Fundamentals of Convective Cooling
With the exception of space applications, there are hardly any practical thermal cooling problems that do not include convection, Convection involves heat transfer between the surface of a solid and its surrounding fluid. The rate at which heat is transferred is evaluated by
This equation only looks simple! h-the heat transfer coefficient-varies depending on the flow regime, i.e., laminar or turbulent, geometry and fluid properties. If we rewrite the convection equation slightly differently, we obtain:
q=Q/A is called the heat flux and is heat transfer rate per unit area. The units for heat transfer coefficient (h) is (W/(m2 C) or Btu/(hr ft2 F)). T∞ is called bulk temperature and is unaffected by the heat input from the solid. In electronics packaging problems, this assumption holds at some times and at other times, one must exercise caution in using this relationship.