A Combined CFD and Flow Network Modeling Approach for Vehicle Underhood Air Flow and Thermal Analysis

Conventional CFD analysis for underhood thermal management is quite involved and time consuming because of the complex geometry and flow distributions. As an alternative to full scale CFD modeling, a hybrid method of vehicle underhood air flow and thermal analysis is presented in this paper, using the principle of flow network modeling (FNM) and CFD. In the present method, the entire flow domain in underhood is broken into various air flow passages, which are represented in a FNM model by nodes and links. For each individual air flow passage selected, CFD analysis is carried out to obtain the pressure drop (ΔP) vs. flow rate (Q) relation by considering various air flow rates, leading to a characteristic curve for each passage. The distribution of flow rates and pressure is then determined by FNM through solving 1D mass and momentum conservation equations over the entire flow network. Subsequently, the air temperature distribution in the underhood space is predicted by energy analysis using measured surface temperature of the components. The results obtained from the simulation are compared with actual experimental measurements, showing good agreement. Using this hybrid modeling approach, the analysis and design cycle time for underhood thermal management can be reduced significantly.