Performance enhancement of combined cooling and power cycle through composition adjustment in off-design conditions

The combined cooling and power cycle has wide applications ascribed to the feasibility of simultaneously providing cooling and electricity. CO2-mixture based combined cooling and power cycle is a promising technology for remarkable performance. However, optimal compositions of working fluid in sub-cycles are usually different when operating with CO2-mixture. In off-design conditions, the mismatch between compositions and sub-cycles may further aggravate. This study employs composition-adjustable combined cooling and power cycle to solve the above problem and off-design performance in various boundary conditions is investigated. A refrigeration truck operated in highway condition is selected as the research objective. The results show that the optimal compositions of working fluid in sub-cycles are disparate in different engine operating conditions and the composition-adjustable system performs better than composition-fixed system in most engine operating points. Beyond satisfying the demand of 7.73 kW (−20 °C) cooling capacity, the total net power output of composition-adjustable system could reach 2.41 kW in the whole operating conditions, which is 7.11% higher than composition-fixed system (2.25 kW). In addition, composition-adjustable system has a much broader operating feasibility to the shift of heat sink inlet temperature and is more suitable for the application with large cooling requirements.