Unlocking the multi-mode energy-saving potential of a novel integrated thermal management system for range-extended electric vehicle

Abstract

The thermal management system of range-extended electric vehicles (REEV) is essential for energy saving. There is a lack of modification methods for enhancing its performance under multiple operating modes. Herein, we present a combined cooling and power cycle-based basic integrated thermal management system (ITMS) for the REEV and propose a generalised performance improvement approach adapted to multiple operating modes. Composed of a waste heat recovery and a cooling subsystem, the basic ITMS can achieve heat recovery and thermal management of the range extender's coolant and recirculated exhaust gas and cools the passenger compartment and battery packs. The factors limiting the basic ITMS are identified through parametric analysis: the low evaporative pressures constrained by the low-temperature waste heat (engine coolant) and cooling target (passenger compartment). In order to unlock the multi-mode potential of the ITMS, we introduce the liquid-vapour separation condenser to separate the working fluid (zeotropic mixture) into two mixtures with different volatility. The high-volatility mixture is utilised to absorb the low-temperature engine coolant's waste heat and generate the low-temperature cooling energy for the passenger compartment, lifting evaporative pressures while keeping the condensation pressure unchanged. Then, a multi-mode comparison verifies the modified system. When the vehicle operates with the range extender on and with/without cooling demand, the vehicle fuel consumption rate can be reduced by 6.6% and up to 12.5%, respectively. When the vehicle runs in pure electric mode and with cooling demand, the ITMS's electrical consumption can be lowered by 7.4%. Accordingly, matching the volatility of the zeotropic working fluid and the thermal management objects enables REEV's ITMS to fulfil substantial energy savings in multiple operating modes.