Study On Influencing Factors Of Local Exhaust System Performance In High Temperature Industrial Building

Industrial production process will produce a lot of waste heat,water vapor,gas pollutants,dust and other harmful substances.Waste heat is often accompanied by gas pollutants or dust at the same time,which results high temperature pollutants.This not only affects the quality of the products produced,but also causes great harm to the physical and mental health of the workers.With the acceleration of industrial process,the problem of industrial pollution is becoming more and more serious.The sources of industrial pollution are the production equipments in the production process.It is an economical and effective way to control pollutant emission to capture and treat pollutants immediately when the equipment produces pollutants.Usually the local exhaust system is used to capture harmful substances after purification and then discharged to the outdoor.In the actual factory,there is not only local exhaust system,but also the overall ventilation of the workshop.In the process of overall ventilation,the background wind will affect the suction effect of the exhaust hood,thus reducing the collection efficiency of the exhaust hood.This paper summarizes the research status of buoyant jet,exhaust hood and industrial pollutants at home and abroad.By building a high-temperature experimental platform,three kinds of experiments of the exhaust hood closing,the exhaust hood opening and the local exhaust system with background wind were carried out,and the lattice experimental data of air velocity,temperature and gaseous pollutant concentration were obtained and analyzed respectively,providing detailed experimental data for the simulation calculation.The simulation model verified by experiment is used to further study the design method of improving the local exhaust system.The results show that when the console has a heat source and the exhaust hood is not opened,due to the acceleration effect of buoyancy,the airflow velocity above the console increases first and then decreases with the increase of the height.The maximum wind speed is at 0.2-0.3m above the console,while the height continues to increase and the wind speed gradually decreases.When the exhaust hood is opened and there is no heat source on the operating table,the airflow velocity above the operating table first decreases gradually,and then increases gradually after reaching the minimum value about 0.3m from the outlet of the operating table.When the exhaust hood is opened and the heat source temperature of the operation table is low,the airflow velocity above the operation table first increases gradually,reaches the maximum value at 0.2m away from the outlet of the operation table and then decreases gradually,and then increases gradually when approaching the exhaust hood.When the exhaust hood is opened and the heat source temperature of the operating table is high,the airflow velocity above the operating table increases with the increase of the height.The updraft formed by the heat source of the operating platform has obvious influence on the carbon dioxide transmission and diffusion,and the efficiency of the exhaust hood on carbon dioxide capture is higher in the case of heat source.The background wind makes the temperature field and pollutant concentration field overall shift to the downstream of the background wind,resulting in a small amount of pollutant spills.However,the air temperature and pollutant concentration in the center area of the operation platform are slightly larger than those without background wind.The effect of background wind on the collecting efficiency of exhaust hood is further studied in this paper.When the background wind is large,the collection efficiency of the exhaust hood will be affected.When the size and direction of the background wind are constant,the collection efficiency of the exhaust hood will increase with the increase of the exhaust air volume,but there is an upper limit of the collection efficiency.Combined with simulation calculation and thermophysical analysis,a formula for calculating the transverse offset distance of pollutant transfer under the condition of background wind and buoyant jet interference is proposed,which provides a basis for the design of exhaust hood under the condition of background wind and buoyant jet influence.