CFD analysis of flow balancing in suction hoods

Three fume hoods are used to extract fumes from three workstations. The hoods are mounted in series on a suction duct. There is a problem of balancing the flow rates in each of the suction hoods. It is proposed to check it using the numerical simulation tool in (CFD Computational Fluid Dynamics). The ventilator for creating the suction vacuum is not modeled and a volumetric flow is imposed on the horizontal section at the top of the duct. This sheath is connected to a chimney via a treatment plant which are not taken into account in the simulation.

Initial Geometry

hood n°1 50%

hood n°2 29%

hood n°3 21%

The method chosen here for balancing the flow rates in the three hoods is the arrangement of a diaphragm in the duct leading to the first hood in order to create pressure drops in the most powered circuit.

Diaphragm sizing

hood n°1 33%

hood n°2 39%

hood n°3 28%

In addition to the flow rates in the hoods, the velocity and pressure fields are visualized in order to go further in optimizing the flow balancing. This also makes it possible to identify areas of possible recirculation which could cause dust accumulations, be responsible for the occurrence of vibrations or simply create an excessive pressure drop. It is interesting to check the variation of the flow-pressure operating point with the addition of the diaphragm by comparing the excess charge losses with the characteristic curve of the fan.