Experimental Study on Heat Transfer Enhancement by Using Textile Flap Oscillation

Abstract

This paper experimentally studies a new method to enhance heat transfer in which a soft textile flap flutters and slaps a hot plate surface, due to fluid-structure interaction. The self-sustained periodic slapping of the textile flap against the heat transfer surface disrupts the boundary layers and thus, increases the heat transfer between the air and plate surface. Heat transfer coefficients in the presence of textile flaps of different shapes and sizes were measured while oscillatory motion of the flaps was recorded. The results show that rectangular flaps provide consistent heat transfer enhancement with increases in heat transfer coefficient observed of up to 42%, from 113 W·m−2·K−1 in the absence of a textile flap, to 161 W·m−2·K−1 in the presence of a rectangular textile flap, at a wind speed of 18.5 m·s−1. It is found that the Nusselt number in the presence of rectangular flaps varies with the flap oscillation frequency in a nonlinear fashion and that the maximum heat transfer coefficient generally occurs when the dimensionless flow-induced oscillation frequency is in the range of 0.22 to 0.32. These results show the potential of using self-sustained oscillating textile flaps to enhance the convective heat transfer in various heat exchangers.