Exhaust hood performance and its improvement technologies in industrial buildings:A literatu rereview

The pollutant control performance of exhaust hoods plays a crucial role in the indoor air quality and energy consumption of ventilation systems in industrial buildings.To better understand the impact of local ventilation on the industrial indoor environment,this paper presents a literature review of exhaust hood performance and its improvement technologies.To create an index for evaluating the performance of exhaust hoods,the capture velocity,capture efficiency,flow ratio of pollutant emissions and exhaust airflow and energy consumption are first introduced.A number of factors affecting exhaust hood performance are assessed such as hood type,hood opening size,exhaust rate,installation distance,pollution source emission and environmental disturbance.Compared to structural improvement methods,the use of active airflow is a more effective way to improve the exhaust hood performance.The most commonly used methods for determining the exhaust rate are the controlled speed method and the flow ratio method.The use of an exhaust hood with an appropriate exhaust rate and jet parameters(for an active air-assisted hood)can effectively improve the pollutant control performance and reduce the energy consumption that would be wasted on the redundant exhaust rate.With more information focused on exhaust hood performance,this work suggests more effective strategies for improving indoor air quality and reducing energy consumption in industrial buildings.

Impact of different human walking patterns on flow and contaminant dispersion in residential kitchens:Dynamic simulation study

The effects of different human walking patterns on contaminant dispersion in residential kitchens were investigated through computational fluid dynamics simulation with the dynamic mesh method.A tracer gas experiment was performed to verify the feasibility and accuracy of the simulation method.Flow characteristics induced by human walking were minutely described,and the transient capture efficiency of the range hood was adopted to assess the impact of human walking quantitatively.Human walking parallel to a counter,human walking parallel to a counter manned by another human,and human walking toward a counter were studied.Results showed that the mutual effect of the wake and thermal plume caused contaminant dispersion and decreased the performance of the range hood as the human subject walked beside the counter.Even a standing person operated ahead the counter,the wake would affect the thermal plume in a certain extent.The decrement of capture efficiency approached 0.5 in the most unfavorable situation.Moreover,the coaction of the positive/negative pressure zone and impinging air jet drew the thermal plume to the human body.The fluctuation of capture efficiency in this condition was moderate relative to that for the human walking pattern beside the counter.This research could provide a comprehensive overview of different human walking patterns and their impact on residential kitchens and thereby facilitate the maintenance of kitchen air quality.