Thermal Modelling of Heat Transfer Between Ambient Air and Powerpack

Sammanfattning

This report presents the creation and evaluation of an air-cooling steady state modelfor a Volvo Cars powerpack. It should simulate the heat transfer and temperaturesfrom the components of the powerpack. Especially interesting is how the NVH(Noise Vibration Harshness) encapsulation affects the cooling performance. Thisencapsulation is a thin foam layer that surrounds the motor and dampens the noisecaused by it. A 1D model already existed that handled the internal heat generationand the liquid cooling of the powerpack. Twenty chosen operating conditions wereiteratively calibrated between the 1D model and a full car 3D model to yield heattransfer coefficients (HTC) for each thermal node in the extension. They were chosenas variable sweeps (sweeping over multiple values for one variable while keeping therest constant) from a central base case, yielding four to five data points to analyseeach variable’s impact separately. The results show that the air-cooling increases as afraction of the total cooling as the car velocity and driveshaft torque increases. It alsoshows that most air-cooling bypasses the encapsulation, meaning the encapsulationhas little impact on the performance. When compared with physical measurementsthe accuracy of the model is low. This is most likely caused by the lack of calibrationfor operating conditions where multiple variables were changed from the base case. Itis therefore recommended that future work includes additional operating conditionsto simulate. This could not be done in this project due to time and computationalconstraints.