Microscale Vapor Bubble Interactions During Subcooled Nucleate Boiling on a Heated Wire

2007 ◽  
Author(s):  
Lu Zhang ◽  
David M. Christopher
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Bubble Behavior ◽  
Transfer Rates ◽  
Bubble Interactions ◽  
Heated Wire ◽  
Nucleate Boiling Heat Transfer ◽  
Transfer Mechanisms

Bubbles have been observed moving along heated wires during subcooled nucleate boiling as they are driven by Marangoni convection around the bubbles. This paper presents more detailed observations of the vapor bubble interactions and moving bubble behavior during subcooled nucleate boiling on a heated microwire. The experimental results show that moving bubbles coalesce or rebound from other bubbles and that bubbles hop on the wire. These observations show how bubble interactions significantly affect nucleate boiling heat transfer rates and how Marangoni flow plays an important role in microscale nucleate boiling heat transfer mechanisms.

Identification of Pool Boiling Heat Transfer Mechanisms From a Wire Immersed in Saturated FC-72 Using a Single-Photo/LDA Method

1996 ◽  
Vol 118 (1) ◽  
pp. 117-123 ◽  
Author(s):  
C. N. Ammerman ◽  
S. M. You ◽  
Y. S. Hong
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Flow Rate ◽  
Boiling Heat Transfer ◽  
Laser Doppler Anemometry ◽  
Volumetric Flow Rate ◽  
Nucleate Boiling ◽  
Nucleate Boiling Heat Transfer ◽  
Unique Method ◽  
Transfer Mechanisms

A unique method to determine the vapor volumetric flow rate above a heated wire utilizing a single photograph and laser-Doppler anemometry is developed and discussed. The volumetric flow rate is combined with additional analyses to determine the overall contributions to the total heat flux from four nucleate boiling heat transfer mechanisms (latent heat, natural convection, Marangoni flow, and microconvection). This method is applied to a 75-μm wire immersed in a saturated, highly wetting liquid (FC-72). Latent heat is identified as the dominant mechanism in the fully developed nucleate boiling regime.

Comparison of Heat Transfer Rates Around Moving and Stationary Bubbles During Nucleate Boiling

2005 ◽  
Author(s):  
David M. Christopher ◽  
Hao Wang ◽  
Xiaofeng Peng
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Nucleate Boiling ◽  
High Heat ◽  
Marangoni Flow ◽  
Transfer Rates ◽  
High Heat Transfer ◽  
Nucleate Boiling Heat Transfer ◽  
Bubble Movement ◽  
Transfer Mechanisms

Nucleate boiling is known to be a very efficient method for generating high heat transfer rates from solid surfaces into liquids; however, the fundamental physical mechanisms governing nucleate boiling heat transfer are not well understood. This paper describes a numerical analysis of the heat transfer mechanisms around stationary and moving bubbles on a very thin microwire. The numerical analysis accurately models the experimentally observed bubble movement and fluid velocities. The analytical model was then used to study the heat transfer mechanisms around the bubbles. The analysis shows that the primary heat transfer mechanism is not the direct heat transfer to the bubble, but rather the large amount of convection around the outside of the bubble induced by the Marangoni flow that transfers at least twice as much energy from the wire than the heat transfer directly under the bubble. The enhanced heat transfer due to the Marangoni flow was evident for both stationary and moving bubbles.

An Overview: Analysis of Heat and Mass Transfer in Fractal Media by Fractal Geometry and Technique

2010 ◽  
Author(s):  
Boming Yu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Porous Media ◽  
Heat And Mass Transfer ◽  
Oil Recovery ◽  
Fractal Geometry ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
Fractal Media ◽  
Nucleate Boiling Heat Transfer

In the past three decades, fractal geometry and technique have received considerable attention due to its wide applications in sciences and technologies such as in physics, mathematics, geophysics, oil recovery, material science and engineering, flow and heat and mass transfer in porous media etc. The fractal geometry and technique may become particularly powerful when they are applied to deal with random and disordered media such as porous media, nanofluids, nucleate boiling heat transfer. In this paper, a summary of recent advances is presented in the areas of heat and mass transfer in fractal media by fractal geometry technique. The present overview includes a brief summary of the fractal geometry technique applied in the areas of heat and mass transfer; thermal conductivities of porous media and nanofluids; nucleate boiling heat transfer. A few comments are made with respect to the theoretical studies that should be made in the future.

Visualization of Boiling Heat Transfer on Micro Porous Coated Surface in Confined Space

2013 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Chien-Fu Liu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Confined Space ◽  
Two Phase ◽  
Nucleate Boiling Heat Transfer ◽  
Coated Surface

Numerous researches have been developed for pool boiling on microporous coated surface in the past decade. The nucleate boiling heat transfer was found to be increased by up to 4.5 times than that on uncoated surface. Recently, the two-phase micro heat exchangers have been considered for high flux electronic devices cooling. The enhancement techniques for improving the nucleate boiling heat transfer performance in the micro heat exchangers have gotten more importance. Previous studies of microporous coatings, however, have been restricted to boiling in unconfined space. No studies have been made on the feasibility of using microporous coatings for enhancing boiling in confined spaces. This study provides an experimental observation of the vapor generation and leaving processes on microporous coatings surface in a 1-mm confined space. It would be helpful for understanding the mechanism of boiling heat transfer and improving the design of two-phase micro heat exchangers. Aluminum particles of average diameter 20 μm were mixed with a binder and a carrier to develop a 150 μm thickness boiling enhancement paint on a 3.0 cm by 3.0 cm copper heating surface. The heating surface was covered by a thin glass plate with a 1 mm spacer to form a 1 mm vertical narrow space for the test section. The boiling phenomenon was recorded by a high speed camera. In addition to the three boiling regimes observed by Bonjour and Lallemand [1], i.e., isolated deformed bubbles, coalesced bubbles and partial dryout at low, moderate and high heat fluxes respectively in unconfined space, a suction and blowing process was observed at the highest heat flux condition. Owing to the space confinement, liquid was sucked and vapor was expelled periodically during the bubble generation process. This mechanism significantly enhanced the boiling heat transfer performance in confined space.

Pool Boiling Heat Transfer with Nanotube Arrays Surface on Titanium

2012 ◽  
Vol 550-553 ◽  
pp. 2913-2916 ◽  
Author(s):  
Jin Liang Tao ◽  
Xin Liang Wang ◽  
Pei Hua Shi ◽  
Xiao Ping Shi
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Test Fluid ◽  
Porous Coating ◽  
Pool Boiling Heat Transfer ◽  
Nucleate Boiling Heat Transfer ◽  
Boiling Heat Transfer Coefficient

In this paper, a new porous coating was formed directly on the surface of titanium metal via anodic oxidation. And by the SEM, the morphology of the coating, which is composed of well-ordered perpendicular nanotubes, was characterized. Moreover, taking deionized water as the test fluid, a visualization study of the coating on its pool boiling heat transfer performance was made. The results demonstrated that compared with the smooth surface, the nucleate boiling heat transfer coefficient can increase 3 times while the nucleate boiling super heat was reduced 30%.

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