Experimental investigation of an indirect-expansion solar-assisted multi-functional heat pump system under various working modes

Heat pumps have become a promising energy-saving technology amongst the growing problem of pollution and increasing cost of tradition energy. In this study, a novel indirect-expansion solar-assisted multi-functional heat pump system with the functions of space heating, water heating and space cooling has been proposed. The working mode can be easily switched according to the user’s needs by controlling the refrigerant valve. The performance of the system operating under different working modes was tested under a stable external environment in the enthalpy difference lab with solar simulator. The results showed that the IX-SAMHP system could realise five different working modes with relatively high COP. For space cooling mode and air source space heating mode, the system worked in steady state under the stably external environment temperature with the COP of 2.57 and 2.86 respectively. For solar water heating mode, the performance could be improved by utilising solar energy as a heat source. When the irradiation increased from 0W/m² to 500 W/m², the heating time shortened by 30 minutes. For solar space heating mode, the average heat capacity and COP increased by 38.4% and 31.9% respectively, with the initial water temperature increasing from 20°C to 40°C.