Thermodynamic analysis and optimization of a novel N2O–CO2 cascade system for refrigeration and heating

In this study, a natural refrigerant based cascaded system, with nitrous oxide as the low temperature fluid and carbon dioxide as the high temperature fluid, is analyzed for simultaneous cooling and heating applications. Effects of significant design and operating parameters on system performance are studied. Optimization of intermediate pressure for maximum COP for various design and operating parameters are presented as well. Results show that use of internal heat exchanger has marginal influence on system performance. Due to similar thermodynamic properties of nitrous oxide and carbon dioxide, the optimized intermediate temperature turns out to be independent of the performance of gas cooler and evaporator for a given operating condition. Due to the same reason, N2O as low temperature fluid and CO2 as high temperature fluid in a cascade arrangement exhibit similar behavioural trends in a system where the fluids are swapped.