The inaccuracy of heat transfer characteristics of insulated and non-insulated circular duct while neglecting the influence of heat radiation

2009 ◽  
Vol 50 (11) ◽  
pp. 2856-2863 ◽  
Author(s):  
Tsung-Lieh Hsien ◽  
King-Leung Wong ◽  
Shiue-Jie Yu
Keyword(s):  
Heat Transfer ◽  
Heat Radiation ◽  
Heat Transfer Characteristics ◽  
Circular Duct ◽  
Transfer Characteristics

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

2012 ◽  
Vol 516-517 ◽  
pp. 322-327 ◽  
Author(s):  
King Leung Wong ◽  
Wen Lih Chen ◽  
Yung Chin Chiu
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Radiation Effect ◽  
Ambient Air ◽  
Heat Radiation ◽  
Heat Transfer Characteristics ◽  
Circular Duct ◽  
Transfer Characteristics ◽  
Internal Fluid ◽  
Fluid Convection

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.

Inaccuracy of Heat Transfer Characteristics for Pin Fins Considering the Influence of Heat Radiation

2011 ◽  
Vol 199-200 ◽  
pp. 1513-1517
Author(s):  
Fu Jen Wang ◽  
Jung Chieh Chang ◽  
Kuo Chien Lin ◽  
King Leung Wong
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Radiation Effect ◽  
Heat Radiation ◽  
Convection Coefficient ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Pin Fins

Pin fins are widely applied in heat exchanger industry. The heat transfer characteristics of pin fins can be found in many textbooks and handbooks related to heat transfer or heat exchanger. However, most heat transfer experts recognized from their own experiences that the heat radiation effect equation contained the fourth order exponential of temperature and the emissivity of oxidized metal are higher, the inaccuracy of heat transfer rate might be higher while ignoring the effect of heat radiation. In this study, numerical simulation using computational fluid dynamics (CFD) code was conducted to verify the heat transfer characteristics of pin fins. It is found that the error of heat transfer rate generated by ignoring heat radiation will be as high as 45 % while heat convection coefficient is 10 (Wm-2K-1 ) associated with the emissivity of fin surface is 1.0. It also revealed the heat radiation effect cannot be neglected for pin fins, especially for the application under high emissivity and low heat convection coefficient conditions.

The Critical Heat Transfer Characteristics of an Insulated Sphere Considering Heat Radiation

2010 ◽  
Author(s):  
King Leung Wong ◽  
José Luis León Salazar ◽  
Jane W. Z. Lu ◽  
Andrew Y. T. Leung ◽  
Vai Pan Iu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Radiation ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics
Sign in / Sign up

Export Citation Format

Share Document