Electrohydrodynamic effects on bubble dynamics during nucleate pool boiling under the leaky dielectric assumption

Bubble dynamics is the most important subphenomenon, which basically affects the nucleate pool boiling heat transfer coefficient. Previous investigations state that the effect of physical properties of liquid and vapor phases on bubble departure diameter are often conflicting. In this article, extensive new experimental data are presented for the bubble departure diameter for various electrolyte aqueous solutions over a wide range of heat fluxes and concentrations. Experimental results show that the bubble detachment diameter increase with increasing either boiling heat flux or electrolyte concentration. Experimental results also present a close relation between the dimensionless capillary and bond numbers. A new model for the prediction of vapor bubble departure diameter in nucleate boiling for the electrolyte solutions is proposed, which predicts the experimental data with a satisfactory accuracy.

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Simulation of Single Bubble Dynamics in Nucleate Pool Boiling Using a Conservative Level Set Method

Volume 3: Combustion, Fire and Reacting Flow; Heat Transfer in Multiphase Systems; Heat Transfer in Transport Phenomena in Manufacturing and Materials Processing; Heat and Mass Transfer in Biotechnology; Low Temperature Heat Transfer; Environmental Heat Transfer; Heat Transfer Education; Visualization of Heat Transfer ◽

10.1115/ht2009-88155 ◽

2009 ◽

Author(s):

Muhammad Sajid ◽

Rachid Bennacer

Keyword(s):

Surface Tension ◽

Level Set ◽

Bubble Dynamics ◽

Pool Boiling ◽

Heated Wall ◽

Nucleate Pool Boiling ◽

Vapor Interface ◽

Level Set Function ◽

Conservative Level Set ◽

Liquid Vapor

Most energy conversion systems and cooling devices employ nucleate pool boiling because of its high efficiency of heat exchange. It is a liquid-vapor phase change process associated with ebullition, characterized by cyclic growth and departure of vapor bubbles from heated wall and greatly influenced by the bubble growth mechanism. Bubble dynamics is difficult to simulate due to the difficulty of tracking the liquid vapor interface without smearing it, the discontinuity in material properties due to high density ratio and the need to take surface tension into account that introduces a jump in the pressure field. This paper focuses on the accurate representation of surface tension effects on bubble dynamics in nucleate pool boiling. The complete Navier-Stokes equations are solved and liquid-vapor interface is captured using a conservative level-set technique, curvature of interface is computed using the level set function and surface tension forces are evaluated as a body force according to the continuum surface force method. This enables us to simulate flows with large density and viscosity differences, to capture the shape of the deforming interface of the bubble while maintaining good mass conservation. The ability of the model is demonstrated with the numerical example of a growing bubble.

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Experimental Study of Effect of Nucleation Site Size on Bubble Dynamics during Nucleate Pool Boiling Heat Transfer

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.592-594.1596 ◽

2014 ◽

Vol 592-594 ◽

pp. 1596-1600 ◽

Cited By ~ 3

Author(s):

Abdul Najim ◽

Anil R. Aacharya

Keyword(s):

Heat Transfer ◽

Boiling Heat Transfer ◽

Bubble Dynamics ◽

Bubble Diameter ◽

Pool Boiling ◽

Growth Period ◽

Nucleation Site ◽

Hypodermic Needle ◽

Nucleate Pool Boiling ◽

Pool Boiling Heat Transfer

In this paper, effect of nucleation site size on bubble dynamics during nucleate pool boiling heat transfer in saturated water is studied experimentally. Single bubble was generated using right angle tip of a hypodermic needle as a nucleation site. The hypodermic needles were used of inner diameters 0.413mm, 0.514mm, and 0.603 mm with a constant depth of 25mm. The bubble dynamics was studied using SONY Cyber-shot DSC-H100 camera operating at 30 frames per second at atmospheric pressure and at a wall superheat of 5K. The results show that, bubble diameter, bubble height and bubble volume increases with increase in diameter of nucleation site. The bubble growth period is found to be dependent on nucleation site size, and it decreases with increase in diameter of nucleation site. This happens because as volume of vapor bubble increases, buoyancy force starts dominates the capillary force and bubble detaches earlier. Effect of nucleation site size on bubble departure diameter and bubble release frequency is also discussed.

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