Research On Energy Efficiency Optimization And Its Influence Mechanism Of Large-scale Central Air Conditioning Chilled Water System Considering Load Randomness

Large-scale central air-conditioning system is a typical multi-variable,non-linear,strong coupling,and large lag system.As the scale of the building continues to expand,the topological structure of the chilled water pipe network that matches it has become more complex and diverse.The mismatch between the design and selection of the chilled water system and the actual operating load results in the air-conditioning system being in partial-load operation for a long time,with low system operating efficiency and high operating energy consumption.Therefore,under the premise of ensuring the comfort of end users,considering the random distribution characteristics of the load of each node of the air conditioning pipe network,exploring the energy efficiency optimization method of the central air conditioning chilled water system and its influence mechanism,it is certain to solve the technical problems of energy saving operation and optimization design of the chilled water system The guiding significance.This paper studies the optimization of chilled water system energy efficiency characteristics and its influence mechanism under random load constraints,constructs a fancoil system thermal calculation model and a hybrid pipe network hydraulic calculation model,and studies the end of each branch of the chilled water system and the pipe network under variable load conditions.Coupled operation characteristics,using the sub-optimal calculation method based on sub-optimal control theory of random walking + optimization area division to construct the chilled water system energy efficiency optimization model,and put forward the chilled water system global energy efficiency evaluation index—pipe network energy utilization efficiency,analysis Under different load distribution types,the influence of the distribution of pipe diameters of various types of pipe sections on the energy efficiency characteristics of the system.The goal is to design a sub-optimal pipe network that has certain adaptability to each load distribution type.The results show that: sub-optimal calculation The method is applied to the optimization of the energy efficiency characteristics of the central airconditioning chilled water system and has a good optimization effect.The change of the initial value of the optimization calculation independent variable affects the optimization calculation result within 5%,and the optimization calculation result is stable.Compared with the traditional design,the optimized design of the pipe network increases the initial investment cost of the pipe network,reduces the annual operating cost,and reduces the annual conversion cost of the pipe network.Compared with the traditional pipe network design method under various load conditions,the optimized design of the pipe network system has the same energy efficiency There is a certain degree of improvement,and the maximum and minimum increase in energy utilization efficiency of the pipeline network is 4.6% and 1.6% respectively.Exploring the sensitivity of pipe diameters of various types of pipe sections to random loads and the influence of pipe network size,chilled water inlet temperature and the actual operating life cycle of the system on the overall energy efficiency characteristics of the system.The results show that the terminal load and outdoor environmental parameters Under the same premise,as the scale of the pipe network increases,the energy utilization efficiency of the pipe network decreases.The larger the pipe network scale,the more obvious the improvement of the energy efficiency of the optimized design pipe network.The optimized design of each pipe network scale working condition is compared with the traditional design.The maximum and minimum differences in energy utilization efficiency of the pipe network are 1.92% and 0.17%;when the return water temperature remains unchanged,the higher the chilled water inlet temperature,the lower the energy use efficiency of the pipe network.As the chilled water temperature increases,optimization The energy efficiency difference between the design and the traditional design of the pipe network increased from 0.76% to 6.72%;as the actual operating life of the pipe network increases,the energy use efficiency of the pipe network gradually increases,and the difference between the optimized design and the traditional design The increase in the actual operating life of the pipe network increased from 0.18% to 1.97%.The greater the actual operating life of the pipe network,the more obvious the improvement in the energy efficiency of the optimized design of the pipe network.