Performance of annular thermoelectric couples by simultaneously considering interface layers and boundary conditions

Annular thermoelectric couple (ATEC) is advantageous in eliminating the contacting thermal resistance between the flat-plate thermoelectric couple and the round-shaped heat source/heat sink, which can maximize the energy utilization. For a more precise performance prediction, a theoretical ATEC model is established with consideration of the interface layers, which adopts the boundary conditions of constant heat flux (Q(in)) on the hot side and convection on the cold side. Boundary condition of heat flux can match many applications of waste energy recovery and low-grade energy utilization, and convection boundary condition can match many practical cooling systems as well. New analytical solutions for the temperature field and performance are obtained in this work. The results show that the variation trend of performance with the annular shape parameter S-r is entirely different between under constant temperature boundary conditions and under boundary conditions of heat flux and convection. Impedance of interface layers causes temperature profile reduction and performance degradation, especially in relatively short ATECs. Increasing the length of thermoelectric leg can improve the performance of ATECs and diminish effects of interface layers. This study is beneficial for designing the actual annular thermoelectric generators.