Optimum design on the performance parameters of a two-stage combined semiconductor thermoelectric heat pump

A new cycle model of a two-stage combined semiconductor thermoelectric device that is used as a heat pump is established. The influence of Joule heating due to the electric current and heat leak due to the temperature difference between the hot and the cold junctions on the performance of the system is investigated. The general expressions of three important performance parameters, the coefficient of performance (COP), the rate of heat pumping and the power input, are derived. The maximum COP and the corresponding parameters are calculated. The internal structure parameter of the thermoelectric device is optimized. The reasonable range of the electric current is determined. The results obtained here are compared with those of a single-stage semiconductor thermoelectric heat pump. The advantages of two-stage combined thermoelectric heat pumps are expounded. Moreover, it is shown that when the range of the temperatures between the heated space and the low-temperature heat reservoir is large, a single-stage thermoelectric heat pump will lose its function, so a two-stage combined thermoelectric heat pump must be used.