A CFD model to predict pressure loss coefficient in circular ducts with a motorized damper

The pressure loss coefficient was determined for a circular duct with a circular damper using computational fluid dynamics. The CFD package Star-CD was used to predict the air flow and pressure distribution in the duct. A three dimensional computational fluid dynamics model was developed and simulated for five different positions of the damper ranging from partially opened position to completely opened position. The available standard k-epsilon model for high Reynolds number was used. The duct was also simulated for different flow conditions by varying the Reynolds number. The code generated the pressure drop across the damper, which was used to compute the pressure loss coefficient.;The model was initially tested for grid independency. A diameter along the cross-section downstream of the damper was considered and the velocity component in the direction of the flow was verified for the grid independency. The mesh size of 400,000 cells obtained from grid independency was used for all the models. The pressure loss coefficient determined varied considerably with the damper angle. The pressure loss coefficient was high at low angles of opening indicating greater pressure losses. The Reynolds number had little impact on the k-factors. The predicted values were also compared with previous studies and were found to be in general good agreement. The knowledge of the pressure losses and the pressure loss coefficient can be used as a parameter for the direct digital control of the HVAC systems in order to obtain better efficient systems.