1. A Diffusion-Absorption-Refrigeration (DAR) system for air conditioning (DAAC) is developed. It is directly driven by heat, uses a bubble pump to replace the mechanical pump, uses three-component working fluid, and operates under the same system pressure level. Hence, it is quiet, long lasting and environmental friendly. To investigate the practicality of using the DAAC system for air conditioning, the thermodynamic model is derived first, and then an experimental prototype is built for validation. From the experimental results under various operating conditions, it is found that the bubble pump is the key component that dominates the system performance, so it should be designed carefully with respect to the designed cooling capacity and operating condition. Meanwhile, the system also shows good performance under the ambient temperature disturbance. / 2. A novel absorption air conditioning system based on solar energy and energy storage is proposed. This system uses Lithium-Bromide water solution as refrigerant and is powered by solar energy. Moreover, a new energy storage technique is also proposed to transform and store the solar energy in the form of chemical potential difference of the working fluid. Thus, the system flexibility and energy usage efficiency are improved. To validate the system design, the thermodynamic models for the air conditioning system are developed. Then by computer simulation, the system characteristics and performance are achieved under the proposed operation strategy. It is found that the proposed air conditioning system is energy efficient with high energy storage density and shows great potential in the future. / 3. A complex absorption air conditioning system is proposed by using an advanced energy storage technology called Variable Mass Energy Transformation and Storage (VMETS). This system is based on both compression and absorption refrigeration, uses water-LiBr or ammonia-water as working fluid, and can shift the off-peak electric energy for effective air conditioning. The key of the technology is to regulate the chemical potential by controlling the refrigerant mass fraction in the working fluid with respect to time. By using a solution storage tank and a refrigerant storage tank, the energy transformation and storage can be carried out at the desirable time to provide the low cost air conditioning efficiently. Based on the derived system models, the system characteristics and performance under two system strategies, full-storage and partial-storage strategies, are investigated in details. By computer simulation, it is found that the VMETS technology has high energy conversion efficiency. / 4. A novel thermoelectric air conditioning system is developed. Different from the conventional air conditioning systems, this system is based on the thermoelectric effect and semiconductor technology. It consists of thermoelectric (TE) modules, a power supply, a water circulation system and a computer control system. The thermoelectric system has three functions: heating, cooling, and power generation. To improve the efficiency, it uses the so-called symbiotic generation to optimize the energy usage. In order to investigate the system performance, a theoretical model is developed. By computer simulation, it is found that the system can achieve acceptable performance for cooling and heating under a typical condition. A small experimental model is also built, and the testing result confirms the simulation results. / 5. An intelligent thermal comfort controller is developed to improve the comfort level for air conditioning system. This controller adopts Predicted Mean Vote (PMV) as the control objective rather than the conventional temperature control, and takes six variables into consideration. Meanwhile, a kind of direct neural network (NN) control algorithm is designed by combining a proposed energy saving strategy. By computer simulation, it is found that this controller can achieve high comfort level and energy saving for the conventional Heating, Ventilation and Air-Conditioning (HVAC) systems. Moreover, a compact thermal comfort controller is also developed for the DAAC system. / 6. A cost-effective Fault Detection and Diagnosis (FDD) method is proposed for HVAC system to maintain the energy saving and thermal comfort. It combines the model-based method and the neural network classifier, so it is called Model-Based Fault Detection and Diagnosis method (MBFDD). To validate the performance, the MBFDD is applied to a HVAC system by simulation. Based on the derived system models, the output variables sensitive to the faults can be selected. After pre-processing the acquired data under normal and faulty conditions, the MBFDD based on neural network classifier can be trained first, and then used for on-line monitoring and FDD. The simulation results show that this method is efficient for the HVAC system, and is able to enhance the comfort level and energy saving as well as the system health and safety. / Air conditioning system plays an important role in modern living. Every year millions of air conditioning systems are made and sold. Consequently, even small technological improvement may add up to significant energy saving. Currently, most of the air conditioning systems are based on the compression refrigeration technology, which uses electricity as power and chlorofluorocarbon (CFCs) as refrigerant. Facing the ever-increasing energy and environmental crisis in the world, developing energy-efficient and environmental-friendly air conditioning system is of great importance. / This thesis presents the research on developing air conditioning systems by employing several kinds of technologies: (1) absorption refrigeration technology; (2) bubble pump technology; (3) energy storage technology; (4) renewable energy technology; (5) thermoelectric refrigeration technology; (6) thermal comfort control technology; and (7) fault detection and diagnosis technology. Based on these technologies, this thesis addresses the following topics: / Liang Jian. / "June 2006." / Adviser: Ruxu Du. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6700. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 175-194). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

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by Chow Kar Tak, Kelly, Chan Wai Shing, Cheung Wai Hung, Daniel. / Includes questionnaire in Chinese. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves [33]-[35]). / Chapter 1. --- Introduction --- p.1 / Chapter 2. --- The Room Air Conditioners Market in Hong Kong and Zhu Hai --- p.3 / Chapter 3. --- Sample Characteristics --- p.4 / Chapter 4. --- Choice Criteria of Room Air Conditioning Units --- p.7 / Chapter 4.1 --- Country of Brand --- p.12 / Chapter 4.2 --- Country of Production --- p.15 / Chapter 4.3 --- Price --- p.20 / Chapter 4.4 --- Quietness --- p.22 / Chapter 4.5 --- Reliability --- p.23 / Chapter 4.6 --- Additional Features --- p.24 / Chapter 4.7 --- Size --- p.25 / Chapter 5. --- Conclusion --- p.26 / Appendix A -List of Tables / Appendix B -Reference / Appendix C - Survey Questionnaire for Hong Kong / Appendix D - Survey Questionnaire for Zhu Hai

Air-cooled condensers are routinely designed for a variety of applications, including residential air-conditioning systems. Recent attempts at improving the performance of these heat exchangers have included the consideration of microchannel tube, multilouver fin heat exchangers instead of the more conventional round tube-plate fin designs. In most packaged air-conditioning systems, however, the condenser surrounds the compressor and other auxiliary parts in an outdoor unit, with an induced draft fan at the top of this enclosure. Such a configuration results in significant mal-distribution of the air flow arriving at the condenser, and leads to a decrease in performance. This work addresses the issue of mal-distribution by adapting the air-side geometry to the expected air flow distribution. A microchannel tube, multilouver fin condenser is first designed to transfer the desired heat rejection load for an air-conditioning system under uniform air flow conditions. Tube-side pass arrangements, tube dimensions, and fin and louver geometry are varied to arrive at a minimum mass, 2.54 kg condenser that delivers the desired heat load of 14.5 kW. The design model is then used to predict the performance of the condenser for a variety of air flow distributions across the heat exchanger. It is found that for a 50% air flow mal-distribution, the required condenser mass increases to 2.73 kg. The air-side geometry (fin density and height) of the condenser is then systematically changed to optimally distribute the air-side surface area across the condenser to best address the mal-distributed air flow. It is found that linear fin density and height variations from the mean value of 40% and 20%, respectively, keeping the mean fin density and height the same, reduce the required condenser mass to 2.65 kg even for this mal-distributed air-flow case. The influence of geometry variations on heat transfer coefficients, fan power and other performance measures is discussed in detail to guide the judicious choice of surface area and tube-side flow area allocations for any potential air flow mal-distribution. The results from this study can be used for the design of air-cooled condensers under realistic flow conditions.

Enhanced Finned-Tube Condenser Design and Optimization Susan W. Stewart 173 pages Directed by Dr. Sam V. Shelton Finned-tube heat exchangers are widely used in space conditioning systems, as well as any other application requiring heat exchange between liquids and gases. Their most widespread use is in residential air conditioning systems. Residential systems dictate peak demand on the U.S. national grid, which occurs on the hot summer afternoons, and thereby sets the expensive infrastructure requirement of the nations power plant and electrical distribution system. In addition to peak demand, residential air conditioners are major energy users that dominate residential electrical costs and environmental impact. The only significant opportunity for electrical power use reduction of residential air conditioners is in technology improvement of the finned-tube heat exchangers, i.e., condenser and evaporator coils. With the oncoming redesign of these systems in the next five years to comply with the regulatory elimination of R-22 used in residential air conditioners today, improvement in the design technology of these systems is timely. An air conditioner condenser finned-tube coil design optimization methodology is derived and shown to lead to improved residential air conditioner efficiency at fixed equipment cost. This nonlinear optimization of the 14 required design parameters is impractical by systematic experimental testing and iteration of tens of thousands condenser coils in an air conditioning system. The developed methodology and results can be used in the redesign of residential systems for the new mandated environmentally friendly refrigerants and to meet increasing regulatory minimum system efficiencies. Additionally, plain fins and augmented fins, (louvered), are compared using the developed model and optimization scheme to show the effect of the augmentation on system performance. Furthermore, an isolated condenser model was developed using condenser entropy generation minimization as the figure of merit to minimize the model complexity and computation time. Isolated model optimizations are compared with the system model optimum designs.