Experimental study on a water and air source high-temperature heat pump using a low GWP refrigerant.

A high-temperature heat pump using a low GWP refrigerant, such as R1234yf or R454C, were experimentally investigated to supply hot water. The temperature of hot water ranged from 45 °C to 90 °C for R1234yf and ranged from 45 °C to 75 °C for R454C, while the temperature of supplied water ranged from 6 °C to 24 °C. The temperature of heat sources ranged from 7 °C to 25 °C. Degrees of sub-cooling of sub-critical heat pump cycles ranged from 10 °C to 70 °C because large temperature-rise was needed to heat supplied water. A test apparatus and measurement system were presented. The test results using R1234yf and a water-source evaporator were discussed in comparison with the test results of the former work using R1234yf and an air-source evaporator. The test results using R1234yf and a water-source evaporator were discussed in comparison with the test results using R454C.