Assessment of a mini-channel condenser at high ambient temperatures based on experimental measurements working with R134a, R513A and R1234yf

Abstract

In this work, the potentiality of R513A and R1234yf as replacement refrigerants for R134a is experimental and numerically studied. The former substances exhibit Global Warming Potentials (GWP) that are 44% and 0.3% of the value for R134a (GWP = 1300). Thus, due to these lower values of GWP, they are promoted to substitute R134a according to environmental considerations. Nevertheless, these considerations should take into account the global environmental impact of the system, which depends not only of GWP but also of the energy consumption of the compressor. This last parameter depends on the thermal performances of the refrigerant.The research focuses on the performances of the diabatic phase-change processes within a mini-channel tube at high condensing temperatures. The use of this geometry is because mini-channel heat exchangers allow decreasing refrigerant charge and, consequently, direct emissions. Indirect emissions are also reduced because of the high heat transfer coefficients (HTC) obtained at these geometries.The results, based on experimental data and empirical correlations to fit them, show, for the tested experimental conditions, that R134a presents higher frictional pressure drop and HTC than R513A and R1234yf. Therefore, the substitution of R134a by the studied alternatives is analysed in detail to determine the power consumption in the compressor, the charge of the system, and the global heat power transferred. The analysis includes an estimate of the Total Equivalent Warming Impact (TEWI) in several scenarios to determine under which conditions, the substitution of R134a by R513A or R1234yf is a better alternative.