Study on effect of deflector structure on trapping performance of laboratory exhaust cabinets

In order to explore the pollutant diffusion law inside the exhaust cabinet and improve the pollutant trapping performance of the exhaust cabinet, in this paper, the influence of the deflector structure on the pollutant trapping performance of the upper and lower combined exhaust cabinet is investigated by using experimental and computational fluid dynamics methods. Taking the maximum pollutant concentration in the operation window as the evaluation index, the effects of different upper deflector angles, top slit distances and lower deflector shapes on the trapping performance of the cabinet are analysed. The results show that with the reduction of the upper deflector angle and the top slit distance, the pollutant trapping effect of the exhaust cabinet is significantly enhanced. When the angle is less than 50 degrees, the enhancement effect is not significant, and when the top slit distance reaches the critical value of 8.9 mm, the continued reduction of the distance plays a deteriorating role in the pollutant controlling effect. The use of the lower deflector’s mesh structure 2 and 3 can greatly enhance the performance of pollutant trapping, and the maximum pollutant concentration of the operation window can be significantly increased with the use of the two types of mesh structures. Their maximum pollutant concentration in the operation window is reduced by about 25.7% and 70.6%, respectively, compared with the working conditions without mesh structures. This study can provide a reference for the optimization of the deflector structure of the upper and lower combined exhaust cabinet.