Challenges and Opportunities of Numerically Simulating the Idle Load Case for Vehicle Thermal Management

Collective life-cycle data is needed when developing components like elastomer suspension mounts. Life-time prediction is only possible using thermal load frequency distributions. In addition to current extreme load cases, the Idle Load Case is examined at Mercedes-Benz Car Group as a collective load case for Vehicle Thermal Management (VTM) numerical simulations in early development stages. It combines validation opportunities for HVAC, cooling and transmission requirements in hot-country-type ambient conditions. Experiments in climatic wind tunnels and coupled 3D CFD and heat transfer simulations of the Idle Load Case have been performed. Measurements show steady conditions at the end of the load case. Decoupling of the torque converter, changes in ambient temperature and the technical implementation of a wind barrier for still air conditions exhibit influence on component-level results. Solar load, however, does not significantly change the examined component temperatures. Despite the challenge of a variety of influences on boundary conditions, numerical simulation using the standard simulation process with testing boundary conditions is shown to reproduce experimental results. Simulation data is used to explain phenomena observed in measurements and variation in their results, as well as to help interpret the influence of ambient conditions. Additionally, as one support point of a generalized collective, it is a necessary step towards establishing thermal load collectives and thus facilitating component dimensioning and testing. For further improvement, the dependence on experimental boundary conditions can be reduced by using 1D-simulation tools. This enables the transfer of this load case towards earlier development stages.