Research on water pump and terminal control methods of centralized heating systems using variable-flow air-source heat pumps

 In this paper, a mathematical model of the variable-flow air-source heat pump (ASHP) for building heating is established to study the ASHP system performance under different water pump control modes. The results show that in order to maintain the high performance of the heat pump unit, the minimum economic flow rate is 30% of the rated flow rate. Among the three control modes, the power consumption of the water pump controlled by the pressure difference of the main supply and return water pipe is the highest, and that of the most disadvantageous end branch is the lowest. Compared with the pressure difference control of the main supply and return water pipe, the most disadvantageous end branch pressure difference control pump can save energy by 0-31.84%. Among the three control modes, the total power consumption of the temperature difference control system is always the largest, the pressure difference control at the most disadvantageous end is the lowest, and the average value of their difference reaches 6.20% under the high load rate. Both pressure difference control and temperature difference control can meet the heating needs of buildings, but the room temperature fluctuation of the pressure difference control is smaller, so it is suitable for places with higher room temperature requirements.