Theoretical Study of A Thermoelectric-assisted Vapor Compression Cycle for Air-source Heat Pump Applications

In this paper, a thermoelectric-assisted vapor compression cycle (TVCC) is proposed for applications in air-source heat pump systems. Compared with the basic vapor compression cycle (BVCC), the TVCC using a thermoelectric heat exchanger (THEX) could enhance the heating capacity of the system in an energy-efficient way. To demonstrate the performance characteristics of TVCC, a case study on this cycle applied to a small air-source heat pump water heater has been conducted based on the developed mathematical model. Performances of both the new TVCC and BVCC are also compared. The simulation results show that the TVCC has 46.3%-103.0% increase and 14.7%-52.5% reduction in heating capacity and COP compared with those of the BVCC, respectively, under given conditions. Especially, at a higher evaporating or condensing temperature, the TVCC has better improvements in heating capacity. When there is no significant difference in COPs among the two cycles, the TVCC still performs better than BVCC by 13.0% in heating capacity by selecting the appropriate intermediate temperature. In addition, the TVCC can also achieve an improvement of 16.4%-21.7% in both the heating COP and capacity under the above given conditions, when compared with the BVCC with an assistant electric heater that is provided with the equivalent power input of THEX. Thus, the advantage of TVCC in heating capacity could be beneficial to the applications in small heat pumps if there is always need for auxiliary electric heat to solve the problem of low heating capacity of a heat pump at a low ambient temperature.