Estimating Temperature Rise in Electronic Equipment Cases

In the design of airborne electronic equipment of minimum size and weight, the ambient temperature rating of components is often limiting. This ambient temperature is the equilibrium temperature inside the case, and may determine either the choice of components or the need for external cooling means. Calculation of equilibrium temperature requires knowledge of the power dissipated in the case and the rate of heat transfer to the surroundings by conduction, convection, and radiation. To avoid often laborious calculation, a series of charts are presented as an aid to estimating temperature rise. Graphical corrections for pressure altitude are given, together with a discussion of the effects of case color, high-speed aircraft skin temprerature, and other variables.