October 20, 2016

The hydrodynamic and heat transfer behaviour downstream of a channel obstruction in the laminar flow regime

  • Jeffers N.
  • Punch J.
  • Stafford J.
  • Waddell A.

Microfluidic systems have been proposed as potential solutions for the cooling of next-generation Integrated Circuits (ICs) and Photonics Integrated Circuits (PICs). For PICs, integration of microfluidics may enable greater laser-bar array densities and, consequently, greater transmission bandwidth. To cool the micrometer scale hot-spots produced by the laser-bars, a passively actuated structure situated in a micro--channel could regulate temperature by disturbing flow in a target location as required. To this end, a proof-of-concept passive structure was developed from a Shape Memory Alloy (SMA), and demonstrated at the millimeter scale in previous work. The objective of this study is to measure the heat transfer augmentation at a target surface downstream of the obstruction. Two experiments were performed to measure the flow field and heat transfer downstream of the test pieces in a square miniature channel for a range of Reynolds numbers (Re = 48 - 176) and opening area ratios (Beta = 0.2 - 0.5): using Particle-Image Velocimetry (PIV) and infrared (IR) thermography of a Joule-heated foil respectively. A 50% improvement was observed in the foil area averaged heat transfer coefficient (relative to the unobstructed channel) for Re = 176 and Beta = 0.19. A correlation was developed to interpolate Nusselt number (Nu) from a given Re and Beta for the studied geometry, and analysis of the correlated exponents showed an improvement in heat transfer relative to a simple pillar obstruction. This was attributed to the wake that formed downstream of the test pieces. The findings of this work are relevant to the modeling and design of practical microfluidic systems for targeted hot-spot cooling in future integrated circuit packaging.

View Original Article

Recent Publications

June 04, 2017

A New PRACH Transmission Scheme in Unlicensed Spectrum

  • Luo Z.
  • Meng Y.
  • Tao T.

For the unlicensed spectrum, the occupied bandwidth requirement is demanded by some regulations. The legacy scheme of Physical Random Access Channel (PRACH) for Long Term Evolution (LTE) cannot satisfy it. In this paper, we propose a novel PRACH transmission scheme to satisfy the requirement of unlicensed spectrum based on preamble ...

June 01, 2017

Mutual service processes in Euclidean spaces: existence and ergodicity

  • Baccelli F.
  • Mathieu F.
  • Norros I.

Consider a set of objects, abstracted to points of a spatially stationary point process in R-d, that deliver to each other a service at a rate depending on their distance. Assume that the points arrive as a Poisson process and leave when their service requirements have been fulfilled. We show ...

June 01, 2017

Incentivizing social media users for mobile crowdsourcing

  • Aiello L.
  • Karaliopoulos M.
  • Koutsopoulos I.
  • Micholia P.
  • Morales G.
  • Quercia D.

We focus on the problem of contributor-task matching in mobile crowd-sourcing. The idea is to identify existing social media users who possess domain expertise (e.g., photography) and incentivize them to perform some tasks (e.g., take quality pictures). To this end, we propose a framework that extracts the potential contributors' expertise ...