Experimental and theoretical studies on air exchange of portable devices

Small electronic devices are nowadays used in varying conditions, which expose them to stresses, which should be recognized and take into account in the planning work. The exact structure of the devices of interest may be very complicated to be used in diffusion and fluid mechanical calculations. Therefore, we performed leakage analysis, fitted to approximate analytical diffusion and air-exchange models, by helium injection method for one mobile phone type. In order to extend the applicability of our models we developed a more complicated numerical model for diffusion, thermal conduction and free convection inside the phone. The application of numerical model led an estimated range of values of 3 - 10 1/h for air-exchange coefficients in case of operational mobile phone.