Tracking the two-phase flow through a vehicle cowl box

Abstract

The penetration of rainwater through the heating, ventilation and air conditioning (HVAC) system of a vehicle directly affects the provision of thermal comfort within the vehicle passenger compartment. Present vehicle designs restrict considerably the air management processes owing to reduced space and tighter packaging. In this study, a cowl box, the first element of the vehicle HVAC system, is examined through the scrutiny of the flow field prevailing within it. Particular attention is paid to the effects of cowl flooding on water ingress. The work described is both experimental and computational. An optical anemometer is used to acquire the experimental data within a transparent model of a cowl box. The results are then used to validate and tune the computational fluid dynamics (CFD) calculations performed on the same cowl geometry as well as to perform parametric studies of the features that affect the rainwater penetration. The phenomenon of rainwater ingress has integrated factors with the overall vehicle geometry, body seals at the cowl space, wipers set-up, HVAC blower set-up, rain intensity and road conditions. Therefore, in addition to the model- scale experiments, a full-scale vehicle is examined in the Flow Diagnostics Laboratory (FDL) climatic wind tunnel. The results obtained, using non-intrusive instrumentation, are also used to verify the computational model.