Use of Vortex Generators and Ribs for Heat Transfer Enhancement at the Top Surface of a Uniformly Heated Horizontal Channel With Mixed Convection Flow

Abstract

Although secondary flows driven by buoyancy forces enhance heat transfer from the bottom surface of a heated, horizontal channel, heat transfer coefficients at the upper surface are known to remain near forced convection levels. In situations where performance is limited by the maximum local temperature, such as the cooling of electronic circuitry, enhanced heat transfer at one surface may be of little advantage if approximately equivalent enhancement does not exist at the opposite surface. Hence differences between top and bottom surface conditions may prevent a designer from taking full advantage of buoyancy-driven flows. This note reports on exploratory experiments to assess the feasibility of using mechanical vortex generators or perforated ribs at the top surface of a uniformly heated channel to provide comparable enhancement at both surfaces.