Reduced-scale experimental investigation on ventilation performance of a local exhaust hood in an industrial plant

• Measured velocity vector results inferred that the length of existing hood may have been too long.
• Confined airflow boundaries, flow rates and source strengths are critical to capture efficiency.
• Safe operation heights in the upper space of industrial plants are recommended.

Local ventilation systems are widely used in industrial production processes to capture heat release and/or gaseous/particulate contaminants. The primary objective of this study was to determine important empirical factors on local pollutant capture efficiency and characteristics of thermal stratification in the working areas of industrial plants. Investigated factors were confined airflow boundaries, flow rates of the exhaust hoods, source strengths, airflow obstacles and distances between sources and exhaust hoods. Reduced-scale experiments were conducted with a geometric scale of 1:15 corresponding to a portion of the blast furnace workshop of a steel plant. The dependency of capture efficiency on Archimedes numbers was established. The results showed that confined airflow boundaries, flow rates of the exhaust hoods and source strengths were important empirical factors on pollutant capture efficiency. Hood performance was also evaluated by thermal stratification heights in the plants. This study could help improve the capture efficiency of local ventilation systems used in industrial plants. Safe operation heights are recommended in the upper space of industrial plants based on the thermal stratification in the plants.