A Truck Engine Compartment Heat Dissipation Characteristics Analysis

The performance of cooling system is directly related to power, economy and reliability.Because a truck underhood is overheating when taken a road test, in this paper, the CFD simulation method is used to simulate the flow field and temperature field. The complex geometric model is simplified and the computational domain and boundary conditions are set. Then the truck finite element model is established. According to the analysis of vehicle internal and external flow field, when at high-speed driving, aerodynamic drag coefficient is0.63and lift coefficient is0.23and the gas flow smoothly and flow characteristics of vehicle are good.Considering the influence of convection, radiation and other heat transfer factors, the analyses of the flow field and temperature field of maximum torque and rated power conditions are carried out. The results show that the gas flow of the whole underhood is good but the presence of heat retention and recirculation in small space affects the cooling performance of cooling system and underhood.The influence of fan layout on the heat dissipation of underhood in idling condition is researched. It is found that IRFM layout made the cooling condition better than IFRM layout and the heat distribution is related to a variety of factors such as air flow. For the car of IRFM layout, the greater the distance between fan and radiator the better heat dissipation and there is an optimal distance which is related with the shape of fan between fan and engine making the best cooling performance.According to the principle of minimum cost and optimal engineering, the modification of adding guide plate and barrier plates is carried out. Simulation results show that most of heat recirculation is avoided and ambient temperature of intake air of underhood decrease obviously, besides the efficiency of the cooling system is improved in different degrees and the cooling performance of underhood is promoted.Finally, thermal balance test is carried out in the laboratory room and some temperatures of the corresponding conditions are measured. The result shows that experimental and simulation values are basically the same and error is in reasonable range, so the accuracy of the simulation is verified.