Growth of Micro Bubbles on Micro-Configured Metal-Graphite Composite Surfaces and Boiling Enhancement

2008 ◽  
Author(s):  
David Chao ◽  
Nengli Zhang ◽  
Wen-Jie Yang
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Active Sites ◽  
Nucleate Boiling ◽  
Transfer Enhancement ◽  
Growth Processes ◽  
Graphite Composite ◽  
Boiling Enhancement ◽  
Structure Of Metal ◽  
Graphite Fibers

A series of studies in nucleate boiling phenomena on metal-graphite composite surfaces has been investigated by Prof. Wen-Jei Yang and their associates. It has been discovered that the unique micro-configured construction of the composite surfaces plays a crucial role in the enhancement of boiling heat transfer. The present paper focuses on the formation and growth processes of micro bubbles and the micro/nano scale boiling behavior to reveal the mechanism of boiling heat transfer enhancement on the unique surfaces. The growth processes of the micro and macro bubbles are analyzed and formulated followed by an analysis of bubble departure. Based on these analyses, the enhancement mechanism of the pool boiling heat transfer on the composite surfaces is clearly revealed. The micro-configured composite surfaces provide more even distribution of a great number of stable boiling active sites through the graphite fibers. Consequently, the heat conduction through the layers is increased, which provides the power of phase change at the interfaces on bubble bottoms. Experimental results convincingly demonstrate the enhancement effects of the unique structure of metal-graphite composite surfaces on boiling heat transfer.

Macro- to Microscale Boiling Heat Transfer From Metal-Graphite Composite Surfaces

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Wen-Jei Yang ◽  
Nengli Zhang ◽  
Daniel L. Vrable
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Boiling Heat Transfer ◽  
Thermal Hysteresis ◽  
Bubble Formation ◽  
Nucleate Boiling ◽  
Transfer Enhancement ◽  
Bubble Generation ◽  
Composite Surface ◽  
Graphite Composite

This paper introduces a novel heat transfer enhancement surface, referred to as metal-graphite composite surface. It is comprised of high thermal conductivity graphite microfibers interspersed within a metal matrix (copper or aluminum) to enhance the bubble formation at the nucleation sites, and significantly improve the nucleate boiling heat transfer. Experiments revealed that its boiling heat transfer enhancement is comparable or in some respect even superior to the commercially available boiling heat transfer enhancement surfaces such as porous boiling surface and integral roughness surface. In addition, it does not result in any extra pressure loss and it minimizes surface fouling. Macro- to microscale heat transfer phenomena of the composite surfaces is treated. Discussions include characteristics of the surface, enhancement mechanisms, critical heat flux, boiling thermal hysteresis, bubble generation, growth and departure, and applications in electronic cooling, and under reduced gravity conditions.

Surface Effects on Confinement-Driven Pool Boiling Enhancement in Vertical Parallel-Plate Channels

2005 ◽  
Author(s):  
Karl J. L. Geisler ◽  
Avram Bar-Cohen
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Boiling Heat Transfer ◽  
Parallel Plate ◽  
Nucleate Boiling ◽  
The Other ◽  
Transfer Enhancement ◽  
Channel Spacing ◽  
Boiling Enhancement ◽  
And Behavior

Evidence of confinement-driven boiling heat transfer enhancement in vertical channels is very well documented in the literature and much has been observed about its nature and behavior. However, the majority of the available correlations is empirically-based and they tend to be very restricted in their range of applicability and portability. In order to further elucidate the effect of this type of geometrical confinement on boiling heat transfer, an experimental study has been performed on vertical, rectangular parallel-plate channels immersed in the dielectric liquid FC-72. The enhancement of nucleate boiling performance with decreased channel spacing was found to depend on the type of heater employed but could not be explained by the surface roughness. On the other hand, degradation of the Critical Heat Flux (CHF) limit with decreasing channel spacing was found to be independent of the surface and to be well predicted by a correlation available in the literature.

Effect of Heat Flux on Pool Boiling Heat Transfer Enhancement (Numerical Investigation Approach)

2020 ◽  
Author(s):  
T. S. Mogaji ◽  
O. A. Sogbesan ◽  
Tien-Chien Jen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Numerical Investigation ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Transfer Enhancement

Abstract This study presents numerical investigation results of heat flux effect on pool boiling heat transfer enhancement during nucleate boiling heat transfer of water. The simulation was performed for five different heated surfaces such as: brass, copper, mild steel, stainless steel and aluminum using ANSYS simulation software at 1 atmospheric pressure. The samples were heated in a domain developed for bubble growth during nucleate boiling process under the same operational condition of applied heat flux ranged from 100 to 1000 kW/m2 and their corresponding heat transfer coefficient was obtained numerically. Obtained experimental data of other authors from the open literature result is in close agreement with the simulated data, thus confirming the validity of the CFD simulation method used in this study. It is found that heat transfer coefficient increases with increasing heat flux. The results revealed that in comparison to other materials tested, better heat transfer performance up to 38.5% and 7.11% is observed for aluminum and brass at lower superheated temperature difference conditions of 6.96K and 14.01K respectively. This behavior indicates better bubble development and detachment capability of these heating surface materials and could be used in improving the performance of thermal devices toward producing compact and miniaturized equipment.

Mechanism of Nucleate Boiling Heat Transfer Enhancement From Microporous Surfaces in Saturated FC-72

2002 ◽  
Vol 124 (3) ◽  
pp. 500-506 ◽  
Author(s):  
J. H. Kim ◽  
K. N. Rainey ◽  
S. M. You ◽  
J. Y. Pak
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Enhancement ◽  
Latent Heat ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Direct Result ◽  
Vapor Flow ◽  
High Heat Flux ◽  
Transfer Enhancement

The present study is an experimental investigation of the nucleate pool boiling heat transfer enhancement mechanism of microporous surfaces immersed in saturated FC-72. Measurements of bubble size, frequency, and vapor flow rate from a plain and microporous coated 390 μm diameter platinum wire using the consecutive-photo method were taken to determine the effects of the coating on the convective and latent heat transfer mechanisms. Results of the study showed that the microporous coating augments nucleate boiling performance through increased latent heat transfer in the low heat flux region and through increased convection heat transfer in the high heat flux region. The critical heat flux for the microporous coated surface is significantly enhanced over the plain surface due to decreased latent heat transfer (decreased vapor generation rate) and/or increased hydrodynamic stability from increased vapor inertia; both of which are a direct result of increased nucleation site density.

Enhanced Boiling Heat Transfer From Micro-Porous Cylindrical Surfaces in Saturated FC-87 and R-123

1997 ◽  
Vol 119 (2) ◽  
pp. 319-325 ◽  
Author(s):  
J. Y. Chang ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
High Heat ◽  
Bulk Liquid ◽  
High Heat Flux ◽  
High Flux ◽  
Boiling Enhancement ◽  
Nucleate Boiling Heat Transfer ◽  
Enhanced Boiling

The present research is an experimental study of pool boiling heat transfer from cylindrical heater surfaces immersed in saturated FC-87 and R-123. The baseline heater surfaces tested are plain, integral-fin with 709 fins/m, and commercial enhanced (High-Flux and Turbo-B). In addition, a highly effective micro-scale enhancement coating is applied to the plain and integral-fin surfaces to augment nucleate boiling heat transfer. Experiments are performed to understand the effects of surface micro- and macro-geometries on boiling heat transfer. The boiling performance of the micro-porous enhanced plain and integral-fin surfaces are compared with the High-Flux and the Turbo-B surfaces. At high heat flux conditions, the break down of the bulk liquid feed mechanism reduces boiling enhancement from the cylindrical surfaces.

Determination of the Boiling Enhancement Mechanism Caused by Surfactant Addition to Water

1996 ◽  
Vol 118 (2) ◽  
pp. 429-435 ◽  
Author(s):  
C. N. Ammerman ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Boiling Heat Transfer ◽  
Laser Doppler Anemometry ◽  
Sodium Dodecyl ◽  
Volumetric Flow Rate ◽  
Nucleate Boiling ◽  
Similar Data ◽  
Boiling Enhancement ◽  
Transfer Mechanisms

In the present investigation, boiling heat transfer coefficients are measured for an electrically heated 390-μm-dia, platinum wire immersed in saturated water, and in water mixed with three different concentrations of sodium dodecyl sulfate (an anionic surfactant). The addition of a surfactant to water is known to enhance boiling heat transfer. A recently developed photographic/laser-Doppler anemometry measurement technique is used to quantify the vapor volumetric flow rate departing from the wire during the boiling process. The volumetric flow rate data are used to calculate the latent heat and, indirectly, the convection heat transfer mechanisms that constitute the nucleate boiling heat flux. Comparisons are made to determine how the heat transfer mechanisms are affected by the surfactant addition, and thus, which mechanism promotes boiling enhancement. The present data are also compared with similar data taken for a 75-μm-dia wire immersed in saturated FC-72 (a highly wetting liquid) to provide increased insight into the nature of the boiling heat transfer mechanisms.

scholarly journals Experimental study of nucleate boiling heat transfer enhancement by using surfactant

2011 ◽  
Vol 2 (3-4) ◽  
pp. 195-209 ◽  
Author(s):  
R.I. Elghanam ◽  
M.M.EL. Fawal ◽  
R. Abdel Aziz ◽  
M.H. Skr ◽  
A. Hamza Khalifa
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Enhancement ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Transfer Enhancement ◽  
Nucleate Boiling Heat Transfer
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