Suction vs. Pressure Forced Air Cooling-Part II

In present compact electronic equipment, efficient cooling is a prime design factor. Certain aspects of the current state of the art of cooling are subjected to continuing controversy. In an electronic equipment, cooled by forced air flow, fans may be placed at the air inlet location, at the air outlet, or at both locations. Depending on the location of fans, a different air flow pattern is generated within the equipment. One essential factor which determines cooling efficiency is the escape of air from the module circuit chamber to adjacent spaces in the equipment. The escaping air ceases to absorb heat from the electronic modules. Thus, cooling efficiency is closely linked to the containment of air, or air flow pattern, and hence, to the fan location. A logical and a mathematical analysis on the subject is here presented. Mathematical results are summarized. An appendix contains detailed mathematical derivations.