scholarly journals Pool Boiling Heat Transfer Coefficients Up to Critical Heat flux on Low-fin and Turbo-B Surfaces

2011 ◽  
Vol 23 (3) ◽  
pp. 179-187 ◽  
Author(s):  
Yo-Han Lee ◽  
Dong-Soo Jung
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients

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.

Enhancement of Pool Boiling and Critical Heat Flux in Self-Rewetting Fluids at Above Atmospheric Pressures

2011 ◽  
Author(s):  
Mostafa Morovati ◽  
Hitesh Bindra ◽  
Shuji Esaki ◽  
Masahiro Kawaji
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Heat Pipes ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Bubble Sizes ◽  
Butanol Solution

Pool boiling experiments have been conducted with a self-rewetting fluid consisting of an aqueous butanol solution to study the boiling heat transfer enhancement at pressures of 1 ∼ 4 bars. Although self-rewetting fluids have been used to enhance the performance of heat pipes, boiling heat transfer characteristics are yet to be fully understood especially at pressures above atmospheric. Pool boiling experiments with aqueous butanol solutions were performed using an electrically heated platinum wire to obtain pool boiling heat transfer data up to the Critical Heat Flux (CHF). Aqueous butanol solutions with butanol concentrations 2–7% showed enhanced heat transfer coefficients and CHF data at various pressure levels. In comparison to water, aqueous butanol solutions showed 20–270% higher values of CHF at pressures up to 4 bars. The bubble sizes were also observed to be significantly smaller in self-rewetting fluids compared to those in water at the same pressure. This observation was consistent even at higher pressures. However, for the highest butanol concentration tested (7%), the CHF enhancement was diminished at higher pressures.

A Painting Technique to Enhance Pool Boiling Heat Transfer in Saturated FC-72

1995 ◽  
Vol 117 (2) ◽  
pp. 387-393 ◽  
Author(s):  
J. P. O’Connor ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Reference Surface ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Enhanced Surface

A benign method of generating a surface microstructure that provides pool boiling heat transfer enhancement is introduced. Pool boiling heat transfer results from an enhanced, horizontally oriented, rectangular surface immersed in saturated FC-72, indicate up to an 85 percent decrease in incipient superheat, a 70 to 80 percent reduction in nucleate boiling superheats, and a ∼ 109 percent increase in the critical heat flux (CHF = 30 W/cm2), beyond that of the nonpainted reference surface. For higher heat flux conditions (19 to 30 W/cm2), localized dryout results in increased wall superheats (8 to 48°C). The enhanced surface heat transfer coefficients are four times higher than those from the reference surface and similar to those from the Union Carbide High Flux surface. Photographs that identify differences in bubble size and departure characteristics between the painted and reference surfaces are presented.

Nucleate Pool Boiling Heat Transfer Coefficients of Distilled Water (H2O) and R-134a/Oil Mixtures From Rib-Roughened Surfaces

1997 ◽  
Vol 119 (1) ◽  
pp. 142-151 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Chun-Jen Weng
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Distilled Water ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Oil Mixtures ◽  
R 134A ◽  
Rib Roughened

Measurements of pool-boiling heat transfer coefficients in distilled water and R-134a/oil mixtures with up to 10 percent (by weight) miscible EMKARATE RL refrigeration lubricant oil are extensively studied for a smooth tube and four rib-roughened tubes (rib pitch 39.4 mm, rib height 4 mm, rib width 15 mm, number of rib element 8, rib angle 30 deg–90 deg). Boiling data of pure refrigerants and oil mixtures, as well as the influences of heat flux level on heat transfer coefficient, are presented and discussed. A correlation is developed for predicting the heat transfer coefficient for both pure refrigerants and refrigerant-oil mixtures. Moreover, boiling visualizations were made to broaden our fundamental understanding of the pool boiling heat transfer mechanism for rib roughened surfaces with pure refrigerants and refrigerant-oil mixtures.

Effect of Nano-Particles on Pool Boiling Heat Transfer of Refrigerant 141b

2007 ◽  
Author(s):  
Da-Wei Liu ◽  
Chien-Yuh Yang
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Nano Particles ◽  
Test Results ◽  
Tube Surface ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients

Fluids with nano-sized particles have been proved that may effectively enhance the single-phase convective heat transfer performance. For pool boiling heat transfer, the published test results seems conflicted to each other. Some measured heat transfer coefficient decreased with increasing particle concentration but some showed no appreciable difference. This study provides an experimental investigation on pool boiling heat transfer performance of refrigerants R-141b with and without nano-sized Au particles on horizontal plain tubes. The test results show that the boiling heat transfer coefficients increase with increasing nano-particles concentration. At particles concentration of 1.0%, the heat transfer coefficient is more than twice higher than those without nano-particles. However, the heat transfer coefficients decreased for each test after every 5 days and finally close to those of R-141b without nano-particles. The SPM investigation shows that the test tube surface roughness decreased from 0.317 μm before boiling test to 0.162 μm after test. Further investigation by TEM and Dynamic Light Scattering particle analyzer shows that the nano-particles aggregated from 3 μm before test to 110 μm after test. This results show that the nano-sized Au particles are able to significantly increase pool boiling heat transfer of refrigerant R-141b on plain tube surface. The tube surface roughness and particle size changed after boiling test. Both of these effects degrade the boiling heat transfer coefficients.

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