Air flow field near a welding exhaust hood

Local ventilation is the most important method in the control of welding fumes. The present practice for dimensioning local exhaust is to select capture velocity and then calculate the required air flow, assuming that the contaminant source is located on the hood center-line. Empirical and analytical formulas for these centerline velocities have been derived for simple exhaust hood configurations. However, in more complex cases the velocities may be difficult to estimate. In this study a turbulent air flow field for a flanged welding exhaust hood was calculated numerically using the FLUENT computer code based on the finite volume method. The turbulence model used in the simulation was the standard two-equation κ-ε turbulence model. The accuracy of the calculations was verified by experimental measurements conducted under controlled conditions. The air velocities were measured with a laser-Doppler anemometer, which is a nonintrusive optical measurement method. The results showed that the complex shape of the welding hood has little effect on the air velocities in front of the exhaust hood. The air flow into the unobstructed exhaust hood can be predicted quite accurately provided that the calculation grid and the calculation domain are properly chosen. The results give guidelines for the proper position of the hood relative to the welding point.