A clarification of the adiabatic heat transfer coefficient as applied to convective cooling of electronics

The objective is to clarify the concept of adiabatic heat transfer coefficient and its application by reviewing its origins and by examining a series of numerical experiments on a well-defined model problem. The model problem consists of a series of one-dimensional thermal sources spaced on one wall of a parallel planes channel. Flow into the channel is either forced by an external blower, or induced into the channel by buoyancy, that is by natural drafting. Results are examined for the base case of non-conducting substrate. The effects of substrate conduction and local buoyancy effects are subsequently introduced and examined. The important conclusion is that the adiabatic heat transfer coefficient is not dependent on temperature history, depending solely on local hydrodynamics. Two important factors which influence the adiabatic heat transfer coefficient are local buoyancy and board conduction effects. Results are discussed for the cases of buoyancy induced channel flow. The usefulness of the adiabatic heat transfer coefficient for the case of natural convection is considered