Improved Passenger Thermal Comfort Prediction in the Preprototype Phase by Transient Interior CFD Analysis Including Mannequins

It is the overall objective in the development of automotive climate control systems to guarantee a subjective feeling of thermal comfort for each passenger. The fulfillment of all physical specification parameters of a HVAC unit, such as airflow, temperature, etc., does not automatically achieve this goal. Engineers need to ensure that the consequences of the HVAC design lead to the desired demands inside the passenger compartment. In this paper a method will be presented that enables a time dependent detailed prediction of personal thermal comfort for each passenger in standard cooldown or warm-up tests. In addition to calculating overall comfort ratings for each passenger, transient local body segment comfort ratings can be calculated to determine local variations in comfort. It is therefore possible to discover reasons for potential discomfort in a much more detailed way. To accomplish this, mannequins are added to the CFD model of the cabin. These mannequins are subdivided into different body parts, such as head, chest, arms, etc. This is done in conformance with VISTEON's comfort model that is used to convert the results of the CFD analysis, such as temperature and velocity on the mannequin surfaces, into a subjective comfort rating. The basis of the time dependent CFD calculation is a very robust, fast and accurate finite element flow solver. VISTEON has developed a parametric three dimensional modeling technique which allows the engineer to rapidly build and change a CFD model of the passenger cabin. The tool is used in the early stages of the development process before detailed CAD data of the interior and prototypes are available.