Effects of evaporator load on vapour compression refrigeration system using eco friendly hydrocarbon refrigerants with sub cooling

摘要

The main objective is to study the effect of evaporator load on performance of vapour compression refrigeration system with eco friendly refrigerants with and without sub-cooling. Mixture of Propane (R290) and Isobutene (R600a) is used as alternate refrigerant to Hydro Fluorocarbon (HFC) and Chlorofluorocarbon (CFC) compounds in this analysis. Performance analysis is investigated at different loads in evaporator. Hydrocarbon mixture (HCM) is an alternative refrigerant for HFC and CFC compounds due to their lower Global Warming Potential (GWP) and zero Ozone Depletion Potential (ODP). Computational analysis is carried out to study the performance of the proposed mixture and also compared with conventional refrigerants R12 and R134a with respect to condensing temperature. In order to operate the refrigeration system at economical mode, the evaporator is loaded at various load conditions like 25%, 50%, 75% and 100%. Various performance parameters like discharge temperature, compressor input power, heat rejected in the condenser, refrigeration effect and Coefficient of Performance (COP) are investigated at various loads in the evaporator. The analysis is carried out for condensing temperature from 30℃ to 65℃ and evaporator is maintained at -10℃. As per computational analysis, discharge temperature and pressure ratio of HCM is about 3.9-7.4%, 16.4-24.9% lower than R134a and about 2.8-9.4%, 5.5-8.6% lower than R12. Volumetric efficiency of HCM is about 1.8-6.5%, 2% higher than R134a and R12 respectively. From the experimental load analysis, 75% load in the evaporator gave better results in terms of higher refrigeration effect and COP, lower discharge temperature and low compressor input power consumption as compared to other loads. Heat rejection rate for 75% load is moderate with 50% load. COP is about 8.5-24%, 2.9-11.9%, 1.9-5.5% higher than 25%, 50% and 100% loads respectively. Under sub cooling analysis in 3℃, 4℃ and 5℃, the COP of the 75% load is about 1.1-9.3%, 2.5-13.4% and 2.5-14.5% higher than 50% load respectively. Based on computational analysis HCM could be used as an eco friendly refrigerant in the refrigeration system. The experimental results show that 75% load of evaporator having the feature of economic mode to operate the refrigeration system.