Seite - 144 - in Hybrid Electric Vehicles

under different operating conditions. The specifications of its parameters, such as the cool- ant’s flow rate and coolant’s inlet temperature are of great importance for system’s efficiency and they will be calculated through the applied optimization algorithm. Since these param- eters have essential effect on HEV’s energy management, their values have to be carefully selected. For example, a high value for coolant’s flow rate will conclude to increased energy consumption by the pump in order to circulate the liquid. Likewise, the heat exchanger should be capable of restoring coolant’s temperature while its capacity will remain as low as possible. During this procedure, cooling channel’s dimensions will be considered as vari- ables. An aluminium alloy (6060-T6) with good mechanical properties has been selected for the channel, while ethylene-glycol mixed with water (50-50 volumetric proportion) has been chosen as coolant. The applied methodology involves the following the steps: (a) the deter- mination of the thermal properties of all involved materials (including the shell, the tire and the insulation materials), (b) the specification of motor’s heat resources and the ambient tem- perature, (c) the calculation of the boundary conditions in the air gap and other motor’s parts and (d) the modification of the 2D thermal modelling according to the prevailing conditions. Figure 12. Cross section of the in-wheel motor topology, in which the accurate position of cooling channel is depicted. Hybrid Electric Vehicles144