Preparation and properties of thermoelectric pipe-type modules

Different versions of thermoelectric modules composed of p-type Ca ₃Co₄O₉ (Co-349) and n-type CaMnO₃ (Mn-113) bulks, which have a pipe shape, were constructed using Ag electrodes, Ag paste and stainless steel tubes. Power generation was carried out in flame by combustion of natural gas. Water flowed inside the stainless steel tube for cooling. The number of pairs of oxide thermoelectric legs was 10-60. The devices were connected with the stainless steel tube coated with ZrO₂ by thermal spray using a dielectric paste composed of silica glass and iron oxide. The module consisting of 10 pairs of legs can generate about 20mW in a condition of 1053K of temperature around it, 293K and 16cm³/min of water temperature and flow rate inside the stainless steel tube, respectively. The power generation was carried out three times with intermediate cooling and kept on for 1h each time. Deterioration in power and internal resistance of the module were not observed after the third combustion. The module consisting of 54 pairs of legs can generate 1.5V, 0.28W and steam simultaneously by installing in an instantaneous water heater