AN ANALYTICAL SOLUTION TO TRANSIENT HEAT-CONDUCTION IN A COMPOSITE REGION WITH A CYLINDRICAL HEAT-SOURCE

An approximate analytical solution to the transient heat-conduction problem in a large composite region with an internal cylindrical source is presented. The generalized orthogonal expansion technique is utilized in deriving the solution. Such problems are encountered in the design or simulation of the ground-coupled hear exchangers used in ground-coupled heat pumps. Solutions are presented for the nondimensional temperature as a function of the ratios of the thermal conductivities and thermal diffusivities of the two materials in the layers. To verify the correctness of the solution, comparisons are made between the two-layer composite solution and the classical homogeneous cylindrical source solution and a finite difference solution.