Experimental investigation for effects of electronic expansion valve opening on exergy loss in transcritical CO₂ system

To improve the performance of transcritical CO₂ system, the effects of electronic expansion valve (EEV) opening on the exergy loss of different components in the transcritical CO₂ system were investigated. The experimental table for the transcritical CO₂ system with an EEV was constructed, and the operation parameters of the CO₂ system were measured under constant water inlet temperature and different EEV opening. Based on the experimental data, the effects of the EEV opening on the COP, the total exergetic efficiency of system and relative exergy loss of all components were analyzed. The exergetic efficiency for the different components was also presented at the optimal EEV opening, and with the gas cooler side water inlet temperature of 30°C and the evaporator side water inlet temperature of 15°C. According to relative exergy loss and exergetic efficiency for all components at the optimal EEV opening, the improvement room of the components was analyzed. The results show that the compressor and the gas cooler account for 49.4% and 18.9% of the total exergy loss respectively, and the exergetic efficiencies of these two components are 60.7% and 37.6% respectively. Thus compressor and gas cooler are endowed with abundant improving potential.