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.

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.

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.

scholarly journals Effect of Heat Transfer on the Growing Bubble with the Nanoparticles/Water Nanofluids in Turbulent Flow

2021 ◽  
Vol 8 (1) ◽  
pp. 95-102
Author(s):  
Ahmed K. Abu-Nab ◽  
Ali F. Abu-Bakr
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Turbulent Flow ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Theoretical Data ◽  
Superheated Liquid ◽  
Two Phase ◽  
The Mathematical Model

This paper is devoted to study the effect of heat transfer on the temperature distribution in a superheated liquid during the growth of vapour bubbles immersed in different types of nanoparticles/water nanofluids between two-phase turbulent flow. The mathematical model is formulated and solved analytically depending on Scriven's theory and using the modification of the method of the similarity parameters between two finite boundaries. The characteristics of vapour bubble growth and temperature distribution are obtained by using the thermo-physical properties of nanoparticles nanofluids. The results indicate that the nanoparticle volume concentration reduces the bubble growth process under the effect of heat transfer. The better agreements are achieved, for bubble dynamics in turbulent nanofluid using the appropriate numerical and theoretical data for the values of concentration rate of nanoparticles χ=0,0.2,0.4. The temperature distribution surrounding the regime of bubble growth in pure water is more intensive than in other cases of Al2O3/H2O, Fe3O4/H2O and CuO/H2O nanofluids in turbulent flow. A Comparison of the current solution with previous works is carried out and discussed.

Microscale Heat Transfer Measurements During Subcooled Pool Boiling of Pentane: Effect of Bubble Dynamics

2010 ◽  
Author(s):  
Payam Delgoshaei ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Growth Time ◽  
Two Phase ◽  
Time Resolved ◽  
Earth Gravity ◽  
Transfer Mechanisms

Measurements of space and time resolved heat transfer during subcooled pool boiling of pentane in earth gravity were obtained using a microscale heater array. Data from individual heater elements in the array were synchronized with bottom and side view images from two high-speed cameras. The heat transfer mechanisms during bubble growth were found to be dependent on bubble dynamics and bubble growth time. Single phase heat transfer mechanisms (transient conduction and/or microconvection) were found to be dominant for single bubbles with short growth times. Two phase heat transfer mechanisms (microlayer evaporation and/or contact line evaporation) were found to be dominant for bubbles with longer growth times.

A Photographic Study on the Effects of Hydrophobic-Spot Size and Subcooling on Local Film Boiling

2013 ◽  
Author(s):  
Bambang Joko Suroto ◽  
Masahiro Tashiro ◽  
Sana Hirabayashi ◽  
Sumitomo Hidaka ◽  
Masamichi Kohno ◽  
...  
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Bubble Dynamics ◽  
Pure Water ◽  
Nucleate Boiling ◽  
Spot Size ◽  
Copper Surface ◽  
Film Boiling ◽  
Working Fluid ◽  
Boiling Regime

The effects of hydrophobic circle spot size and subcooling on local film boiling phenomenon from the copper surface with single PTFE (Polytetrafluoroethylene) hydrophobic circle spot at low heat flux has been investigated. The experiments were performed using pure water as the working fluid and subcooling ranging from 0 and 10K. The heat transfer surfaces are used polished copper block with single PTFE hydrophobic circle spot of diameters 2, 4 and 6 mm, respectively. A high-speed camera was used to capture bubble dynamics and disclosed the sequence of the process leading to local film boiling. The result shows that local films boiling occurs on the PTFE circle spot at low heat flux and was triggered by the merging of neighboring bubbles. The study also showed that transition time required for change from nucleate boiling regime to local film boiling regime depends on the diameter of the hydrophobic circle spot and the subcooling. A stable local film boiling occurs at the smallest diameter of hydrophobic spot. Subcooling cause the local film boiling occur at negative superheat and oscillation of bubble dome.

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.

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.

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