Theoretical And Experimental Study On Variable Composition Capacity Regulation Of A Heat Pump System Using Refrigerant Mixtures

The variable composition capacity regulation can be defined as the regulation of cooling capacity or heating capacity of the system by changing composition of the mixture in the system according to characteristics of the zeotropic mixtures. Comparing with other capacity regulation methods, it has a good modulation effect and can avoid additional energy consumption as well as many other problems such as compressor sympathetic vibration, leakage etc. Therefore, it has a good future. This thesis conquered the limitations of former systems with several new methods and made a theoretically and experimentally study on the performances of a novel air source heat pump system using refrigerant mixtures based on previous studies. The main research contents are as follows:1. The research history and present status of variable composition capacity regulation systems at home and abroad were briefly reviewed. Based on the conventional systems, the author proposed a novel system in which a variable composition device is used in the low-pressure section of the cycle. It has a simple structure and can easily be controlled.2. Presenting a brief overview of recent advances in refrigerant mixtures on capacity controllable residential heat pumps. According to the theoretical and experimental results, the application of ternary refrigerant mixtures in capacity-modulation heat pumps is firstly indicated, and the advantages of ternary refrigerant mixtures over binary refrigerant mixtures are simply analyzed. Secondly, the thermodynamic numerical simulation shows that the mixtures of R32/R125/R227ea, R32/R143a/R227ea. R32/R143a/R134a and R32/R125/R134a are potential candidates. The suitable mixture for variable capacity regulation is selected according to the thermodynamic characteristics of the cycle, distillation characteristics and impacts on environment. Finally, R32/R125/R134a is determined as the best mixture for further research.3. Comparing the difference of fractionation effects between simple separation and rectifying column separation with binary and ternary refrigerant mixtures;...