Experimental investigation of a CO2 trans-critical cycle with IHX for chiller application and its energetic and exergetic evaluation in warm climate

This article presents comparative study of performance of a CO2 trans-critical chiller with and without internal heat exchanger (IHX), operating in warm climate (up to 45 °C) based on experimental data in energetic and exergetic perspective. Experiments are conducted following ARI guidelines and the results are presented for two sets of evaporator temperatures (−5°C and 0 °C) and for four different ambient temperatures (32 °C, 35 °C, 40 °C and 45 °C) for a range of gas cooler pressure within 80 to 110 bar. Also investigated is the effect of air flow velocity over gas cooler on the cycle performance. The optimal air velocity over the gas cooler is found to be near 1 m·s−1. Effect of fan efficiency on the fan power and COP are also presented. The experimental results demonstrate advantage of adoption of IHX in high ambient for chiller application. At high ambient (45 °C), the advantage of use of IHX is recorded to be 5.71% and 5.05% in energy and exergy efficiency respectively, at evaporator temperature of −5°C while the same are found 5.01% and 4.60% respectively, at evaporator temperature of 0 °C. Increase in compressor discharge temperature is also observed for IHX cycle. IHX is found to have the least contribution towards system irreversibility.