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TECHNICAL BRIEFS

# A Transient Technique for Measuring the Effective Thermal Conductivity of Saturated Porous Media With a Constant Boundary Heat Flux

[+] Author and Article Information
H. T. Aichlmayr1

Sandia National Laboratories, 7011 East Avenue, Livermore, CA 94550htaichl@sandia.gov

F. A. Kulacki

Department of Mechanical Engineering, The University of Minnesota, Minneapolis, MN 55455kulacki@me.umn.edu

1

Corresponding author.

J. Heat Transfer 128(11), 1217-1220 (Feb 21, 2006) (4 pages) doi:10.1115/1.2352791 History: Received May 11, 2005; Revised February 21, 2006

## Abstract

An experimental technique for measuring the effective thermal conductivity of saturated porous media is presented. The experimental method is based on the transient heating of a semi-infinite cylinder by a constant heat flux at the boundary. The data reduction technique is unique because it avoids determining the effective thermal diffusivity and quantifying the boundary heat flux. The technique is used to measure the effective thermal conductivity of glass-water, glass-air, and steel-air systems. These systems yield solid-fluid conductivity ratios of 1.08, 25.7, and 2400, respectively. The solid phases consist of $3.96mm$ glass spheres and $14mm$ steel ball bearings, which give mean porosities of 0.365 and 0.403. In addition, particular attention is paid to assessing experimental uncertainty. Consequently, this study provides data with a degree of precision not typically found the literature.

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## Figures

Figure 1

Effective conductivity measurement apparatus. The cylindrical test chamber is 22.2cm in diameter and 40.6cm long (reproduced from Ref. 1).

Figure 3

Results of this study compared to previous investigators [6,10-14]. A porosity of 0.38 is assumed when computing the Maxwell limits.

Figure 2

Typical uncertainty limits encountered when determining ke (glass-water system, l=30mm). The effective conductivity is determined by fitting a regression line to the data. Also, time increases from right to left on the ordinate; consequently the uncertainty in ξ decreases with time.

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