Perforated ventilation ducts: Part 2, validation of an air distribution model.

摘要

The mathematical model for air flow distribution pattern in a perforated duct was validated by measuring the flow performance in 4 experimental ducts with aperture ratios of 0.5, 1.0, 1.5 and 2.0. The basic assumptions of the model were upheld. Theskin friction loss calculated from the momentum equation was the same as that provided by the energy equation. The energy equation can be used to evaluate the regain coefficient without considering friction losses. The regain coefficient and the energy correction factor were almost unity for turbulent flow. The discharge coefficient was constant and approximately 0.65, along the full length of the perforated duct. Frictional losses occurred along the length of the duct but had no significant effect on the discharge angle. The discharge angle (alpha) can be calculated from the duct average air velocity (V) and the potential outlet air jet velocity (V0).