Parametric analysis of a vehicle power and cooling/heating cogeneration system

Abstract

We propose a vehicle power and cooling/heating cogeneration energy supply system (VCESS) and investigate its thermodynamic characteristics under various working conditions. The cogeneration system includes a top engine cycle and a bottom waste heat recovery (WHR) cogeneration cycle using zeotropic mixtures as working fluids. The bottom cycle recovers the exhaust and coolant sensible heats of top engine cycle at different temperatures, and thermal match in two WHR evaporators and the condenser is considered. A VCESS model was built and verified via a quantitative analysis of the energy demands and waste heats characteristics of a commercial vehicle under different working conditions. The thermodynamic performances of the VCESS are discussed considering the actual vehicle energy demands. The proposed cogeneration system indicates prominent thermodynamic performance advantages with the ambient temperature lower than the comfort cabin temperature requirement. The overall thermal efficiency of the cogeneration system is improved as the ratio of exhaust heat to coolant heat is increased and reaches its maximal value at the highest vehicle speed when refrigeration is not required. The optimal operation pressure ratio of turbine inlet pressure to condensing pressure and working fluids composition exists at given ambient temperature. The overall thermal efficiency of the cogeneration system decreases sharply at the extreme vehicle velocity and extreme high ambient temperature.