Study of the comparison of the exergy and energy analyses of the 𝑪���𝑶���𝟐���/𝑵���𝑯���𝟑��� and 𝑪���𝑶���𝟐���/R134a cascade refrigeration system to be used in supermarkets

Abstract

Various techniques are being researched to refrigerate our stored products at a desired temperatures in supermarkets. In this report, via the exergy and energy analyses, the 𝐶𝑂2/𝑁𝐻3 and 𝐶𝑂2/R134a cascade refrigeration systems were compared to determine which of the system suited best the supermarket application. The coefficient of performance (COP) was calculated as a measure of the energy analysis while on the other side the sum of the individual exergy destructions in each of the components which is equivalent to the total exergy destruction was a measure of the exergy analysis. The cascade refrigeration comprised of two refrigeration systems connected in series in which one of the system will in lower temperature circuit (LTC) while the other will be in the higher temperature circuit. The cooling space temperature and cooling capacity employed in this report were -40°C and 40 kW. In both the exergy and energy analyses the temperature at the LTC evaporator and condenser, cascade condenser temperature difference and HTC condenser were varied individually to obtain the desired results. The analyses result showed that 𝐶𝑂2/𝑁𝐻3 cascade refrigeration system was more efficient than the 𝐶𝑂2/R134a system as it had lower values for the total exergy destruction and higher COP values. Furthermore, in both cascade systems maximum exergy destruction occurred in the condenser followed by the compressor.