Hydraulic Simulation And Experimental Study On The Multi-Source And Ring-shaped Heating Network

With the development of urban central heating, multi-source and ring-shaped heating network receive more and more attention for its low energy consumption, high economic efficiency, safety and reliability, operability, and other advantages. Due to more heat sources and complex topology, it is difficult for the multi-source and ring-shaped heating network to grasp the hydraulic operating conditions and hydraulic characteristics, especially the determination of hydraulic intersection points, which can have direct impact on the actual range of supply for each heat source. So the operation of the multi-source and ring-shaped heating network should make sure that the hydraulic pipe network reaches an equilibrium state. The definition of intersection’s position can ensure the quality of the heating network and meet users’heat demand.Firstly, according to the graph theory、the Kirchhoff’s law、the pipeline characteristic equation and the ring energy equation, it’s useful to establish the hydraulic calculation’s simulation model of multi-source and ring-shaped networks with MATLAB software. By comparing and analyzing the data, the square resistance region formulas are adopted as pipe resistance calculation formula. In the multi-source simulation model, the minimum sum of squares method is firstly used to distribute ring-shaped network flow, and adjust the resistance of the valves to reach each user’s ideal flow. According to the distributed flow on both sides of the intersection user, the flow distribution of the ring-shaped network, and the entire network users’resistance can be drawn out. What’s more, by simplifying the ring-shaped network into branch-shaped network, the network hydraulic calculation complexity can be reduced under the premise of the exact calculation accuracy.Secondly, the thesis sets up a multi-source and ring-shaped heating experimentalnetwork, and the laboratory equipment includes pumps, electromagnetic flow meters, pressure gauges, thermometers, ball valves, balancing valves, stainless steel tubes with different diameters and so on. The major operating parameters of the experimental network, such as flow, pressure and temperature are monitored online. And the experimental network can form various modes of pipe network by opening and closing valves. Aiming to the two types of the single and double sources and ring-shaped heating network, the hydraulic simulation models are established. At the same time, based on the established simulation model and the corresponding network, the location of the hydraulic intersection and hydraulic characteristics problems were simulated and experimented to study when the pipe network is in hydraulic balance.In the simulation model, by changing the supply and the return pipe valves、individual user’s valves, the users’pressure and flow rate variation can be drawn out, and the intersection’s location in the model is consistent with the location from the experimental data. In a single-source ring-shaped heating network, the maximum deviation of users’pressure difference and flow are 1.06% and 3.24% respectively, while in a double-source ring-shaped heating network, the maximum deviation of user’s pressure difference and flow are 1.17% and 3.52% respectively. By comparing simulation model data and experimental data of the two networks, we can demonstrate the effectiveness and reliability of the hydraulic model for multi-source and ring-shaped heating networks. The research results from comparing and analyzing experimental and simulation model will have certain practical significance on hydraulic balance adjustment about large multi-source and ring-shaped heating network in the future.