Study On The Characteristics Of Push-pull Ventilation System Of Parallel Flow Affected By Different Sizes Of Obstacles

With the social industrial production continues to advance in the technology andscale, industrial buildings on the number and size of is growing. At the same time,the problem of the health and safety caused by the pollution of indoor environment inindustrial building is more and more serious. How to effectively control pollution, inorder to provide operation personnel safety environment, to make equipment run safelyand to ensure the quality of products become an urgent need. Push-pull ventilation ofparallel flow has lots of advantages which make it control pollution air well,such assmall exhaust air volume, energy saving, flexible control area, strong ability to resistexternal airflow disturbance, small speed fluctuation of supply air and lateralcomponent, small attenuation the direction of the air supply jet. Therefore, push-pullventilation of parallel flow system in the control of indoor environment in industrialbuildings is becoming more and more attention. So far, however, study on theregularity of the airflow is still lack of perfect theory, limiting its popularization andapplication. There may be obstacles in the push-pull field, even machine equipment,the product itself and the operator play the role of the obstacle. However study on theimpact of flow field by obstacles is insufficient, and there is no specific design methodabout push-pull ventilation of parallel flow system with obstacles. Considering of this,study on the characteristics of push-pull ventilation system of parallel flow affected bydifferent sizes of obstacles is carried out in this paper so as to make reference andadvice for engineering practice. Theoretical analysis is used to research the basic characteristics of flow fieldwhen obstacles exist in the flow field, in addition, experimental test and numericalsimulation study as research methods also was used in this paper. The width and lengthand height of different size of the obstacles the influence factors was used to analysethe velocity field and air trapping efficiency of the push-pull ventilation system. At thelast chapter, design optimization studies on push-pull ventilation system of parallel flowwith obstacle was carried out.This research conclusions are as follows:(1) The system can almost completely capture polluted airflow when the obstaclewidth is less than the width of the push outlet. When the obstacle width is larger thanthe width of the push outlet, Streamline curvature is large and there is controlweaknesses at the edge of the zone of separation flow and reversed flow. When the ratioof obstacle width and push outlet width is1and4/3, The pollution air capture efficiencyis96.89%and95.73%respectively.(2)The effect of the obstacle width on the width direction and height directionflow field is mall. The capacity of the push-pull flow to control the effect of flow fieldarousing from different obstacles in length is almost same.(3) The obstacles can be surrounded by the push-pull flow fieled when the widthof the obstacles is less than the width of the push and pull outlet. when the height ofobstacle is larger than the height of the push and pull outle, there is control weaknessesat the edge of the zone of separation flow and reversed flow on the top of the obstacle.(4) The width of the zone composed of separation flow, attached again flow andreversed flow in the width direction of the obstacles is Related to the windward area.The length of leeside vortices zone is Related to the windward area too.The relationbetween the width and windward area, the length and windward area are proposed bymenas of the software in this paper. The air velocity in flow stagnation zone, the fluidattached again and reversed region and the vortex area is low, therefore polluted airresidence time longer and density is bigger.(5)The pull outlet airflow velocity based on the method of Lin Tailang limit flowratio is too large. The pull outlet airflow velocity can decrease through rational analysisV3which is equal to Seventy percent of Vj3is recommended. Advice that the dimension of the push and pull outlet is greater than or equal to the dimension ofobstacle is proposed. The dimension of the flang should be reasonably increased sothat push pull flow is wide and the ability of system to control the air flow is improved.