Indirect refrigeration cycle with heat pump functionality for hybrid and electric vehicles.

The air conditioning system of a passenger car causes significant power consumption. For Hybrid and Electric Vehicles the energy consumption for heating of the cabin at low ambient temperatures in particular plays an important role, considering that there is only little or no waste heat available. Electric (resistance) heating of the cabin air drastically reduces the driving range. Additionally, in case of electric vehicles there may be a demand for cooling of the traction battery at high ambient temperatures. In contrary, the waste heat of the power electronics could be used for cabin heating at low ambient temperatures if its temperature level is raised by means of a heat pump. This manuscript illustrates simulation results as well as test bench measurements of an indirect refrigeration system with heat pump functionality. The proposed system may considerably lower the energy consumption for air conditioning of the passenger cabin and offers ways to incorporate additional heat sinks as well as sources in a simple manner. The system aims for higher efficiencies in heating and dehumidification mode compared to conventional systems and should facilitate the vehicle’s overall thermal management. The natural refrigerant R744 is used as working fluid because of its negligible global warming potential (compared to other refrigerants) and favourable thermodynamic properties for heat pump applications.

乘用车空调系统会带来显著的电力消耗。对于混合动力汽车与纯电动汽车而言，低温环境下座舱采暖的能耗尤为关键——究其原因在于此类车辆几乎或完全无法利用废热。采用电（电阻）加热座舱空气的方式会大幅缩减车辆续航里程。此外，在环境温度较高时，纯电动汽车还需要对牵引动力电池（traction battery）进行散热。与之相对的是，若通过热泵（heat pump）提升功率电子器件的废热温度，则可将其用于低温环境下的座舱采暖。本文阐述了一款具备热泵功能的间接制冷系统的仿真结果与台架测试数据。所提出的这套系统可大幅降低乘用车座舱空调的能耗，并能以简便方式集成额外的热汇与热源。相较于传统系统，该系统在采暖与除湿模式下可实现更高的能效，同时有助于优化车辆的整体热管理。本次研究选用天然制冷剂R744作为工质，原因在于其全球变暖潜势（global warming potential, GWP）可忽略不计（相较于其他制冷剂），且具备热泵应用所需的优异热力学性能。