Inaccuracy of Heat Transfer Characteristics of a Metal Duct Neglecting Heat Radiation Effect in Ambient Air

King Leung Wong; Wen Lih Chen; Yung Chin Chiu

doi:10.4028/www.scientific.net/AMR.516-517.322

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HomeAdvanced Materials ResearchAdvanced Materials Research Vols. 516-517Inaccuracy of Heat Transfer Characteristics of a...

Inaccuracy of Heat Transfer Characteristics of a Metal Duct Neglecting Heat Radiation Effect in Ambient Air

Abstract:

A heat radiation equation contains 4th exponential order of temperature which makes mathematics analysis complicated and time-consumption. Most heat transfer experts and scholars believe, based on their own experiences, that the heat radiation effect can be ignored in situations of small temperature difference between duct surfaces and surroundings. This paper studies in detail for complete heat transfer characteristics of a circular duct with heat radiation effect taken into account. It is found that, in some practical conditions, the heat radiation effect can not be ignored especially in cases of lower ambient convection heat coefficients and larger surface emissivities, as well as the smaller the duct size and/or the greater the duct conductivity and/or internal fluid convection coefficients, even though the temperature-difference between inner and outer fluid-temperatures of duct is low to 1 °C. It is found that the conventional LMTD method (ignoring heat radiation) cannot be applied to calculate the total heat transfer rate of a single-duct heat exchanger located in ambient air, such as condenser and evaporator.

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Periodical:

Advanced Materials Research (Volumes 516-517)

Pages:

322-327

DOI:

https://doi.org/10.4028/www.scientific.net/AMR.516-517.322

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Online since:

May 2012

Authors:

King Leung Wong, Wen Lih Chen, Yung Chin Chiu

Keywords:

Heat Convection, Heat Radiation, LMTD, Metal Duct

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