An Experimental Investigation of COP Enhancement in a Heated Vapor Compression Cycle Using an Intermediate Flash Tank

The goal of this research is to minimize the electrical energy consumption and emissions of the refrigeration cycle as a step towards sustainable refrigeration. The Vapor Compression Cycle (VCC) relies mainly on electrical energy; however, the developed Heated Vapor Compression Cycle (HVCC) relies on electrical energy as well as solar energy, which lowers our dependence on electrical energy and improves environmental sustainability. The objective of this research is to improve the coefficient of performance (COP) of the HVCC in comparison to the VCC by adding an intermediate flash tank to the capillary tube. The intermediate flash tank converts the wet refrigerant into saturated liquid, which decreases the quality of the refrigerant at the entrance of the evaporator and consequently improves the cooling potential, i.e., the cooling power. The proposed concept was examined for four different refrigerants, i.e., R502, R407c, R22 and R410a, and at four different intermediate pressures. Also, the influence of the heating temperature on the HVCC as a function of intermediate pressure was examined. It was found that, for all the examined refrigerants, decreasing the intermediate flash tank pressure improves the COP of the cycle. The HVCC operating with R410a has the highest COP, i.e., 6.2, at an intermediate flash tank pressure of 165 psi and a heating temperature of 100 °C, while R407c has the highest COP of 4.8 when compared with R502 and R22 when operating under the same pressures. Adding a flash tank to the HVCC operating with refrigerant R410a can improve the COP of the cycle by more than 40% and by more than 25% in the case of refrigerant R407c. Such improvement in the performance of the cycle reduces electrical energy consumption and improves the environmental sustainability of the cycle.