Abstract: Based on the experimental data of temperature and relative humidity examined by several sensors in a car during one day, the exponential model for temperature as a function of time and the closed-box model for calculation of relative humidity are put forward. With computational fluid dynamics (CFD) method, the finite model of car is built, then the relationship of temperature with time is demonstrated. The value of the constam calculated form the CFD simulation agrees with the exponential model very well. The results form the experiments and simulations here can be adopted as an important basis for developing new technology of reliability design for automotive electronics.

Key words: Car’s environment, CFD method, Relative humidity, Temperature