Optimal diameter of district heating pipe network based on the hybrid operation of distributed variable speed pumps and regulating valves

Abstract

The district heating system that uses the hybrid operation of distributed variable speed pumps and regulating valves can effectively reduce the pressure level at the far-end of the heating network, while retaining the energy saving advantages of the distributed variable speed pump system and ensuring the safe operation of the heating network. In this study, pipe network optimization based on genetic algorithm was used to determine the pipe diameter required for the hybrid operation of distributed variable speed pumps and regulating valves. A mathematical model was established to evaluate the economic efficacy based on the annual equivalent cost. The zero-pressure difference point was evaluated to optimize the pipe diameter. A real pipe network was assessed to evaluate the efficacy of the method, and a sensitivity analysis of pressure constraints and economic factors was conducted. Our results show the system of hybrid operation of distributed variable speed pumps and regulating valves can reduce the annual equivalent cost by about 10.35% compared to the conventional central circulating pump system. In addition, the annual energy consumption due to heat loss and pump operation is only 0.36% higher than that of the conventional central circulating pump system.