Theoretical analysis and experimental research on transcritical CO2 two stage compression cycle with two gas coolers (TSCC + TG) and the cycle with intercooler (TSCC + IC)

As one of the natural refrigerants, CO2 is a potential substitute for synthesized refrigerants with favorable environmental properties. In order to improve the performance of the CO2 transcritical compression cycle, the performance of the two stage compression cycle with two gas coolers (TSCC + TG) and the two stage compression cycle with intercooler (TSCC + IC) were analyzed, respectively. Under the given calculation condition, the optimum intermediate pressure of the cycle TSCC + TG and the TSCC + IC are 7.09 MPa and 5.89 MPa, and the maximal COP are 2.77 and 3.08, respectively. Range of the given evaporating temperature and outlet temperature of gas cooler, the experimental testing shows that the performance of cycle TSCC + IC are 11.88% and 10.87% better than that of the cycle TSCC + TG, respectively. Range of the given inlet temperature and cooling water volume flow of gas cooler, the refrigeration COP (COPc) and heat COP (COPh) of the cycle TSCC + IC are average 10.97% and 4.39% higher than that of the cycle TSCC + TG. Range of the given inlet temperature and chilled water volume flow of evaporator, the refrigeration COP (COPc) and heat COP (COPh) of the cycle TSCC + IC are average 10.71% and 3.67% higher than that of the cycle TSCC + TG, respectively. The error between theoretical calculation and experimental testing is not exceeds 20%.

► CO2 is a potential substitute for synthesized refrigerants with favorable properties.
► The COP of TSCC + TG and TSCC + IC is 2.77 and 3.08 at optimum intermediate pressure.
► Experimental testing performance of cycle TSCC + IC is better than the cycle TSCC + TG.
► COP of cycle TSCC + IC is higher than cycle TSCC + TG given cooling water volume flow.
► Error between theoretical calculation and experimental testing is not exceeds 20%.