Simulation and Validation of Passenger Compartment Soaking and Cooling under Solar Load

Predicting the thermal comfort of the passenger compartment or the vehicle cabin using computational fluid dynamics (CFD) analysis helps reduce the cost and time of a heating ventilation and air-conditioning (HVAC) system development in any new vehicle program. This paper presents the simulation results of cabin soaking and cooling analysis done on an actual sports utility vehicle (SUV) prototype under constant solar load using the commercial CFD package Fluent™. These results are compared with test results. Cabin cooling and soaking analysis for a closed loop system that would include the HVAC system, the IP duct and the cabin with the air-conditioner (AC) operating in the recirculation mode is simulated. The heat rejected in the evaporator is assumed to be constant and this closed loop system analysis eliminates the need to be dependent on test results for input conditions like air flow rate and air temperature at duct inlet ports. This analysis helps us to predict the HVAC performance at cabin level and identify the hot spots inside the cabin if any. The air flow rate developed by HVAC system at particular applied rated rotational speed, air flow split at IP duct outlets and temperature predictions made inside the cabin for both soaking and cooling are in good agreement with test results.