Droplet control of a local exhaust hood enhanced by air curtains

Local exhaust hoods are widely used to control pollutants in industrial buildings. The hoods are often not installed in the optimum position due to the limitations of equipment layout and worker operation, which leads to a poor control effect. This study proposed a twin boundary curtain ventilation (TBCV) system using twin boundary curtains to assist an exhaust hood to address these limitations and improve ventilation efficiency. The airflow distribution and droplet control of the system were studied experimentally and numerically. It was found that the TBCV system had a low flow rate and good control effect on droplets while being flexible to install. The flow rate of the TBCV system was less than 1/5 of that of the traditional upper exhaust hood when the hood height was 3 times the tank width. The offset distance of the hood could reach twice the tank width, and the hood width could be reduced to half the tank width. Air curtain temperature close to ambient air temperature was conducive to forming the TBCV system. The escape rate of droplets below 100 mu m was lower than 0.13% in the TBCV system. Only droplets larger than 50 mu m in diameter escaped when the exhaust hood offset the source due to gravity. For the TBCV system, this study guided the installation position and size of the exhaust hood and clarified the removal efficiency for droplets with different diameters.

Automated summary

This study proposed a twin boundary curtain ventilation (TBCV) system to assist an exhaust hood, aiming to improve the limitations of traditional hood position and control efficiency. Experimental and numerical research showed that the TBCV system had low flow rate, good droplet control effect, and flexibility in installation.