Influence of exhaust hood geometry on the capture efficiency of lateral exhaust and push–pull ventilation systems in surface treatment tanks

Abstract

In a local exhaust ventilation system, where the pollutant or the emitted flows are captured near the generated source, the knowledge of the capture efficiency is necessary to evaluate performance. This article reports a study of the influence of the exhaust hood slot height on the capture efficiency. For this study, the emission of gases and vapors from open surface tanks used in industrial treatments has been simulated in an installation fitted with two ventilation systems: lateral exhaust and push-pull. Several configurations were possible by varying the geometrical and operational conditions. Both qualitative and quantitative evaluations have been performed, the former through observations of the flows using smoke and the latter by using sulfur hexafluoride as tracer gas. The results obtained on capture efficiency for both ventilation systems tested with several exhaust slot height and as a function of the operating flows rates, are presented. It was found that varying the exhaust slot height between 15 and 45 cm had no effect on capture efficiency. The results show that there are no significant differences between the exhaust slots heights tested, although, in the case of 60 cm for lateral exhaust ventilation, the efficiency was slightly lower.

Research on the axial velocity change rule of desktop slot exhaust hood

“…Zhang Baiqing 6 ) studied the optimum aspect ratio of the strip gap. Enrique González 7 ) studied the effect of slot height on trapping efficiency. Zhou Shulin 8 ) studied the slot open area and airflow uniformity of exhaust hood.…”

Research on Flow Field Characteristics Affected by Obstacles of Pull-Push Ventilation System of Plating Tanks through Numerical Simulation

“…To verify the simulation models, combining with BW-GAXT NO 2 (2) Computer simulation is useful to simulate pullpush ventilation system's performance under various conditions, and benefit to determine the best matched velocities of push air flow and pull air flow to avoid equipment costs due to the change of the size, leaving less experimental cost and shortened experimental period.…”

“…When controlling pollutant, push-pull ventilation system can save up to 50% of flow rate than lateral exhaust [1], and it is prior to any other hoods when the hood is far away from pollutant generation (eg, more than 2m). Nowadays, push-pull ventilation system is widely chosen to capture harmful gas and vapor [2] and fumes [3]. Since it controls the pollutants through the associative action of pull hood and push hood, we should determine the best effective and matched velocities of them.…”

The investigation of the dust-air flow close to the vertical rotating cylinder local exhaust

“…М естные отсосы являются надежными и эффективными устройствами для улавливания и локализации пылегазовых выбросов. Работа систем местной вытяжной вентиляции сопряжена с высокими энергетическими затратами, из-за чего данные системы и технологии производства непрерывно совершенствуют [1][2][3][4][5]. Одним из способов повышения диапазона захвата вредностей местными отсосами открытого типа является использование искусственно созданного вихря (торнадо).…”