Effects of Displacement and Frequency of Oscillating Flow on Heat Transfer in a Porous Channel

Abstract

The development in modern electronics has resulted in rapid increases in power densities for electronic packages. Traditional cooling methods are not capable of removing such high heat fluxes. It is imperative to find new methods to cool high-speed electronic components. One of these methods is to implement a channel filled with a high conductivity porous medium. Many investigations have been conducted on the heat transfer of a channel filled with porous media. However, steady flow through a porous channel still yield a higher temperature difference along the flow direction. It is conceivable that oscillating flow through a porous channel will produce a more uniform temperature distribution due to the two thermal entrance regions of oscillating flow. Some researchers have investigated forced convective heat transfer in porous channels in oscillating flow with different kinds of porous media. Their results showed that the operating temperatures of electronic components can be reduced significantly when an oscillatory flow device is employed. However, research into the two critical factors of displacement and frequency for oscillating flow in a porous channel is very sparse. This paper presents the experimental results of an investigation into the effects of varying flow displacement and frequency on heat transfer enhancement in a porous channel subject to oscillating flow. A comparison was made between the heat transfer performance of oscillating flow through a plate channel without a porous medium and a channel filled with sintered metal foam. The maximum displacements of oscillating flow were varied from 52 to 68 mm and frequencies of oscillation ranged from 1 to 10 Hz. The characteristics of pressure drop, the effects of the dimensionless amplitude of displacement and dimensionless frequency of oscillating flow on heat transfer in porous channel were analyzed. The results revealed that heat transfer in oscillating flow is significantly enhanced by employing porous media in a plate channel. The cycle-averaged local Nusselt number increases with both kinetic Reynolds number Reω and the dimensionless amplitude of flow displacement A0. Based on the experimental data, a correlation equation of the length-averaged Nusselt number with the dimensionless parameters of Reω and A0 is obtained for a porous channel with L/Dh = 3. This correlation equation will be useful to determine heat transfer rates in oscillating flow through a porous channel for applications in electronics cooling.