Enhancing Heat Transfer from a Porous Plate with Transpiration Cooling

Abstract

The present study is focused on developing structural solid surface geometry to improve heat transfer by cooling of air with transpiration cooling. Effects of flow rate of water (ṁwater= 0.000083, 0.000116, 0.000166, 0.000249 kg/s) and particle diameter of porous plate (Dp= 40, 50, 100, 200 μm) on local wall temperature and cooling efficiency of porous plate and the system inside a rectangular channel with air as a hot gas stream and water as a coolant were investigated experimentally. High performance polyethylene as a porous media was used not only to form a thermal barrier but also an active cooling plate by evaporating water from the surface of porous media to cool air. Temperatures were measured by T-type thermocouples. Two electric heaters were used to support enough power to the system. It was observed that increasing water flow rate did not cause a prominent decrease on surface temperature and cooling efficiency of porous plate. The higher injection rates result in further increase of the cooling effectiveness. Cooling efficiency of porous plate changed from 38 to 90 %. Increasing water flow rate as a coolant causes a prominent increase on cooling efficiency of the system. Increasing water flow rate three times causes an increase of 26.4 % on cooling efficiency of the system. Decreasing particle diameter causes a significant decrease on surface temperature. Difference of cooling efficiency of porous plate from Dp=40 to Dp=200 μm decreases from 12% to 2 % from inlet region to end of porous plate.