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B2: Module design
Thermoelectric devices (TEDs) consist of two dissimilar semiconductors connected at a junction. TEDs work as electric power generators when the junction is exposed to a temperature differential. A TED with flow channels directing a working fluid through a heat exchanger integrated into the interconnecting shoes is an integrated thermoelectric device (iTED). Compared to conventional TEDs, iTEDs increase heat input to the TE elements by reducing the thermal resistance between the heat source and sink and the TE elements, promoting higher performance.
This study experimentally investigates the thermoelectric performance of iTEDs applied to waste-heat recovery. The iTED is constructed by bonding p- and n-type bismuth telluride materials to the surface of the interconnectors with the integrated heat exchanger. By keeping the cross-sectional flow area constant and a constant cold side temperature, the effects of hot fluid inlet temperatures (50<Th [oC] <250), flow rates ( 3,200<Re<10,000) and load resistance RL values on device voltage-current characteristics, power output, and conversion efficiency are investigated.
Experiments were conducted in ambient environment. Inlet and outlet temperatures of dry air were measured with K type thermocouples and provided QH. Thermal images were taken with an IR camera. The cold side temperature was maintained constant via recirculating water chilled heat sinks. The temperatures, voltage, current and resistance data was obtained using an Agilent data-acquisition system.
The preliminary results (P0, V-I, thermal images) were obtained for an iTED with a rectangular flow channel heat exchanger for several hot fluid flow rates with various inlet temperature . As the flow rate increases the temperature differential between the hot and cold junctions increases, resulting in a higher power output. Furthermore, for a given Re and Th, a maximum power output is achieved at an optimum current.