Thermodynamic analyses and optimization of a transcritical N2O refrigeration cycle

Abstract

Thermodynamic analyses as well as optimization studies based on maximum cooling COP of a transcritical N2O cycle and both energetic and exergetic comparisons with CO2 cycle are presented in this article. Effects of superheating, internal heat exchanger and expansion turbine are studied as well. An expression for optimum discharge pressure has been developed. Variation trends of optimal parameters for the N2O system are similar to that of a CO2 system. The N2O cycle exhibits higher cooling COP, lower compressor pressure ratio and lower discharge pressure and temperature, and higher second law efficiency when compared to CO2 based systems; however, it is inferior in term of volumetric cooling capacity at the optimum condition. Effect of superheating in evaporator is negligible and effect of introducing an internal heat exchanger is moderate whereas effect of employing a work recovery turbine is significant on COP improvement and discharge pressure reduction at the optimal condition for both working fluids. © 2009 Elsevier Ltd and IIR.