Real Evaluation of Thermal Comfort in the Car Passenger Compartment

Abstract

Thermal comfort is in increasing demand from motorists bound to cover more mileage than ever before in car driving. As a result car makers are striving for improved climate conditions inside the car to meet passenger demand for more comfortable trips. A crucial question arises: ‘How can such improved conditions be developed into a product, when a dynamic system capable of responding to customers' subjective sensations does not exist?’ They cannot be achieved through the conventional ‘robust design’ philosophy or the engineering shelf approach whose main targets are: product development from the design stages, a reduced lead time to market, the set-up of competitive products, as well as an ‘objective’ measurement of the end product performance. What is actually needed in designing satisfactory air conditioners is a dynamic simulation system capable of instantly monitoring ‘subjective’ sensations variously experienced by car passengers. To this end, a piece of gauging equipment was set up at Fiat to measure thermo fluid dynamic comfort conditions in real time, and trace back any local discomfort sources. The manikin used for such tests was a valuable example of providing a measuring instrument to meet subjective customers' requirements. Such a dummy is normally employed in Fiat climatic wind tunnels to determine a comfort index according to standard specifications. Reference limits were defined to correlate both experimental and test results with actual customers' requirements. Useful suggestions were also included to improve every sensor used throughout testing.