Effect of oscillation frequency on wall shear stress and pressure drop in a rectangular channel for heat transfer applications

7th European Thermal-Sciences Conference

Blythman, R.^1 ; Persoons, T.^1 ; Jeffers, N.^2 ; Murray, D.B.^1

Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, Dublin 2, Ireland^1

Thermal Management Research Group, Efficient Energy Transfer (ET) Department, Bell Labs Research, Alcatel-Lucent Ireland, Blanchardstown Business and Technology Park, Snugborough Rd, Dublin 15, Ireland^2

关键词: Heat transfer applications;    Heat Transfer enhancement;    Oscillation frequency;    Overall thermal resistance;    Particle image velocimetries;    Thermal boundary layer;    Thermal enhancement;    Two-dimensional rectangular;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/745/3/032044/pdf
DOI  :  10.1088/1742-6596/745/3/032044

来源: IOP

【 摘 要 】

The exploitation of flow unsteadiness in microchannels is a potentially useful technique for enhancing cooling of future photonics systems. Pulsation is thought to alter the thickness of the hydrodynamic and thermal boundary layers, and hence affect the overall thermal resistance of the heat sink. While the mechanical and thermal problems are inextricably linked, it is useful to decouple the parameters to better understand the mechanisms underlying any heat transfer enhancement. The current work characterises the behaviour of the wall shear stress and pressure gradient with frequency, using experimental particle image velocimetry (PIV) measurements and the analytical solution for oscillatory flow in a two-dimensional rectangular channel. Both wall shear stress and pressure gradient are augmented with frequency compared to steady flow, though the pressure gradient increases more significantly as a result of growing inertial losses. The three distinct regimes of unsteadiness are shown to display unique relationships between the parameters pertinent to heat transfer and should therefore be considered independently with respect to thermal enhancement capability. To this end, the regime boundaries are estimated at Womersley number Wo = 1.6 and 28.4 in a rectangular channel, based on the contribution of viscous and inertial losses.