Maximum thermal spreading resistance for rectangular sources and plates with nonunity aspect ratios

An exact three-dimensional (3-D) solution is derived for the steady-state heat conduction equation with the source on an otherwise adiabatic surface and Newtonian cooling on the opposing surface. Dimensionless solutions are provided for maximum and source-averaged thermal spreading resistances. The solution for unit-source contours in a plane perpendicular to the source plane is also included. Maximum thermal spreading resistance plots are provided for several source-to-plate edge length ratios and source aspect ratios (plate maintained square). The Newtonian cooling effects are incorporated via a Biot number. Examples illustrate application of the theory.