Investigating the exergetic and environmental effects of subcooling and superheating processes on the performance of direct expansion systems

Abstract

Recently, subcooling and superheating applications, which are proposed as an approach for the efficient use of energy, have positive effect on the emission next to increasing the energy efficiency. This study examines energetic, exergetic, and environmental effects of subcooling and superheating processes in cooling applications separately. In this study, a direct expansion system(DX), which is usedwidely in supermarket cooling applications, is taken into consideration. The evaporator temperatures of -25 °C and 0 °C, the refrigerants of R-22, R-404A, and R-134a, which are preferred widely in DX systems, and minimum and maximum leakage rates of 3 and 30 % are taken as reference values for the analysis. According to the results, while subcooling and subheating processes increase approximately 10 % of COP and exergy efficiencies based on refrigerants and decrease CO2 emissions for all refrigerants. The study also concluded with an emphasis on the importance of subcooling and superheating applications, especially for DX systems and the importance of the preference refrigerant