Analysis of Combined Power and Refrigeration Generation Using the Carbon Dioxide Thermodynamic Cycle to Recover the Waste Heat of an Internal Combustion Engine

A novel thermodynamic system is proposed to recover the waste heat of an internal combustion engine (ICE) by integrating the transcritical carbon dioxide (CO2) refrigeration cycle with the supercritical CO2 power cycle, and eight kinds of integration schemes are developed. The key parameters of the system are optimized through a genetic algorithm to achieve optimum matching with different variables and schemes, as well as the maximum net power output (W-net). The results indicate that replacing a single-turbine scheme with a double-turbine scheme can significantly enhance the net power output (W-net) and lower the inlet pressure of the power turbine (P-4). With the same exhaust parameters of ICE, the maximum W-net of the double-turbines scheme is 40%-50% higher than that of the single-turbine scheme. Replacing a single-stage compression scheme with a double-stage compression scheme can also lower the value of P-4, while it could not always significantly enhance the value of W-net. Except for the power consumption of air conditioning, the net power output of this thermodynamic system can reach up to 13%-35% of the engine power when it is used to recover the exhaust heat of internal combustion engines.