Performance of constant exhaust ventilation for removal of transient high-temperature contaminated airflows and ventilation-performance comparison between two local exhaust hoods

Transient high-temperature contaminated airflows generated during the pouring of high-temperature materials are widespread in Chinese industrial plants. In this study, the performance of both the local exhaust and the general exhaust with a constant flow rate to remove these transient contaminants was experimentally investigated, and the ventilation performance was compared between two local exhaust hoods. This study focused on the dispersion and removal characteristics of contaminant concentrations under the conditions of high-temperature airflows. The results showed that the cumulative contaminant concentration could be divided into four time slots and that there was a time lag between the cumulative concentration of the local and general exhaust. Additionally, the fitting formula of time-varying concentration decay was discussed to highlight the advantages of the designed hood performance. Finally, the dynamic evaluation index (TCRRt) for evaluating exhaust hoods on removing transient contaminants was proposed, and the connections between the proposed index and the traditional capture efficiency were illustrated. The minimum TCRRt for the improved exhaust hood was invariably greater than that for the existing hood for each hood flow rate. This study demonstrates that increasing the containment volume of the exhaust hood can help to remove transient high-temperature contaminants in industrial plants.