Continuum and Molecular Dynamics Simulations of the Growth of a Vapor Bubble on a Heating Surface: Exploring the Mechanism of Nucleate Boiling Heat Transfer
Item
-
Title
-
Continuum and Molecular Dynamics Simulations of the Growth of a Vapor Bubble on a Heating Surface: Exploring the Mechanism of Nucleate Boiling Heat Transfer
-
Identifier
-
d_2009_2013:0a18704070a9:10974
-
identifier
-
11408
-
Creator
-
Bao, Jinyong,
-
Contributor
-
David Rumschitzki
-
Date
-
2011
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Chemical engineering | contact line | molecular dynamics simulation | nucleate pool boiling
-
Abstract
-
Starting with a completely rewritten code for the conductively-driven quasi-static vapor bubble growth in an axisymmetric, cylindrical cell comprised of solid and liquid phase of finite thicknesses under small Reynolds, Peclet, Capillary and Bond numbers to verify L. Huang's (our prior Ph.D. student) earlier results, we couple the solution of the quasi-static problem with three simple, somewhat ad hoc models of contact line motion and relax the assumption of small Bond number to simulate the growth of an incipient bubble until gravity begins to slowly deform the vapor bubble and then to detach it from the solid heater surface. A simple physical theory is developed to explain that when the bubble density is not too high, the bubble volume vs time approaches a 3/2 power before gravity begins to deform its shape, independent of contact line motion models and system parameters such as the conductivity ratio of the liquid to solid and degree of wall superheat.;On the other hand, contact line motion does have a significant effect on bubble deformation and detachment. Molecular dynamics (MD) is employed to determine the contact line motion in a nano-scale version of our three-phase system because MD not only includes heat transfer, but also fluid flow, which can remove many restrictions of the earlier continuum calculation in our nano-size system. Instead of nucleating a bubble by cavitation, we nucleate a vapor bubble by heating the bottom of the solid upon which the fluid sits at constant pressure. Under a uniform body force that, due to the scale of MD is far larger than terrestrial gravity, we then track the bubble's growth driven by heat transfer from the conducting heated solid until detachment. Its contact line motion is monitored and the effects of wettability of solid surface, temperature-slip of fluid-solid interface and the choice of the interaction between the solid and the fluid have also been discussed. Unfortunately, this temperature slip mitigates some of the effects of the contact line that the continuum modeling (without temperature slip) finds so crucial at macroscopic scales.
-
Type
-
dissertation
-
Source
-
2009_2013.csv
-
degree
-
Ph.D.
-
Program
-
Engineering
