Energy efficiency evaluation of the use of R513A as a drop-in replacement for R134a in a water chiller with a minichannel condenser for air-conditioning applications

Abstract

This work presents an experimental assessment on the use of R513A refrigerant as a drop-in replacement for R134a in a water chiller for air-conditioning applications. The study discusses from an energy efficiency point of view this replacement option for warm countries. A vapor-compression refrigeration system (VCRS) working with a minichannel air heat exchanger as a condenser and driven by a 0.92 kW piston-type compressor was used to compare the performance of both refrigerants. A fixed water inlet temperature of 12 °C and a fixed outlet temperature of 7 °C were set for all the experiments whereas different air temperatures (between 20 and 35 °C) and velocities were tested at the condenser side. In all the cases studied, R513A showed an energy efficiency ratio (EER) worse than R134a for cooling capacities between 1.8 and 2.5 kW. On average, EER of R513A was 24% worse than that of R134a. The higher vapor density of R513A at the suction side of the compressor resulted in a higher mass flow rate and a lower isentropic and mechanical efficiency when compared to those of R134a. In the present application, the efficiency of the reciprocating compressor was found to be sensitive to the refrigerant mass flow rate. When R513A was used as a drop-in, the mass flow rate increased ~15% what resulted in a significant increase of the pressure drop in some lines, an increase of the compressor compression ratio and a reduction of ~8% in both the isentropic and mechanical efficiencies of the reciprocating compressor.