Spatio-temporal distribution of gaseous pollutants from multiple sources in industrial buildings with different flow patterns

Energy consumption of industrial buildings has remained continuously high,and the environmental quality requirements are also constantly improving.Only by improving industrial environmental control technology based on the transport mechanism of the pollution,can the energy consumption of industrial building environmental control be further reduced,and the environmental quality of industrial buildings can be improved as well.Therefore,after verifying the numerical simulation by experiments,this study uses a self-label method to investigate the spatio-temporal distribution of gaseous pollutants from multiple time-series sources in industrial plants with different length-span ratios.The results show that,the polluted flow in plants with different aspect ratios have different flow patterns:(i)the,,Back-mixingw flow pattern occurs when the ratio of ventilation rate 6 and polluted flow rate at the exhaust height b is less than 1,i.e.,G/L_(p)<1,and(ii)the"One-way"flow pattern occurs when G/L_(p)>1.For plants with the"Back-mixing"pattern,the following source pollutants enter a density stratified environment induced by the retained pre-source pollutants.The flow of following source pollutants released at the same intensity as the precursor source can reach the roof,while those with low velocity and density difference may be blocked during the ascending process.The maximum height zm of the flow of the following source is related to both the initial Froude number Fr_(o)of the following source and the unsteady vertical density gradient of the fluid in the indoor environment dpa/dz.For plants with the,,One-way,/pattern,the flow from the following source enters into an environment with approximately uniform density.Under the condition of positive buoyancy,design parameters of ventilation corresponding to the vicinity of G/L_(p)=1 may be the optimal solution for safety and energy conservation.

Experimental study on the flow field and economic characteristics of parallel push-pull ventilation system

Push-pull ventilation systems provide excellent control of contaminants and harmful gases.However,since both a push inlet and a pull outlet are used in the push-pull ventilation system,the flow rate required by the system is large.In that case,the energy consumption of the system is large.The purpose of this paper is to study the flow field and economic characteristics of a parallel push-pull ventilation system by reducing the flow rate of the exhaust outlet,which will be achieved by reducing the size of the exhaust hood.The three commonly used push-pull ventilation systems were analyzed:a high velocity push-pull system with high air supply velocity,a low velocity push-pull system with wide airflow and small velocity,and a parallel push-pull system with wide airflow and uniform air supply velocity.Results showed that the parallel push-pull ventilation system was the only one in which the flow rate of the exhaust outlet could be reduced,reducing the overall energy consumption.Under conditions of the parallel air supply jet,the diffusion range of contaminants in the push-pull flow field was the smallest and reducing the exhaust air flow rate did not affect the capture efficiency of pollutants.These results may be useful in guiding the design of push-pull ventilation system and optimize economic constraints.

Correlation analysis of three influencing factors and the dust production rate for a free-falling particle stream

The effects of three factors （i.e., drop height h, hopper outlet diameter do, and material temperature T] on the dust generation rate derived from a free falling particle stream were investigated via filll factorial experiments. The correlation between the three factors and dust generation rate was also analysed. Results show that Tand h affect the first fugitive dust rate largely, whereas the second fugitive dust rate is mainly dominated by h and do. Through analysing the first fugitive dust percentage data, it is found that h and T should be considered first for higher temperatures and lower flow rates, whereas h and do can be considered under contrasting conditions, and h should be controlled in the remaining two sets of conditions. Relationships between the influencing factors and total and first fugitive dust rates were developed via multiple regression to quantify the dust emission rates for different contact surfaces （rigid or water）.