ICONE23-1123 Study of bubble lift-off from a vertical heated surface in pool boiling

Advancement in the experimental techniques have brought new insights into the microscale boiling phenomena, and provide the base for a new physical interpretation of flow boiling heat transfer. A new modeling framework in Computational Fluid Dynamics has been assembled at MIT, and aims at introducing all necessary mechanisms, and explicitly tracks: (1) the size and dynamics of the bubbles on the surface; (2) the amount of microlayer and dry area under each bubble; (3) the amount of surface area influenced by sliding bubbles; (4) the quenching of the boiling surface following a bubble departure and (5) the statistical bubble interaction on the surface. The preliminary assessment of the new framework is used to further extend the portability of the model through an improved formulation of the force balance models for bubble departure and lift-off. Starting from this improved representation at the wall, the work concentrates on the bubble dynamics and dry spot quantification on the heated surface, which governs the Critical Heat Flux (CHF) limit. A new proposition is brought forward, where Critical Heat Flux is a natural limiting condition for the heat flux partitioning on the boiling surface. The first principle based CHF is qualitatively demonstrated, and has the potential to deliver a radically new simulation technique to support the design of advanced heat transfer systems.

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Development of Lift-Off Diameter Model of Bubbles Generated on Horizontal Tube

Volume 8B: Heat Transfer and Thermal Engineering ◽

10.1115/imece2014-36826 ◽

2014 ◽

Author(s):

Sung Uk Ryu ◽

Seok Kim ◽

Dong-Jin Euh

Keyword(s):

Heated Surface ◽

Horizontal Tube ◽

Force Balance ◽

Convective Boiling ◽

Azimuthal Position ◽

Flux Partitioning ◽

Balance Analysis ◽

Lift Off ◽

The Moment ◽

Surrounding Liquid

In this study, the theoretical correlation for the lift-off diameter of bubbles generated on a horizontal tube is proposed. A force balance analysis in the direction normal to the heated surface at the moment of the bubble lift-off was performed to develop the model. According to the developed model, the bubble lift-off diameter depends strongly on the azimuthal position of the horizontal tube, the relative velocity between a bubble and surrounding liquid, the properties of the bubble, and the liquid. The developed model can be applicable to define the sub-model of wall heat flux partitioning for natural and forced convective boiling.

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Numerical Simulation and Experimental Validation of the Dynamics of a Single Bubble During Pool Boiling Under Constant and Time-Varying Reduced Gravity Conditions

Heat Transfer: Volume 2 ◽

10.1115/ht2003-47125 ◽

2003 ◽

Author(s):

H. S. Abarajith ◽

D. M. Qiu ◽

V. K. Dhir

Keyword(s):

Numerical Simulation ◽

Heated Surface ◽

Bubble Diameter ◽

Pool Boiling ◽

Growth Period ◽

Single Bubble ◽

Time Varying ◽

Reduced Gravity ◽

System Pressure ◽

Vapor Liquid

The numerical simulation and experimental validations of the growth and departure of a single bubble on a horizontal heated surface during pool boiling under reduced gravity conditions have been performed here. A finite difference scheme is used to solve the equations governing mass, momentum and energy in the vapor liquid phases. The vapor-liquid interface is captured by level set method, which is modified to include the influence of phase change at the liquid-vapor interface. The effects of reduced gravity conditions, wall superheat and liquid subcooling and system pressure on the bubble diameter and growth period have been studied. The simulations are also carried out under both constant and time-varying gravity conditions to benchmark the solution with the actual experimental conditions that existed during the parabolic flights of KC-135 aircraft. In the experiments, a single vapor bubble was produced on an artificial cavity, 10 μm in diameter microfabricated on the polished silicon wafer, the wafer was heated electrically from the back with miniature strain gage type heating elements in order to control the nucleation superheat. The bubble growth period and the bubble diameter predicted from the numerical simulations have been found to compare well with the data from experiments.

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A Possible Mechanism for the Formation of Unwettable Dry Spots on the Heated Surface under Nucleate Boiling: Part I. Basic Models and Characteristics of Heterogeneous Nucleate Pool Boiling at a Low Pressure

Physics of Atomic Nuclei ◽

10.1134/s1063778819080167 ◽

2019 ◽

Vol 82 (8) ◽

pp. 1194-1205

Author(s):

Yu. M. Zhukov ◽

D. S. Urtenov

Keyword(s):

Heated Surface ◽

Pool Boiling ◽

Low Pressure ◽

Nucleate Boiling ◽

Nucleate Pool Boiling

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On the Mechanism of Pool Boiling Critical Heat Flux Enhancement in Nanofluids

Journal of Heat Transfer ◽

10.1115/1.4000746 ◽

2010 ◽

Vol 132 (6) ◽

Cited By ~ 71

Author(s):

Hyungdae Kim ◽

Ho Seon Ahn ◽

Moo Hwan Kim

Keyword(s):

Heat Flux ◽

Critical Heat Flux ◽

Heated Surface ◽

Pure Water ◽

Pool Boiling ◽

Nucleate Boiling ◽

Titania Nanoparticles ◽

Nanoparticle Layer ◽

Wall Superheat ◽

Dry Spot

The pool boiling characteristics of water-based nanofluids with alumina and titania nanoparticles of 0.01 vol % were investigated on a thermally heated disk heater at saturated temperature and atmospheric pressure. The results confirmed the findings of previous studies that nanofluids can significantly enhance the critical heat flux (CHF), resulting in a large increase in the wall superheat. It was found that some nanoparticles deposit on the heater surface during nucleate boiling, and the surface modification due to the deposition results in the same magnitude of CHF enhancement in pure water as for nanofluids. Subsequent to the boiling experiments, the interfacial properties of the heater surfaces were examined using dynamic wetting of an evaporating water droplet. As the surface temperature increased, the evaporating meniscus on the clean surface suddenly receded toward the liquid due to the evaporation recoil force on the liquid-vapor interface, but the nanoparticle-fouled surface exhibited stable wetting of the liquid meniscus even at a remarkably higher wall superheat. The heat flux gain attainable due to the improved wetting of the evaporating meniscus on the fouled surface showed good agreement with the CHF enhancement during nanofluid boiling. It is supposed that the nanoparticle layer increases the stability of the evaporating microlayer underneath a bubble growing on a heated surface and thus the irreversible growth of a hot/dry spot is inhibited even at a high wall superheat, resulting in the CHF enhancement observed when boiling nanofluids.

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A Three-Dimensional Numerical Modelling of Atmospheric Pool Boiling by the Coupled Map Lattice Method

Heat Transfer: Volume 2 ◽

10.1115/ht2005-72497 ◽

2005 ◽

Author(s):

A. Gupta ◽

P. S. Ghoshdastidar

Keyword(s):

Thermal Diffusion ◽

Heated Surface ◽

Pool Boiling ◽

Three Dimensional ◽

Coupled Map Lattice ◽

Lattice Method ◽

Copper Strip ◽

Basic Objective ◽

Cml Model ◽

Bubble Rising

In the present paper, the characteristic atmospheric pool boiling curve is qualitatively reproduced for water on a temperature controlled thin copper strip having comparable length and breadth by the coupled map lattice (CML) method using a three-dimensional boiling field model. The basic objective of the work is to improve the prediction of the critical heat flux (CHF) with respect to the 2D CML model of Ghoshdastidar et al. [10]. The work models saturated pool boiling of water at 1 bar on a large (much larger than the minimum wavelength of 2D Taylor waves) and thin horizontal copper strip. The pool height is 0.7 mm, indicating thin film boiling. In the present model, it is assumed that boiling is governed by (a) nucleation from cavities on a heated surface, (b) thermal diffusion, (c) bubble rising motion and associated convection, (d) phase change and (e) Taylor instability. The changes with respect to 2D model are primarily with respect to 3D modelling of thermal diffusion and 2D distribution of nucleating cavity sizes. The predicted CHF is 1.57 MW/m2 as compared to the actual value of 1.3 MW/m2 and 0.36 MW/m2 predicted by the 2D CML model of Ghoshdastidar et al. [10]. It can be said that for the first time a coupled map lattice method which is essentially qualitative in nature has been able to predict the CHF of saturated pool boiling of water at 1 bar very close to the actual value.

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