INVESTIGATING THE PERFORMANCE OF R134A DOMESTIC REFRIGERATOR RETROFITTED WITH R290 (PROPANE) AND R600A (ISO-BUTANE) REFRIGERANTS IN THREE DIFFERENT SIZE OF CAPILLARY TUBE IN A REFRIGERATING SYSTEM.

Abstract

In Nigeria, most of the vapour compression based refrigeration systems continue to run on halogenated refrigerants due to its excellent thermodynamic and thermo-physical properties. However, the halogenated refrigerants have adverse environmental impacts such as ozone depletion potential and global warming potential. Hence, it is necessary to search for alternatives to halogenated refrigerants. R290 (Propane) and R600a (Iso-butane) are two environmentally friendly refrigerants while R134a (Hydrofluorocarbon) is a common halogenated refrigerant. This study evaluated the performance of R290 and R600a refrigerants retrofitted into an R134a refrigerator. The temperatures at the four units (compressor, condenser, dryer/filter and evaporator) of the refrigerator were taken at different ambient temperature ranging from 15oC to 33oC. Also, pressures at both the inlet and outlet of the compressor were taken using the run time of 8 hours. Propane (R290) and iso-butane (R600a) were both charged in separately into the domestic refrigerator after R134a has been discharged, thoroughly flushed and evacuated. All tests were repeated for R290 and R600a. The data obtained was used to compute the following system performance parameters: refrigeration capacity, compressor power input, Coefficient of Performance (COP) and compression ratio. Average COP, average refrigeration capacities (kW), average compressor power (kW) and compression ratio of 0.499, 0.92, 0.188; 0.55, 0.49, 0.38; 1.82, 1.63, 1.25 and 6.02, 6.38, 6.67 were obtained using R600a, R290 and R134a respectively. The standard deviation for average COP, average refrigeration capacity(kW), average compressor power and average pressure ratio of 0.052,0.218,0.04; 0.023,0.072,0.065; 0.92,0.62,0.43 and 0.17, 0.17, 0.14 were obtained. Overall assessment showed that R600a and R290 have a relatively low compression ratio and better COP. The COP and compression ratio were used to quantify the performance of a refrigeration cycle. Low compression ratio increased refrigeration efficiency and decreased compressor energy consumption which indicated better system performance and reliability providing longer life to the domestic refrigerator. The average refrigeration capacity and compressor power obtained during test using R600a and R290 were higher than those of R134a indicating an effective cooling power of R600a and R290 over R134a