Dissertations / Theses on the topic 'Waste heat recovery boiler'

This thesis deals with the design of a Heat Recovery Steam Generator (HRSG). Theintroductory part is devoted to a brief description of the boiler, the specified parametersand the compilation of the temperature profile. The main computational part of thiswork is divided into 6 parts. The first contains preparatory calculations, including thecalculation of boiler eiciency. In the second part, a flue gas duct is designed. This isfollowed by a thermal calculation of the boiler for all heat exchange surfaces. The last 3parts deal with the design of the drum, piping and the loss of boiler draft calculation.

This master’s thesis deals with the design of a heat recovery steam generator. The introductory part of the thesis is dedicated to waste heat boilers, their division and their utilization in combined cycles gas turbine. In the following chapter, an analysis of the existing combined heat and power plant operation is performed. In the next part of the thesis, the conceptual layout of the new source is designed. Subsequently, the thermal calculation of the boiler is carried out as well as the design of individual heat exchanging surfaces. The sixth chapter deals with the strength calculation of the boiler and the outer piping, chambers and drum are designed here. At the end of the thesis there are described off-design states of the new combined cycle gas turbine.

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.

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.

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.

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

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.

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.

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

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.

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.

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.

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.

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

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.

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.

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?

Approved for public release; distribution is unlimited
This thesis presents the effect of exhaust tube length-to-diameter (L/d) ratio, jacket-to-tube diameter (D/d) ratio, coolant inlet and outlet placements, exhaust gas swirling conditions, and tube materials (steel, copper, Inconel, and ceramic) on heat recovery performance, exhaust side pressure drop, and temperature profile in the exhaust gas Waste Heat Recovery Unit (WHRU). Non-dimensional parametric studies of a selected counter-flow Water Jacket WHRU was conducted using analytical and Computational Fluid Dynamic (CFD) models. Exhaust gas Reynolds numbers between 20,000 and 400,000, representative of exhaust gas flow in the exhaust stacks of U.S.Marine Corps’ MEP803A diesel generators and the U.S.Navy's 501-K17 gas turbine generators, were used. Results indicate heat recovery increases with higher L/d, D/d, and swirling exhaust gases conditions but with a severe pressure drop penalty. Addition of a solid heat spreader at the exhaust gas inlet and the use of suitable tube materials were also found to influence temperature profiles in the WHRU and mitigate adverse temperature gradients to some extent without any additional pressure drop penalty. Optimal laterally shifted placement of coolant inlet and outlet was found to improve heat recovery by up to 19% and was very effective at mitigating adverse temperature profiles, which improves the reliability of exhaust gas WHRU.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (leaves 32-33).
Less than 30% of the energy in a gallon of gasoline reaches the wheels of a typical car; most of the remaining energy is lost as heat. Since most of the energy consumed by an internal combustion engine is wasted, capturing much of that wasted energy can provide a large increase in energy efficiency. For example, a typical engine producing 100 kilowatts of driveshaft power expels 68 kilowatts of heat energy through the radiator and 136 kilowatts through the exhaust. The possibilities of where and how to capture this lost energy are examined in this paper. The solution of recovering heat energy from the exhaust through the catalytic converter with a Stirling engine was examined due to its practicality. A novel approach for combining a Stirling engine and a catalytic converter that would be effective was designed. The power output and efficiency of the Stirling Engine were analyzed and it was found that the average overall car efficiency could be raised 7% with the new design.
by Joaquin G. Ruiz.
S.B.

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%.

Anaerobic digestion has great potential as an energy source. Not only does it provide an effective method for waste mitigation, but it has the potential to generate significant quantities of fuel and electricity. In order to ensure efficient digestion and biomass utilization, however, the system must be continuously maintained at elevated temperatures. It is technically feasible to supplement such a system with outside energy, but it is more cost effective to heat the system using only the produced biogas. While there is considerable literature covering the theory of anaerobic digestion, there are very few practical studies to show how heat utilization affects system operation. This study considers the effect of major design variables (i.e. heat exchanger efficiencies and biogas conditioning) on promoting a completely self-sustaining digestion system. The thesis considers a real world system and analyzes how it can be improved to avoid the need of an external energy source.

En l’actual context energètic, l'ús de la calor residual industrial (CRI) representa una oportunitat atractiva de substituir el consum d'energia primària per un mitjà amb baix nivell d'emissions i baix cost. Aquesta calor es pot recuperar i reutilitzar en altres processos, ser transformada en electricitat o calor.Tot i el seu prometedor potencial, aquest CRI no s’utilitza. L'objectiu d'aquesta tesi doctoral és el de superar algunes de les barreres tecnològiques i d'informació actuals que dificulten l’ús d’aquesta fot d’energia. En primer lloc, s’ha identificat el potencial mundial actual de CRI a escala de. En segon lloc, es va generar noves avaluacions d’estimació del potencial de CRI: a la indústria de la manufactura espanyola i en la indústria de minerals no metàl•lics Europea. Finalment, es va tractar la recuperació i reutilització d'aquesta calor mitjançant l’emmagatzematge d’energia tèrmica i es va avaluar exhaustivament els casos pràctics on aquesta tecnologia ha estat implementada.
En el actual contexto energético, el uso del calor residual industrial (CRI) representa una oportunidad atractiva de sustituir el consumo de energía primaria por un medio de bajo nivel de emisiones y de bajo coste. Este calor se puede recuperar y reutilizar en otros procesos, ser transformado en electricidad o en calor. A pesar de su prometedor potencial, este CRI está actualmente en desuso. El objetivo de esta tesis doctoral es el de superar algunas de las barreras tecnológicas y de información que existen actualmente en la utilización de esta fuente de energía. En primer lugar, se ha identificado el potencial mundial actual de CRI a escala de país. En segundo lugar, se generaron nuevas evaluaciones de estimación del potencial de CRI: en la industria de la manufactura española y en la industria de minerales no metálicos Europea. Finalmente, se trató la recuperación y reutilización de este calor mediante almacenamiento de energía térmica y se evaluó exhaustivamente los casos prácticos donde esta tecnología ha sido implementada.
In the current energy context, the use of industrial waste heat (IWH) provides an attractive opportunity to substitute primary energy consumption by a low-emission and low-cost energy carrier. Despite its potential, IWH is largely untapped. This heat can be recovered and reused in other processes, transformed into electricity or heat. The aim of this PhD is to overcome some of the current technological and information barriers and to provide the literature and the researchers with more knowledge of the topic and supporting its widespread development. First, current IWH potential worldwide at country scale was identified. Second, new assessments to estimate the regional IWH potential were generated: in the Spanish manufacture industry as well as in the European non-metallic mineral industry. Finally, its reuse by means of thermal energy storage (TES) was analysed and an exhaustive research of current case studies was performed.

The waste heat recovery technologies have become very relevant since many industrial plants continuously reject large amounts of thermal energy during normal operation which contributes to the increase of the production costs and also impacts the environment. The simulation programs used in industrial engineering enable development and optimization of the operational processes in a cost-effective way. The company Chematur Engineering AB, which supplies chemical plants in many different fields of use on a worldwide basis, was interested in the investigation of the possibilities for effective waste heat recovery from the hydrogenation of dinitrotoluene, which is a sub-process in the toluene diisocyanate manufacture plant. The project objective was to implement waste heat recovery by application of the Organic Rankine Cycle and the Absorption Refrigeration Cycle technologies. Modeling and design of the Organic Rankine Cycle and the Absorption Refrigeration Cycle systems was performed by using Aspen Plus® simulation software where the waste heat carrier was represented by hot water, coming from the internal cooling system in the hydrogenation process. Among the working fluids investigated were ammonia, butane, isobutane, propane, R-123, R-134a, R-227ea, R-245fa, and ammonia-water and LiBr-water working pairs. The simulations have been performed for different plant capacities with different temperatures of the hydrogenation process. The results show that the application of the Organic Rankine Cycle technology is the most feasible solution where the use of ammonia, R-123, R-245fa and butane as the working fluids is beneficial with regards to power production and pay-off time, while R-245fa and butane are the most sustainable choices considering the environment.

Av den frigjorda energin för en lastbils bränsle är omkring 30% i form avspillvärme i avgassystemet. Med implementation av ett spillvärmeåtervinningsystem går det att återvinna en del av den frigjorda energin i form av elektricitet till lastbilens elsystem. Två termoelektriska generatorer använder avgaserna som värmekälla och ett kylmedel som kall källa för att åstakomma en temperaturdifferans i generatorerna. Med hjälp av Seebeck-effekten går det att omvandla temperaturdifferansen till elektricitet och på så sätt avlastas motorns generator vilket medför en lägre bränsleförbrukning. Detta examensarbete innefattar utvecklandet av en funktion som maximerar nettoeffekten utvunnen från systemet. Funktionen som utvecklats är döpt till Maximum Net-power Point Tracking (MNPT) och har som uppgift att beräkna referensvärden som styrningen av systemet skall uppnå för att få ut maximal nettoeffekt. En simuleringmiljö i Matlab/Simulink är uppbyggd för att kunna implementera en kontrollstrategi för styrningen av kylmedlet samt avgasledning via bypass-ventiler. Systemet har blivit implementerat i en motorstyrenhet på en testrack somkommunicerar via CAN där givare så som temperatur och tryck avläses. Systemet har ej blivit implementerat på lastbilen då samtliga fysiska komponenter ej blev färdigställda under examensarbetets gång. En fallstudie genomfördes i simuleringsmiljön och resultaten visade att användningen av en MNPT-funktion tillät upp till 300% ökning av den återinförda nettoeffekten till lastbilens elsystem jämfört med utan användning av kontrollalgoritmer, och upp till 50% ökning jämfört med statiska referensvärden.
About 30% of the released energy of a truck’s fuel is waste heat in the exhaustsystem. It is possible to recover some of the energy with a waste heat recovery system that generates electricity from a temperature difference by utilising the Seebeck-effect. Two thermoelectric generators are implemented on a truck and utilises the exhaust gas as a heat source and the coolant fluid as a cold source to accomplish a temperature difference in the generators. The electricity is reintroduced to the truck’s electrical system and thus reducing the load on the electrical generator in the engine which results in lower fuel consumption. This thesis includes the construction of a function that maximises the netpowerderived from the system. The function developed is named Maximum Net Power Point Tracking (MNPT) and has the task of calculating reference values that the controllers of the system must achieve in order to obtain maximumnet-power. A simulation environment has been developed in Matlab/Simulink in order to design a control strategy to three valves and one pump. The system has been implemented on a engine control unit that has been mounted on a test rack. The engine control unit communicates through CAN to connected devices. The system has not been implemented on the truck due that all the physical components were not completed during the time of the thesis. A case study has been conducted and the results proves that the use of an MNPT-function allows up to 300% increase in regenerated net power into the trucks electrical system compared with no control algorithms, and up to 50% compared with static reference values.

The combination of the continuously growing demand of energy in the world, the depletion of oil and its sharp price increase, as well as the urgent need for cleaner and more efficient fuels have boosted the global trade of liquefied natural gas (LNG). Nowadays, there is an increasing interest on the design philosophy of the LNG receiving terminals, due to the fact that the existing technologies either use seawater as heating source or burn part of the fuel for regasifying LNG, thus destroying the cryogenic energy of LNG and causing air pollution or harm to marine life. This investigation addresses the task of developing novel systems able to simultaneously regasify LNG and generate electric power in the most efficient and environmentally friendly way.    Existing and proposed technologies for integrated LNG regasification and power generation were identified and simple, efficient, safe and compact alternatives were selected for further analysis. A baseline scenario for integrated LNG regasification and power generation was established and simulated, consisting of a cascaded Brayton configuration with a typical small gas turbine as topping cycle and a simple closed Brayton cycle as bottoming cycle. Various novel configurations were created, modeled and compared to the baseline scenario in terms of LNG regasification rate, efficiency and power output. The novel configurations include closed Rankine and Brayton cycles for the bottoming cycle, systems for power augmentation in the gas turbine and combinations of options. A study case with a simple and compact design was selected, preliminarily designed and analyzed according to characteristics and costs provided by suppliers. The performance, costs and design challenges of the study case were then compared to the baseline case. The results show that the study case causes lower investment costs and a smaller footprint of the plant, at the same time offering a simple design solution though with substantially lower efficiencies.

Performance of two different waste heat recovery systems (one based on Rankine cycle and the other one using thermoelectricity) combined with non-hybrid, mild-hybrid and full hybrid systems are investigated. The vehicle under investigation was a 440hp Scania truck, loaded by 40 tons. Input data included logged data from a long haulage drive test in Sweden.All systems (waste heat recovery as well as hybrid) are implemented and simulated in Matlab/Simulink. Almost all systems are modeled using measured data or performance curves provided by one manufacturer. For Rankine system results from another investigation were used.Regardless of practical issues in implementing systems, reduction in fuel consumption for six different combination of waste heat recovery systems and hybrid systems with different degrees of hybridization are calculated. In general Rankine cycle shows a better performance. However, due to improvements achieved in laboratories, thermoelectricity could also be an option in future.This study focuses on “system” point of view and therefore high precision calculations is not included. However it can be useful in making decisions for further investigations.

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The Secretary of the Navy has ordered the U.S. Navy and Marine Corps to reduce energy usage. This study explores how to optimize placement and size of a non-intrusive waste heat recovery device for energy recovery in exhaust ducts. Additionally, it explores the effect that a device has on the exhaust infrared signature by analyzing the change in the bulk temperature at the exhaust outlet. Optimal device placement and size is dependent on duct geometry, external heat transfer coefficient, and flow characteristics, namely Reynolds number. Infrared signature intensity reductions of 1–14% are only achievable with unpractically long thermoelectric generator devices and high external heat transfer coefficients. Doubling the external heat transfer coefficient increases heat recovery by 15–30% for low Reynolds number flows (104) and 75–90% for high Reynolds number flows (105~106). In low Reynolds number flows (~104), device position can account for a 75% change in energy recovery whereas high Reynolds number flows (~106) have unexpected areas of higher heat transfer. Position changes can increase heat recovery 10–70%, while increasing device size may only marginally improve results. Identifying local maxima for heat transfer, especially in high Reynolds number flows (~106), is counterintuitive because of unexpected recirculation zone effects.

A typical long-haul heavy duty Diesel engine currently rejects up to 50% of the total fuel energy in the form of heat. Due to increasing CO2 emissions and fuel costs, there is a growing interest in techniques that can even partially utilise this wasted resource to improve the overall system efficiency. Fluid Bottoming Cycles (FBC) including Rankine and organic Rankine cycles offer one means towards converting waste heat into usable power. This thesis investigates the potential of FBCs to improve the net power of two computationally modelled (Ricardo WAVE V8.1) 10 litre engine platforms operating at Euro 6 emission levels.

A number of car engines operate with an efficiency rate of approximately 22% to 25% [1]. The remainder of the energy these engines generate is wasted through heat escape out of the exhaust pipe. There is now an increasing desire to reuse this heat energy, which would improve the overall efficiency of car engines by reducing their consumption of fuel. Another benefit is that such reuse would minimize harmful greenhouse gases that are emitted into the environment. Therefore, the purpose of this project is to examine how the wasted heat energy can be reused and/or recovered by use of a heat recovery system that would store this energy in a hybrid car battery. Green turbines will be analyzed as a possible solution to recycle the lost energy in a way that will also improve the overall automotive energy efficiency.

This report is a thesis for BTH in collaboration with the company Saab Kockums AB. In order to meet future environmental and economical demands, a vessel must reduce its fuel consumption to have a smaller climate impact and save money. Waste heat recovery systems (WHRS) captures the thermal energy generated from a process that is not used but dumped into the environment and transfers it back to the system. Thermal energy storage (TES) is the method of storing thermal energy which allows heat to be used whenever necessary. Some applications of TES are seasonal storage, where summer heat is stored for use in the winter or when ice is produced during off-peak periods and used for cooling later. The purpose of this study is to investigate the possibilities of utilising a vessel’s waste heat by converting thermal energy into electrical energy. This thesis also aims to investigate conditions for SaltX Technology’s nano-coated salt as a potential solution for thermal energy storage. Initially, the expectations and requirements a future WHRS were investigated in a function analysis. Continuously, the method consisted of a combination of a literature review and dialogue with stakeholders. The literature review was used as a tool to identify, select and study concepts of interest built on scientifically proven facts. Dialogues with stake holders were held as a complement to the literature study to find information. The study showed that an organic Rankine cycle has the highest efficiency for low-medium temperature heat and is therefore most suitable to recover thermal energy from the cooling water. The concept of a steam Rankine cycle is most suitable for recovering thermal energy from the exhaust gases for direct use.The study obtained conditions and important properties for storing thermal energy in salt for later use. Finally, the result showed that a Stirling engine is the most efficient concept for conversion of stored energy into electrical energy. The conclusions are that there are great possibilities for waste heat recovery on marine defence platforms. A Stirling engine for energy conversion in combinations with thermal energy storage shows most promise as a future waste heat recovery system on this type of marine platform.
Denna rapport är ett examensarbete för BTH i samarbete med företaget Saab Kockums AB. Arbetet utforskar möjligheterna att möta framtida miljömässiga och ekonomiska krav genom att låta fartyg minska sin bränsleförbrukning. System för återvinning av spillvärme (WHRS) fångar upp värmeenergi som vanligtvis kyls ner eller släpps ut i naturen och för den tillbaka till systemet. Termisk energilagring (TES) är metoder för lagring av värme som gör det möjligt att använda termisk energi när det behövs. Vissa applikationer av TES är säsongslagring, där sommarvärme lagras för användning på vintern eller när is produceras under vintern och används för kylning senare. Syftet med denna studie är att undersöka möjligheterna att utnyttja ett fartygs spillvärme genom att omvandla termisk energi till elektrisk energi. Detta examensarbete syftar också till att undersöka förhållandena för hur SaltX Technology’s nanobelagda salt kan användas som en potentiell lösning för lagring av termisk energi. Inledningsvis undersöktes WHRS:s förväntningar och krav i en funktionsanalys. Fortsättningsvis bestod metoden av en kombination av en litteraturstudie och dialoger med intressenter. Litteraturstudien användes som ett verktyg för att identifiera, välja och studera intressanta koncept baserade på vetenskapligt beprövade fakta. Dialoger hölls som ett komplement till litteraturstudien för att hitta information. Studien visade att en organisk Rankine-cykel har den högsta verkningsgraden för låg-medelhög temperatur och därför är bäst lämpad för att återvinna energi buren i kylvattnet samt att en ång-Rankine-cykel är bäst lämpad för att utnyttja energin från avgaserna för direkt användning. Studien erhöll förhållanden för termisk energilagring i salt samt viktiga parametrar för systemet. Slutligen visade resultatet att en Stirlingmotor är det mest effektiva konceptet för omvandling av lagrad energi till elektrisk energi. Slutsatserna är att det finns stora möjligheter för återvinning av restvärme på marina försvarsplattformar. En Stirlingmotor för energiomvandling i kombination med termisk energilagring visar störst potential som ett framtida system för återvinning av spillvärme på denna typen av plattformar.

Regulations for ICE-based transportation in the EU seek carbon dioxide emissions lower than 95 g CO2/km by 2020. In order to fulfill these limits, improvements in vehicle fuel consumption have to be achieved. One of the main losses of ICEs happens in the exhaust line. Internal combustion engines transform chemical energy into mechanical energy through combustion; however, only about 15-32% of this energy is effectively used to produce work, while most of the fuel energy is wasted through exhaust gases and coolant. Therefore, these sources can be exploited to improve the overall efficiency of the engine. Between these sources, exhaust gases show the largest potential of Waste Heat Recovery (WHR) due to its high level of exergy. Regarding WHR technologies, Rankine cycles are considered as the most promising candidates for improving Internal Combustion Engines. However, the implementation of this technology in modern passenger cars requires additional features to achieve a compact integration and controllability in the engine. While industrial applications typically operates in steady state operating points, there is a huge challenge taking into account its impact in the engine during typical daily driving profiles. This thesis contributes to the knowledge and characterization of an Organic Rankine Cycle coupled with an Internal Combustion Engine using ethanol as working fluid and a swash-plate expander as expansion machine. The main objective of this research work is to obtain and quantify the potential of Organic Rankine Cycles for the use of residual energy in automotive engines. To do this, an experimental ORC test bench was designed and built at CMT (Polytechnic University of Valencia), which can be coupled to different types of automotive combustion engines. Using these results, an estimation of the main variables of the cycle was obtained both in stationary and transient operating points. A potential of increasing ICE mechanical efficiency up to 3.7% could be reached at points of high load installing an ORC in a conventional turbocharged gasoline engine. Regarding transient conditions, a slightly simple and robust control based on adaptive PIDs, allows the control of the ORC in realistic driving profiles. High loads and hot conditions should be the starting ideal conditions to test and validate the control of the ORC in order to achieve high exhaust temperatures that justify the feasibility of the system. In order to deepen in the viability and characteristics of this particular application, some theoretical studies were done. A 1D model was developed using LMS Imagine.Lab Amesim platform. A potential improvement of 2.5% in fuel conversion efficiency was obtained at the high operating points as a direct consequence of the 23.5 g/kWh reduction in bsfc. To conclude, a thermo-economic study was developed taking into account the main elements of the installation costs and a minimum Specific Investment Cost value of 2030 €/kW was obtained. Moreover, an exergetic study showed that a total amount of 3.75 kW, 36.5% of exergy destruction rate, could be lowered in the forthcoming years, taking account the maximum efficiencies considering technical restrictions of the cycle components.
Las normativas anticontaminantes para el transporte propulsado por motores de combustión interna alternativos en la Unión Europea muestran límites de emisión menores a 95 g CO2/km para el año 2020. Con el fin de cumplir estos límites, deberán ser realizadas mejoras en el consumo de combustible en los vehículos. Una de las principales pérdidas en los Motores de Combustión Interna Alternativos (MCIA) ocurre en la línea de escape. Los MCIA transforman la energía química en energía mecánica a través de la combustión; sin embargo, únicamente el 15-32% de esta energía es eficazmente usada para producir trabajo, mientras que la mayor parte es desperdiciada a través de los gases de escape y el agua de refrigeración del motor. Por ello, estas fuentes de energía pueden ser utilizadas para mejorar la eficiencia global del vehículo. De estas fuentes, los gases de escape muestran un potencial mayor de recuperación de energía residual debido a su mayor contenido exergético. De todos los tipos de Sistemas de Recuperación de Energía Residual, los Ciclos Rankine son considerados como los candidatos más prometedores para mejorar la eficiencia de los MCIA. Sin embargo, la implementación de esta tecnología en los vehículos de pasajeros modernos requiere nuevas características para conseguir una integración compacta y una buena controlabilidad del motor. Mientras que las aplicaciones industriales normalmente operan en puntos de operación estacionarios, en el caso de los vehículos con MCIA existen importantes retos teniendo en cuenta su impacto en el modo de conducción cotidianos. Esta Tesis contribuye al conocimiento y caracterización de un Ciclo Rankine Orgánico acoplado con un Motor de Combustión Interna Alternativo utilizando etanol como fluido de trabajo y un expansor tipo Swash-plate como máquina expansora. El principal objetivo de este trabajo de investigación es obtener y cuantificar el potencial de los Ciclos Rankine Orgánicos (ORC) para la recuperación de la energía residual en motores de automoción. Para ello, una instalación experimental con un Ciclo Rankine Orgánico fue diseñada y construida en el Instituto Universitario "CMT - Motores Térmicos" (Universidad Politécnica de Valencia), que puede ser acoplada a diferentes tipos de motores de combustión interna alternativos. Usando esta instalación, una estimación de las principales variables del ciclo fue obtenida tanto en puntos estacionarios como en transitorios. Un potencial de mejora en torno a un 3.7 % puede ser alcanzada en puntos de alta carga instalando un ORC en un motor gasolina turboalimentado. Respecto a las condiciones transitorias, un control sencillo y robusto basado en PIDs adaptativos permite el control del ORC en perfiles de conducción reales. Las condiciones ideales para testear y validar el control del ORC son alta carga en el motor comenzando con el motor en caliente para conseguir altas temperaturas en el escape que justifiquen la viabilidad de estos ciclos. Para tratar de profundizar en la viabilidad y características de esta aplicación particular, diversos estudios teóricos fueron realizados. Un modelo 1D fue desarrollado usando el software LMS Imagine.Lab Amesim. Un potencial de mejora en torno a un 2.5% en el rendimiento efectivo del motor fue obtenido en condiciones transitorias en los puntos de alta carga como una consecuencia directa de la reducción de 23.5 g/kWh del consumo específico. Para concluir, un estudio termo-económico fue desarrollado teniendo en cuenta los costes de los principales elementos de la instalación y un valor mínimo de 2030 €/kW fue obtenido en el parámetro de Coste Específico de inversión. Además, el estudio exergético muestra que un total de 3.75 kW, 36.5 % de la tasa de destrucción total de exergía, podría ser reducida en los años futuros, teniendo en cuenta las máximas eficiencias considerando restricciones técnicas en los componentes del ciclo.
Les normatives anticontaminants per al transport propulsat per motors de combustió interna alternatius a la Unió Europea mostren límits d'emissió menors a 95 g·CO2/km per a l'any 2020. Per tal d'acomplir aquests límits, s'hauran de realitzar millores al consum de combustible dels vehicles. Una de les principals pèrdues als Motors de combustió interna alternatius (MCIA) ocorre a la línia d'escapament. Els MCIA transformen l'energia química en energia mecànica a través de la combustió; però, únicament el 15-32% d'aquesta energia és usada per produir treball, mentre que la major part és desaprofitada a través dels gasos d'escapament i l'aigua de refrigeració del motor. Per això, aquestes fonts d'energia poden ser utilitzades per millorar l'eficiència global del vehicle. Considerant aquestes dues fonts d'energia, els gasos d'escapament mostren un potencial major de recuperació d'energia residual debut al seu major contingut exergètic. De tots els tipus de Sistemes de Recuperació d'Energia Residual, els Cicles Rankine són considerats com els candidats més prometedors per millorar l'eficiència dels MCIA. No obstant, la implementació d'aquesta tecnologia en els vehicles de passatgers moderns requereix un desenvolupament addicional per aconseguir una integració compacta i una bona controlabilitat del motor. Mentre que les aplicacions industrials normalment operen en punts d'operació estacionaris, en el cas dels vehicles amb MCIA hi han importants reptes a solucionar tenint en compte el funcionament en condicions variables del motor i el seu impacte en la manera de conducció quotidiana del usuari. Aquesta Tesi contribueix al coneixement i caracterització d'un Cicle Rankine Orgànic (ORC) acoblat amb un motor de combustió interna alternatiu (MCIA) utilitzant etanol com a fluid de treball i un expansor tipus Swash-plate com a màquina expansora. El principal objectiu d'aquest treball de recerca és obtenir i quantificar el potencial dels ORCs per a la recuperació de l'energia residual en motors d'automoció. Per aconseguir-ho, una instal·lació experimental amb un ORC va ser dissenyada i construïda a l'Institut "CMT- Motores Térmicos" (Universitat Politècnica de València). Esta installació pot ser acoblada a diferents tipus de MCIAs. Mitjançant assajos experimentals en aquesta installació, una estimació de les principals variables del cicle va ser obtinguda tant en punts estacionaris com en punts transitoris. Un potencial de millora al voltant d'un 3.7% pot ser aconseguida en punts d'alta càrrega instal·lant un ORC acoblat a un motor gasolina turboalimentat. Pel que fa a les condicions transitòries, un control senzill i robust basat en PIDs adaptatius permet el control del ORC en perfils de conducció reals. Les condicions ideals per a testejar i validar el control de l'ORC són alta càrrega al motor començant amb el motor en calent per aconseguir altes temperatures d'escapament que justifiquen la viabilitat d'aquests cicles. Per tractar d'aprofundir en la viabilitat i característiques d'aquesta aplicació particular, diversos estudis teòrics van ser realitzats. Un model 1D va ser desenvolupat usant el programari LMS Imagine.Lab Amesim. Un potencial de millora al voltant d'un 2.5% en el rendiment efectiu del motor va ser obtingut en condicions transitòries en els punts d'alta càrrega com una conseqüència directa de la reducció de 23.5 g/kWh al consum específic. Per concloure, un estudi termo-econòmic va ser desenvolupat tenint en compte els costos dels principals elements de la installació i un valor mínim de 2030 €/kW va ser obtingut en el paràmetre del Cost Específic d'Inversió. A més, l'estudi exergètic mostra que un total de 3.75 kW, 36.5% de la taxa de destrucció total d'exergia, podria ser recuperat en un pròxim, considerant restriccions tècniques en els components del cicle i tenint en compte les màximes eficiències que es poden aconseguir.
Royo Pascual, L. (2017). Study of Organic Rankine Cycles for Waste Heat Recovery in Transportation Vehicles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84013
TESIS

Global efforts makes buildings successively more energy efficient. This results in that the percentage of the total energy in the building that is lost to the sewage system, in the form of hot water, is increasing. The characteristics of the wastewater originating from the urban water cycle makes it an attractive heat source which is relatively unexploited. Wastewater heat recovery (WWHR) systems is a group of systems designed to reduce a buildings use of external energy sources by recovering the heat out of the wastewater before it is let out into the sewage.         The focus of this report is a parametric study performed on a WWHR system that utilises thermal storage tanks for accumulation of wastewater and a heat pump equipped with heat exchangers for the heat recovery. The studied variables are the amount of energy that the system is able to recover out of the wastewater and the seasonal average COP of the heat pump. The change of these two variables were analysed both as an affect of parameters dependent of system design and on consumption patterns of the residents of the building. The results showed that by properly designing the system the recovery degree can be increased by 31.5 percentage points reaching values above 90 % and the seasonal average COP can be increased by 13.5 % reaching values of 5.13. However, these two variables stands in contrast to each other were maximising one will reduce the other and it is proposed that it is important to take both into account when evaluating a WWHR system. It is also shown that the consumption related parameters have a relatively big effect on the system. The change in recovery degree as a result of these non-controllable parameter is 14 percentage points and the seasonal average COP changes with 4.2 %.         The system performance as a result of changing the U-value of the heat exchanger connecting the system to the domestic hot water circuit was also analysed. This showed an exponential relation between the U-value and delivered energy from the heat pump. The results showed that an increase of the U-value from 50 W/K to 6000 W/K increased the yearly energy supplied with 37.6 % but an increase from 1000 W/K to 6000 W/K increased the yearly supplied energy with less than 1 %. This result highlights the importance of properly dimensioning the heat exchanger.

The performance of microchannel heat exchangers was assessed in gas-to-liquid applications in the order of several tens of kWth . The technology is suitable for exhaust heat recovery systems based on organic Rankine cycle. In order to design a light and compact microchannel heat exchanger, an optimization process is developed. The model employed in the procedure is validated through computational fluid-dynamics analysis with commercial software. It is shown that conjugate effects have a significant impact on the heat transfer performance of the device.

In this work, we investigate harvesting thermoelectric energy from wasted heat in fluid networks and propose a generic tool for the simulation and sizing of thermoelectric energy harvesters, that can be used in industrial applications to convert expended heat energy into electricity. Current models found in the literature are often based on very specific applications or are too general in nature to truly explore the optimization of a wide range of potential thermoelectric applications. The model developed in this work is highly customizable permitting the optimization of a large number of varying systems. We develop a theoretical model to accurately estimate the recovered energy considering the nonlinearities of the thermoelectricity and heat transfer equations. Taking into account that a real thermoelectric energy harvester always comprises multiple thermoelectric modules placed with respect to the flow direction, both thermal and electrical series-parallel configurations have also been considered. The new model has been analysed and validated under steady and transient states with experimental data. The proposed energy harvesting system is easily scalable, to cater to a variety of applications with different requirements, while improving the energy recovery and operational lifetime of energy sources. On the other hand, this new model is coded in the TRNSYS environment, hence it can be used in design, performance optimization and further application of thermoelectric energy harvesters. The programmed module will serve as the key component of the software package that will predict the performance of the thermoelectric heat recovery unit used in common thermal systems
En aquest treball s’investiga la recuperació termoelèctrica en xarxes de fluids i es proposa una eina genèrica per a la simulació i dimensionament de recuperadors termoelèctrics, els quals, poden ser utilitzats en aplicacions industrials per convertir l'energia tèrmica residual en electricitat. Els models actuals que es troben en la literatura es basen sovint en aplicacions molt específiques o són massa generals per analitzar realment el comportament de recuperadors en aplicacions reals. El model desenvolupat en aquest treball és altament adaptable pel que permet estudiar un gran nombre de sistemes diferents. S’ha desenvolupat un model teòric per estimar amb precisió l'energia recuperada tenint en compte les no linealitats de les equacions termoelèctriques i de transferència de calor. Tenint en compte que un recuperador termoelèctric comprèn sempre múltiples mòduls termoelèctrics col·locats en respecte a la direcció de flux, ambdues configuracions sèrie-paral·lel tant la tèrmica com l’elèctrica s'han considerat. El nou model ha estat analitzat i validat sota diversos estats estacionaris i transitoris a partir de dades experimentals. El model de recuperador proposat s’ha codificat per tal de treballar en l’entorn TRNSYS, de manera que pot ser utilitzat en el disseny i optimització de recuperadors termoelèctrics, és fàcilment escalable, permet atendre a una gran varietat d'aplicacions i requisits i, per tant, ajudar a la seva implantació en aplicacions reals. Aquest mòdul servirà per predir el comportament de recuperadors de calor termoelèctrics aplicats en sistemes tèrmics convencionals

This dissertation describes the preparation and investigation of crystal structure and thermoelectric properties of solid-solutions within three families of layered bismuth oxychalcogenides: BiOCuCh (Ch = S, Se, Te), Bi2YO4Cu2Se2, and Bi2O2Ch (Ch = Se, Te). The crystal structures of all materials were investigated using powder X-ray and neutron diffraction (for BiOCuCh). BiOCuCh (Ch = S, Se, Te) compounds crystallise in the ZrCuSiAs structure type (P4/nmm space group), and are composed of fluorite-type [Bi2O2]2+ and anti-fluorite-type [Cu2Ch2]2- slabs, stacked alternatively along the c – axis. Results show that BiOCuCh (Ch = S, Se, Te) are p-type semiconductors. The electrical conductivity increases while thermal conductivity decreases systematically with changing from S to Te in these compounds. Analysis of neutron diffraction data shows that the rattling behaviour of copper in a rigid framework (BiOCh) is at the origin of their low thermal conductivity. The figure of merit increases with increasing atomic weight of the chalcogenide. BiOCuSe shows the larger potential for thermoelectric applications in terms of its combination of economic cost and properties. Therefore, the effect of doping with divalent cations (Pb2+, Cd2+, Zn2+) on BiOCuSe was studied. Results show that substitution of trivalent Bi3+ with a 4-5 at.% of divalent Pb2+ leads to an enhancement of the power factor and a high figure of merit (ZT ~ 0.62 at 673 K), whilst the substitution of monovalent Cu+ with divalent Cd2+ or Zn2+ leads to an increase in the magnitude of the electrical resistivity and the Seebeck coefficient. In addition, a reduction of the thermal conductivity (κ ~ 0.77 W m−1 K−1) is achieved in ball-milled Bi0.95Pb0.05OCuSe. Bi2YO4Cu2Se2 crystallises in the Sr2Mn3Sb2O2 structure type (I4/mmm space group), and consists of fluorite-type [Bi2MO4]+ and anti-fluorite-type [Cu2Ch2]- layers stacked alternatively along the c – axis. It possesses metallic behaviour, with hole charge carriers and a fairly low figure of merit (ZT ~ 3x10-2 at 673 K). This behaviour is related to the oxidation state of the copper (+1.5) in which more hole charge carriers have been produced. Bi2O2Ch (Ch = Se, Te) crystallises in the anti-ThCr2Si2 structure (I4/mmm space group) and comprises fluorite-type [Bi2O2]2+ and square net Ch2- stacked alternatively along the c – axis. Results show that Bi2O2Te1-xSex (0 ≤ x ≤ 0.25) are n-type semiconductors, and that Bi2O2Te shows the highest figure of merit (ZT ~ 1.3x10-1 at 573 K) while Bi2O2Te1- xSex (0.5 ≤ x ≤ 1) and Bi2O2Se1±δ(0.05 ≤ δ ≤ 0.15) solid solutions show insulating behaviour.

From the point of view of energy importance and the environmental impacts associated with conventional energy production methods, and for the purpose of low-grade waste heat recovery, this thesis demonstrates an investigative approach to develop and test a novel, environmentally friendly small-scale Rankine based power generation prototype system. To fulfil the aim, a range of systems of different technologies, and employing different working fluids were investigated to identify the most efficient, cost-effective system for the application. These systems are the absorption power generation system, and the flood expansion power generation system employing CO2/Lubricant mixture as the working fluid, the CO2 SRC power system, and finally the ORC system employing newly developed HFOs and HCFOR1233zd(E) refrigerants. The CO2/lubricant working fluid mixture was experimentally investigated and thermodynamically modelled. The performance of the investigated systems was theoretically evaluated by computer simulations. The results revealed that the ORC outperformed all other investigated systems, achieving thermal efficiency and net thermal power output of 14.36% and 4.81 kW respectively with R1233zd(E). In addition, the evaluation confirmed the capability of the new refrigerants to replace conventional refrigerants. A small-scale R1233zd(E) ORC prototype system utilising a specially developed scroll expander was constructed and tested. In the First Experiment, an automotive motor was utilised as the electric generator. The system’s optimum performance was 7.87% thermal efficiency, 1.39 kW expander power output, and 180 W electric power output. The main source of performance limitation was identified as the lower capability of the steam humidifier heat source, in addition to the speed mismatch between the expander and the motor, the poor performance of the circulation pump, and the piping configuration in relation to the positions of heat exchangers. Piping and the position of heat exchangers were altered, the motor was replaced by an alternator and the second experiment commenced in which the best overall experimental performance of 7.6% thermal efficiency, 1 kW expander power output, 246 W electric power output, was achieved. Very poor pump efficiency and a large power loss through the power transmission mechanism to the alternator were observed. Upon completion of the experiments, the theoretically predicted performance was validated, and the experimentally obtained results were compared to those of similar ORCs from literature. The comparison revealed that for the utilised expander type, a mass flow rate of 0.074 kg/s, and a pressure ratio of 4.5, achieves the best expander efficiency of 75%. From an economic point of view, the R1233zd(E) ORC was shown to be a very attractive and safe investment even for scaled- up systems. The thesis concluded that the ORC technology remains the most efficient, flexible technology for low-grade heat recovery, and the evaluation of R1233zd(E) for the first time expressed the attractive potentials of the refrigerant in ORC applications. Finally, justified recommendations were made to replace the heat source and refrigerant pump and to test other types of expander in order to improve the performance of the R1233zd(E) ORC prototype system.

In an attempt to reduce the dependence on fossil fuels, a variety of research initiatives has focused on increasing the efficiency of conventional energy systems. One such approach is to use waste heat recovery to reclaim energy that is typically lost in the form of dissipative heat. An example of such reclamation is the use of waste heat recovery systems that take low-temperature heat and deliver cooling in space-conditioning applications. In this work, an ejector-based chiller driven by waste heat will be studied from the system to component to sub-component levels, with a specific focus on the ejector. The ejector is a passive device used to compress refrigerants in waste heat driven heat pumps without the use of high grade electricity or wear-prone complex moving parts. With such ejectors, the electrical input for the overall system can be reduced or eliminated entirely under certain conditions, and package sizes can be significantly reduced, allowing for a cooling system that can operate in off-grid, mobile, or remote applications. The performance of this system, measured typically as a coefficient of performance, is primarily dependent on the performance of the ejector pump. This work uses analytical and numerical modeling techniques combined with flow visualization to determine the exact mechanisms of ejector operation, and makes suggestions for ejector performance improvement. Specifically, forcing the presence of two-phase flow has been suggested as a potential tool for performance enhancement. This study determines the effect of two-phase flow on momentum transfer characteristics inside the ejector while operating with refrigerants R134a and R245fa. It is found that reducing the superheat at motive nozzle inlet results in a 12-13% increase in COP with a 14-16 K decrease in driving waste heat temperature. The mechanisms of this improvement are found to be a combination of two effects: the choice of operating fluid (wet vs. dry) and the effect of two-phase flow on the effectiveness of momentum transfer. It is recommended that ejector-based chillers be operated such that the motive nozzle inlet is near saturation, and environmentally friendly dry fluids such as R245fa be used to improve performance. This work provides critical methods for ejector modeling and validation through visualization, as well as guidance on measures to improve ejector design with commensurate beneficial effects on cooling system COP.

The purpose of this thesis is to experimentally determine the feasibility of an ejector based, waste heat recovery driven refrigeration system applied to the data center environment in order to reduce operational cooling costs. A comprehensive literature review is detailed to determine the current state of the ejector refrigeration research and assess the initial direction of this thesis. A simplified model was created to perform preliminary performance estimations and system sizing before constructing an experimental system apparatus to evaluate the model predictions. The pressures and temperatures used in the model and instituted in the experimental system are based on the maximum temperatures typically observed in computing servers (50-75°C). Precision controlled heaters are used to simulate the computer server heat, and R245fa is used as the working fluid. Performance results ranged from 0.06 to 0.13.