Study On Mixing Characteristics Of Parallel Push-pull Ventilation System

Push-pull ventilation system is an effective ways to control industrial pollutants.Reducing the degree of mixing of pollutants and supply airflow is of great significance for improving pollutant capture efficiency,reducing exhaust air volume,and designing an economical and energy-saving system.In this paper,the method of combining theory,numerical simulation and experiment is mainly used to study the influence of air supply uniformity and air supply direction on the mixing characteristics of the push-pull flow field.On this basis,the economics of the parallel push-pull ventilation system is explored,with a view to providing a theoretical basis and basis for more accurately reducing system energy consumption and optimizing the push-pull ventilation system.First,in order to evaluate the mixing characteristics of ambient air along the flow path,the evaluation indexes of ambient air mixing rate were proposed,and five air supply distribution models were designed according to the actual situation.It was found that linear up and side type had the highest mixing amount of ambient air,followed by uniform and linear down type.On this basis,the ambient air mixture under different influence factors is studied.The results show that different influence factors will not change the distribution law of ambient air volume under different supply air distribution.In this paper,two types of pollutants,the face type and the point source type,are designed,and the mixing efficiency of different types of pollutants in the flow field is studied under different distribution of supply air.The results show that the mixing efficiency of pollutants is the lowest under linear up distribution of face type pollutants and the lowest under uniform distribution of point source pollutants.On this basis,the design idea that the distribution of air supply should be selected reasonably according to the type of pollutants and the control idea of the system is put forward.Secondly,this paper establishes five models of air supply direction to study the mixing characteristics of the push-pull ventilation system under different air supply directions.The study found that the mixing amount of ambient air in the inconsistent air supply direction may decrease or increase compared to the consistent air supply direction.However,the overall ambient air volume and the mixing efficiency of pollutants mixed along the air supply direction will definitely increase.Finally,based on the above analysis,the economic experiment of parallel flow push-pull ventilation system was established,and three different push-pull ventilation systems with different distribution and direction of air supply were designed,parallel push-pull ventilation system,low-speed push-pull ventilation system and high-speed push-pull ventilation system.The flow rate of the system is reducing by reducing the height of the exhaust hood,and used flow visualization technology and pollutant concentration measurement technology to observe the distribution of pollutants.The results of the study found that compared to the other two types of push-pull ventilation systems,when the exhaust flow of the parallel flow push-pull ventilation system will decrease to 29% of the original design,most of the pollutants can still be effectively controlled.Based on this,this paper proposes a new design method concept for the parallel push-pull ventilation system,that is,the exhaust hood of the parallel flow push-pull ventilation system only needs to remove the polluted airflow,and does not need to suction all the polluted airflow and the supply air.The above research conclusions provide a basis for the design and optimization of the air supply parameters of the push-pull ventilation system in the future.