Bubble Dynamics and Heat Transfer during Bubble Growth in Nucleate Boiling

2002 ◽  
Author(s):  
Qiang Bai ◽  
Yasunobu Fujita
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Nucleate Boiling

Numerical Study of Bubble Growth on a Micro-Finned Surface

2011 ◽  
Author(s):  
Woorim Lee ◽  
Gihun Son
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Removal Rate ◽  
Bubble Formation ◽  
Experimental Studies ◽  
Nucleate Boiling ◽  
Finned Surface ◽  
Fin Spacing

Bubble growth on a micro-finned surface, which can be used in enhancing boiling heat transfer, is numerically investigated by solving the conservation equations of mass, momentum, and energy. The bubble deformation or the liquid-vapor interface is determined by the sharp-interface level-set method, which is modified to include the effect of phase change and to treat the contact angle and the evaporative heat flux from the liquid microlayer on an immersed solid surface of a microfin. The numerical method is applied to clarify bubble growth and heat transfer characteristics on a surface including fin and cavity during nucleate boiling which have not been provided from the previous experimental studies. The effects of single fin, fin-cavity distance, and fin-fin spacing on the bubble dynamics are investigated. The micro-fin is found to affect the activation of cavity. The fin-cavity configuration is found to determine the bubble formation in a cavity. The vapor removal rate is also observed to significantly depend on the fin-fin spacing.

Nucleate Boiling Heat Transfer and Bubble Dynamics of Water-in-Polyalphaolefin Nanoemulsion

2018 ◽  
Author(s):  
Jiajun Xu ◽  
James McLaurin ◽  
Cyree Beckett
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Nucleate Boiling ◽  
Temperature History ◽  
Distribution Data ◽  
Growth Data ◽  
Surrounding Water ◽  
Time Resolved

In this study, an experimental study of the nucleation heat transfer and bubble dynamics inside the Water-in-PAO nanoemulsion fluid has been performed. Synchronized highspeed video and infrared thermography are used here to capture time-resolved temperature distribution data for the boiling surface and direct visualization of the bubble cycle. Data gathered included measurements of bubble growth versus time, as well as temperature history of the heater surface underneath the bubbles. Our findings demonstrate a substantial increase in nucleate heat transfer (i.e., heat transfer coefficient), and significantly different bubble dynamics of nanoemulsion fluid compared to pure water. The bubble growth rate of the nanoemulsion lies in the diffusion-controlled regime, and the growth data fit a power law at n ≈ 0.3. This is similar to the authors’ previous study of a similar fluid and is very different from conventional fluids. While the heat transfer mechanisms behind are not completely understood yet, it is hypothesized that the interfacial structures and thermal transport between surfactant molecules surrounding water nanodroplets and the base PAO fluid at elevated temperature may contribute to that.

Simulation of Nucleate Boiling With Interfacial Temperature Gradients and Sharp Interface

2018 ◽  
Author(s):  
Isaac Perez-Raya ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Contact Line ◽  
Growth Rates ◽  
Bubble Growth ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Heat Fluxes ◽  
Temperature Gradients ◽  
Interfacial Temperature

Effective heat transfer techniques benefit the development of nuclear and fossil fuel powered steam generators, high power electronic devices, and industrial refrigeration systems. Boiling dissipates large heat fluxes while keeping a low and a constant surface temperature. However, studies of the fluid behavior surrounding the bubble and the heat transfer near the contact-line are scare due to difficulties of flow visualization, chaotic conditions, and small length scales. The preset study shows the simulation of bubble growth over a heated surface from conception to departure. The computation of mass transfer with interfacial temperature gradients leads to proper bubble growth rates. Models to include the interface sharpness uncover the dynamic and thermal interaction between the interface and the fluid. Results indicate that the nucleation of a bubble (in water at 1 atm with 6.2 K wall superheat) has an influence region of 2Db (where Db is the departure bubble diameter). In addition, results reveal a thin thermal film near the interface that increases the heat transfer at the contact-line region. Numerical bubble growth rates compare well with experimental data on single bubble nucleation.

Synchronized High-Speed Video and Infrared Thermometry Study of Bubble Dynamics During Nucleate Boiling of Nanoemulsion

2017 ◽  
Author(s):  
Robert Stephenson ◽  
Jiajun Xu
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Bubble Dynamics ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Heat Diffusion ◽  
Temperature History ◽  
Pure Ethanol ◽  
High Speed Video ◽  
Significant Difference

In this study, a combination of synchronized high-speed video (HSV) and infrared (IR) thermography was used to characterize the nucleation, growth and detachment of bubbles generated during nucleate boiling inside the nanoemulsion fluid. The Ethanol/Polyalphaolefin nanoemulsion fluid was formed by dispersing ethanol nanodroplets into base fluid Polyalphaolefin, in which these nanodroplets can serve as the pre-seed boiling nuclei. With this unique combination, it allows controlled nucleation, time-resolved temperature distribution data for the boiling surface and direct visualization of the bubble cycle to track bubble nucleation and growth. Data gathered included measurements of bubble growth versus time, as well as 2D temperature history of the heater surface underneath the bubbles. Our findings demonstrate a significant difference of bubble dynamics between the nanoemulsion fluid and pure ethanol, which may also account for the substantial increase in heat transfer coefficient and critical heat flux of nanoemulsion fluid. It is also observed here that the bubbles occurred inside the nanoemulsion fluid appear to be more uniform and two orders-of-magnitude larger in size. While the growth rate of the bubbles inside pure ethanol was found to be heat diffusion controlled at a coefficient around ½, which however, dropped to be around 0.3 for nanoemulsion fluid. Further study on this unique system will help reveal its heat transfer mechanisms.

A New Method for Estimating Bubble Diameter At Different Gravity Levels for Nucleate Pool Boiling

2021 ◽  
Author(s):  
Sandipan Banerjee ◽  
Yongsheng Lian ◽  
Yang Liu ◽  
Mark Sussman
Keyword(s):  
Heat Transfer ◽  
Growth Rate ◽  
Vapor Bubble ◽  
Bubble Growth ◽  
Bubble Diameter ◽  
Nucleate Boiling ◽  
New Method ◽  
Space Applications ◽  
Earth Gravity ◽  
Micro Gravity

Abstract Nucleate boiling has significant applications in earth gravity( in industrial cooling applications) and micro-gravity conditions (in space exploration, specifically in making space applications more compact). However, the effect of gravity on the growth rate and bubble size is not yet well understood. We perform numerical simulations of nucleate boiling using an adaptive Moment-of-Fluid (MoF) method for a single vapor bubble (water or Perfluoro-n-hexane) in saturated liquid for different gravity levels. Results concerning the growth rate of the bubble, specifically the departure diameter and departure time have been provided. The MoF method has been first validated by comparing results with a theoretical solution of vapor bubble growth in super-heated liquid without any heat-transfer from the wall. Next, bubble growth rate, bubble shape and heat transfer results under earth gravity, reduced gravity and micro-gravity conditions are reported and they are in good agreement with experiments. Finally, a new method is proposed for estimating the bubble diameter at different gravity levels. This method is based on an analysis of empirical data at different gravity values and using power-series curve fitting to obtain a generalized bubble growth curve irrespective of the gravity value. This method is shown to provide a good estimate of the bubble diameter for a specific gravity value and time.

Inner Phase Change Behavior of Small Liquid Droplet on Heated Solid Surface

2011 ◽  
Author(s):  
Gui Lu ◽  
Yuan-Yuan Duan ◽  
Xiao-Dong Wang
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Bubble Dynamics ◽  
Liquid Droplet ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Boiling Regime ◽  
Change Behavior ◽  
Cyclical Process ◽  
Transient Boiling

An experimental investigation was conducted to visually observe the transient boiling in an individual water droplet on different heated solid surfaces, covering the free surface evaporation, nucleate, transition and spheroidal boiling regime. Diversified bubble dynamics, phase change and heat transfer behaviors for different boiling regimes of droplet were discussed in present work. In nucleate boiling regime, plenty nucleate bubbles with uniform diameters were confined within the bottom of the droplet, enhancing the heat transfer and cooling performance. The surface properties had great effects on the bubble dynamics in this regime. In the transition boiling regime, the phase change behaviors of a droplet displayed a cyclical process, restricted, sole-bubble and metastable cyclical styles were observed in the experiments. A vapor film between the droplet and surface exists in the spheroidal boiling regime, leading to the random movement of droplet above the heated surface and prolonging the lifetime of droplet significantly.

Numerical Study of Lateral Merger of Vapor Bubbles During Nucleate Pool Boiling

2003 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Bubble Dynamics ◽  
Stokes Equations ◽  
Numerical Study ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Three Dimensions ◽  
Navier Stokes ◽  
Wall Heat Transfer ◽  
Simple Method

Nucleate boiling is one of the most efficient modes of heat transfer. At the start of nucleate boiling, isolated bubbles appear on the heating surface, the regime known as partial nucleate boiling. Transition from isolated bubbles to fully developed nucleate boiling occurs with increase in wall superheat, when bubbles begin to merge in vertical and lateral directions. The laterally merged bubbles form vapor mushrooms, which stay attached to the heater surface via numerous vapor stems. The present study is performed to numerically analyze the bubble dynamics and heat transfer associated with lateral bubble merger during transition from partial to fully developed nucleate boiling. The complete Navier-Stokes equations in three dimensions along with the continuity and energy equations are solved using the SIMPLE method. The liquid vapor interface is captured using the Level-Set technique. Calculations are carried out for multiple bubble-merger in a line and also in a plane and the bubble dynamics and wall heat transfer are compared to that for a single bubble. The results show that the merger process significantly increases the overall wall heat transfer. It is also found that the orientation of the bubbles strongly influences different heat transfer mechanisms.

Visualization of a Single Boiling Bubble in a DC Electric Field

2011 ◽  
Author(s):  
Feng Chen ◽  
Dong Liu ◽  
Yaozu Song ◽  
Yao Peng
Keyword(s):  
Heat Transfer ◽  
Life Cycle ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Wall Temperature ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Nucleate Boiling ◽  
Dc Electric Field

The application of electric field has been demonstrated as an effective way to enhance pool boiling heat transfer. In past studies, adiabatic experiments were often conducted to simulate the dynamics of nucleate bubbles in the presence of an electric field, where gas bubbles were injected from an orifice, to avoid complexities involved in the nucleate boiling experiments. While adiabatic studies yield useful information of the bubble dynamics, further studies about bubble dynamics during nucleate boiling heat transfer are still necessary for a full understanding of the effects of applied electric field on the liquid-vapor phase change heat transfer. In this paper, the dynamics of a single boiling bubble in a direct current (DC) electric field was studied experimentally employing R113 as the working fluid. The life cycle of the boiling bubble was visualized using high-speed photography and was compared with that of an injected nitrogen bubble. Under the same electric field, a more appreciable elongation along the field direction was observed for the boiling bubble. A modified relationship between the bubble deformation and the electrical Weber number was proposed for the boiling bubble. As the electric field strength increases, it was found that, although the growth time of the boiling bubble increases, the waiting period decreases. However, it was also found that, the change of the whole life cycle with electric field strength increasing is relevant to the wall temperature. In this work, the wall temperature measured in the vicinity of the nucleation site upon the bubble departure decreases when the electric field is applied.

Sign in / Sign up

Export Citation Format

Share Document