Study On Air Distribution Model Based On Indoor Double Diffusion Pollutant Risk Control System

Compared with the indoor environment of civil buildings,the production process of industrial workshops is often accompanied by thermal pollution and heavy gravity gas pollution.Moreover,because the industrial pollution gas often presents the characteristics of high concentration and large gravity,it is usually deposited in the work area under the action of negative buoyancy,affecting human health and working environment.Considering the practical needs of indoor gaseous pollutants control,indoor work environment protection and indoor ventilation of buildings,this paper conducts research based on different air distribution forms and focuses on key issues such as different air supply and exhaust modes,air supply velocity,heat source intensity and pollution source intensity.The main work includes the following aspects:(1)Based on different ventilation modes(upper left side/lower right side air supply,same side/different side air exhaust),the influence of different heat source intensity and air supply velocity on indoor heat and mass transport characteristics,heat and mass transfer performance and ventilation efficiency was studied when the pollution source intensity was constant.(2)Based on different ventilation modes,the effects of three typical pollution source intensities and air supply velocity on heat and mass transport characteristics and ventilation efficiency were studied.The results show that the distribution of temperature and pollutants is related to the size of vortices near the wall of heat source and pollution source.The larger the vortices on the surface of heat source(or pollution source),the wider the distribution range of temperature(or pollutants).The heat and mass transfer rates on the surface of heat source and pollution source are affected by the surface flow state.When the flow state changes to turbulent flow,the heat and mass transfer rate increases significantly.Different air supply modes have opposite double effects on indoor heat,pollutant transport and ventilation.On the whole,for the ventilation mode of upper left side and lower right side,when the Reynolds number Re is less than 9868,the arrangement on the same side of the exhaust outlet has smaller heat and pollutant diffusion radius.When the Reynolds number is greater than 17763,the arrangement on the opposite side of the exhaust outlet has greater heat and pollutant transport capacity.For the ventilation mode with air supply on the upper left side and exhaust outlet on the lower right side,there is a critical Re in the process of temperature and pollutant ventilation efficiency changing with Reynolds number Re,which significantly increases the ventilation efficiency.When the intensity of pollution source is constant,the critical Re corresponding to the sudden increase point of ventilation efficiency has a linear function relationship with the Rayleigh number Ra.The greater the heat source intensity,the greater the required air supply velocity.When the heat source intensity is constant,the critical Re corresponding to the sudden increase point of ventilation efficiency has an exponential function relationship with the buoyancy ratio N.The greater the pollution source intensity is,the greater the required velocity is.(3)The influence of the comprehensive buoyancy effect caused by the relative strength between heat source and pollution source on indoor heat and mass transfer rate and ventilation efficiency when the air supply velocity is constant.When7894<Re<15789,with the gradual increase of Fr number,the average heat and mass transfer rate showed a characteristic law of“first decreasing and then increasing,and gradually becoming stable”.The relationship between the critical Fr number corresponding to the sudden increase point of ventilation efficiency and Re is an exponential function,Fr=a×exp(-1/bRe)+c.