Analysis of the temperature distribution in a guarded hot plate apparatus for measuring thermal conductivity

A guarded hot plate apparatus (GHPA) is used to measure the thermal conductivity of insulating materials. This apparatus uses a circular heat source. It was studied the applications of such kind of heat sources. The particular problem for which the solution is developed here concerns with the use of a heater embedded in a central plate and guard ring to generate a heat flux. An elegant closed form analytical solution was obtained for this problem. The Green’s function formulation was used to compute the distribution of temperatures in the central plate and the guard. The analytic results were compared with measurements made on aluminum plates and it was found that they are in good agreement with experimental data with a standard deviation of 3%. These results can be used for obtaining the average temperature in the plates, which are used as the representative temperature. Likewise, the position of the main temperature zone was determined; this position is the one where the thermocouples should be placed on the plates of GHPA.