Thermodynamic performance evaluation of HFC refrigerants for the chiller system simulated by hot gas bypass cycle

Idres Azzat Hamakhan

Abstract


The competitive of the building air-conditioning equipment pushes manufactures to develop and improve the performance and efficiency of their products. This process is cost and time consuming for testing the whole units. In this study, for the first time a modified proposed test block with hot gas bypass cycle (HGBP), based on the experimental compressor map, has been used as a model to investigate the theoretical performance of the chiller system. The model assumes one dimensional steady state conditions and uses an experimental compressor map to predict the thermodynamic performance of the system.  A computational model, using the software program EES (EES-V8.4), in a single stage of the chiller system with HGBP cycle based on the first and second law analyses are presented for the prediction of the effects of the pressure ratio, degree of superheating and sub-cooling, condenser temperature, outdoor air temperature and humidity ratio on the exergy destruction, exergetic efficiency, gas power and coefficient of performance (COP) of the chiller system. The performance of the implemented model with various hydrofluorocarbon (HFC) refrigerants such as R134a, R152a and R423a are compared. The results, firstly, indicates that the modified model with applying the energy and exergy analysis works for all kind of working refrigerants including HFC refrigerants. Secondly, the performance of the compression refrigeration system based on the experimental compressor map data to choose the right compressor can help engineers to design a high quality unit before going to design the system practically.  The results indicate that R423a has a higher coefficient of performance as compared to the rest of the refrigerants. The developed simulation model helped to establish the strong dependence between system performances and the compressor map.


Keywords


compressor map, pressure ratio, energy, exergy, hot gas by pass cycle

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