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Heat Transfer Enhancement in Rectangular Channels using Pulsating Flow

Research Staff

Richard Blythman ([javascript protected email address])

Richard is currently pursuing his PhD under the supervision of Dr. Tim Persoons and Prof. Darina B. Murray. His PhD research focuses on pulsatile flow heat transfer enhancement in liquid cooled heat sinks for electronics and photonics thermal management.

Principal investigators
Prof. Darina Murray ([javascript protected email address], Tel: +353 1 896 1129)
Dr. Tim Persoons ([javascript protected email address], Tel: +353 1 896 1936)

Description

The exploitation of flow pulsation, which has been found to increase heat transfer by as much as 40% in minichannel heat sinks at low Reynolds numbers [1], is a potentially useful technique for enhanced cooling of high-end photonics and electronics systems. It is thought that pulsation alters the thickness of the hydrodynamic and thermal boundary layers, and hence affects the overall thermal resistance of the heat sink. The aim of this work is to explicitly demonstrate the mechanism underlying any heat transfer augmentation using localised, time-resolved measurements of the velocity and temperature fields.

The first study involves quantification of the fluid mechanics of pulsatile flow in a rectangular channel using particle image velocimetry (PIV). It is found that the transient characteristics of the measured pulsating (non-zero mean) and oscillating (zero mean) velocity profiles are dependent on the frequency of oscillation, in agreement with the analytical solution for flow in a rectangular channel [2]. At high frequencies (see Figure below), a large velocity overshoot is observed close to the wall, resulting from the interaction of near-wall viscous stresses and inertial effects of the main fluid body. Steep velocity gradients are observed in the near-wall region and local flow reversal occurs during the pulsation cycle despite an invariably positive mean flow rate. Future studies will aim to illuminate the effect of such behaviour on local cooling at the channel wall using infrared (IR) thermography measurements.

[1] T. Persoons, T. Saenen, T. Van Oevelen, and M. Baelmans, “Effect of flow pulsation on the heat transfer performance of a minichannel heat sink,” Journal of Heat Transfer, vol. 134, no. 9, p. 091702, 2012
[2] C. Fan and B. Chao, “Unsteady, laminar, incompressible flow through rectangular ducts,” Zeitschrift für angewandte Mathematik und Physik ZAMP, vol. 16, no. 3, pp. 351–360, 1965

Funding Body

Irish Research Council (Enterprise Partnership Programme), Bell Labs Ireland