Development of Thermal Performance Test Method for Coolant Heater Core Products for Electric Vehicle Applications

During thermal performance testing, achieving thermal balance between two fluid mediums of any heat exchanger is critical. Heat balance ratio (HBR) measures the heat transfer imbalance between two sides (source and sink) in a heat exchanger and also helps in ensuring accuracy of test data. There could be many factors which may lead to the imbalance in thermal performance of the sample under testing e.g. sensors accuracy, test operating range, sample orientation, hysteresis in the data acquisition systems etc. Therefore, a testing procedure needs to be established to achieve a better heat balance ratio as low as less than ±5%, which accounts for errors during instrumentation processes, flow losses & manual errors during testing. The current experimental study focuses on a typical coolant aluminium brazed heater core product which is used in automotive applications for passenger cabin heating during the cold climate conditions, windshield demisting and defrosting. In this study, three geometrically different heater core samples have been tested inside the calorimeter bench for the measurement of thermal performance and heat balance ratio using the proposed methodology. Heater core inlet air temperature sensor was used for maintaining the inlet temperature parameter. Heater core inlet & outlet air temperature measurement was done using thermocouple (TC’s) grid. Coolant side temperatures are measured using Resistance Temperature Detector (RTD) sensors. This methodology was validated for1:1 Ethylene Glycol+Water mixture and for tube and fin type heat exchanger. The currently existing testing methodologies exhibitHBR in the range of +10% to +30%, whilst the proposed method showed great improvement maintaining HBR less than ±5%& hence the new test method looks promising.