Dynamic Hydraulic Simulation And Optimization Of Central Heating System In A Campus

The heating system of a university and its"source network end"integrated hierarchical fine control and energy saving transformation were investigated and analyzed.The investigation and analysis showed that the perfection of the system heat meter information and the accuracy of the pressure gauge measurement played an important role in the intelligent control and operation of the heat network,and the system also had a certain hydraulic and thermal imbalance.Based on the different heat types of the system,the operation scheme of time-divided and zonal complementary intermittent heating in winter vacation was proposed.The intermittent regulation test was carried out on nine unmanned thermal entrances on February 26and 27,2020.The operation results show that the energy saving effect of intermittent regulation can reach more than 50%.If the intermittent heating method based on time division and complementary division is adopted during the whole winter vacation in2020,the gas volume can be saved by 100,000 m³ and the load stability of the boiler in the station can be ensured.A dynamic hydraulic optimization model of the system was established to solve the problem of hydraulic and thermodynamic imbalance in the current system.The model was designed to minimize the energy consumption of the pump,and the pump frequency,valve opening and thermal inlet flow were optimized by nonlinear programming optimization algorithm.Based on the model,if the heating season2019-2020 adopts the dynamic hydraulic regulation operation mode,the energy consumption will be significantly reduced.The results show that the water pump energy consumption under the hourly,day and night dynamic regulation mode is51.2MW·h,55.7MW·h and 62.1MW·h,respectively,which are 38.2%,32.7%and25.0%lower than the actual operation mode.After optimization,the operating flow is reduced,and the heating load is reduced at the same time.Compared with the actual operation,the heating load can be reduced by 9.0%,7.6%and 5.5%,respectively.In addition,if the system carries out dynamic hydraulic regulation under ideal load,the energy consumption of the ideal pump operation is 32.7MW·h,which is 56.3%lower than the actual operation,and the heat load is 32.4%lower than the actual operation.The heating system has a large space for improvement and improvement.Due to added new load at the end of the system in 2020-2021 heating season,the model parameters were calibrated and verified experimentally,and within the range of10%of valve opening error,the opening of each control inlet valve under constant frequency operation of the pump could be accurately predicted.The actual operation shows that the existing pumps and boilers can meet the normal operation of the system after the new load is added.For the new load,after ensuring the flow in the period of the highest load demand,the oversupply of the flow in other periods,especially at night,can be reduced through dynamic hydraulic optimization,and the pressure difference demand of the new load can be ensured at the same time.This is for If warm maintain large temperature difference of small flow rate（7.3℃for the return water temperature difference）,and the actual operation（1.8～7.3℃）for the backwater temperature difference than which can reduce the frequency of water pump to run the Numbers and optimize operation,the optimized 2020.11.3-2021.2.28 during operation the pump power consumption,a total of 35.7 MW·h,61.1%lower than the actual running water pump power consumption,reduced electricity to reduce 28321yuan,the CO₂ emissions by 44023 kg.It should be noted that it is difficult to meet the pressure differential demand when the flow rate is low in the operation of large temperature difference.Because the flow rate of the uncontrolled end is low in the early stage of heating,the pressure difference between supply and return water under this flow condition is significantly lower than the capital pressure difference of the inlet（62-86 kPa）according to the hydraulic model.Therefore,although the load demand can be met under the condition of large temperature difference,it is uncertain whether the water circulation can be ensured well.Therefore,it can be considered to increase the head of the water pump or adopt the distributed pressure to the household.