Multifractality and Universality of Thermal Fluctuations in Terrestrial and Micro-Gravity Pool Boiling

2021 ◽  
Author(s):  
Ankit Saini ◽  
Vinod Srinivasan
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Thermal Fluctuations ◽  
Nucleation Site ◽  
Boiling Crisis ◽  
Temporal Correlations ◽  
Multiple Pressures ◽  
Microgravity Conditions ◽  
Spatio Temporal

Abstract Nucleation site interaction in pool boiling is well known to cause intermittent bubble growth and departure. Such interactions can cause long-term temporal correlations in spatio-temporal fluctuations of temperature and heat flux, and may affect the conditions leading to the onset of boiling crisis. In this study, we check for the presence of such long-term correlations. A multifractal analysis is carried out on heat flux fluctuations recorded in pool boiling experiments under terrestrial and microgravity conditions. The Hurst exponent is shown to progressively decrease as the wall temperature is increased, attaining a value close to 0.5 near the onset of boiling crisis. This trend persists for multiple pressures and levels of bulk subcooling, and may serve as an indicator of proximity to the boiling crisis. Similar experiments performed with an identical setup under terrestrial gravity conditions are shown to exhibit similar trends.

scholarly journals Numerical investigation of nucleate pool boiling heat transfer

2016 ◽  
Vol 20 (suppl. 5) ◽  
pp. 1301-1312
Author(s):  
Andrijana Stojanovic ◽  
Vladimir Stevanovic ◽  
Milan Petrovic ◽  
Dragoljub Zivkovic
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Heated Wall ◽  
Wall Surface ◽  
Two Phase ◽  
Site Density ◽  
Nucleation Sites ◽  
Nucleation Site Density

Multidimensional numerical simulation of the atmospheric saturated pool boiling is performed. The applied modelling and numerical methods enable a full representation of the liquid and vapour two-phase mixture behaviour on the heated surface, with included prediction of the swell level and heated wall temperature field. In this way the integral behaviour of nucleate pool boiling is simulated. The micro conditions of bubble generation at the heated wall surface are modelled by the bubble nucleation site density, the liquid wetting contact angle and the bubble grow time. The bubble nucleation sites are randomly located within zones of equal size, where the number of zones equals the nucleation site density. The conjugate heat transfer from the heated wall to the liquid is taken into account in wetted heated wall areas around bubble nucleation sites. The boiling curve relation between the heat flux and the heated wall surface temperature in excess of the saturation temperature is predicted for the pool boiling conditions reported in the literature and a good agreement is achieved with experimentally measured data. The influence of the nucleation site density on the boiling curve characteristic is confirmed. In addition, the influence of the heat flux intensity on the spatial effects of vapour generation and two-phase flow are shown, such as the increase of the swell level position and the reduced wetting of the heated wall surface by the heat flux increase.

On the Relation between Nucleation Site Density and Critical Heat Flux of Pool Boiling

2017 ◽  
Vol 39 (17-18) ◽  
pp. 1498-1506 ◽  
Author(s):  
Ke Wang ◽  
Shengjie Gong ◽  
Bofeng Bai ◽  
Weimin Ma
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Site Density ◽  
Nucleation Site Density

scholarly journals Nucleate pool boiling heat transfer: Review of models and bubble dynamics parameters

2021 ◽  
pp. 69-69
Author(s):  
Andrijana Stojanovic ◽  
Srdjan Belosevic ◽  
Nenad Crnomarkovic ◽  
Ivan Tomanovic ◽  
Aleksandar Milicevic
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Power Plants ◽  
Pool Boiling ◽  
Nucleation Site ◽  
Nucleate Pool Boiling ◽  
Numerical Work ◽  
Efficient Operation ◽  
Pool Boiling Heat Transfer

Understanding nucleate pool boiling heat transfer and, in particular the accurate prediction of conditions that can lead to critical heat flux, is of the utmost importance in many industries. Due to the safety issues related to the nuclear power plants, and for the efficient operation of many heat transfer units including fossil fuel boilers, fusion reactors, electronic chips, etc., it is important to understand this kind of heat transfer. In this paper, a comprehensive review of analytical and numerical work on nucleate pool boiling heat transfer is presented. In order to understand this phenomenon, existing studies on boiling heat transfer coefficient and boiling heat flux are also discussed, as well as characteristics of boiling phenomena such as bubble departure diameter, bubble departure frequency, active nucleation site density, bubble waiting and growth period and their impact on pool boiling heat transfer.

scholarly journals Investigations of near-wall bubble behavior in wire heaters pool boiling

2020 ◽  
pp. 333-333
Author(s):  
Kailun Guo ◽  
Chenglong Wang ◽  
Dalin Zhang ◽  
Wenxi Tian ◽  
Guanghui Su ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Percolation Theory ◽  
Pool Boiling ◽  
Prediction Method ◽  
Bubble Behavior ◽  
Scale Free ◽  
Boiling Crisis ◽  
First Time ◽  
Near Wall

The current work establishes a pool boiling CHF prediction method based on percolation theory. For the first time, we observe the experimental bubble footprint?s power-law distributions with almost the same exponent in wire heaters? water pool boiling crisis, which is borne out strongly that boiling crisis is a typical continuum percolative scale-free behavior, and its characteristics seems not to be influenced by the critical heat flux value. The proposed one-dimensional Monte Carlo(MC) method successfully simulates the phase transition of interactive near-wall bubbles. This research enriches and extends applications of continuum percolation theory in boiling phenomena, and could be an instruction for the followed critical heat flux enhancement studies.

Nucleate Pool Boiling on Ribbed Surfaces With Micro-Roughness at Low and Moderate Heat Flux

1999 ◽  
Vol 121 (2) ◽  
pp. 376-385 ◽  
Author(s):  
S.-S. Hsieh ◽  
C.-J. Weng ◽  
J.-J. Chiou
Keyword(s):  
Heat Flux ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Nucleation Site ◽  
Nucleate Pool Boiling ◽  
Site Density ◽  
R 134A ◽  
Microlayer Evaporation ◽  
Two Parameters ◽  
Nucleation Site Density

Nucleate pool boiling correlation was developed for five different rib-type roughened tube geometries (including plain tube) with different rib angles of 30 deg, 45 deg, 60 deg, and 90 deg for both distilled water and R-134a as the working media. A scanning electron micrograph (SEM) examination was made for these horizontal roughened tubes. Bubble departure diameter, frequency of bubble emission, and the active nucleation site density with the influence of the rib angle for this type of roughened surface were obtained. Boiling heat flux incorporating natural convection, nucleate boiling, and microlayer evaporation mechanisms following Benjamin and Balakrishnan (1996) was predicted. Heat transfer correlation was also developed in terms of the degree superheat and active nucleation site density. The dependence for these two parameters was found in favorable agreement with that of previous study for smooth surfaces.

Enhancement of Saturation Boiling of PF-5060 on Microporous Surface

2011 ◽  
Author(s):  
Saeil Jeon ◽  
Byeongnam Jo ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Flux ◽  
Silicon Wafer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Nucleation Site ◽  
Copper Surface ◽  
Porous Surface ◽  
Site Density ◽  
Porous Copper ◽  
Dry Out

Pool boiling experiments were conducted to investigate the saturation boiling of PF-5060 dielectric liquid on micro porous copper surface. The micro porous surface is deposited on a copper coated silicon wafer diced to a size of 40 mm × 68 mm. Reference experiments were performed using a bare silicon wafer of the same size. Experiments are also performed using deionized water that was degassed prior to the experiment. The experimental results show that there is ∼48% enhancement of heat flux in nucleate boiling regime on the micro porous copper surface, compared to that on a bare surface for pool boiling of PF-5060. The measurement uncertainty for heat flux in these experiments is estimated to be ∼15%. The enhanced surface area provided by the micro porous copper surface as well as the reduction in the magnitude of the Taylor instability wavelength on a copper surface, increase in the nucleation site density on the porous surface, capillary replenishment of the dry out regions and the increase in transient heat transfer from the porous surface — are postulated to be the enhancement mechanisms for the observed augmentation in heat flux values.

INVESTIGATING THE RELATIONSHIP BETWEEN SURFACE WICKABILITY AND CRITICAL HEAT FLUX DURING POOL BOILING

2018 ◽  
Author(s):  
Youngsup Song ◽  
Yangying Zhu ◽  
Daniel J. Preston ◽  
H. Jeremy Cho ◽  
Zhengmao Lu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
The Relationship

THE CRITICAL HEAT FLUX AT THE POOL BOILING OF SOME BINARY LIQUID MIXTURES

2019 ◽  
Author(s):  
Samson Semenovich Kutateladze ◽  
G.I. Bobrovich ◽  
I. I. Gogonin ◽  
N.N. Mamontova ◽  
V.N. Moskvicheva
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
Liquid Mixtures ◽  
Binary Liquid Mixtures ◽  
Binary Liquid
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