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RESEARCH PAPERS: Heat Diffusion

An Experimental Evaluation of the Effective Thermal Conductivities of Packed Beds at High Temperatures

[+] Author and Article Information
K. Nasr, R. Viskanta, S. Ramadhyani

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907

J. Heat Transfer 116(4), 829-837 (Nov 01, 1994) (9 pages) doi:10.1115/1.2911455 History: Received June 01, 1993; Revised January 01, 1994; Online May 23, 2008

Abstract

Combined conduction and radiation heat transfer in packed beds of spherical particles was investigated. Three different packing materials (alumina, aluminum, and glass) of various particle diameters (2.5 to 13.5 mm) were tested. Internal bed temperature profiles and corresponding effective thermal conductivities were measured under steady-state conditions for a temperature range between 350 K and 1300 K. The effects of particle diameter and local bed temperature were examined. It was found that higher effective thermal conductivities were obtained with larger particles and higher thermal conductivity packing materials. The measured values for the effective thermal conductivity were compared against the predictions of two commonly used models, the Kunii–Smith and the Zehner–Bauer–Schlünder models. Both models performed well at high temperatures but were found to overpredict the effective thermal conductivity at low temperatures. An attempt was made to quantify the relative contributions of conduction and radiation. Applying the diffusion approximation, the radiative conductivity was formulated, normalized, and compared with the findings of other investigators.

Copyright © 1994 by The American Society of Mechanical Engineers
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