Thermal protection is an important task in the development process of Mercedes Benz. Therefore a combination of heat exchangers and fans are applied for engine cooling. In some cases the set-up of fan and heat exchangers can cause a flow field, in which the temperature and velocity are strongly non-homogeneous in front of the engine fan. Under these conditions the thermal behaviour of the axial fan cannot be simulated in a proper way with the commonly applied quasi-steady Multiple Reference Frame model (MRF). For a reliable prediction of the thermal behaviour unsteady numerical simulations or additional experimental data are thus required.
In the present work we propose a strategy to remedy the current shortcoming in the MRF. It is found that the wrong prediction of the temperature field after the fan is caused by the simplification of the energy transfer through the fan. Therefore, the mean flow field through the fan is first generated with MRF. Afterwards the corresponding radial and circumferential displacement of the temperature is calculated based on the retention time in the fan. The results are compared with experimental data from a test bench, unsteady RANS and the MRF model without the above described correction.