Abstract
Keywords - Thermal Comfort, Car Cabin, Thermal Mannequin, Equivalent Temperature, Computational Fluid Dynamics
Abstract - Thermal comfort sensation is mainly a psychological phenomenon and the only direct method of evaluating a vehicle thermal environment is the use of human subjects. However, by simulating in detail the heat loss of the human body and its relation with the thermal environment parameters, the effect of a vehicle microclimate in each body part can be objectively determined.
Unlike in buildings indoor spaces, in typical vehicle thermal environments one commonly can observe temperature asymmetries, local airflows and body heating/cooling. To compute this kind of environment parameters, besides the development of new instruments and experimental methods, Computational Fluid Dynamics (CFD) codes have been more and more used in the recent past. Researchers and car manufactures have been interested in developing a predictive model capable of integrating all the main environmental parameters to provide an accurate predictive tool for evaluation of the thermal comfort felt by vehicles occupants.
The final goal of the work here presented is the development of a numerical human model capable of reproducing the human thermal behaviour for evaluation of thermal comfort in passenger car cabins.
To attain this objective, a real scale laboratory model of a car cabin was constructed with a simplified geometry. Inside this compartment, several thermal environment conditions were generated and tests were carried out with and without the presence of a thermal mannequin capable of reproducing the human thermal behaviour. In the tests performed without the mannequin, the flow parameters were mapped by an automatically controlled traversing mechanism carrying a rack with eight low velocity thermal anemometers.
A Computer Aided Design (CAD) model, for both the cabin and the thermal mannequin, was built and, with these last, a coherent grid was generated in order to proceed with the computation of the flow parameters simulating the same thermal conditions by means of a CFD code.
In this phase of the work, the CFD simulations were made considering the mannequin (CAD model) as a geometrical barrier, with zero temperature gradient as boundary condition.
To evaluate thermal comfort, the Equivalent Temperature Index was calculated for each body part and for the whole body.