Effect of buffer tank capacity on performance of air-source heat pumps at low ambient temperature

In the performance testing laboratory of air-source heat pump units, the experiments are carried out on the performance of 2 205 kW and 3 675 kW air-source heat pumps with direct supply and 100 L and 150 L buffer tanks respectively to explore the effects of adding different capacity buffer tanks and different operation modes on the operation performance of hot water air-source heat pumps. The results show that when the ambient temperature is -6 ℃, the heating capacity of the 3 675 kW unit adding 100 L and 150 L buffer tank decreases by 9.6% and 10.2% than that of the direct supply, respectively, and the COP decreases by 9.5% and 9.9%, respectively. After the addition of a 100 L buffer tank, the heating capacity of the 2 205 kW unit decreases by 6.3% and COP decreases by 7.0% compared with the direct supply. Compared with the continuous operation mode, the heating capacity of the intermittent operation mode 2 in direct supply, adding 100 L and 150 L buffer tank increases by 2.5%, 4.5% and 5.0%, respectively, and the COP increases by 1.8%, 3.7% and 4.5%, respectively.