scholarly journals Enhancement of Pool Boiling Heat Transfer over Plain and Rough Cylindrical Tubes

2021 ◽  
Vol 39 (2) ◽  
pp. 329-336
Author(s):  
Farhan M. Haidary ◽  
Md. Rabbi Hasan ◽  
Mohammad Adib ◽  
Sadman H. Labib ◽  
Md. Jubayer Hossain ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Roughness ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Orientation Angle ◽  
Horizontal Tube ◽  
Vertical Tube ◽  
Smooth Tube ◽  
Pool Boiling Heat Transfer

This study investigates the pool boiling heat transfer of water over cylindrical heating tubes for different orientations and surface roughness of the tubes. First, two orientations of a smooth heating tube, horizontal and vertical, were used in the boiling chamber. For a given heat flux, the heat transfer coefficient achieved with the horizontal tube was always higher than that for the vertical tube. To investigate the influence of surface roughness, a rough heating tube with a fully rough outer surface was developed through a metal etching process. Under the same range of wall superheat, the rough tube enhanced the heat transfer rate significantly compared to the smooth tube. Finally, a modified heating tube (MHT) was developed by axially roughening half of the surface of an originally smooth tube. The orientation angle of the rough surface of this MHT was varied from 0° (horizontal-upward) to 180° (horizontal-downward) in the chamber. The heat flux increased significantly with the increase of orientation angles from 0° to 90° (the maximum of 80 kW/m2 at 90°), whereas the same decreased as the orientation angle is further increased from 90° to 180°. Results revealed that the bubble dynamics over the heating tubes play a vital role in pool boiling performance.

Effects of Heat Exchanger Tube Parameters on Nucleate Pool Boiling Heat Transfer

1998 ◽  
Vol 120 (2) ◽  
pp. 468-476 ◽  
Author(s):  
Moon-Hyun Chun ◽  
Myeong-Gie Kang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Roughness ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Tube Diameter ◽  
Nucleate Pool Boiling ◽  
Pool Boiling Heat Transfer ◽  
Horizontal Tubes ◽  
Vertical Tubes

In an effort to determine the combined effects of major parameters of heat exchanger tubes on the nucleate pool boiling heat transfer in the scaled in-containment refueling water storage tank (IRWST) of advanced light water reactors (ALWRs), a total of 1966 data points for q″ versus ΔT have been obtained using various combinations of tube diameters, surface roughness, and tube orientations. The experimental results show that: (1) increased surface roughness increases the heat transfer coefficient for both horizontal and vertical tubes, and the effect of surface roughness is more pronounced for the vertical tubes compared to the horizontal tubes, (2) the two heat transfer mechanisms, i.e., increased heat transfer due to liquid agitation by bubbles generated and reduced heat transfer by the formation of large vapor slugs and bubble coalescence, are different in two regions of low heat flux (q″ ≤ 50 kW/m2) and high heat flux (q″ > 50 kW/m2) depending on the orientation of tubes and the degree of surface roughness, and (3) the heat transfer rate decreases as the tube diameter is increased for both horizontal and vertical tubes, but the effect of tube diameter on the nucleate pool boiling heat transfer for vertical tubes is greater than that for horizontal tubes. Two empirical heat transfer correlations for q″, one for horizontal tubes and the other for vertical tubes, are obtained in terms of surface roughness (ε) and tube diameter (D). In addition, a simple empirical correlation for nucleate pool boiling heat transfer coefficient (hb) is obtained as a function of heat flux (q″) only.

Experimental Research on CO2 Pool Boiling Heat Transfer Outside a Single Tube

2016 ◽  
Author(s):  
Shengchun Liu ◽  
Ziteng Dong ◽  
Wenkai Zhang
Keyword(s):  
Heat Transfer ◽  
Experimental Research ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Smooth Tube ◽  
Transfer Enhancement ◽  
Pool Boiling Heat Transfer ◽  
Theoretical Support ◽  
Enhancement Factors ◽  
The Relationship

Both theoretical and experimental research on CO2 physical characteristics and pool boiling heat transfer are taken in this paper. It is analyzed that CO2 pool boiling heat transfer outside the screwed and smooth tube based on experimental study. It is resulted with the relationship between heat transfer coefficient, evaporating pressure and the heat flux. It is also indicated the enhancement factors of three screwed tube compared with smooth tube. The results provides a basis for promoting CO2 heat transfer enhancement, and also provides a theoretical support in engineering.

Nucleate Pool Boiling Heat Transfer of R134a and R134a-PVE Lubricant Mixtures on Smooth and Five Enhanced Tubes

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Wen-Tao Ji ◽  
Ding-Cai Zhang ◽  
Nan Feng ◽  
Jian-Fei Guo ◽  
Mitsuharu Numata ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Saturation Temperature ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Enhanced Tubes ◽  
Mass Fractions

Pool boiling heat transfer coefficients of R134a with different lubricant mass fractions for one smooth tube and five enhanced tubes were tested at a saturation temperature of 6°C. The lubricant used was polyvinyl ether. The lubrication mass fractions were 0.25%, 0.5%, 1.0%, 2.0%, 3.0%, 5.0%, 7.0%, and 10.0%, respectively. Within the tested heat flux range, from 9000 W/m2 to 90,000 W/m2, the lubricant generally has a different influence on pool boiling heat transfer of these six tubes.

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