Numerical Study of a Single Bubble Sliding on a Downward Facing Heated Surface

2006 ◽  
Vol 129 (7) ◽  
pp. 877-883 ◽  
Author(s):  
Ding Li ◽  
Vijay K. Dhir
Keyword(s):  
Numerical Study ◽  
Heated Surface ◽  
Three Dimensional ◽  
Single Bubble ◽  
Wall Heat Transfer ◽  
Heater Surface ◽  
Vapor Interface ◽  
Sliding Motion ◽  
Energy Equations ◽  
Sliding Distance

In this study, a complete three-dimensional numerical simulation of single bubble sliding on a downward facing heater surface is carried out. The continuity, momentum, and energy equations are solved using a finite-difference method. Level-set method is used to capture the liquid-vapor interface. The shape of the sliding bubble changes from a sphere, to an ellipsoid and finally to a bubble-cap. The wall heat flux downstream of the sliding bubble is much larger than that upstream of the bubble. This indicates that wall heat transfer is significantly enhanced by sliding motion of the bubble. The bubble shape and sliding distance predicted from numerical simulations is compared with data from experiments.

A Numerical Study of a Single Bubble Sliding on a Downward Facing Heating Surface

2005 ◽  
Author(s):  
Ding Li ◽  
Sathish Manickam ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Heating Surface ◽  
Single Bubble ◽  
Bubble Shape ◽  
Heater Surface ◽  
3D Numerical Simulation ◽  
Vapor Interface ◽  
Energy Equations ◽  
Sliding Distance

In this study, a complete 3D numerical simulation of single bubble sliding on a downward facing heater surface is carried out. The continuity, momentum and energy equations are solved using finite difference method and the level-set method is used to capture the liquid-vapor interface. The shape of sliding bubble changes from initially spheroids, to ellipsoids and finally to bubble-cap. The temperature gradient downstream the sliding bubble is much larger than that upstream the bubble. This indicates the sliding bubble enhances the heat transfer significantly. The bubble shape and sliding distance predicted from numerical analysis is compared with the experimental data.

Numerical Study of Single Bubble Dynamics During Flow Boiling

2007 ◽  
Vol 129 (7) ◽  
pp. 864-876 ◽  
Author(s):  
Ding Li ◽  
Vijay K. Dhir
Keyword(s):  
Bubble Dynamics ◽  
Numerical Study ◽  
Flow Boiling ◽  
Three Dimensional ◽  
Horizontal Surface ◽  
Single Bubble ◽  
Bulk Liquid ◽  
Interface Heat Transfer ◽  
Single Bubble Dynamics ◽  
Energy Equations

Three-dimensional numerical simulation of single bubble dynamics during nucleate flow boiling is performed in this work. The range of bulk liquid velocities investigated is from 0.076to0.23m∕s. The surface orientations at earth normal gravity are varied from an upward facing horizontal surface to vertical through 30, 45, and 60deg. The gravity levels on an upward facing horizontal surface are varied from 1.0ge to 0.0001ge. Continuity, momentum, and energy equations are solved by finite difference method and the level set method is used to capture the liquid-vapor interface. Heat transfer within the liquid micro layer is included in this model. The numerical results have been compared with data from experiments. The results show that the bulk flow velocity, heater surface orientation, and gravity levels influence the bubble dynamics.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

A Three-Dimensional Numerical Study of Tin Droplets Landing Sequentially on a Solid Surface

2002 ◽  
Author(s):  
R. Ghafouri-Azar ◽  
J. Mostaghimi ◽  
S. Chandra
Keyword(s):  
Surface Deformation ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Sequential Deposition ◽  
Free Surface Deformation ◽  
Energy Equations ◽  
Simulated Images ◽  
D Model ◽  
Shape And Size

A three-dimensional (3-D) model of spreading and solidification was used to investigate the sequential deposition of two tin droplets for different offset landing. Numerical simulations predicted the shape and size of the landing tin droplet as it spread over a previously landed splat. The model applies a fixed-grid Eulerian control volume to solve the fluid dynamics and energy equations. The Volume of Fluid (VOF) algorithm is used to track the free surface deformation. The comparison of the simulated images and experimental photographs validated the prediction of the model.

Three-Dimensional Temperature Distribution in EHD Lubrication: Part II—Point Contact and Numerical Formulation

1993 ◽  
Vol 115 (1) ◽  
pp. 36-45 ◽  
Author(s):  
Kyung-Hoon Kim ◽  
Farshid Sadeghi
Keyword(s):  
Temperature Distribution ◽  
Film Thickness ◽  
Numerical Study ◽  
Control Volume ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Lubricant Film ◽  
Numerical Formulation ◽  
Energy Equations

A numerical study of Newtonian thermal elastohydrodynamic lubrication (EHD) of rolling/sliding point contacts has been conducted. The two-dimensional Reynolds, elasticity and the three-dimensional energy equations were solved simultaneously to obtain the pressure, film thickness and temperature distribution within the lubricant film. The control volume approach was employed to discretize the differential equations and the multi-level multi-grid technique was used to simultaneously solve them. The discretized equations, as well as the nonorthogonal coordinate transformation used for the solution of the energy equation, are described. The pressure, film thickness and the temperature distributions, within the lubricant film at different loads, slip conditions and ellipticity parameters are presented.

Experimental Study of Heat Transfer in an Evaporating Meniscus on a Moving Heated Surface

2005 ◽  
Vol 127 (3) ◽  
pp. 244-252 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Wai Keat Kuan ◽  
Abhijit Mukherjee
Keyword(s):  
Heated Surface ◽  
Water Flow Rate ◽  
Transient Heat Conduction ◽  
Heater Surface ◽  
Copper Block ◽  
Vapor Interface ◽  
Circular Nozzle ◽  
Axis Of Rotation ◽  
Insight Into

A stable meniscus is formed by a circular nozzle dispensing water over a heated circular face of a rotating cylindrical copper block. The nozzle is offset from the axis of rotation of the copper block and thus a moving meniscus is formed on the surface. The water flow rate, heater surface temperature, and the speed of rotation are controlled to provide a stable meniscus with continuous evaporation of water without any meniscus breakup. The study provides an important insight into the role of the evaporating liquid-vapor interface and transient heat conduction around a nucleating bubble in pool boiling.

A Numerical Study of Single Bubble Dynamics During Flow Boiling

2004 ◽  
Author(s):  
Ding Li ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Flow Boiling ◽  
Forced Flow ◽  
Single Bubble ◽  
Horizontal Line ◽  
Vapor Interface ◽  
Single Bubble Dynamics ◽  
Liquid Vapor

Nucleate flow boiling is a liquid-vapor phase-change process associated with high heat transfer rates. A complete 3D numerical simulation of single bubble dynamics on surfaces inclined at 90°, 45° and 30° to the horizontal line and subjected to forced flow parallel to the surface is performed in this work. The continuity, momentum and energy equations are solved with finite difference method and the level-set method is used to capture the liquid-vapor interface. The heat transfer contribution of the micro-layer between the solid wall and evolving liquid-vapor interface is included in this numerical analysis. The effect of dynamic contact angle is also included. The numerical result of bubble growth and sliding distance have been compared with experimental data.

A Numerical Study of the Effect of Contact Angle on the Dynamics of a Single Bubble During Pool Boiling

2002 ◽  
Author(s):  
H. S. Abarajith ◽  
V. K. Dhir
Keyword(s):  
Heat Flux ◽  
Contact Angle ◽  
Bubble Growth ◽  
Numerical Study ◽  
Heated Surface ◽  
Pool Boiling ◽  
Growth Period ◽  
Single Bubble ◽  
Liquid Phases ◽  
Bubble Growth And Departure

The effect of contact angle on the growth and departure of a single bubble on a horizontal heated surface during pool boiling under normal gravity conditions has been investigated using numerical simulations. The contact angle is varied by changing the Hamaker constant that defines the long-range forces. A finite difference scheme is used to solve the equations governing mass, momentum and energy in the vapor and liquid phases. The vapor-liquid interface is captured by the Level Set method, which is modified to include the influence of phase change at the liquid-vapor interface. The contact angle is varied from 1° to 90° and its effect on the bubble departure diameter and the bubble growth period are studied. Both water and PF5060 are used as test liquids. The contact angle is kept constant throughout the bubble growth and departure process. The effect of contact angle on the parameters like thermal boundary layer thickness, wall heat flux and heat flux from the microlayer under various conditions of superheats and subcoolings is also studied.

Numerical Study of an Evaporating Meniscus on a Moving Heated Surface

Volume 3 ◽  
2004 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Numerical Study ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Two Dimensions ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Wall Heat Transfer ◽  
Parallel Plates

The present study is performed to numerically analyze an evaporating meniscus on a moving heated surface. This phenomenon is similar to the one observed at the base of a vapor bubble during nucleate boiling. The complete Navier-Stokes equations along with continuity and energy equations are solved. The liquid vapor interface is captured using the level set technique. A column of liquid is placed between two parallel plates with an inlet for water at the top to feed the meniscus. The location of water inlet at the top is kept fixed and the bottom wall is imparted with a velocity. Calculations are done in two-dimensions with a fixed distance between the plates. The main objective is to study the velocity and temperature fields inside the meniscus and calculate the wall heat transfer. The results show that the wall velocity creates a circulation near the meniscus base causing increased wall heat transfer as compared to a stationary meniscus. The local wall heat transfer is found to vary significantly along the meniscus base, the highest being near the advancing contact line.

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