HEAT TRANSFER INVESTIGATION ON A SINGLE ARTIFICIAL NUCLEATE SITE: INFLUENCE OF THE WALL ORIENTATION ON THE BUBBLE BEHAVIOR

2018 ◽  
Author(s):  
Mohammed Zamoum ◽  
Herve Combeau ◽  
Lounes Tadrist
Keyword(s):  
Heat Transfer ◽  
Bubble Behavior ◽  
Nucleate Site

Subcooled Boiling of Surfactant Solutions

2000 ◽  
Author(s):  
G. Hetsroni ◽  
M. Gurevich ◽  
A. Mosyak ◽  
R. Rozenblit ◽  
L. P. Yarin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Speed ◽  
Heated Surface ◽  
Pure Water ◽  
Video Camera ◽  
Subcooled Boiling ◽  
Bubble Behavior ◽  
Boiling Hysteresis

Abstract During subcooled boiling of pure water and water with cationic surfactants, the motion of bubbles and the temperature of the heated surface were recorded by both a high-speed video camera and an infrared radiometer. The results show that the bubble behavior and the heat transfer mechanism for the surfactant are quite different from those of clear water. Bubbles formed in Habon G solutions were much smaller man those in water and the surface was covered with them faster. Boiling hysteresis is found for degraded solutions. Dependencies of heat transfer coefficient for various solutions were obtained and compared. The boiling curves of surfactant are quite different from the boiling curve of pure water. Experimental results demonstrate that the heat transfer coefficient of the boiling process can be enhanced considerably by the addition of a small amount of Habon G. The experiments show that the limitations of the ER technique with respect to frequency response are outweighed by its unique capacity to measure wall temperature distribution with high spatial resolution over an area encompassing many nucleation sites and over long periods.

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.

Heat Transfer and Bubble Movement of Double- and Single-Side Heating Subcooled Flow Boiling in Narrow Channels

2005 ◽  
Author(s):  
Liang-Ming Pan ◽  
Chuan He ◽  
Ming-Dao Xin ◽  
Tien-Chien Jen ◽  
Qinghua Chen
Keyword(s):  
Heat Transfer ◽  
Flow Boiling ◽  
Narrow Channel ◽  
Nucleate Boiling ◽  
Bubble Behavior ◽  
Subcooled Flow Boiling ◽  
Narrow Channels ◽  
Subcooled Flow ◽  
Single Side ◽  
Micro Channels

Compared with conventional channels, narrow and micro channels have significant heat transfer enhancement characteristic. With smooth internal surface, such channels can efficiently avoid encrustation at the washing of the high-speed liquid. Moreover, heat transfer elements can be easily assembled. These types of channels have been adopted extensively in many engineering applications, e.g. microelectronic cooling, advanced nuclear reactor, cryogenic, aviation and space technology and thermal engineering. Geometrical size of flow passage-away affects heat exchange of flow boiling, with the result that the bubble in narrow channel acts very different from those in non-narrow channel. This paper experimentally compared the bubble behavior with different heating methods of narrow rectangular channels, and the bubble behavior of subcooled flow boiling of R-12 in the narrow channels both with double side and single heating. Experimental settings are: the heating length of test-section is 400 mm, the cross-section is 35 mm in width and 2mm in gap size, mass flux is 700∼1500 kg.m−2.s−1, the heat flux is 25∼70kW.m−2 and the pressure is 1.3∼2.0 MPa. Comparisons were made on Onset of Nucleate Boiling (ONB) point and bubble characters with various flow patterns. Results revealed that the characteristics of double and single side heating shown good agreement with proper modifications.

Bubble Behavior in Pool Boiling Heat Transfer between Two Plates with a Narrow Gap

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Jin Sub Kim ◽  
Dong Hwan Shin ◽  
Yeonghwan Kim ◽  
Seung M. You ◽  
Jungho Lee
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Thin Liquid Film ◽  
Ground Plane ◽  
Pool Boiling ◽  
High Heat Flux ◽  
Narrow Gap ◽  
Bubble Behavior ◽  
Military Technology ◽  
Technology Cooperation

Abstract The pool boiling phenomena, which may occur at high heat flux in the planar heat pipe such as vapor chamber and thermal ground plane (TGP), were visually investigated in the vertical orientation by capturing the bubble behavior within a narrow gap between two plates using distilled water at 1 atm. The size of two copper plates is 80×80 mm2 and the 10×10 mm2 ceramic heater, which simulates the high power chip, was bonded to the backside of the bottom plate. The gap between two plates was adjusted from 3 mm to 0.5 mm using spacers. It was observed that the generated bubble spreads laterally throughout the channel between the plates as decreasing the gap. Thin liquid film forms beneath the flattened bubble and the thin film evaporation improves heat transfer at the narrow gaps of 3 and 1 mm. However, further reduction of the gap down to 0.5 mm brings about an increase of the dried region, resulting in the deterioration of boiling heat transfer. [This work was supported by the Civil-Military Technology Cooperation Program of the Institute of Civil-Military Technology Cooperation (ICMTC), with a grant funded by the Defense Acquisition Program Administration and the Ministry of Trade, Industry and Energy (Grant No. 18CM5017).]

CFD Analysis on Wall Boiling Model During Subcooled Boiling in Vertical Narrow Rectangular Channel

2018 ◽  
Author(s):  
Tingting Ren ◽  
Changqi Yan ◽  
Meiyue Yan ◽  
Shengzhi Yu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Model ◽  
Rectangular Channel ◽  
Subcooled Boiling ◽  
Site Density ◽  
Rectangular Channels ◽  
Two Fluid Model ◽  
Nucleate Site ◽  
Two Fluid

Two-fluid model is a common method to simulate the subcooled flow boiling heat transfer, in which the wall boiling model is mainly used for the partition of wall heat flux and the mass transfer between two phases on the wall. The model determines the amount of vapor phase and predicts the cross-sectional void fraction in the channel, nucleate site density and bubble departure diameter play an important role in the accurate prediction of wall boiling model. Eulerian two-fluid model coupled with Rensselaer Polytechnic Institute (RPI) wall boiling model is employed to simulate the heat transfer characteristics and boiling phenomena in vertical narrow rectangular channels by using FLUENT code. Based on the experimental data of subcooled boiling in vertical narrow rectangular channel, different combinations of nucleate site density and bubble departure diameter correlations are used to calculate under different conditions of heat flux and inlet subcooling. Comparing the calculated heat transfer coefficients along the vertical height with experimental results, it can be found that these two parameters have a significant effect on the subcooled boiling heat transfer in narrow rectangular channels. Different parameter combinations lead to differences in wall heat flux distribution, different heat flux and inlet subcooling also have different effects on these models, which eventually lead to different evaporative heat flux, thus affecting the prediction of void fraction.

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