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1
Gillott, Mark C. "A novel mechanical ventilation heat recovery/heat pump system." Thesis, University of Nottingham, 2000. http://eprints.nottingham.ac.uk/12148/.
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The trend towards improving building airtightness to save energy has increased the incidence of poor indoor air quality and associated problems, such as condensation on windows, mould, rot and fungus on window frames. Mechanical ventilation/heat recovery systems, combined with heat pumps, offer a means of significantly improving indoor air quality, as well as providing energy efficient heating and cooling required in buildings. This thesis is concerned with the development of a novel mechanical ventilation heat recovery/heat pump system for the domestic market. Several prototypes have been developed to provide mechanical ventilation with heat recovery. These systems utilise an annular array of revolving heat pipes which simultaneously transfer heat and impel air. The devices, therefore, act as fans as well as heat exchangers. The heat pipes have wire finned extended surfaces to enhance the heat transfer and fan effect. The systems use environmentally friendly refrigerants with no ozone depletion potential and very low global warming potential. A hybrid system was developed which incorporated a heat pump to provide winter heating and summer cooling. Tests were carried out on different prototype designs. The type of tinning, the working fluid charge and the number and geometry of heat pipes was varied. The prototypes provide up to 1000m3/hr airflow, have a maximum static pressure of 220Pa and have heat exchanger efficiencies of up to 65%. At an operating supply rate of 200m3/hr and static pressure 100Pa, the best performing prototype has a heat exchanger efficiency of 53%. The heat pump system used the hydrocarbon isobutane as the refrigerant. Heating COPs of up to 5 were measured. Typically the system can heat air from 0°C to 26°C at 200m3/hr with a whole system COP of 2. The contribution to knowledge from this research work is the development of a novel MVHR system and a novel MVHR heat pump system and the establishment of the performances of these systems.
2
Rolston, R. M. "The transfer of heat to a ground-source heat pump." Thesis, Queen's University Belfast, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373542.
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Böttcher, Christof. "An automotive carbon dioxide air-conditioning system with heat pump." Thesis, Port Elizabeth Technikon, 2003. http://hdl.handle.net/10948/206.
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The refrigerant circuits of car air-conditioning systems are fitted with so-called open type compressors, because there is only a lip seal preventing the refrigerant from leaking from the compressor housing to the atmosphere. In addition, the cycle uses damping elements between the compressor and the other components on the suction and pressure lines to reduce vibration and noise transfer from the engine to the car body. Both the lip seal and damping elements result in loss of refrigerant as they are made from elastomers and leak with age, and, under high temperature conditions inside the engine room, these elements also allow a relatively high permeation of the refrigerant gas to the atmosphere. With very high refrigerant losses in the older R12 -cooling cycles and the damage caused by this gas to the ozone layer in the stratosphere, the Montreal protocol phased out this refrigerant and the car industry was forced to revert completely to R134a until 1994/95. R134a has no ozone depletion potential, but it has a direct global warming potential, and, therefore, leakages also have to be minimised. R134a has, because of its molecular size, a high permeation potential and, hence, all the refrigerant hoses are lined internally. Unfortunately, these hoses also leak with age and significant refrigerant loss will occur [1] R134a can therefore only be viewed as a solution until an alternative refrigerant with no direct global warming potential has been developed. Candidates for new refrigerants are natural substances such as hydrocarbons or carbon dioxide [2]. Unfortunately, both substances have disadvantages and their use is restricted to special cases, for e.g. hydrocarbons are flammable and are not used in car air-conditioners, but in Germany it is used as a refrigerant in household refrigerators with hermetic cycles. What makes the implementation of carbon dioxide (CO2) difficult are the high system pressures and the low critical point [3].
4
Tough, M. C. "A heat transfer model of forced convection, cross flow heat exchangers used in space heating." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259171.
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PERONE, CLAUDIO. "Controlled mechanical ventilation to reduce primary energy consumption in air conditioning of greenhouses." Doctoral thesis, Università degli studi del Molise, 2018. http://hdl.handle.net/11695/83654.
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Per garantire condizioni di crescita ottimali di una serra è necessario un controllo molto accurato delle condizioni climatiche interne. Nella prima parte di questo lavoro sono descritte le principali soluzioni impiantistiche attualmente disponibili per il condizionamento delle serre. Tuttavia, questi sistemi richiedono generalmente elevati costi di investimento. Inoltre, anche i costi operativi risultano elevati affinché una soluzione sia efficiente senza ridurre la resa e la qualità del raccolto. Pertanto il condizionamento invernale dell’aria all’interno di una serra avviene per mezzo di combustibili fossili.
L’uso di un sistema di ventilazione meccanica contribuisce a un corretto controllo della temperatura, dell’umidità relativa e della velocità di CO2. Tuttavia, la letteratura riguardante l’applicazione della ventilazione meccanica con recupero di calore per il condizionamento delle serre è molto povera.
Nella sezione 2 vengono descritti il prototipo di ventilazione meccanica e le due camere climatiche, per la riproduzione delle condizioni esterne e interne (costruite in laboratorio). L’unità di recupero è dotata di una pompa di calore ed è in grado di aumentare l’energia termica recuperata dall’aria espulsa attraverso uno scambiatore di calore ad alta efficienza.
Un primo studio è stato condotto per valutare le prestazioni energetiche durante il controllo della temperatura nella stagione invernale. Le prove riportate nella sezione 3 sono state eseguite a diversi valori simulati dell’aria esterna TO (-5 °C, 0 °C, 5 °C e 10 °C) e interna (20 °C di riferimento). Ogni prova è stata eseguita con una portata di ventilazione di 535 m3/h. Il coefficiente di prestazione di sistema (COPs) è di 9.50 a 0 °C, 8.86 a 5 °C e 6.62 a 10 °C. Durante le prove effettuate a -5 °C il compressore si è comportato come uno on-off. Ciò è dovuto a un meccanismo di sicurezza per lo sbrinamento dell’evaporatore. Inoltre, la portata di ventilazione si è ridotta per evitare temperatura di mandata troppo bassa. Durante le altre prove, i COPs totali diminuiscono quando la temperatura esterna aumenta, a causa di una minore differenza tra entalpia dell’aria interna ed esterna.
Per studiare un caso reale il prototipo è stato installato in serra presso Vivaio Verde Molise, Termoli - Italia. L’apparato sperimentale, descritto in dettaglio nella sezione 4, è costituito dal sistema di ventilazione meccanica, un condotto forato per la distribuzione dell’aria, un sistema di nebulizzazione per regolare l’umidità e un sistema di supervisione per acquisire i dati dal campo. Un altro sistema di supervisione dedicato consente di misurare e raccogliere tutti i parametri del prototipo, come i parametri termofisici del flusso d’aria, i parametri termofisici del circuito frigorifero, lo stato e gli allarmi dell’unità.
I primi test, effettuati sul controllo della temperatura nella stagione invernale, sono analizzati nella sezione 5. I dati rilevati mostrano che la temperatura dell’aria interna (impostata a 27 °C) è opportunamente regolata gestendo l’unità con la sonda di riferimento installata sulla ripresa. Si evidenzia solo un piccolo offset dovuto aella perdita di calore nel condotto e al posizionamento della griglia di ripresa (su un lato). Inoltre, il sistema ha mostrato prestazioni energetiche notevoli: COPs (medio) di 5.4 e 5.7 alla temperatura dell’aria esterna di 18.0 °C e 15.7 °C rispettivamente.
Infine, nella sezione 6 vengono illustrate le principali conclusioni del lavoro.In order to ensure optimal growing conditions inside greenhouse it becomes necessary a very close control of the internal climate conditions. In the first section, the available conditioning plant solutions are described. However, these systems generally require high investment costs. In addition, also high operational costs are required for an efficient solution without reducing yield crop or quality. Therefore, the winter conditioning of the internal air of a greenhouse occurs by means of fossil fuels. The use of a mechanical ventilation system contributes to a proper control of temperature, relative humidity and CO2 rate. However, the literature about the application of mechanical ventilation with heat recovery applied in greenhouses conditioning is very poor. For this purpose a research is being carried out. In section 2 a prototype of a mechanical ventilation unit and two climate rooms, for the reproduction of external and internal (built in laboratory) conditions, are described. The recovery unit is equipped with a heat pump and is able to increase the thermal energy recovered by the flow of exhaust air and through a high efficiency heat exchanger. A first study was carried on to evaluate the energy performances of the system during the control of temperature in winter season. Tests reported in section 3 were performed at different temperature values of simulated outdoor air TO (-5 °C, 0 °C, 5 °C and 10 °C) and a fixed (reference) internal simulated greenhouse temperature (20 °C). Each trial was performed with a ventilation flow rate of 535 m3/h. The resulting Coefficient Of Performance of the overall system (COPs) is 9.50 at 0 °C, 8.86 at 5 °C and 6.62 at 10 °C respectively. It has to be highlighted that during the trials carried out at -5°C the compressor behaved as an on-off type. This is due to a safety mechanism for the defrost of the evaporator. In addition, the ventilation flow rate was reduced to avoid a too low value of the supply air temperature. For the other trials (TO = 0 °C or 5 °C), the overall COPs decreases when the external temperature increases, due to a lower difference between external and indoor air enthalpy. To study a real case the mechanical ventilation unit was also installed at service of a greenhouse at Vivaio Verde Molise, Termoli – Italy. The experimental apparatus, described in detail in section 4, consists of the mechanical ventilation system, a perforated duct for air distribution, a fog system to adjust humidity and a supervision system to acquire the field data. Another dedicated supervision system allows measuring and collecting all the parameters of the prototype, such as thermophysical parameters of the airflow, thermophysical parameters of the refrigerant circuit of the heat pump, status and alarms of the unit. First tests, carried out on temperature control in winter season, are analysed in section 5. They show that the indoor air temperature (set at 27 °C) is suitable regulated by driving the unit with the reference probe installed on the recovery side. Only an offset of few Celsius degree is observed due to duct heat loss and the recovery grid placed on one side. Moreover, the mechanical ventilation system had also shown notable energy performance: COPs (mean value) of 5.4 and 5.7 at outdoor air temperature of 18.0 °C and 15.7 °C respectively. Finally, section 6 displays the main conclusions of the present work.
6
Ahmad, Mardiana Idayu. "Novel heat recovery systems for building applications." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/13852/.
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The work presented in this thesis will explore the development of novel heat recovery systems coupled with low carbon technologies, and its integration to become one device with multifunction (building integrated heat recovery/cooling/air dehumidifier. In the first part of this thesis, an experimental performance of an individual heat recovery unit using Micro Heat and Mass Cycle Core (MHM3C) made of fibre papers with cross flow arrangement has been carried out. The unit was tested in an environmental control chamber to investigate the effects of various parameters on the performance of heat/energy recovery unit. The results showed that as the airflow rate and temperature change increase, the efficiency decreases whilst recovered energy increases. Integrating heat recovery system in energy-efficient system represents significant progress for building applications. As part of the research, the integration of heat recovery using a cross-flow fixed-plate with wind-catcher and cellulose fibre papers of evaporative cooling units have allowed part of the energy to be recovered with the efficiency of heat recovery unit ranged from 50 to 70%, cooling efficiency ranged from 31 to 54%. In another case, the integration of heat recovery system with building part so called building integrated heat recovery (BIHR) was explored using polycarbonate plate with counter-flow arrangement. It introduces a new approach to MVHR system, an established technology that uses a modified insulation panel, linking the inside and outside of a building, to recover heat while extracting waste air and supplying fresh air. In this configuration it is not only acts a heat recovery, but also as a contribution to building thermal insulation. From the experiments conducted, it was found that through an energy balance on the structure, the efficiency of BIHR prototype was found to be 50 to 61.1 % depending on the airflow rate. This efficiency increases to the highest value of 83.3% in a full-scale measurement on a real building in Ashford, Kent as the area of heat transfer surface increases. The increasing of heat surface area again proved a better performance in terms of efficiency as the results on another full scale measurement on a real house in Hastings, Sussex showed to be 86.2 to 91.7%. With the aiming to have a high performance system, a new improvement design of BIHR' corrugated polycarbonate channels with four airstreams has significant advantages over the previous prototype BIHR with two airstreams. The recovered heat is increased by more than 50%. With the issue of thermal comfort in hot region area and problems with conventional air conditioning system, a study of BIHR system with fibre wick structure for different hot (summer) air conditions using different working fluids was carried out. For the first case, water was used to give a direct evaporative cooling effect which is suitable to evaluate the system performance under hot and dry climatic conditions and the second case, potassium formate (HCOOK) solution was used as liquid desiccant for dehumidification under hot and humid climate conditions. By supplying the water over the fibre wick structure, with a constant airflow rate of 0.0157m3/s, the efficiency increased with increasing intake air temperature. The efficiency ranged from 20 to 42.4% corresponding to the minimum and maximum of intake air temperature of 25°C and 38.2°C, respectively. With the variation of airflow rate, the efficiency of the system was found to be 53.2 to 60%. In second case, the HCOOK solution with concentration of 68.6% has been selected as the desiccant and for a defined airflow rate of 0.0157m3/s, heat recovery efficiency of about 54%, a lower desiccant temperature of 20°C, with higher intake air temperature and relative humidity produces a better dehumidification performance with a good moisture absorption capacity. Therefore, this system is expected to be used efficiently in hot and humid regions. The research is novel in the following ways: • The development of multifunction device in one system; building integrated, heat recovery, cooling, desiccant dehumidification. • The design and development of BIHR is an advanced technology of building thermal insulation and heat recovery. The novel BIHR -fibre wick cooling/dehumidification system has the potential to compete with conventional air conditioning systems under conditions involving high temperature and high moisture load.
7
Liu, Shuli. "A novel heat recovery/desiccant cooling system." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/11602/.
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The global air temperature has increased by 0.74± 0.18 °C since 1905 and scientists have shown that CO2 accounts for 55 percentages of the greenhouse gases. Global atmospheric CO2 has been sharply increased since 1751, however the trend has slowed down in last fifty years in the Western Europe. UK and EU countries have singed the Kyoto agreement to reduce their greenhouse gas emissions by a collective average of 12.5% below their 1990 levels by 2020. In the EU, 40% of CO2 emission comes from the residential energy consumption, in which the HVAC system accounts for 50%, lighting accounts for 15% and appliances 10%. Hence, reducing the fossil-fuel consumption in residential energy by utilizing renewable energy is an effective method to achieve the Kyoto target. However, in the UK renewable energy only accounts for 2% of the total energy consumption in 2005. A novel heat recovery/desiccant cooling system is driven by the solar collector and cooling tower to achieve low energy cooling with low CO2 emission. This system is novel in the following ways: • Uses cheap fibre materials as the air-to-air heat exchanger, dehumidifier and regenerator core • Heat/mass fibre exchanger saves both sensible and latent heat from the exhaust air • The dehumidifier core with hexagonal surface could be integrated with windcowls/catchers draught • Utilises low electrical energy and therefore low CO2 is released to the environment The cooling system consists of three main parts: heat/mass transfer exchanger, desiccant dehumidifier and regenerator. The fibre exchanger, dehumidifier and regenerator cores are the key parts of the technology. Owing to its proper pore size and porosity, fibre is selected out as the exchanger membrane to execute the heat/mass transfer process. Although the fibre is soft and difficult to keep the shape for long term running, its low price makes its frequent replacement feasible, which can counteract its disadvantages. A counter-flow air-to-air heat /mass exchanger was investigated and simulation and experimental results indicated that the fibre membranes soaked by desiccant solution showed the best heat and mass recovery effectiveness at about 89.59% and 78.09%, respectively. LiCl solution was selected as the working fluid in the dehumidifier and regenerator due to its advisable absorption capacity and low regeneration temperature. Numerical simulations and experimental testing were carried out to work out the optimal dehumidifier/regenerator structure, size and running conditions. Furthermore, the simulation results proved that the cooling tower was capable to service the required low temperature cooling water and the solar collector had the ability to offer the heating energy no lower than the regeneration temperature 60℃. The coefficient-of-performance of this novel heat recovery/desiccant cooling system is proved to be as high as 13.0, with a cooling capacity of 5.6kW when the system is powered by renewable energy. This case is under the pre-set conditions that the environment air temperature is 36℃ and relative humidity is 50% (cities such as Hong Kong, Taiwan, Spain and Thailand, etc). Hence, this system is very useful for a hot/humid climate with plenty of solar energy. The theoretical modelling consisted of four numerical models is proved by experiments to predict the performance of the system within acceptable errors. Economic analysis based on a case (200m2 working office in London) indicated that the novel heat recovery/desiccant cooling system could save 5134kWh energy as well as prevent 3123kg CO2 emission per year compared to the traditional HVAC system. Due to the flexible nature of the fibre, the capital and maintenance cost of the novel cooling system is higher than the traditional HVAC system, but its running cost are much lower than the latter. Hence, the novel heat recovery/desiccant cooling system is cost effective and environment friendly technology.
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Chen, Xiangjie. "Investigations of heat powered ejector cooling systems." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/29721/.
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In this thesis, heat powered ejector cooling systems was investigated in two ways: to store the cold energy with energy storage system and to utilize low grade energy to provide both electricity and cooling effect. A basic ejector prototype was constructed and tested in the laboratory. Water was selected as the working fluid due to its suitable physical properties, environmental friendly and economically available features. The computer simulations based on a 1-0 ejector model was carried out to investigate the effects of various working conditions on the ejector performance. The coefficients of performance from experimental results were above 0.25 for generator temperature of lI5°C-130 °C, showing good agreements with theoretical analysis. Experimental investigations on the operating characteristics of PCM cold storage system integrated with ejector cooling system were conducted. The experimental results demonstrated that the PCM cold storage combined with ejector cooling system was practically applicable. The effectiveness-NTU method was applied for characterizing the tube-in-container PCM storage system. The correlation of effectiveness as the function of mass flow rate was derived from experimental data, and was used as a design parameter for the PCM cold storage system. In order to explore the possibility of providing cooling effect and electricity simultaneously, various configurations of combined power and ejector cooling system were studied experimentally and theoretically. The thermal performance of the combined system in the range of 0.15-0.25 and the turbine output between 1200W -1400W were obtained under various heat source temperatures, turbine expansion ratios and condenser temperatures. Such combined system was further simulated with solar energy as driving force under Shanghai climates, achieving a predicted maximum thermal efficiency of 0.2. By using the methods of Life Saving Analysis, the optimized solar collector area was 30m2 and 90m2 respectively for the system without and with power generation. The environmental impacts and the carbon reductions of these two systems were discussed.
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Chen, Jiu Fa. "Optimization of vapour compression air conditioner/heat pumps using refrigerant mixtures." Thesis, University of Leeds, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343629.
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Boswell, Michael John. "Gas engines for domestic engine-driven heat pumps." Thesis, Oxford Brookes University, 1992. http://radar.brookes.ac.uk/radar/items/37f7ed18-4b86-6ab3-8ba6-1c27947fb1ce/1.
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An experimental and theoretical investigation has been undertaken into the performance of a small prototype, water-cooled, gas-fuelled engine designed for use as a domestic heat pump prime mover. In light of the application, fuel type and capacity, both experimental and theoretical study of similar engines is at best poorly documented in the literature. A comprehensive engine test facility has been set up, incorporating extensive calorimetry, a separate lubrication system, emissions monitoring and high speed data acquisition for in-cylinder pressure measurement and analysis. Two new experimental cylinder heads have been designed together with new induction and exhaust systems, both to improve performance and to enable further investigation of the combustion process. A preliminary parametric study of the combustion process established that the thermal efficiency and emission levels are strongly dependent on operational and design variables and that a lean, fast-burning combustion process in a slow speed engine coupled with careful control of other operating variables had the potential for improving efficiency, reducing emissions, and lowering frictional losses and noise levels with enhanced durability. Accordingly, new information has been obtained relating to rates of heat release, energy flows and emission levels over a wide range of design and operating conditions with utility for and consistent with an envelope of conditions appropriate to such a lean burn strategy. Modelling techniques have been developed and used as diagnostic tools in conjunction with the experimental data to investigate the influence of operating and design variables on rates of heat release and energy flows. The models have been validated using the experimental data over a wide range of operating conditions and incorporated into a thermodynamic engine model for use as a sub-model in an overall heat pump model. The experimental and theoretical programme has provided a valuable insight into the lean burn strategy and realised a considerable improvement in the performance of the prototype engine. The theoretical study benefits from a new approach to small gas engine design and development.
11
Ward, Jack. "Conventional and modular design of domestic heat pumps." Thesis, Sheffield Hallam University, 1999. http://shura.shu.ac.uk/20498/.
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This thesis is concerned with an experimental and theoretical investigation of domestic heat pumps. The development of heat pumps in the 1970's did not meet the original expectations and this thesis examines the reasons why. The items considered included cycling and unsteady conditions created whilst matching the heat pump's output to meet a space heating load. A detailed study was made of the hermetically sealed refrigerant compressor, the heat exchangers, and the refrigerant pressure and temperature control systems. In addition to the conventional heat pump a study was made of the advantages gained from modular designed heat pumps. The application of heat pumps to U.K. dwellings and climatic conditions was studied together with the suitability of thermostatic control. Initial studies were made of the operation of a demonstration unit. This showed how intermittent operation would reduce a heat pump performance and was followed by the development of a computer model which simulated the complete refrigerant circulation system. This allowed a study to be made of a heat pump performance at part load conditions. A computer model of the complete refrigerant cycle was developed which aided in the design and construction of a heat pump which used refrigerant R12. This was followed by the construction of a second test rig using R 134(a). The completed R 134(a) test rig was installed in an environmental chamber which could simulate outdoor weather conditions. Results from the test rigs indicated that the performance was greatly affected by on/off cycling an item that was further investigated.
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Ahmad, S. "Heat exchanger networks : Cost tradeoffs in energy and capital." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376511.
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Houston, Stephen Douglas. "Tube-side flow and heat transfer in package boilers." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/804.
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James, K. A. "Dynamic mathematical modelling of refrigeration systems and heat pumps." Thesis, London South Bank University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383651.
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McGurn, Sean J. T. "Application of heat transfer models to boiler fouling monitoring." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282256.
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Mohammad, W. S. "Space air-conditioning of mechanically-ventilated rooms : computation of flow and heat transfer." Thesis, Cranfield University, 1986. http://hdl.handle.net/1826/4022.
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Computational studies of two- and three-dimensional, turbulent
recirculating flows within mechanically-ventilated enclosures are
reported. Two principal cases are examined: (i) two-dimensional
offset jets: and (ii) three-dimensional flow induced in rooms by
supply jets emanating from low or high side-wall registers. The
calculations were undertaken using iterative finite-domain proceedures
which solve the conservation equations for mass, momentum and
enthalpy, together with additional transport equations for the
turbulent kinetic energy and its dissipation rate . The effect of
buoyancy waS. explicitly accounted for when modelling these equations,
in order that they could be employed to simulate buoyant flow in
ventilated rooms. Computations of the mean velocity, temperature and
convective heat transfer distribution are reported, and compared with
experimental data where available.
A modified version of the two-dimensional elliptic code of Pun
and Spalding (1977) was employed to simulate the offset jet case.
These involve the discharge of a turbulent jet parallel to a flat
surface and eventually attaching to it. The investigations covered a
wide range of offset ratio (3.5-32.4). and the computed flow
properties are compared with measurements from several sources. These
comparisons show good agreement downstream of the reattachment point,
while some discrepancies are evident upstream from this location. The
differences therefore occur mainly in the recirculating flow region,
and are believed to arise from shortcoming in the starting profiles,
the turbulance model and the treatment of the near-wall flow.
A three-dimensional elliptic finite-domain code was developed to
simulate the complex, jet-induced flow within rectangular enclosures.
The code was verified using both laminar and turbulent flow test cases
on simpler geometries. Comparisons with the measurements and
predictions reported by previous researchers were employed for this
purpose. Subsequentlyr the ventilated room simulations were
undertaken using three different ventilation arrangements with thermal
conditions corresponding to isothermall non-buoyant (constant
property) and buoyancy"affected flows. The computations were again
compared with experimental and numerical predictions of previous
researchers. This comparison displayed generally good agreement with
these sources.
A study of the flow and convective heat exchange within a
warm-air heated rom, for which buoyancy effects are significant# is
also reported in a bound paper (Alamdari, Hammonda nd Mohammad, 1986)
for three different heat loads. Its aim to assess the balance between
accuracy and economy provided by the present higher-level method
compared with the intermediate-level convection model of Alamdari and
Hammond (1982) when used to supply building thermal simulation
programs with accurate convection heat transfer data. The computed
results of both models were compared, and indicate that the
intermediate-level is a valuable alternative source that can satisfy
the needs of building thermal modellers. It provides resonable
accuracy at a very modest cost in computing terms.
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Mempouo, B. "Investigations of novel heat pump systems for low carbon homes." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12043/.
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The European standard EN15450 states that the Coefficient of Performance (COP) target range for a Ground Source Heat Pump (GSHP) installation should lie within the range of 3.5 to 4.5; when used for heating a building, and a typical Air-Source Heat Pump (ASHP) has a COP of 2.0 to 3.0 at the beginning of the heating season and then decrease gradually as the ambient air becomes cooler, whereas a typical GSHP is in the range of 3.5 –4.0, also at the beginning of the heating season and then decrease gradually as heat is drawn from the ground. For these reasons, in the middle of winter, when the COP drop, the heat pumps can generally only be considered as a ‘pre-heating’ method for producing higher temperature heat such as domestic hot water. In addition soil presents certain difficulties, due to the high cost of drilling to position coils in the ground compare to air source, although frost formation on the evaporator in winter limits also limit the use of air source. Though technology advances or are needed to overcome those issues. The aims of this project, therefore, were firstly to reduce the drilling length of the ground heat exchanger of the ground source heat pumps and to maintain high COPs of the air and ground source heat pumps from beginning to the end of the heating season; and secondly to develop a viable alternative evaporator for air source heat pumps to reduce frost formation during winter. These were achieved; the first aim through the combination of ground loops with solar-air panels or solar roof/collectors roof to ground heat exchangers loops to reduce the length of the boreholes, and to reduce the freezing effects around the boreholes, hence increase or maintain a constant temperature during heating season. The second aim was also achieved through development and validation of novel air source heat pump evaporator, using Direct Expansion (DX) black flat plate absorber or/and vacuum tubes for frost reduction. In this thesis, in order to achieve the above aims; four aspects of investigations have been independently investigated as following: 1- Preliminary investigation on Direct Expansion (DX) Solar Source Heat Pump system. 2- Investigation on the performance of the DX- PV/heat pipe heat pump system to reduce frost and enhance the COP of the air source heat pumps, 3- A small scale testing on the heat injection on energy piles for residential buildings for earth charging by means of solar roof/collectors 4- A field trial testing of the performance of the combination of solar-air thermal collectors with conventional GSHP with shorter ground heat exchangers (48m deep) to charge the ground and reduce freezing effects around the piles after heating cycle. From the simulation results, the novel PV/hp-HP system has a COP ranging from 4.65 to 6.16 with an average of 5.35. The condenser capacity ranging from 33 to 174 W would provide the heat source for space heating and domestic hot water. The energy performance of the novel PV/hp-heat pump was not as good as expected due to the low solar radiation. It should be much better in some low latitude locations with better solar radiation. The results of this thesis have shown that the length of ground source boreholes could be considerably reduce by about 60% compare to conventional boreholes using a combination of solar-air collectors with the GSHP and the average COP of 3.7 was achieved.
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Zhao, Xudong. "Investigation of a novel heat pipe solar collector/CHP system." Thesis, University of Nottingham, 2003. http://eprints.nottingham.ac.uk/11255/.
Full textAbstract:
The European Union has an ongoing commitment to reducing CO2 emission as highlighted by its agreement at the Kyoto Summit. One approach to achieving these reductions would be to develop alternative energy sources for major energy demanding sectors. In the EU, about 40% of all energy consumed is associated with buildings and of this, about 60% is utilised in the housing sector. A major part of the energy demand of buildings could be met by utilising renewable energy sources, e.g. solar energy. Existing large-scale plants for power generation prevent efficient utilisation of the waste hot water produced. This means that to meet electricity demand, vast quantities of fossil fuels are burnt releasing unwanted pollutants (e.g., CO2 and NOx) into the atmosphere. Over the last decade, small-scale CHP plants have been introduced for many applications with proven environmental and economic benefits. In addition, solar energy has been used to generate electricity and provide hot water in conjunction with the CHP plants. Investigation of a hybrid heat pipe solar collector/CHP system was carried out in this research. The system is powered by solar and gas energy as well as the boiler waste heat to provide electricity and heating for residential buildings. Compared to the relevant system configurations, this system has the following innovative features: The solar collector was integrated with exhaust flue gas channels that allowed both solar energy and waste heat from exhaust gas to be utilised. Heat pipes as high efficiency heat transfer devices were incorporated in the collector panel. Both miniature and normal heat pipes were investigated, and this resulted in two types of collectors, e.g., thin membrane heat pipe solar collector, and hybrid heat pipe solar collector, to be produced for this application. A compact, lightweight turbine was applied in this system. Novel refrigerants, including n-pentane and hydrofluoroethers (HFEs), were employed as the working fluids for the CHP system. Use of the system would save primary energy of approximately 3,150kWh per year compared to the conventional electricity and heating supply systems, and this would result in reduction of CO2 emission of up to 1.5 tonnes. The running cost of the proposed system would also be lower. The research initially investigated the thermal performance of several heat pipes, including micro/miniature heat pipes, normal circular and rectangular heat pipes, with/without wicks. An analytical model was developed to evaluate the heat transport capacity for these heat pipes. A miniature heat pipe with parallel piped channel geometry was proposed. The variation of heat transport capacity for either micro/miniature or normal heat pipes with operation temperature, liquid fill level, inclination and channel geometry were investigated. Investigation of the operating characteristics of the selected heat pipes, e.g., two miniature and one mini heat pipes, and two normal heat pipes, was then carried out using both the numerical technique and experimental testing. It was found that the results from tests were in good agreement with the numerical predictions when the test conditions were close to the simulation assumptions. The research work further involved the design, modelling, construction and tests of two innovative heat pipe solar collectors, namely, the thin membrane heat pipe solar collector and the hybrid heat pipe solar collector. A computer model was developed to analyse the heat transfer in the collectors. Two collector efficiencies, η and η1, were defined to evaluate their thermal performance, which were all indicated as the function of a general parameter (tmean-ta)/In. Effects of the top cover, manifold as well as flue gas temperature and flow rate (for hybrid collector only) on collector efficiencies were investigated using the computer model developed. Laboratory tests were carried out to validate the modelling predictions and experimentally examine the thermal performance of the collectors. Comparison was made between the modelling and testing results, and the reasons for error formation were analysed. The research then considered the issues of the micro impulse-reaction turbine, which was another part of the integrated system. The structure configuration, coupling pattern with the generator as well as internal geometry contour of the turbine were described. The velocity, pressure and turbulent kinetic energy of the flow in the turbine were determined using numerical CFD prediction. In addition, experimental tests were carried out using a prototype system. The results of CFD simulation and testing show good agreement. This indicates that CFD can be used as a tool of optimizing turbine geometry and determining operating conditions. The research finally focused on the integrated system which brought the heat pipe solar collector, boiler and micro turbine together. The individual components, configurations and layout of the system were illustrated. Theoretical analysis was carried out to investigate thermodynamic cycle and heat transfer contained in the combined system, which is based on the assumption that the system operated on a typical Rankine cycle powered by both solar and gas energy. Tests for the prototype system was carried out to realistically evaluate its performance. Two types of turbine units were examined; one is an impulse-reaction turbine, and the other is a turbo-alternator. The turbo-alternator was found to be too small in capacity for this system thereby affecting its output significantly. The micro impulse reaction turbine was considered a better option. A typical testing showed that the majority of heat required for the turbine operation came from the boiler (7.65kW), and very little (0.23kW) from the solar collector. The gas consumption was 8.5kW. This operation resulted in an electricity output and domestic hot water generation, which were 1.34kW and 3.66kW respectively. The electrical efficiency was 16% and the thermal efficiency was 43%, resulting in an overall efficiency of 59%. Increasing the number of the collectors used would result in reduced heat output from the boiler. This would help in improving system performance and increasing efficiencies. In this application, number of collectors used would be 4 as the flue gas flow rate would only be sufficient to provide 4 to 5 such collectors for heat recovery. The research resulted in the proposal of another system configuration. The innovative concept is illustrated in Chapter 8, and its key technical issues are discussed.
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El-Hawat, Salem M. "Numerical modelling of flow and heat transfer for high-performance surfaces." Thesis, University of Brighton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251804.
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Tomski, Thomas. "The design of shell-and-tube heat exchangers using expert systems." Thesis, University of Brighton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314803.
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White, Peter. "On the application of artificial intelligence techniques to heat exchanger design." Thesis, University of Ulster, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281354.
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Al-Dadah, Raya Khalil. "Electrohydrodynamic boiling heat transfer enhancement at the evaporator of refrigeration plants." Thesis, London South Bank University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386293.
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Babus'Haq, Ramiz F. "Optimal heat transfer design for district-heating and cooling pipelines in air-filled cavities." Thesis, Cranfield University, 1986. http://hdl.handle.net/1826/4214.
Full textAbstract:
District-heating and/or cooling systems are gradually becoming
popular all over the world for heating and/or cooling of
large premises.
Current conventional practice for the DHC underground
distribution networks is to place the supply and the return pipelines
side-by-side in air-filled trencRe's. However, t present
investigation has shown that by optimising the location of the
pipelines, the thermal insulation provided by the air around the
pipes can be maximised. This is achieved by placing the hot pipeline
above the cold one, the exact position depending upon the
temperatures involved. For most purposes, it is recommended that
the displacement ratio for the hot pipe is to be at -0.7 or -0.08
and that of the cold pipe at 0.05 or 0.67 for district heating or
cooling respectively [i. e. the hot and cold pipes being placed in
the upper and lower halves of the trench respectively].
Each chapter is presented in such a way that it can be read
independently of the others as far as possible.
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Fu, Yu. "Investigation of solar assisted heat pump system integrated with high-rise residential buildings." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14582/.
Full textAbstract:
The wide uses of solar energy technology (solar thermal collector, photovoltaic and heat pump systems) have been known for centuries. These technologies are intended to supply domestic hot water and electricity. However, these technologies still face some barriers along with fast development. In this regards, the hybrid energy system combines two or more alternative technologies to help to increase the total efficiency of the system. Solar assisted heat pump systems (SAHP) and photovoltaic/thermal collector heat pump systems (PV/T-HP) are hybrid systems that convert solar radiation to thermal energy and electricity, respectively. Furthermore, they absorb heat first, and then release heat in the condenser for domestic heating and cooling. The research initially investigates the thermal performance of novel solar collector panels. The experimental results indicate an average daily efficiency ranging from 0.75 to 0.96 with an average of 0.83. Compared with other types of solar collectors, the average daily efficiency of novel solar thermal collectors is the highest. The research work further focuses on the integrated system which combines solar collector and air source heat pump (ASHP). The individual components, configurations and layout of the system are illustrated. Theoretical analysis is conducted to investigate thermodynamic cycle and heat transfer contained in the hybrid system. Laboratory tests are used to gauge the thermal performance of the novel SAHP. A comparison is made between the modelling and testing results, and the reasons for error formation are analysed. The research then considers the specially designed PV/T collector that employs the refrigerant R134a for cooling of PV modules and utilizes the glass vacuum tubes for reducing the heat loss to the ambient air. The PV/T collector consists of 6 glass vacuum tube-PV module-aluminium sheet-copper tube (GPAC) sandwiches which are connected in series. The theoretical analysis and experimental tests all give the satisfactory results of up to 2.9% improvement of electrical efficiency compared with those without cooling. The research finally focuses on the integrated heat pump system where the PV/T collector acts as evaporator. Based on the energy balance of the four main components of the heat pump system, a mathematical model of the heat pump system is presented. When the instantaneous ambient temperature and solar radiation are provided, results are obtained for the spatial distributions of refrigerant conditions, which include temperature, pressure, vapour quality and enthalpy. Detailed experimental studies are carried out in a laboratory. Three testing modes are proposed to investigate the effect of solar radiation, condenser water flow rate and condenser water supply temperature on energy performance. The testing results show that an average coefficient of performance (COP) reached 3.8,4.3 and 4.0 under the three testing modes with variable radiation, condenser water supply water temperature and water flow rate, respectively. However, this could be much higher for a large capacity heat pump system using large PV panels on building roofs. The COP increases with the increasing solar radiation, but decreases as the condenser water supply temperature and water flow rate increases.
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Yik, Frances Wai Hung. "Methodologies for simulating heat and moisture transfer in air-conditioned buildings in sub-tropical climates." Thesis, Northumbria University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357106.
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Byerley, Aaron R. "Heat transfer near the entrance to a film cooling hole in a gas turbine blade." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329915.
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Worall, Mark. "An investigation of a jet-pump thermal (ice) storage system powered by low-grade heat." Thesis, University of Nottingham, 2001. http://eprints.nottingham.ac.uk/11111/.
Full textAbstract:
This thesis investigates a novel combination of a jet-pump refrigeration cycle and a thermal (ice) storage (TIS) system that could substantially reduce the electrical energy requirements attributable to comfort cooling.Two methods of TIS were identified; spray ice TIS would use evaporative freezing to store ice on a vertical surface,and encapsulated ice TIS would freeze a bed of encapsulated elements by sublimation freezing.Thestudy also investigates jet-pump refrigeration at partload and a convergent-divergent design manufactured from a thermoset plastic to make recommendations for performance enhancement for a system that has a low COP. An experimental rig was built to investigate the novel concepts in the laboratory. Encapsulated ice TIS was superior to spray ice TIS because, for the same nominal secondary flow, sublimation freezing causes an increase in coolth storage rate of about 10 % compared to evaporative freezing. Encapsulated ice stores experience difficulties in fully discharging their coolth (approximately 6% in this case), but spray ice TIS can be used to produce an ice/brine slurry enabling all of the ice to be used, and so may be more suitable if the unmelted ice represents a large proportion of the cooling capacity. Approximately 85 % to 90 % of the ice formed on the vertical surface during spray ice TIS testing was formed by evaporative freezing from a falling film. At high saturation conditions, heat is transferred mainly by conduction across the falling film. Both the growth of an ice layer on a vertical surface and freezing of encapsulated elements were found to be successful, but a large data spread was observed during spray ice TIS testing. It was thought that a variation in the steady-state saturation conditions in the evaporator/ice store was caused by variability of droplet size distribution from the spray nozzle flow, which may make a full-scale system unreliable. The COP of the spray ice TIS system was approximately 0.15 compared to a COP of approximately 0.25 found during encapsulated ice TIS testing. The difference was because of the use of an over-expanded primary nozzle, which restricted secondary flow and increased momentum losses. A primary nozzle that expands close to the design evaporator saturation conditions should be used to maximise entrainment ratio. The COP of a jet-pump TIS is low, but a system designed to operate at off-peak periods could increase the COP to about 0.8 by taking advantage of the lower ambient conditions. The measurement of entrainment ratio was used successfully to determine ice storage rate and COP. This was valid because of the assumption that the saturation conditions in the evaporator/ice store approached steady-state. However, over longer periods that would be found in large-scale systems, the ice storage rate and entrainment ratio may fall substantially. The steady-state assumption could still be used to observe the change in evaporator conditions by sampling over short time intervals (30 minutes). At part-load, increases in evaporator saturation temperature could increase entrainment ratio substantially (50 % increase) for only a small reduction in critical pressure lift ratio Ns *(15 % reduction). A variation in chilled water temperature could be used to boost entrainment ratio at the peak demand. The variation in Ns* is too small to use this strategy to control the jet-pump with respect to condenser operating conditions. The entrainment ratio is approximately proportional to the diff-user to primary nozzle area ratio. A doubling of entrainment ratio was attained for only a 15% reduction in Ns*. The change in geometry from a constant area throat to a convergent-divergent design caused the flow through the jet-pump to vary with outlet conditions indicating that secondary flow was not choked. Higher entrainment ratios and pressure lift ratios were observed, but the entrainment ratio varied with outlet conditions in the form of peaks and troughs, making its operation unpredictable. This was thought to be caused by the restriction in secondary flow area due to the interaction of the primary jet and the curved wall. The convergent-divergent design manufactured from a thermoset plastic was successfully tested, showing that a plastic material can be used as a material of construction. In principle, a large number of jet-pump units could be manufactured from a single mould, reducing the first cost. The investigation proved the concept of jet-pump TIS. Waste-heat could be utilised over 24 hours and year round, increasing the efficiency of the process. The use of a convergent-divergent throat design, multiple geometry jet-pumps and operation at off-peak periods can maximise the performance over a cooling season, and be competitive with other TIS and chiller systems. The mass production of jet-pumps using injection moulding techniques could reduce substantially the capital cost of a system. All of these factors should encourage the development of such systems, so that the harmful emissions caused by the use of air conditioning systems can be minimised.
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Grbál, Jakub. "Analýza větrání banky." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409864.
Full textAbstract:
The aim of the diploma thesis is the simulation of different types of air conditioners using the CFD methods. The main goal of this thesis is to design the most suitable type of air conditioning in the consideration room, due to the air flow rate in the residental area. The conclusion of the work is to devote the design of air conditioning system with the application of selected type of air conditioning based on the results of CFD simulations.
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Tanton, D. M. "Some aspects of the use of water-filled heat stores in gas-fired central-heating systems." Thesis, Cranfield University, 1986. http://hdl.handle.net/1826/4186.
Full textAbstract:
Water-filled heat stores present a convenient, relatively
inexpensive means of optimising the use of diminishing gas stocks for
the central-heating of buildings. The British Gas Corporation
recently launched a series of central-heating units with storage, for
use in the domestic sector, whose benefits include: -
reduced boiler size,
more efficient boiler operation,
load-levelling at the hours of peak gas demand.
This thesis is divided into three parts. Part I examines the
inherent advantage of a with-storage, domestic, central-heating system
over a conventional system, by means of two simple computer-simulation
programs. A minimum efficiency advantage of about 5% is anticipated;
the variation of this advantage with the values of certain key
parameters has been assessed. Part II is an interim report of a
full-scale field trial in the commercial sector; a large (3.3m3) store
was fitted in the heating system of a London school, and its
performance during the first weeks of its operation is presented here.
Returning to the domestic sector, Part III presents a study of the use
of two integral heat exchangers in the storage vessels of the above
domestic units, whereby hot water can be drawn instantaneously. An
attempt to optimise this domestic hot-water facility has been made.
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Chauvet, L. P. J. "Theoretical and experimental evaluations of the convective and conductive heat transfers in a domestic hot-water store." Thesis, Cranfield University, 1991. http://hdl.handle.net/1826/4209.
Full textAbstract:
The design of a water based thermal store for use in a domestic
central heating system has been investigated theoretically,
experimentally and numerically. The transient operation of the
store during both the space heating and domestic hot-water
modes of operation have been investigated separately.
Heat transfer correlations in terms of Nusselt and Rayleigh
numbers have been developed in order to predict the natural
convection heat transfer coefficient for the outside surface of
the horizontal axis finned tube heat exchanger coil located
within the store. These heat-transfer correlations can predict
the value of the heat transfer coefficient with an accuracy of
better than 5% and are in good agreement with existing heat
transfer correlations developed for the same geometry of finned
tubes and modes of heat transfer. The effect of the water flow
rate in the heat exchanger coil on the internal heat transfer
coefficient is also investigated. This flow rate should be
above 4 litre/minute to achieve a high rate of heat-transfer
from the wall of the heat exchanger to the water in the pipe.
A detailed investigation of the use of horizontal and vertical
baffles to increase the effectiveness of heat delivery in the
domestic hot water mode has been carried out. Some improvements
can be achieved by the use of a horizontal flat plate located
in the middle of the store. This plate, when correctly sized
enhances stratification and hence improves the effectiveness of
heat recovery. Vertical plate arrangements and a rectangular
duct situated around the upper heat exchanger coil were found
to be ineffective. However, due to an increased velocity of the
water around the heat exchanger, the external heat transfer
coefficient of the heat exchanger was increased by 12%.
The comparison of experimental observations with computer
simulations of the development of the thermocline in the store
during the space heating mode of operation showed the presence
of a jet in the bottom region of the store at the return inlet.
The jet induces a significant amount of mixing in the store
which reduces the effectiveness of heat recovery. Correlations
in terms of Richardson number and effectiveness of heat
delivery have been developed to characterize the effect of this
jet. An inlet arrangement designed to achieve a Richardson
number exceeding 3 significantly reduces the mixing created by
the jet and can increase the amount of heat delivered in the
space heating mode by approximately 5%.
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Amer, Omar. "A heat pipe and porous ceramic based sub wet-bulb temperature evaporative cooler : a theoretical and experimental study." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43343/.
Full textAbstract:
Worldwide energy demand in buildings represents about 40-50% of the total energy consumption. In hot climates, such as Middle East and North Africa (MENA) countries, about 30% of the national power demand is used for HVAC applications in buildings. This has led to escalation in power demand in buildings for indoor air-cooling and high energy bills. This is exacerbated further by the widespread adoption of energy intensive and commercially dominant vapour compression air conditioning systems as the technology of choice. This research aims to address the potential of novel designs of evaporative cooling systems for space cooling and thermal comfort in buildings with reduced water and energy consumption, and low environmental impact as an alternative to vapour compression where climatically is suitable. High water consumption rates and low cooling effectiveness are some of the issues affecting the performance of existing Indirect Evaporative Coolers (IEC). A new configuration of IEC combining heat pipe heat exchanger and porous ceramic tubes is investigated in this work. The proposed cooler configuration is based on the concept of regenerative IEC system, this system incorporates heat pipes as passive heat transfer elements and porous ceramic tubes as wet medium mounted on the condenser side of the exchanger. The design of the cooler was carried out with consideration for size of the airflows channels, heat pipes for heat transfer, and porous ceramic tubes properties for water evaporation. A mathematical formulation of heat and mass transfer equations was used to develop a computer model to design and optimise the cooling system. Furthermore, a test rig was built to test a laboratory scale cooling unit, evaluate the performance and validate the simulation. The simulation results reveal that the Wet-bulb (WB) effectiveness of the cooler ranged from 0.524 to 1.053, the COP ranged from 6.33 to 17.01, and water consumption rates of the cooler were around 0.875-1.55 (l/kWh) of cooling capacity. Whereas, the experimental performance parameters of the cooler show the WB effectiveness was in the range of 0.422-0.908 for all test conditions, the COP was 4.62-13.16, and water consumption rates varied 0.841-2.82 (l/kWh) of cooling capacity. A good agreement was obtained between the experiments data and numerical results, the maximum errors between measured and computed results was around 3.94% and 4.51% of supply air temperature and humidity, respectively, while the discrepancy was in the range of 8.67-12.90% of the WB effectiveness. The impact of operational and design parameters on the cooler performance was evaluated in a parametric study using the developed numerical model. It was found that increasing the inlet air temperature, decreasing the inlet air flow rate, and/or increasing the working-to-inlet air flow ratio, results in improving the effectiveness and supply air temperature. Whereas, increasing the inlet air wet-bulb temperature depression, increasing the inlet air flow rate, and/or minimising the working-to-inlet air flow ratio leads to enhancing the cooling output and COP of the cooler. Additionally, increasing the thickness and/or the radius of ceramic tube causes a decline of cooler thermal performance. Therefore, it is recommended to operate the cooler at inlet air velocity of 2-2.5 m⁄s, 50% flow ratio of working-to-inlet air, and inlet air relative humidity below 35% for best results of supply air temperature, WB effectiveness, and COP. Whereas, for desert climate conditions, it is recommended to increase the number of heat pipe rows to 20 to insure sufficient cooling effectivity and performance that meet comfort levels. Finally, a brief economic assessment of the cooler annual operational performance for a case study was carried out, this IEC system provide sufficient cooling effectiveness to the conditioned space with significantly low power consumption compared to traditional air conditioner with annual saving of 77.60% of operational costs, and also substantially contribute to minimise CO2 emissions by saving about 86% of electricity consumption.
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Davies, Gareth N. L. "Heat driven adsorption cooling utilising enhanced effective thermal conductivity monolithic adsorbent generators for refrigeration and ice production in developing countries." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364596.
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Kamal, Rajeev. "Optimization and Performance Study of Select Heating Ventilation and Air Conditioning Technologies for Commercial Buildings." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6656.
Full textAbstract:
Buildings contribute a significant part to the electricity demand profile and peak demand for the electrical utilities. The addition of renewable energy generation adds additional variability and uncertainty to the power system. Demand side management in the buildings can help improve the demand profile for the utilities by shifting some of the demand from peak to off-peak times.
Heating, ventilation and air-conditioning contribute around 45% to the overall demand of a building. This research studies two strategies for reducing the peak as well as shifting some demand from peak to off-peak periods in commercial buildings:
1. Use of gas heat pumps in place of electric heat pumps, and
2. Shifting demand for air conditioning from peak to off-peak by thermal energy storage in chilled water and ice.
The first part of this study evaluates the field performance of gas engine-driven heat pumps (GEHP) tested in a commercial building in Florida. Four GEHP units of 8 Tons of Refrigeration (TR) capacity each providing air-conditioning to seven thermal zones in a commercial building, were instrumented for measuring their performance. The operation of these GEHPs was recorded for ten months, analyzed and compared with prior results reported in the literature. The instantaneous COPunit of these systems varied from 0.1 to 1.4 during typical summer week operation. The COP was low because the gas engines for the heat pumps were being used for loads that were much lower than design capacity which resulted in much lower efficiencies than expected.
The performance of equivalent electric heat pump was simulated from a building energy model developed to mimic the measured building loads. An economic comparison of GEHPs and conventional electrical heat pumps was done based on the measured and simulated results. The average performance of the GEHP units was estimated to lie between those of EER-9.2 and EER-11.8 systems. The performance of GEHP systems suffers due to lower efficiency at part load operation. The study highlighted the need for optimum system sizing for GEHP/HVAC systems to meet the building load to obtain better performance in buildings.
The second part of this study focusses on using chilled water or ice as thermal energy storage for shifting the air conditioning load from peak to off-peak in a commercial building. Thermal energy storage can play a very important role in providing demand-side management for diversifying the utility demand from buildings. Model of a large commercial office building is developed with thermal storage for cooling for peak power shifting. Three variations of the model were developed and analyzed for their performance with 1) ice storage, 2) chilled water storage with mixed storage tank and 3) chilled water storage with stratified tank, using EnergyPlus 8.5 software developed by the US Department of Energy. Operation strategy with tactical control to incorporate peak power schedule was developed using energy management system (EMS). The modeled HVAC system was optimized for minimum cost with the optimal storage capacity and chiller size using JEPlus.
Based on the simulation, an optimal storage capacity of 40-45 GJ was estimated for the large office building model along with 40% smaller chiller capacity resulting in higher chiller part-load performance. Additionally, the auxiliary system like pump and condenser were also optimized to smaller capacities and thus resulting in less power demand during operation. The overall annual saving potential was found in the range of 7-10% for cooling electricity use resulting in 10-17% reduction in costs to the consumer. A possible annual peak shifting of 25-78% was found from the simulation results after comparing with the reference models. Adopting TES in commercial buildings and achieving 25% peak shifting could result in a reduction in peak summer demand of 1398 MW in Tampa.
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Maghera-Entwistle, R. I. "Intermittently operated chemical heat pump : Slurried absorption systems and an investigation into the performance characteristics of methanolated potassium hydroxide in powdered form using methanol as the working fluid." Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374001.
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Duarte, Marta. "Heat recovery units in ventilation : Investigation of the heat recovery system for LB20 and LB21 in Building 99, University of Gävle." Thesis, Högskolan i Gävle, Avdelningen för bygg- energi- och miljöteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-21825.
Full textAbstract:
Heating, ventilation and air-conditioning (HVAC) systems are widely distributed over the world due to their capacity to adjust some local climate parameters, like temperature, relative humidity, cleanliness and distribution of the air until the desired levels verified in a hypothetical ideal climate. A review of buildings’ energy usage in developed countries shows that in the present this energy service is responsible for a portion of about 20% of the final energy usage on them, increasing up to 50% in hot-humid countries. In order to decrease this value, more and more different heat recovery systems have been developed and implemented over the last decades. Nowadays it is mandatory to install one of these units when the design conditions are above the limit values to avoid such components, what is possible to verify mostly in non-residential buildings. Each one of those units has its own performance and working characteristics that turns it more indicated to make part of a certain ventilation system in particular. Air-to-air energy recovery ventilation is based on the heat recovery transfer (latent and/or sensible) from the flow at high temperature to the flow at lower temperature, pre-warming the outdoor supply air (in the case of the winter). Therefore, it is important to understand in which concept those units have to be used and more important than that, how they work, helping to visualize their final effect on the HVAC system. The major aims of this study were to investigate the actual performance of the heat recovery units for LB20 and LB21 in building 99 at the University of Gävle and make some suggestions that could enhance their actual efficiency. Furthermore, the energy transfer rates associated to the heat recovery units were calculated in order to understand the impact of such components in the overall HVAC system as also the possible financial opportunity by making small improvements in the same units. To assess the system, values of temperature and flow (among others) were collected in the air stream and in the ethylene-glycol solution that works as heat transfer medium between air streams and is enclosed in pipes that make part of the actual run-around heat recovery units. After some calculations, it was obtained that for the coldest day of measurements, the sensible effectiveness was 42% in LB20 and 47% in LB21, changing to 44% and 43% in the warmer day, respectively. The actual heat transfer representing the savings in the supply air stream is higher on the coldest day, with values of 46 kW in LB20 and 84 kW in LB21, justifying the existence of the heat recovery units even if those ones imply the use of hydraulic pumps to ensure the loop. The low values of efficiency have shown that both heat recovery units are working below the desired performance similarly to the pumps that make part of the same units. This fact, together with the degradation of the units that is possible to observe in the local, indicates that a complete cleaning (followed by a change of the heat transfer medium) of the heat recovery units and a new adjustment of pumps and valves for the further changes, are necessary. By doing this, it is expected to see the year average sensible effectiveness increase to close to 45% in both units which will lead to a potential economic saving of around 41 000 SEK per year.
36
Klučáková, Markéta. "Zpětné získávání tepla ve vzduchotechnice." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-372032.
Full textAbstract:
The diploma thesis solves a project of air-conditioning with heat recovery in the gym and adjacent dressing rooms. Furthermore, experimental measurement of temperature and relative humidity is carried out in one year in an air-conditioning device with a heat recovery heat exchanger.
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Hancerli, Mustafa Yilmaz. "Appropriate Passive Cooling Strategies For Hot And Humid Climates: A Case Study In Cyprus." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609401/index.pdf.
Full textAbstract:
In this study, energy conservation potential of appropriate passive cooling and basic
heat avoidance strategies were investigated for hot and humid climates. Within this
framework, thermal behavior of a case study building that is situated in Cyprus was
assessed by collecting temperature and relative humidity data from various rooms of
the building during certain days in August. Then, by using feasible simulation
strategies of the software tool Summer-Building, the effectiveness of passive cooling
measures in reducing energy consumption were examined, for summer months.
In this context, the case study building was re-evaluated by applying natural
ventilation, night ventilation and ground cooling strategies as well as solar control
and shading devices as overhangs and side fins.
Consequently, based on the results of the evaluation model, it was found that the
proposed passive cooling strategies and basic heat avoidance concepts could provide
more than 50 % energy conservation, relative to the completely air conditioned
reference building, between 1-15 August 2007.
38
Černík, Václav. "Návrh vzduchotechniky a vytápění pro výrobní podnik." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-230487.
Full textAbstract:
This master’s thesis deals with heating and HVAC in production plant ELMET, spol. s r.o. The first part of the thesis concerns reconstruction of the central heating system, which is outdated and unreliable in the time of the writing of the thesis. The second part deals with cooling of mounting of electronics, where technological requirements are not met due to summer overheating. The third part of the thesis concerns ventilation of metalworking hall using waste heat from production machines.
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Snopek, Milan. "Řešení vybraných aspektů chlazení jatek." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226848.
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The topic of my diploma is a solution of selected aspects of cooling slaughterhouses. The main objective is the solution of mechanical cooling from the technical to the physical expression of nature and theoretical foundations comfort cooling.
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Bergr, Josef. "Návrh a optimalizace provozu tepelného čerpadla." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227156.
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The aim of the thesis "Design and optimization of the heat pump" is the project documentation for building permits, finding a suitable source of heat and cold. The problem is solved for a Tesco hypermarket. The device is designed to meet the health, performance and functional requirements for indoor climate. The task of this device is to transport fresh air into the interior cover heat losses in winter and coverage heat gains during the summer. The theoretical part deals with the problem of heat pumps. Special mention is about heat pump air x air. Calculation and design part is a specific proposal, two air conditioners and optimizing for winter. The experimental part deals with the processing of data on existing rooftop units.
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Bareš, Josef. "Návrh větrání a chlazení v rodinném domě." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417131.
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The diploma thesis is focused on a ventilation and cooling design of a family house. Author’s idea was to make summary of theoretical information and project documentation for realization (installation) of the ventilation and cooling. Introduction of the house disposition, theoretical research of a current cooling and ventilation options in residential buildings are parts of this thesis. Next it contains thermal load calculation, two designs of a cooling and three designs of a forced ventilation, dimensioning of the pipelines and financial cost comparison of a purchase, assembly, working and service of a designed systems.
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Belock, Keith Allan. "An energy audit manual for small manufacturing companies with a case study of Maugus Manufacturing Company." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1179851925.
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Tenora, Tomáš. "Solární zisky v budovách." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226020.
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Master’s thesis deals with solar gains in buildings. The thesis presents an overview of the theoretical knowledge to solve solar gain. The thesis deals possibilities of measuring the intensity of solar radiation and evaluation of data from the meteorological station in the experimental part. Application of topic is then used for polyfunctional building. This part aims to show possibilities of design of air conditioning systems for the purpose of making indoor microclimate and their subsequent evaluation.
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Havlátová, Kristýna. "Větrání stravovacích provozů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-371911.
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The master’s thesis deals with design of heat recovery and dehumification for the hotel´s kitchen. The design is made to fullfill functional, hygienic and operational ruqirements for the internal microclimate. The main task of air-conditioning systems is to drain away heat gains and intake of requirement minimum of fresh air. The theoretical part is about analysis of internal microclimate.
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Франовський, Ігор Олександрович, and Ihor Franovskyi. "Дослідження автоматизованої системи управління мікрокліматом приміщень." Master's thesis, Тернопільський національний технічний університет ім. І. Пулюя, Факультет прикладних інформаційних технологій та електроінженерії, Кафедра автоматизації технологічних процесів і виробництв, 2019. http://elartu.tntu.edu.ua/handle/lib/29822.
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Робота виконана на кафедрі автоматизації технологічних процесів і виробництв факультету прикладних інформаційних технологій та електроінженерії Тернопільського національного технічного університету імені Івана Пулюя Міністерства освіти і науки України.
Захист відбудеться «27» грудня 2019 р. о 8.00год. на засіданні екзаменаційної комісії №43 у Тернопільському національному технічному університеті імені Івана ПулюяУ кваліфікаційній роботі розроблено універсальний восьмиканальний мікропроцесорний регулятор-вимірювач регулятор на базі однокристальної мікроЕОМ MSC51 призначений для побудови автоматичних систем контролю і регулювання системи мікроклімату та канального опалення, вентиляційних установок загально-обмінного типу, припливно-витяжної вентиляції канального типу. Прилад виконує наступні основні функції: – дозволяє робити конфігурування функціональної схеми й установку програмованих робочих параметрів за допомогою вбудованої клавіатури керування; – робить вимір фізичних параметрів контрольованих вхідними первинними перетворювачами з урахуванням нелінійності їх «НСХ»; здійснює цифрову фільтрацію вимірюваних параметрів від промислових імпульсних перешкод; – дозволяє робити корекцію вимірюваних параметрів для усунення погрішностей первинних перетворювачів; – здійснює відображення результатів вимірів на вбудованому світлодіодному чотирьохрозрядному цифровому індикаторі; – формує аварійний сигнал при виявленні несправності первинних перетворювачів з відображенням його причини на цифровому індикаторі і при необхідності виводить його на зовнішню сигналізацію; – формує сигнали керування зовнішніми виконавчими механізмами і пристроями відповідно до заданого користувачем законами і параметрами регулювання; – здійснює відображення на вбудованому світлодіодному цифровому індикаторі заданих параметрів регулювання; – формує команди ручного керування виконавчими механізмами і пристроями з клавіатури приладу; – здійснює передачу комп'ютеру інформації про значення контрольованих давачами величин і встановлених робочих параметрів, а також приймає від нього дані на зміну цих параметрів.
The diploma thesis developed a universal eight-channel microprocessor controller-meter controller based on single-crystal microcomputer MSC51 designed for the construction of automatic systems for control and regulation of the system of microclimate and duct heating, ventilation units of general-exchange type, inflow-exhaust ventilation. The device performs the following basic functions: - allows you to configure the functional diagram and to set programmable operating parameters using the built-in control keyboard; - makes measurement of physical parameters controlled by input primary converters taking into account the nonlinearity of their "NSH"; - performs digital filtering of measured parameters from industrial impulse interference; - allows to make correction of measured parameters for elimination of errors of primary converters; - displays the measurement results on the built-in LED four-digit digital indicator; - generates an alarm when a primary converter malfunction is detected by displaying its cause on a digital display and, if necessary, outputs it to an external alarm; - generates control signals for external actuators and devices in accordance with user-defined laws and control parameters; - displays the set control parameters on the built-in LED digital indicator; - generates commands for manual control of actuators and devices from the instrument keyboard; - transmits to the computer information about the values of encoder-controlled values and set operating parameters, and also accepts data from him to change these parameters.
Анотація 3 Зміст 4 Вступ 7 1 Огляд літератури 10 1.1 Вентиляція 10 1.2 Вентиляція з механічним збудженням 10 1.3 Визначення потреби свіжого повітря. 12 1.4 Вимоги до сучасних систем вентиляції. 15 1.5 Кондиціонування повітря 16 1.6 Температура й вологість, швидкість повітря в приміщенні 16 1.7 Великі системи вентиляції 20 2 Науково-методична частина 29 2.1 Моделювання параметрів мікроклімату приміщень 29 2.2 Реалізація математичних моделей для розрахунку параметрів мікроклімату 38 2.3 Визначення ступеню комфортності параметрів мікроклімату. 45 3 Технологічна частина 48 3.1 Технології та методи розподілу повітря в системах управління мікрокліматом 48 3.2.1 Вентиляція перемішуванням 49 3.2.2 Вентиляція витисненням. 50 3.2 Автоматичне керування системою кондиціонування повітря 51 3.3 Залежність енергозбереження, експлуатаційних витрат від технологій систем вентиляції і кондиціонування. 52 4 Конструкторська частина 57 4.1 Призначення пристрою 58 4.2 Умови експлуатації: 59 4.3 Технічні характеристики 59 4.3 Пристрій та функціонування приладу 62 4.3.1. Схема функційна 62 4.3.2 Складові частини схеми 65 4.3.3 Вимірювання вхідних параметрів 68 4.3.4 Опитування давачів 68 4.3.5 Вимір поточних значень вхідних параметрів 69 4.3.6 Цифрова фільтрація вимірів 71 4.3.7 Корекція вимірів 73 4.3.8 Обчислення математичних величин 76 4.3.9 Індикація вимірюваних параметрів 77 4.3.10 Вихідні пристрої 79 4.4 Конструкція приладу 83 4.5 Монтаж приладу на об'єкті 85 4.6 Монтаж зовнішніх зв'язків 86 4.6.1 Загальні вимоги 86 4.6.2 Вказівки по монтажу 87 4.6.3 Підключення приладу 88 4.7 Загальне компонування системи автоматизованого управління параметрами 89 5 Спеціальна частина 91 5.1 Розробка алгоритмів роботи системи 91 5.2 Реалізація алгоритму ШІМ 93 5.3 Розробка основного алгоритму програми управління 95 6 Обгрунтування економчіної ефективності 99 6.1 Оцінка ефективності розробки і впровадження універсальної системи керування мікрокліматичними процесами на базі мікро-ЕОМ MSC 51 99 6.2 Вибір об'єкта для порівняння 99 6.3 Розрахунок капітальних витрат 100 6.4 Розрахунок і порівняння експлуатаційних витрат 100 6.5 Розрахунок амортизаційних відрахувань 100 6.6 Витрати на споживану електроенергію 102 6.7 Витрати на поточний ремонт 103 6.8 Розрахунок інших витрат 106 6.9 Розрахунок ефективності проектованої системи 106 6.10 Розрахунок економічного ефекту від виготовлення та експлуатації системи за розрахунковий період 107 7 Охорона праці та безпека в надзвичайних ситуаціях 110 7.1 Охорона праці 110 7.1.1 Визначення оптимальних умов праці інженера-оператора системи мікроклімату 110 7.1.2 Розрахунок освітленості робочого місця 114 7.2 Безпека в надзвичайних ситуаціях 118 7.2.1 Основні вражаючі фактори ядерних вибухів, їхні параметри і наслідки впливу на людей 118 7.2.2 Методи захисту та безпека підприємств промисловості, відновлення інженерно-технічного комплексу цеху (заводу) 121 7.2.3 Висновки розділу 122 8 Екологія 125 8.1 Актуальність охорони навколишнього середовища 125 8.2 Забруднення довкілля викликані реалізацією дипломного проекту та заходи по їх уникненню 125 8.3 Заходи по зменшенню шкідливих впливів і забруднень 131 Висновок 135 Перелік посилань. 138 Додатки 147
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Kuegler, Kurt W. "Heating, ventilation and air conditioning engineering and design /." Online version of thesis, 1990. http://hdl.handle.net/1850/10982.
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Eftekhari, M. M. "Optimal operation of an air-conditioning plant." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234946.
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Leung, Wai-yip, and 梁偉業. "Indoor air quality and heating, ventilation & air conditioning systemsin office buildings." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31253787.
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Wan, Man Pun. "Comparison of underfloor ventilation systems and ceiling based ventilation system in thermal comfort and indoor air quality aspects /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?MECH%202002%20WAN.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 61-63). Also available in electronic version. Access restricted to campus users.
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Tang, Dechao. "Modelling of heating and air-conditioning system." Thesis, University of Strathclyde, 1985. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21451.
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The shortage of natural resources calls for energy conservation and the changing structure of modern science and technology makes possible the efficient dynamic energy modelling. This thesis presents a general review of existing techniques in the field of building and plant system energy modelling and concentrates on the establishment of a generalised modelling tool - the control volume conservation state space approach - to cope with the developing modern technology. The theoretical basis of this approach is discussed and verified in detail and applications demonstrated to the modelling of HVAC systems and equipment. Using this approach, any component of an HVAC system can be modelled at different levels and the qualities of the model are fully supported by the theoretical background of this approach. A computer programme for heating system simulation has been developed for the purpose of model validation and the validation efforts have been involved in the international cooperated programme of IEA Annex 10 exercises. As a part of group research, the work presented in this thesis has been involved in the development of advanced energy modelling techniques and methodology which has taken place at the ABACUS unit.