Abstract
A new method for determining the velocity pressure loss factor (k-factor) of HvAC duct fittings has been established. The method presented here is based on computational fluid dynamics (CFD) and experimental measurements. The constant-injection tracer-gas technique and a pitot tube were used to measure mean air velocity in a square duct with bends. Pressure distribution along the duct was measured using static pressure tappings. The k-factor was calculated from the measured pressure loss and air velocity for the duct fitting. CFD was used to predict airflow and pressure distribution in the duct. It was found that the accuracy of the prediction depends on the turbulence model and differencing scheme used. Optimum predictions of pressure loss and k-factor were achieved using CFD with a combination of the standard k-e turbulence model and quadratic upstream interpolation scheme. The predicted k-factor was in good agreement with experimental results.
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