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Heat Transfer Research
Импакт фактор: 0.404 5-летний Импакт фактор: 0.8 SJR: 0.264 SNIP: 0.504 CiteScore™: 0.88

ISSN Печать: 1064-2285
ISSN Онлайн: 2162-6561

Выпуски:
Том 50, 2019 Том 49, 2018 Том 48, 2017 Том 47, 2016 Том 46, 2015 Том 45, 2014 Том 44, 2013 Том 43, 2012 Том 42, 2011 Том 41, 2010 Том 40, 2009 Том 39, 2008 Том 38, 2007 Том 37, 2006 Том 36, 2005 Том 35, 2004 Том 34, 2003 Том 33, 2002 Том 32, 2001 Том 31, 2000 Том 30, 1999 Том 29, 1998 Том 28, 1997

Heat Transfer Research

DOI: 10.1615/HeatTransRes.2016009813
pages 49-67

RELIABLE ONE-DIMENSIONAL MODEL APPLIED TO AN INSULATED RECTANGULAR DUCT CONSIDERING THERMAL RADIATION

Ho-Chiao Chuang
College of Mechanical and Electrical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan
Shih-Shih Ku
College of Mechanical and Electrical Engineering, National Taipei University of Technology, Taipei 10608, Taiwan
King-Leung Wong
Kun-Shan University

Краткое описание

The heat-transfer characteristics of an insulated long rectangular duct, considering thermal radiation, are analyzed by using the one-dimensional Plane Wedge Thermal Resistance (PWTR) model and Plate Thermal Resistance (PTR) model in this study. It is found that the errors generated by the PWTR model are all positive and the errors generated by the PTR model are all negative. Thus, the Combined Plate Wedge Thermal Resistance (CPWTR) model generated by paralleling PWTR and PTR models with the proportion factors 0.6 vs. 0.4 (64-CPWTR model) or 0.7 vs. 0.3 (73-CPWTR model) can neutralize the positive and negative errors and yield very accurate results in comparison with the two-dimensional numerical solutions analyzed by a CFD software. The 64-CPWTR model returns better results for practical sizes and practical insulated thickness, and the errors are mostly within 2%; on the contrary, the 73-CPWTR model returns better results for practical sizes and a very cold duct with very large insulated thickness. For the results obtained by the same method as the present study except neglecting thermal radiation, it is found that neglecting the thermal radiation effect is likely to produce very large errors in noninsulated and quite large errors in thinly insulated ducts under conditions of low external convection effect introduced by ambient air and higher surface emissivity. The 73-CPWTR model, without considering thermal radiation, can also generate acceptable results in situations of a very cold rectangular duct with thicker insulation, even when an insulated surface is actually with ε = 0.8.

Ключевые слова: convection, emissivity, rectangular duct, insulation, radiation

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