In this study

a novel defrosting method was developed for an air-source heat pump (ASHP) with a multi-circuit outdoor coil operating in a low-temperature and high-humidity environment. The outdoor heat exchanger of the ASHP is divided into three independent circuits for segmental defrosting. When a defrost operation is required

one of the circuits uses part of the high-temperature gas at the compressor outlet to defrost. At this time

part of the high-temperature gas still enters the indoor heat exchanger for heating

while the other two circuits of the outdoor heat exchanger are used as evaporators. The novel segmental defrosting method was compared with the traditional reverse cycle defrosting (RCD)

and the results indicated that the overall performance of the system was better than that of RCD. Under the conditions of ambient temperature of 1 °C

relative humidity of 80%

and condensing temperature of 40 °C

the reverse cycle defrosting time is 246 s

which is shorter than the segmental defrosting time of 330 s. Further

the energy consumption of reverse circulation is 522.1 kJ

which is lower than that of 735.8 kJ for segmental defrosting. However

reverse cycle defrosting needs to absorb heat from the water-side heat exchanger. An average heating performance of 2.23 kW can be maintained during the defrosting process

with small fluctuations in suction and exhaust pressure and a slow decline in COP

and a continuous heat supply can be achieved during the defrosting process.