Development of Cooling Fan Model and Heat Exchange Model of Condenser to Predict the Cooling and the Heat Resistance Performance of Vehicle

The cooling performance and the heat resistance performance of commercial vehicle are balanced with aerodynamic performance, output power of powertrain, styling, cost and many other parameters. Therefore, it is desired to predict the cooling performance and the heat resistance performance with high accuracy at the early stage of development. Among the three basic forms of heat transfer (conduction, convection and radiation), solving thermal conduction accurately is difficult, because modeling of “correct shape” and setting of coefficient of thermal conductivity for each material need many of time and efforts at the early stage of development. Correct shape means that each part should be attached correctly to generate the solid mesh with high quality. Therefore, it is more efficient and realistic method to predict the air temperature distribution around the rubber/resin part instead of using the surface temperature at the preliminary design stage. The air temperature distribution in the engine compartment is dominated by the flow distribution from fans, the heat rejected by heat exchangers, AC-generator and the convecting heat by surface temperature of parts. In the case of steady middle/high vehicle speed modes, thermal convection has larger effects on the air temperature distribution. To predict these phenomena with high accuracy, the fan model and condenser model are developed. The fan model provides the accurate P-Q performance based on a specification and the flow distribution based on the LES results of the sliding mesh method with low computational cost. The heat rejection by the condenser is concentrated around the inlet tube of core. To reproduce this distribution, the phase change of refrigerant is solved in the condenser model. The accuracy of these models is confirmed by using component experiments and vehicle measurements. Accuracy of heat-exchanger coolant temperature is within 2K and air temperature in the engine compartment is 5K respectively.