Substrate thermal conductivity plays a critical role in the heat removal
in natural convection cooling of discrete heat sources. It is removal
in natural convection cooling of discrete heat sources. It is well
known that printed circuit boards (PCB) used in electronic systems display
strongly anisotropic thermal conduction behavior. In the present
investigation, conjugate conduction, natural convection and radiation heat
transfer from a flush heat source mounted on an orthotropic substrate in
an air filled cubic enclosure is numerically examined. Two types
of boundary conditions are investigated at the back of the substrate: (i)
insulated and (ii) prescribed temperature. The results are presented
as surface temperatures, Nusselt numbers and thermal resistances.
Heat transfer budgets ate presented to illustrate. Heat transfer
budgets are presented to illustrate the combined effects of orthotropic
thermal conductivity and surface radiation. The anisotropy in thermal
conductivity is found to influence the heat transfer in very different
ways for the two boundary conditions considered.
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