Study On The Characteristics Of Flow Field Affected By Obstacle With Push-pull Ventilation

With China rising in the political and economic status of the world, the Chineseindustry is in rapid development of state, accompanied by the increasing number ofincreasingly large scale industrial buildings where they stand. However, the pollutionin the industrial buildings has become increasingly serious, and has become a veryprominent problem. Mechanical ventilation is one of the best and most efficient way tosolve indoor air environment problems, in which the push-pull ventilation systems isvery broad used and concerned because of its high collection efficiency, saving theamount of wind, push and pull flows with strong anti-interference ability. Often thereare many kinds of obstacles existing in practical engineering flow field of push-pullventilation systems. Few people consider the factor there is an obstacle, therefore thispaper focuses on the influences of obstacles to the flow field of push-pull ventilationsystem. First the means of fuming experiments on the push and pull flow field of theventilation system with obstacles are been used to get the qualitative conclusions, thenQuantitative conclusions obtained by experimental tests and numerical simulationmethod.Smoke experiment is an approach to research the influence of obstacles on thepush and pull flow field. After debugging the system, we use smoke generators tosimulate pollutant and analyse pollutant capture efficiency of push and pull flow fieldwith obstacles. Then make comparative analysis of experimental photos and drawqualitative conclusions.The experimental test is one of the important study methods in this article. Designcalculations of the experiment rig is based on flow analogy method proposed by Lin tailang, then debug the experiment rig in accordance with the computational dataincluded the blowing volumetric flow rate Q1, the blowing blow velocity V1, thesuction volumetric flow rate Q3and the suction blow velocity V3.After that, we test theflow field in the conditions of different positions of Obstructions. Ultimately, analysisof experimental data are been made to obtain the size of the region that is influencedby obstacle.We do a research on the flow field of push-pull ventilation system with obstaclesthrough numerical simulation method and get the size of the region that is influencedby obstacles while obstacles are in different positions. The model is optimized bychange the parameters of the size of the outlet and pull hood, while make a discussionon the affect of outlet and pull hood in push-pull ventilation systems with obstacles.According to the affect of obstacles as discussed above, conclusions aresummarized as follows:(1) The comparison of experimental data and numerical simulation shows thatthere are some errors in the numerical simulation and experimental test, but both ofthem show same flow field laws in push-pull ventilation systems with obstructions.Therefore, the numerical simulation is an effective means.(2) In this paper, the obstacle is staff which is the most common in engineeringpractice, there being10conditions based on locations. When the obstacles are in theregion of y≥1.2m or y≤-1.2m, flow of the system is wide and can cover the obstacles,while the change of velocity is uniform both in higher and lower section of height. Atthe same time, there is no significant eddy. Therefore in practical application it can beignored because of its minimal impact.(3) When the obstructions in the flow field are in the area of-1.2m≤Y≤+1.2m,the obstacles have an impact on the flow field. The airflow can’t cover the obstaclesand form a large eddy zone before or after the obstacles, so part of the airflowescapes.while the escape is very small. When the obstructions in the flow field are inthe area of-0.6m≤Y≤+0.6m, the flow pattern is broken，the escape becomeincreasing,which makes the control effect decreases. We should avoid the obstaclesappear in this area in practical application.(4) With the optimization of the model, changing the outlet and pull hood parameters respectively to simulate, data in different operating conditions show that areasonable set of size parameters about outlet,pull hood and the wind flange of pullhood can reduce the impact of obstacles to the flow field of the push-pull ventilationsystems.(5) This study also shows that it has no effect if an obstacle appears in the flowfield in the mainstream border. The outlet should be as wide as possible, while the pullhood and the wind flange should be wide enough if it’s available.