Microbubble emission boiling in scbcooled pool boiling and the role of Marangoni convection in its formation

Abstract An experimental apparatus was designed and fabricated to visually investigate microbubble emission boiling (MEB) phenomena characterized by its extremely high heat dissipation capacity and potential application in the field of thermal engineering. The heating element was a cone copper block with an upper cylindrical section of 10 mm in diameter. A high-speed video camera (Photron: Fastcam SA5) was employed for recording the scenario of MEB. Visualized results show that both the subcooling and noncondensable gas have significant effects on MEB. Remarkable MEB could be observed when the liquid subcooling exceeds 25 K, with a maximum heat flux about 9 MW/m 2 at the subcooling of 60 K. In order to explore the mechanism of MEB, numerical simulations were carried out to obtain the velocity field near a single vapor film on the same heating surface to that in the experiments with the software of “FLUENT”. Simulation results indicates that there exists Marangoni convection around the film under subcooled condition, which is influenced significantly by subcooling as well as thermal properties of the liquid. Strong Marangoni convection around the vapor film and the condensation at interface would induce interfacial waves, likely resulting in the collapse of the film in the case of high subcooling. As a result, it is reasonable to conclude that Marangoni convection is probably one of the key factors triggering the occurrence of MEB.

[1]  Guodong Wang,et al.  Subcooled flow boiling and microbubble emission boiling phenomena in a partially heated microchannel , 2009 .

[2]  Shu Takagi,et al.  Microbubbles emission flow boiling in a microchannel and minichannel , 2004 .

[3]  K. Stephan.  Heat Transfer in Condensation and Boiling , 1992 .

[4]  Ichiro Ueno,et al.  Condensation and Collapse of Vapor Bubbles Injected in Subcooled Pool , 2011 .

[5]  Y. Zeigarnik,et al.  A Study into Development of Instability and Collapse of Vapor Layer on a Heated Solid Hemispherical Surface , 2000 .

[6]  S. Petrovic,et al.  Marangoni heat transfer in subcooled nucleate pool boiling , 2004 .

[7]  N. Zuber.  Hydrodynamic aspects of boiling heat transfer (thesis) , 1959 .

[8]  Yu. L. Shekhter,et al.  Visualization of boiling of subcooled water , 2011 .

[9]  D. Christopher,et al.  Numerical analysis of the dynamics of moving vapor bubbles , 2006 .

[10]  Hiroshi Saitoh,et al.  High Heat Flux Cooling by Microbubble Emission Boiling , 2002, Annals of the New York Academy of Sciences.

[11]  Hiroshi Kawamura,et al.  Enhancement of heat transfer in subcooled flow boiling with microbubble emission , 2005 .

[12]  W. Rohsenow.  A Method of Correlating Heat-Transfer Data for Surface Boiling of Liquids , 1952, Journal of Fluids Engineering.

[13]  泉 亮太郎,et al.  サブクールプール沸騰特性曲線の研究 : 第1報, 局所熱伝達特性とそれにおよぼすサブクール度の影響 , 1981 .

[14]  F. Inagaki,et al.  Subcooled Boiling in the Ultrasonic Field—On the Cause of Microbubble Emission Boiling , 2011 .

[15]  D. Christopher,et al.  Bubble sweeping and interactions on wires during subcooled boiling , 2009 .

[16]  A. Turan,et al.  VOF simulation of marangoni flow of gas bubbles in 2D-axisymmetric column , 2010, ICCS.

[17]  J. Straub,et al.  The origin of thermocapillary convection in subcooled nucleate pool boiling , 2001 .

[18]  J. Betz,et al.  Enhancement of Heat Transfer by Thermocapillary Convection around Bubbles -a Numerical Study , 1994 .

[19]  S. Garimella,et al.  Microbubble Return Phenomena During Subcooled Boiling on Small Wires , 2007 .