Thermal deformation measurement in thermoelectric coolers by ESPI and DIC method

Abstract

Based on the Peltier effect, the thermoelectric cooler (TEC) is a device which can transfer thermal energy through current to conveniently make the module cooled and heated on the opposite sides. Bismuth telluride (Bi 2Te3) is the material commonly used for producing the Peltier effect. An array of small bismuth telluride couples is placed between two ceramic plates and bonded to them. Two electric wires were soldered to each electrode of the TEC and connected to a direct current (DC) power supply. When a DC is applied, heat is moved from one side to another side. Occasionally, the structure of the TEC is cracked or even broken down due to the significant thermal expansion mismatch between the bismuth telluride cubes and the ceramic plates. To ensure the safety of the TEC, it is therefore important to investigate the thermal deformation induced. In this paper, both the electronic speckle pattern interferometry (ESPI) and the digital image correlation (DIC) method were used to measure the small and large thermal deformations induced in a centrally supported TEC, respectively. The results show that the warpage, i.e. the out-of-plane displacement, varies linearly with respect to the temperature difference between the hot and cold plates irrespective the state of deformation (expansion or contraction) of the hot and cold plates.