Experimental Thermodynamic Investigation on the Refrigerant Charge in a Transcritical CO2 Electric Bus Air Conditioning System

Due to its considerable impact on climate, bus air conditioning systems are being pushed take a new and sustainable path. Electric buses relying transcritical CO2 units perceived be eco-friendly future-proof solutions achieving such target. However, in order have highly efficient systems, the charge needs optimized. In this paper energy exergy-based analyses were performed investigate effect of normalized refrigerant system performance by using test rig unit for an 8 m electric bus. Results showed that range 0.248~0.336 was recommended ensure maximum coefficient (COP). addition, sufficient conditions, optimal COP, cooling capacity exergy efficiency 1.716, 18.97 kW 29.79%, respectively, under standard refrigeration condition 35 °C/27 °C. As ambient temperature rose from °C 40 °C, decreased 16.03%, 10.90% 12.22%, respectively. Furthermore, found not sensitive slightly insufficient charge, whereas overcharge observed even beneficial ensuring COP. charging seriously affected irreversible losses indoor outdoor heat exchangers, slight had little component efficiency. Finally, need improve compressor enhance revealed.