Visualization of Airflows in Push-Pull Ventilation Systems Applied to Surface Treatment Tanks

Abstract

A pilot installation was designed that simulates a surface treatment tank fitted with a push-pull ventilation system. The installation contained elements for measuring and controlling the operational variables (flow rate and tank temperature) and smoke generating equipment for injecting smoke through the holes of the push unit and from the tank surface. Visual observation and video recording of the flows involved meant it was possible to follow the qualitative behavior of the push flow rate along the tank surface and to identify any emissions not captured by the exhaust system. It was possible to differentiate the initial semifree push curtain, its impact with the tank surface, the wall jet that moved toward the exhaust, and its entrance into the exhaust. The methodology proposed is complemented by a quantitative technique for measuring the efficiency, using sulfur hexafluoride as tracer, which permits the causes and location of losses in the ventilation system to be determined.

Center-Line Velocity Change Regime in a Parallel-Flow Square Exhaust Hood

“…It shows that the control distance of the supply hood is far greater than that of the exhaust hood. Therefore, the control distance of contaminant in a parallel-flow push-pull ventilation system is mainly extended by the supply air as reported in previous literature [2][3][4][5][6]. Huang et al [7] and Betta et al [8] researched the aerodynamic characteristics and design guidelines of jet push-pull ventilation systems, and Cao et al [9] analyzed the distribution of velocity and SF 6 (sulfur hexafluoride) concentration for uniform flow and jet push-pull ventilation system.…”

“…Because of the parallel-flow, it improves the exhaust hood performance during indoor ventilation, and it can also be combined with a uniform supply hood to produce a parallel-flow push-pull ventilation system. Parallel-flow push-pull ventilation systems [2,3] are widely used, because they can solve many technical problems, such as long-distance control of toxicants, and can effectively control dust and toxic pollutants and ensure the occupational health of workers, owing to their special requirements for velocities and energy saving advantages [4][5][6].…”

Experimental study on one-side confined jets from a parallel-flow outlet in a push–pull ventilation system

“…Since the 1990s, the airflow characteristics of surface treatment tanks with push–pull ventilation systems 10,11 have received attention from studies of computational fluid dynamics (CFD). Then, the general interest in the influencing factors of capture efficiency with push–pull ventilation systems 12–16 was gradually aroused with the development of advanced testing instruments and numerical simulation. Afterwards, design guidelines for push–pull ventilation systems 17–19 were proposed and further studied in surface treatment tanks.…”