Improving the performance of thermal management system for electric and hybrid electric vehicles by adding an ejector

For electric and hybrid electric vehicles, a battery thermal management system (BTMS) is an essential component to maintain a proper operating temperature for the battery pack. In this paper, a modern BTMS involving an evaporator (for cooling passenger cabinet) and a chiller (for cooling battery pack) is investigated under different cooling temperatures. Three systems are studied in which (a) the refrigerant lines coming from the chiller and evaporator have the same temperature (for the basic system), or they have different temperatures to be connected by (b) the mixing chamber, or (c) an ejector for a suggested novel system. For a mixing-chamber based system, the results show that the refrigerant charge decreases by 12% compared to the basic system leading to improving the coefficient of performance (COP) by 4.7%. Alternatively, the ejector can efficiently be used instead of the mixing chamber. One of the advantages for the use of ejector is to increase the inlet pressure of the compressor, resulting in minimizing the required power input. Therefore, COP improvement is found to be in a range of 7.17%–77.9%, compared to the basic system under the investigated conditions. The refrigerant charge and the rejected heat by the condenser decrease by 12% and 14.4%, respectively.