Transient hot plate method with two temperature measurements for thermal characterization of metals

This paper presents a study of the transient hot plate method with simultaneous measurements of front (heated) and rear face temperatures. In contrast to the classical device, a single sample of the material to be thermally characterized is set in contact with a planar heating element and inserted between two pieces of insulating material. The purpose was to simultaneously estimate thermal effusivity and conductivity of metals in a limited time t(2) (< 90 s) using a low-cost device. Heat transfer has been modelled with a quadrupole formalism to simulate the front and rear face temperatures T-0(t) and T-2(t). Simulation is used to fix the minimal thickness of the sample so that the front face temperature remains independent of thermal conductivity during a time t(1) > 30 s. The thermal effusivity is estimated between 0 and t(1) by minimization of the quadratic errors between the experimental curve and the simulated curve TO(t). The thermal conductivity is estimated between 0 and t(2) by minimization of the quadratic errors between the experimental curve and the simulated curve T-2(t). To validate the model and the estimation process, experimental tests were realized on four samples of metals with conductivities varying from 6 to 140 W m(-1) degrees C-1 and having typical area 44.5 x 44.5 mm(2) and thickness varying from 16.7 to 80 mm.