Thermodynamic optimization of cooling techniques for electronic packages

This paper describes several fundamental trade offs that govern the optimization of cooling techniques for heat generating electric devices. Five basic cooling configurations are optimized. It is shown that in forced air cooling above room temperature the fan power requirement is minimum when the heat transfer contact area is optimized to a value that is of the order of 102 A f, where A f is the flow cross-sectional area. This optimal contact area is independent of whether the coolant is mixed or unmixed inside the heat generating enclosure. In air cooling with natural updraft, the heat generation rate (or amount of electronics, or overall thermal conductance) is maximum when the heat transfer contact area is of order 102 A f. In forced convection cooling at cryogenic temperatures, the refrigerator power requirement has minima with respect to the cold-end (refrigeration load) temperature and the heat transfer contact area. The optimal heat transfer area is again of the order of 102 A f.