Designing, modeling, monitoring and control of air conditioning systems.

摘要

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:; 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 sy