Experimental Investigation of the Improvement Potential of a Heat Pump Equipped with a Two-Phase Ejector

In this paper, an experimental investigation of the performance improvement of a heat pump equipped with a two-phase ejector, called an ejector-expansion heat pump (EEHP), is proposed. The system performance of the EEHP is compared with that of a vapor-compression heat pump (VCHP). The improvement potential is determined and discussed. The heat pump test system based on a water-to-water heat pump that can experiment with both the EEHP and the VCHP is constructed. A two-phase ejector with a cooling load of up to 2500 W is installed for the experiment. The results show that the EEHP always produces a higher heating rate and COP(HP )than the VCHP under the specified working conditions. The heating COPHP is increased by 5.7-11.6% depending on the working conditions. It is also found that, under the same heat sink and heat source temperature, the EEHP can produce a lower compressor discharge temperature and a lower compressor pressure ratio than the VCHP. This is evidence that the two-phase ejector can provide the compressor with better working characteristics, which yields a longer compressor lifetime. It is demonstrated that the expansion pressure ratio is key to the performance of the EEHP. A larger expansion pressure ratio yields greater improvement potential when compared with the VCHP.

Automated summary

This paper proposes an experimental study on the performance improvement of the ejector-expansion heat pump (EEHP), which is equipped with a two-phase ejector. The system performance of the EEHP is compared with that of a vapor-compression heat pump (VCHP), and the potential for improvement is determined and discussed. The results show that the EEHP always outperforms the VCHP in terms of heating rate and COP(HP), with an increase in COPHP by 5.7-11.6% depending on the working conditions. It is also observed that the EEHP exhibits lower compressor discharge temperature and pressure ratio, indicating better working characteristics and longer compressor lifetime compared to the VCHP.