Characteristics of a single bubble in subcooled boiling region of a narrow rectangular channel under natural circulation

Zhou, Tao; Duan, Jun; Hong, Do‐Young; Liu, Ping; Cheng, Sheng

doi:10.1016/j.anucene.2013.01.052

Cited by 10 publications

(4 citation statements)

References 7 publications

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“…After normalizing the bubble diameter, it is found that the in natural circulation the bubble growth time accounts for a larger proportion in bubble cycle than in the forced circulation (Zhou et al, 2013).…”

Section: Observation Of Single Sliding Bubble Behaviorsmentioning

confidence: 99%

“…The mechanism of sliding bubble in natural circulation has not been thoroughly understood. Only Zhou et al (Zhou et al, 2013) studied the single bubble characteristics under natural circulation. Compared with the experimental results under the forced circulation with same thermal parameters, the growth time was longer, the departure velocity was higher and the waiting time was shorter.…”

Section: Introductionmentioning

confidence: 99%

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Visualized Experiment of Bubble Behaviors in a Vertical Narrow Rectangular Channel Under Natural Circulation Condition

et al. 2018

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The characteristics of bubble behavior have been in particular interest for decades due to its significant contribution to understanding the mechanism of heat transfer. In the present work, visualized experiment is conducted to study the bubble characteristics in subcooled flow boiling of a narrow rectangular channel under natural circulation. The experiments were performed at pressures of 0.2 MPa, with inlet subcooling ranging from 20 to 60 K and heat flux ranging from 100 to 300 kW/m 2 . A high-speed digital camera is used to capture the pictures of bubble behaviors. A sequence of image processing algorithms is used deal with the original bubble images to get relevant bubble parameters. We observe the whole process of a single sliding bubble lifetime and found most of bubbles slide along the heating surface after detaching the nucleation sites. Five typical sliding bubble growth paths are observed in the present experimental conditions. According to the analysis of the experimental data, it can be found that the liquid subcooling and wall superheat are the main factors that affect the bubble size during sliding in narrow rectangular channel under natural circulation condition. Due to the difference of driving force, the sliding velocity of bubble in forced circulation is always larger than that in natural circulation. At the same time, the bubble velocity changes significantly at different heat flux and shooting location.

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Section: Observation Of Single Sliding Bubble Behaviorsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Visualized Experiment of Bubble Behaviors in a Vertical Narrow Rectangular Channel Under Natural Circulation Condition

et al. 2018

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“…Their measured data was compared with bubble frequency models available in existing literature and an improved version was proposed. Zhou et al (2013) analyzed the behaviour of single bubbles in a narrow vertical rectangular channel. They showed that at high subcooled conditions nucleated bubbles stick to the wall and slide slowly.…”

Section: Introductionmentioning

confidence: 99%

Multi-scale full-field measurements and near-wall modeling of turbulent subcooled boiling flow using innovative experimental techniques

Hassan

2016

Nuclear Engineering and Design

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Multi-phase flows are one of the challenges on which the CFD simulation community has been working extensively with a relatively low success. The phenomena associated behind the momentum and heat transfer mechanisms associated to multi-phase flows are highly complex requiring resolving simultaneously for multiple scales on time and space. Part of the reasons behind the low predictive capability of CFD when studying multi-phase flows, is the scarcity of CFD-grade experimental data for validation. The complexity of the phenomena and its sensitivity to small sources of perturbations makes its measurements a difficult task. Non-intrusive and innovative measuring techniques are required to accurately measure multi-phase flow parameters while at the same time satisfying the high resolution required to validate CFD simulations. In this context, this work explores the feasible implementation of innovative measuring techniques that can provide whole-field and multi-scale measurements of two-phase flow turbulence, heat transfer, and boiling parameters. To this end, three visualization techniques are simultaneously implemented to study subcooled boiling flow through a vertical rectangular channel with a single heated wall. These techniques are listed next and are used as follow: 1) High-speed infrared thermometry (IR-T) is used to study the impact of the boiling level on the heat transfer coefficients at the heated wall, 2) Particle Tracking Velocimetry (PTV) is used to analyze the influence that boiling parameters have on the liquid phase turbulence statistics, 3) Highspeed shadowgraphy with LED illumination is used to obtain the gas phase dynamics. To account for the accuracy and to complement these innovative techniques, redundant and simultaneous measurements are performed by means of thermocouples, flow and power meters, differential and absolute pressure transducers, etc. The present experiments are intended to improve the understanding of subcooled boiling flow and to provide reliable and accurate subcooled boiling flow experimental information for verification and validation of two-phase flow computational models.

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“…In contrast, flashing of hot fluids is more like a boiling process, which is driven principally by the thermal non-equilibrium. The complexity of flashing flows is represented by gas-liquid mixture with rapid phase change and bubble dynamics [5], and numerical studies are directed towards the determination of vapour generation rate. Good reviews have been given by Pinhasi [3] and Liao & Lucas [6].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Interfacial Heat Transfer Models for Flashing Flow with Two-Fluid CFD

Liao

Lucas

2018

Fluids

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Abstract:The complexity of flashing flows is increased vastly by the interphase heat transfer as well as its coupling with mass and momentum transfers. A reliable heat transfer coefficient is the key in the modelling of such kinds of flows with the two-fluid model. An extensive literature survey on computational modelling of flashing flows has been given in previous work. The present work is aimed at giving a brief review on available theories and correlations for the estimation of interphase heat transfer coefficient, and evaluating them quantitatively based on computational fluid dynamics simulations of bubble growth in superheated liquid. The comparison of predictions for bubble growth rate obtained by using different correlations with the experimental as well as direct numerical simulation data reveals that the performance of the correlations is dependent on the Jakob number and Reynolds number. No generally applicable correlations are available. Both conduction and convection are important in cases of bubble rising and translating in stagnant liquid at high Jakob numbers. The correlations combining the analytical solution for heat diffusion and the theoretical relation for potential flow give the best agreement.

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Characteristics of a single bubble in subcooled boiling region of a narrow rectangular channel under natural circulation

Cited by 10 publications

References 7 publications

Visualized Experiment of Bubble Behaviors in a Vertical Narrow Rectangular Channel Under Natural Circulation Condition

Visualized Experiment of Bubble Behaviors in a Vertical Narrow Rectangular Channel Under Natural Circulation Condition

Multi-scale full-field measurements and near-wall modeling of turbulent subcooled boiling flow using innovative experimental techniques

Evaluation of Interfacial Heat Transfer Models for Flashing Flow with Two-Fluid CFD

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