cooling solutions, the supermarket studied in the project had previously used municipal water for cooling of the condenser in the refrigeration system, which is a costly solution that does not utilize the heat. The amount of heat that can be recovered was estimated and compared to the varied amount of heat demand in the supermarket and the rest of the property over a year. Findings show that heat recovery from the refrigeration system create considerable cost savings for both the supermarket owner and the property owner, despite still requiring cooling with municipal water during summer. Financial compensation for delivered heat is difficult to argue for at moment, though it may become relevant if new solutions for cooling of the refrigeration system are proved to be feasible.
Se filen

Conventional energy sources—oil and electricity—dominate the heat supply market. Due to their rising costs and their negative environmental effects on global climate change, it is necessary to develop an alternative heat supply system featuring low cost, high energy efficiency and environment friendliness. At present, it is often challenging to supply heat to detached buildings due to low energy efficiency and high distribution cost. Meanwhile, significant amounts of industrial waste and excess heat are released into the environment without recycling due to the difficulty of matching time and space differences between suppliers and end users. Phase change materials (PCMs), with the advantages of being storable and transportable, offer a solution for delivering that excess heat from industrial plants to detached buildings in sparse, rural areas.   The objective of this thesis is to study PCMs and latent thermal energy storage (LTES) technology, and to develop a mobilized thermal energy storage (M-TES) system that can use industrial waste or excess heat for heat recovery and distribution to areas in need.   Organic PCMs were chosen for study because they are non-toxic and non-corrosive, and they exhibit no phase separation and little sub-cooling when compared to inorganic PCMs. Two major issues including leakage of liquid PCMs and low thermal conductivity. Polyethylene glycol (PEG) was chosen to help analyze the thermal behavior of organic PCMs and PEG-based form-stable composites. To overcome the issue of low thermal conductivity, modified aluminum nitride (AlN) powder was added to the composites. Increased thermal conductivity traded off decreased latent heat. The PEG/EG composite, prepared by mixing the melted PEG into an expanded graphite (EG) matrix showed good thermal performance due to its large enthalpy and high thermal conductivity.   To make a systematic study of the M-TES system, a compact lab-scale system was designed and built. Characteristics of PCM were studied, and the performance of the direct-contact TES container was investigated. A case study using an M-TES system to deliver heat from a combined heat and power (CHP) plant to a small village was conducted. A technical and economic feasibility study was conducted for an integrated heat supply system using the M-TES system. In addition, the options for charging a TES container at a CHP plant were analyzed and compared from the viewpoints of power output, heat output and incomes.
Ångpanneföreningens Forskningsstiftelse (ÅF)