Spreading resistance of isoflux rectangles and strips on compound flux channels

The general expression for the spreading resistance of an isoflux, rectangular heat source on a two-layer rectangular Bur channel with convective or conductive cooling at one boundary is presented. The general expression depends on several dimensionless geometric and thermal parameters. Expressions are given for some two- and three-dimensional spreading resistances for two-layer and isotropic finite and semi-infinite systems. The effect of heat flux distribution over strip sources on two-dimensional spreading resistances is discussed. Tabulated values are presented for three flux distributions, the true isothermal strip, and a related nonisoflux, nonisothermal problem. For narrow strips, the effect of the flux distribution becomes relatively small. The dimensionless spreading resistance for an isoflux square source on an Isotropic square flux tube is discussed, and a correlation equation is reported. The closed-form expression for the dimensionless spreading resistance for an isoflux rectangular source on an isotropic half space is given.