Electric and thermal contact resistances of the new type thermoelectric module assembled by a screwing method

For several years, we have tried to realize a new type module composed of thermoelectric elements assembled by a screwing method to avoid the thermal shear stress. We prepared a test module named the HB-twin module. In order to reduce the electric contact resistance between metallic parts in the module, we used "metallic paste" of liquid InGa+solid Zn. For the electric insulating materials at high and low temperature sides of the module, an alumina thin plate with silicone grease and a "sealing wax sheet" were used, respectively. The thermoelectric generating power and heat transfer properties of the HB-twin module were measured in comparison with those of the HZ-14 module, commercially available, with similar cross-sectional area in which the alumina thin plates were used at both sides. The maximum electric power of the HB-twin module was slightly lower than that of the HZ-14 module. In both modules, the maximum electric power was 50-70% of the generating ability of the element chips owing to the existence of electric contact resistance in the modules. The use of the metallic paste for the HB-twin module proved successful, since the effect of electric contact resistance was not more than that of the HZ-14 module.