Wind tunnel modeling the system performance of alternative evaporative cooling pads in Taiwan region

A compact wind tunnel was developed to simulate evaporative cooling pad–fan systems and to provide direct measurement of system performance. Two alternative materials including one made of coarse fabric PVC sponge mesh 2.5 mm diameter in pinhole and one made of fine fabric PVC sponge mesh in 7.5 mm diameter pinhole were tested as pads in wind tunnel experiment. We have experimentally examined the effects of air velocity, water flow rate, static pressure drop across pad, and pad thickness on evaporative cooling efficiency. Pad face velocities and associated static pressure drops that allow a pad–fan system works were measured. The dimensionless working equations of heat and mass transfer coefficients through various thickness of alternative pad media could be obtained through curve fitting technique based on the measurements. For coarse PVC sponge mesh, hH/hM=1.33ρaCPaLe2/3(Les/Le)1/4; whereas for fine fabric PVC sponge mesh, hH/hM=2.76ρaCPaLe2/3(Les/Le)1/4 were hH is heat transfer coefficient, hM is mass transfer coefficient, ρa is air density, CPa is specific heat of air, Le is Lewis number, and Les is Lewis number at water temperature. Under a system setting of 15 1 min−1 m−2 water flow rate, pad thickness of 150 mm, and air velocities ranged from 0.75 to 1.5 ms−1, the cooling efficiencies for coarse fabric PVC sponge varied from 81.75 to 84.48%, whereas 76.68 to 91.64% for fine fabric PVC sponge. Results of this study will be used to determine operating protocols for future tests investigating criteria.