Improvements to Thermal Management System for Automotive Components

Abstract: Global warming imposes great challenges, and anthropogenic greenhouse gas emissions have to be reduced by active measures. The transportation sector is one of the key sectors where significant reductions are desired. Within a vehicle, the cooling/thermal management system is a subsystem intended for temperature control of automotive components. Reducing the power consumption for thermal management is one of several possible ways to reduce the environmental impact of the vehicle. This report considers an existing reference cooling system, with three separate circuits at different temperature levels. The purpose is to suggest improvements to the reference system with respect to increasing energy efficiency as well as reducing the number of components. Potential improvements are identified during a literature study, and then evaluated one by one. After the first evaluation, four improvements are selected: Firstly, a liquid-to-liquid heat exchanger in high temperature circuit, with connections to both the medium and low temperature circuits. Secondly, common medium/low temperature radiators, which can be allocated according to cooling demand. Thirdly, pipe connections for coolant transfer between the low and medium temperature circuits. Finally, a liquid-cooled condenser in the active cooling system, cooled by the medium temperature circuit. The result is a system with flexible radiator allocation, more even load distribution, ability to heat components using heat losses from other components, and one radiator less than the reference system. A complete system evaluation is performed in order to find the most beneficial arrangement of the components. Steady state calculations are performed in MATLAB, using five different operational cases as input data. Out of six different alternatives, one is recommended for high load operation and another for low load operation. The difference between the two is the position of the condenser, since a low condensation temperature should be prioritized at part load but not at high load. The main uncertainties of this report are steady state calculations, which are not fully reflecting real driving situations, and approximations due to lack of input data. For further work, verification of these results by transient simulations and practical testing is recommended. Removing one of the high temperature radiators could be investigated, as well as downsizing the medium temperature radiator. Integration with the cabin thermal management system, which is beyond the scope of this report, is also a relevant area for future investigation. By suggesting improvements to an automotive subsystem, this report strives to make a difference on a small-scale level, but also to contribute to an ongoing transition process on the global level.