RT Journal Article
ID 60f01f0e55d4286e
A1 Chuang, Ho-Chiao 
A1 Ku, Shih-Shih 
A1 Wong, King-Leung
T1 RELIABLE ONE-DIMENSIONAL MODEL APPLIED TO AN INSULATED RECTANGULAR DUCT CONSIDERING THERMAL RADIATION
JF Heat Transfer Research
JO HTR
YR 2017
FD 2016-11-10
VO 48
IS 1
SP 49
OP 67
K1 convection
K1 emissivity
K1 rectangular duct
K1 insulation
K1 radiation
AB 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.
PB Begell House
LK https://www.dl.begellhouse.com/journals/46784ef93dddff27,293227985b205145,60f01f0e55d4286e.html