Simulation research of a dual-loop booster heat pump system on district heating under ultra-low temperature

Abstract

ULTDH (ultra-low temperature district heating) system improves the shortcoming of significant loss of heating network in traditional district heating systems. This work proposes a dual-loop booster heat pump for ULTDH to improve the heating capacity and COP. The system is modeled by MATLAB, and the water temperature between the two loops is solved by the NSGA-II algorithm (Non-dominated Sorting Genetic Algorithm-II algorithm). The simulation results show that when the heat source temperature changes from 20 °C to 40 °C, the COP and heating capacity of the dual-loop system increase by 43.79% and 90.30%, respectively, which are higher than those of the single-loop system. When the temperature difference between the inlet and outlet of the evaporator is increased, the heating capacity of the dual-loop system is still 7.31–33.47% higher than that of the single-loop system. When the hot water supply temperature is 60 °C, the COP of the dual-loop system is 3.34, which is 23.70% higher than that of the single-loop system. During the whole heating period in Beijing, the dual-loop system can save 17.67 % of the electric energy than the single-loop system. The dual-loop system shows excellent advantages in heating capacity and COP.