A Novel Application of Thermoelectric Modules in an HVAC System Under Cold Climate Operation

Abstract

A vapor compression cycle (VCC) with integrated thermoelectric (TE) modules to boost the heating capacity of the system in an energy-efficient way, especially for cold climate operation, is suggested in this paper. While a baseline heat pump (HP) cycle absorbs heat from a source through an evaporator, the proposed system utilizes TE modules as an intermediate (or third) stage of an otherwise two-stage vapor compression system with a vapor injection compressor. This increases the overall system efficiency and augments the system capacity through the high coefficient of performance (COP) of the TE for small temperature lift conditions. To demonstrate the concept, a prototype refrigerant-to-solid (TE) heat exchanger, consisting of TE modules and microchannel flat tubes, was designed and fabricated so that the whole system could realize an additional 1 kW of heating capacity compared with the baseline system. The TE heat exchanger was integrated into a residential HP unit that uses R-410A as a refrigerant, and the system was tested in a laboratory under the severe condition of −17.8°C, in order to investigate the capacity improvement and the overall COP. Finally, an application of this technique in an automotive heating, ventilating, and air-conditioning system with HFC134a working fluid has been studied for the purpose of providing supplemental heating for electric vehicles and hybrid electric vehicles by establishing a detailed simulation model of a HP system with the TE heat exchanger. Both the laboratory test and the calculation study show that a VCC with integrated TE modules has both reasonable efficiency and increased heating capacity.