Validation of and optimization with a vapor compression cycle model accounting for refrigerant thermodynamic and transport properties: With focus on low-GWP refrigerants for air-conditioning

Abstract

CYCLE_D-HX is a semi-theoretical model that simulates the performance of a vapor-compression cycle with forced-convection heat exchangers for specified temperature profiles of the heat source and heat sink. In this study, we validated CYCLE_D-HX using experimental measurements from a small (< 4 kW capacity) heat pump test apparatus operated in cooling mode. The tested refrigerants included the medium-pressure refrigerant R-134a and candidate replacements with a lower global-warming potential (GWP): R-513A, R-450A, Tern-1 (R-134a/1234yf/1234ze(E) 49.2/33.8/17.0 mass fraction,%), R-515B, and R-1234yf. We also tested high-pressure refrigerant R-410A and candidate replacements with lower-GWP: R-32, R-452B, and R-454B. The model generally agreed with experimental results, with COP and volumetric capacity overpredicted by (0 – 3)% for the basic cycle, and by (0 – 5)% for the cycle with the liquid-line/suction-line heat exchanger (LLSL-HX). We applied the model to evaluate the performance of the refrigerants in a system with optimized refrigerant circuitries in the evaporator and condenser. The simulations showed the lower-GWP medium-pressure refrigerants, including some non-flammable blends, had COP (0.2 – 2.3)% less than R-134a. The lower-GWP high-pressure refrigerants, which all have the ‘2L’ flammability rating, had COP (2.3 – 3.2)% higher than R-410A.