One of the most useful pieces of the device design process: How to choose a cooling system, and deciding if the project at hand requires an active cooling system or free convection or fans. Circling back to determining the need for an active cooling system and assessing, at the beginning of any design effort, if an active cooling system is required, the following flow chart will prove useful.
It starts with the requirements of the device to be cooled. In the case of an electronics system, the junction temperature requirements are supplied by the manufacturer. The same is true for batteries, laser diodes, or even human skin in a medical application. As discussed in the last few posts, the values required are the required device temperature, ambient air temperature, and an estimate of any conduction temperature rise associated with the anticipated packaging. As shown in the chart, active cooling is required if the maximum allowable temperature is less than or equal to the calculated temperature. If the required temperature is greater than the calculated temperature, then passive cooling with fans may be a possible approach.
This flow chart helps with decisions regarding the need for active cooling.