Technical Briefs

Demonstration of Heat Transfer Enhancement Using Ferromagnetic Particle Laden Fluid and Switched Magnetic Fields

[+] Author and Article Information
Mark M. Murray

Department of Mechanical Engineering, United States Naval Academy, Annapolis, MD 21402mmmurray@usna.ed

J. Heat Transfer 130(11), 114508 (Sep 05, 2008) (4 pages) doi:10.1115/1.2970064 History: Received August 06, 2007; Revised June 07, 2008; Published September 05, 2008

A convective heat transfer enhancement technique and the experimental methods used to quantify the improvement in heat transfer and subsequent differential pressure are introduced. The enhancement technique employed time varying magnetic fields produced in a pipe to cause the ferromagnetic particles of a particle laden fluid (mineral oil and iron filings) to be attracted to and released from a heated pipe wall. The ferromagnetic particles acted not only to advect heat from the pipe wall into the bulk fluid but they also significantly modified the flow field, disrupted the boundary layer, allowed cooler fluid to reach the high temperature pipe wall, increased thermal energy transfer directly to the fluid, and contributed to the overall improvement in heat transfer rate. The experimental method utilized to quantify an increased effectiveness of convective heat transfer used an apparatus designed to replicate an internally cooled fin, whose surface temperature was measured with an IR camera. These temperature measurements were utilized to calculate the convective heat transfer coefficient (h) of the fluid within the pipe. The enhancement technique demonstrated a 267% increase in heat transfer coefficient with only a corresponding 48% increase in flow differential pressure for an electromagnetic switching frequency of 2 Hz. It is also found that there were optimum magnetic field switching frequencies for both enhancement and differential pressure magnitudes.

Copyright © 2008 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 1

High speed camera images of iron filings alternately attracted to (a) left and (c) right energized electromagnets in transparent glass tubing

Grahic Jump Location
Figure 2

IR camera images of test section without enhancement (left) and with magnetic field enhancement (right)



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