Study On Optimization Of Intermittent Operation Strategy Of Comprehensive Ventilation System Of Industrial Plant

In recent years,with the continuous improvement of comprehensive emission standards for air pollutants,a large number of highly polluting industrial workshops have undergone closed transformation.The indoor pollutants originally removed by natural ventilation have become mainly removed by mechanical ventilation,resulting in an increasing energy consumption of the ventilation system year by year.Reducing the energy consumption of the ventilation system has become an urgent demand.Therefore,this paper studies the energy-saving potential of intermittent ventilation strategy in industrial exhaust ventilation system.Intermittent ventilation strategy is a kind of intelligent ventilation.This process can be described as: when increasing the ventilation air volume is conducive to improving the indoor air quality or energy efficiency,increase the ventilation air volume;otherwise,reduce the air volume.However,in many factories,the fan of the ventilation system has a constant air volume,which cannot be adjusted arbitrarily and accurately.Therefore,the intermittent ventilation strategy in this study does not change the operating air volume in the process.The intermittent operation strategy can reduce the operation time of the ventilation system by simply turning on and off the fan,thus reducing the energy consumption of the ventilation system.Specific contents include the following aspects:Firstly,based on the ideal well-mixed ventilation model used in the ventilation system design,the basic characteristics and main influence variables of fan energy consumption under the intermittent ventilation strategy are studied.The results show that for the ideal well-mixed ventilation model,the main factors affecting the energy-saving effect of the intermittent ventilation strategy are the upper limit of indoor pollutant concentration and the durability of the fan.In the ideal well-mixed ventilation model,the calculation discriminant of the relative energy consumption of continuous ventilation strategy and intermittent ventilation strategy is given.It shows that the increase of the upper limit of indoor pollutant concentration and the increase of the fan’s switch-off time are beneficial to the energy saving of the intermittent ventilation strategy.On the contrary,the increase of the design air volume will usually lead to the increase of energy consumption of the intermittent ventilation strategy,and may even be more than the continuous ventilation strategy.Secondly,the CFD(computational fluid dynamics)models of the vortex ventilation system and the down-supply and up-exhaust ventilation system in the industrial plant are established.The grid independence verification and the comparison with the experimental data are carried out respectively to verify the accuracy of the established CFD model.Thirdly,the CFD model is used to generate a finite database containing two air distribution modes and operating parameters.To ensure the prediction accuracy of the ANN model,we tested three prediction algorithms used to predict the indoor pollutants concentration,and determined the Levenberg-Marquardt algorithm with the minimum error according to MSE(mean square error)and R(correlation coefficient).The number of cases for training and verification is determined by verifying an incremental case base.Finally,based on the above ANN model,GA(genetic algorithm)is used to optimize the intermittent ventilation strategy of the above two ventilation modes,to minimize the energy consumption of the ventilation system while ensuring the indoor air quality,and to analyze the differences of energy consumption and fan durability of different air distribution modes.The results show that the time to reach the steady airflow state also significantly affects the energy consumption of the intermittent ventilation strategy.When the fan durability requirements meet the time required to reach the stable airflow state,the ventilation system adopting the intermittent ventilation strategy can significantly reduce energy consumption,and the vortex ventilation system and the down-supply and up-exhaust ventilation system reduce 51.69 – 60.68% and 44.17 – 62.25% respectively.And the vortex ventilation system shows a higher energy saving rate in the lower upper limit of indoor pollutant concentration.