A variable flow control logic for heating supply transfer by time-periods in distributed air source heat pump heating systems

To improve the operational stability, economic performance, and energy efficiency of distributed air source heat pump (ASHP) space heating systems, a regulation method was proposed for systems with radiant floor heating. On this basis, a control logic for heating supply transfer by time-periods was proposed to accommodate the slow response characteristics related to pipeline delay and building thermal inertia in distributed ASHP space heating systems. By integrating peak-valley electricity pricing policies and ASHP performance characteristics, the heating supply was optimally allocated among different control time-periods under the constraint of indoor temperature stability, thereby reducing energy consumption and operating costs. A field experiment was conducted in a residential community in Hebei, China. After correction with measured data, the regulation of radiant floor heating (RRFH) curve showed maximum deviations of 0.60 °C and 0.49 °C for supply and return water temperatures, respectively. Sensitivity analysis indicated that the 8 h control time-period provided a practical balance among energy consumption, operating cost, regulation frequency, and implementation complexity. Under the proposed control logic with an 8 h control time-period, the maximum deviations of supply and return water temperatures were 0.72 °C and 0.41 °C, and the indoor temperature of representative rooms remained within ±2 °C of the setpoint. Furthermore, the energy-saving and economic performance of the proposed control logic were evaluated using typical day calculations for four northern cities in China. The results showed total energy-saving and cost-saving rates of about 8% and 10%, respectively.