Measurements for flow resistance coefficient values of perforated plates in natural air convection flows

Abstract

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.A new method of obtaining flow resistance coefficient for perforated plates in low Reynolds number flows, such as natural air convection, was proposed. And some experimental values are obtained from the viewpoint of thermal design of electronic equipment casings where some perforations often used in the outlet and inlet vent to prevent dust from entering the casing. The proposed method is based on the two expressions written for the enthalpy balance and for the balance between aerodynamic resistance and buoyancy force in a ventilation model. By these two expressions, flow resistance coefficient values can be evaluated even when only dissipated power and temperature rise is known. As a result, the relationship of the flow resistance coefficient values for perforated plates, Reynolds number and porosity coefficient is presented in a form fitting for practical engineering use. 18 kinds of perforated plates have been used in this study and the range of Reynolds number defined by the hole diameter and the air velocity in the ventilation duct was from 0.4 to 95. The experimental results include the Reynolds number and porosity coefficient influence on the resistance coefficient for perforated plates, as well as the perforated plates thickness to the diameter of hole effect on the flow resistance coefficient.