R290 HP-Module for Electric Vehicles 2024-37-0031

In contrast to refrigeration circuits in internal combustion engine vehicles (ICEVs) mainly used for cabin cooling, in electric vehicles (EVs) additional functions need to be taken into consideration, e.g., cabin heating, which in ICEVs is realized by the combustion engine’s waste heat, conditioning of the electric battery and drive train components. Additionally, each of these functions demands a different temperature level. Therefore, requirements towards the thermal management in EVs are more challenging. In modern EVs most of these functions are realized by direct refrigerant circuits, which are optimal in terms of efficiency and response time, however, result in greater complexity and different architectures for almost every vehicle model. In addition, the vast majority of EVs worldwide use chemical refrigerants that contain PFAS, e.g. R1234yf, which are known to be persistent and harmful for human health and environment. Natural refrigerants like R290 are considered to be a promising environment friendly substitute, with pressure levels similar to R1234yf and the advantage of having a significantly higher energy efficiency. For refrigerant circuits with R290, indirect systems, with a secondary glycol-water loop are recommended to prevent the flammable refrigerant from entering the cabin, which allows a significant reduction of the refrigerant circuit’s complexity and its control. As part of this work, the proof of concept of an automotive R290 HP-module prototype, is demonstrated. Its capability in terms of cooling and heating power is examined and verified by experimental measurements. The simplicity of its refrigerant circuit and therefore its compact low-weight modular design allows an easy integration in various applications. In addition, it allows to keep a low refrigerant charge level, which reduces the safety risk in case of leakage. Furthermore, a simple numerical tool, for fast and accurate predictions of the steady-state operating conditions of the HP-module, is developed and discussed.