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Research Papers: Experimental Techniques

# Simultaneous Retrieval of Total Hemispherical Emissivity and Specific Heat From Transient Multimode Heat Transfer Experiments

[+] Author and Article Information
G. Venugopal, M. Deiveegan, C. Balaji

Heat Transfer and Thermal Power Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036, India

S. P. Venkateshan1

Heat Transfer and Thermal Power Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036, Indiaspv@iitm.ac.in

1

Corresponding author.

J. Heat Transfer 130(6), 061601 (Apr 23, 2008) (8 pages) doi:10.1115/1.2891221 History: Received January 12, 2007; Revised June 10, 2007; Published April 23, 2008

## Abstract

Transient cooling experiments of a heated vertical aluminum plate with an embedded heater, in quiescent air, were conducted for the simultaneous estimation of total hemispherical emissivity and specific heat of the plate material. During cooling, the heat loss from the hot plate by natural convection and radiation was taken into account. During the experiments, plate temperatures were recorded at several locations using a data acquisition system. A numerically computed transient response of the plate is then compared with the experimentally known transient response to estimate the residual, the minimization of which using Levenberg–Marquardt’s iterative procedure retrieves the parameters pertinent to the problem. The experiments were conducted for three different surface emissivities of the plate obtained by using suitable surface treatment. A consistency test for the present approach was also done by conducting transient heating experiments using the retrieved values of parameters and a comparison of simulated and calculated natural convection heat transfer coefficients as a function of temperature. The experiments have been performed over a temperature range of $320–430K$ and a Rayleigh number range of $2×106–2×107$. The emissivity values are in good agreement with previous reported results.

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## Figures

Figure 1

Schematic of the experimental setup for the transient multimode heat transfer experiments. 1-heated vertical plate; 2-electric heater; 3-side wall of test section (wood); 4-Teflon rod; 5-Steel strip; 6-stainless steel rod; 7-adjusting nut; 8-adjusting nut; 9-perforated wooden panel; 10-wire mesh; 11-stainless steel sheathed thermocouples.

Figure 2

Retrieved values of emissivity as a function of temperature for three samples

Figure 3

Retrieved value of specific heat as a function of temperature

Figure 4

Comparisons of experimental and simulated temperature time curves for aluminum paint coated surface

Figure 5

Comparison of retrieved and calculated heat transfer coefficients using the Churchill correlation

Figure 6

Comparison between constants retrieved and constants specified in the Churchill correlation

Figure 7

The estimated emissivity for polished aluminum surface ε(T) when ϕ=0.0, 0.1, and 0.3

Figure 8

The estimated specific heat cp(T) when ϕ=0.0, 0.1, and 0.3

## Errata

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