Visualization of a principle mechanism of critical heat flux in pool boiling

Bang, In Cheol; Chang, Soon Heung; Baek, Won-Pil

doi:10.1016/j.ijheatmasstransfer.2005.07.006

Cited by 29 publications

(13 citation statements)

References 12 publications

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“…(3)-(5) and Eqs. (6)- (8). Also, experimental observations showed the increase of the density of nucleation sites with the heat flux increase.…”

Section: Modeling Of Vapor Generation Dynamicsmentioning

confidence: 93%

“…The other conclusion in [6,7] is that there is no structured pattern of the boiling two-phase mixture at the occurrence of boiling crisis, hence, there is no validation for the existence of the vapor stems above the vapor blanket at a surface exposed to high heat flux. Bang et al [8] also reported visual observations of the twophase mixture pattern at the instance of the boiling crisis. Again, these results did not show the existence of the vapor stems and the Kelvin-Helmholtz instability as the reason for the CHF.…”

Section: Introductionmentioning

confidence: 95%

“…Then, the density of nucleation sites of 1.5 Â 10 7 m À2 is calculated with Eq. (8). For a fresh heater, a contact angle of 40°, [17] could be assumed, and the predictions of Eqs.…”

Section: Modeling Of Vapor Generation Dynamicsmentioning

confidence: 99%

See 2 more Smart Citations

Numerical prediction of critical heat flux in pool boiling with the two-fluid model

Pezo¹,

Stevanović²

2011

International Journal of Heat and Mass Transfer

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“…(3)-(5) and Eqs. (6)- (8). Also, experimental observations showed the increase of the density of nucleation sites with the heat flux increase.…”

Section: Modeling Of Vapor Generation Dynamicsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

Numerical prediction of critical heat flux in pool boiling with the two-fluid model

Pezo¹,

Stevanović²

2011

International Journal of Heat and Mass Transfer

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“…It is believed that the behavior of the near-wall liquid layer plays a key role in the heat transfer and boiling crisis. To date, most of the published modeling and numerical studies on boiling heat transfer have concentrated on the near-wall liquid layers (i.e., micro-and macrolayers) with the thickness estimated to range from several to hundreds of micrometers in pool boiling (Rajvanshi et al, 1992;Kumada and Sakashita, 1995;Auracher and Marquardt, 2004;Bang et al, 2005;Buchholz et al, 2006;Ono and Sakashita, 2007). Stephan and Kern (2004) phenomena.…”

Section: Introductionmentioning

confidence: 99%

Thin Liquid Film Dynamics and Bubble Behavior in Flow Boiling

Wang

Lin

et al. 2016

Interfac Phenom Heat Transfer

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A profound knowledge of the dynamics of a thin liquid film and bubble behavior in flow boiling is crucial in a thorough study of the physical mechanisms of boiling crisis, which is important to the performance and safety of light water reactors. To address this, in the present study a series of tests were carried out at various water and air flow rates under atmospheric pressure and different heat fluxes in a horizontal copper channel. We employed a developed confocal optical sensor system to detect the variations and integrity of the thin liquid film. Additionally, we used a high-speed camera to capture the bubble behavior in detail and analyzed the effect of the film thickness on bubble behavior. According to our observations, the thinning process of the liquid film is governed by the entrainment under adiabatic or lower heat flux conditions, whereas evaporation becomes more pronounced in a higher heat flux system. The critical film thickness of an integral film is found to be related to the condition of the heating surface and the heat flux. Remarkably, the coalescence of bubbles seldom occurs in flow boiling with the thinner liquid film. The bubble departure diameter increases with an increase in the heat flux and liquid mass flow rate, but decreases with an increase in the gas flow rate. The minimum bubble departure diameter observed using high-speed photography was about 90 µm.

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“…Even for pool boiling, it is believed that the behavior of the near-wall liquid layer plays a key role in heat transfer and boiling crisis. Noteworthily, a good number of analytical models and numerical simulations (Dhir 2006;Stephan and Kern 2004) were based on the concepts of microlayer and macrolayer whose thicknesses were estimated to range from several micrometers to hundreds micrometers (Bang et al 2005;Bhat et al 1986;Cooper 1969;Rajvanshi et al 1992;Kumada and Sakashita 1995;Sakashita and Ono 2009). However, an experimental quantification of such thin liquid films and their dynamics is not straightforward, since the measurement at micro-scale is a challenge, and further complicated by the traditional experimental setups (e.g., pool boiling with heater block) and the chaotic nature of boiling process which impede direct observation and measurement of the thin liquid films, especially under high heat flux conditions.…”

Section: Introductionmentioning

confidence: 99%

Diagnostic techniques for the dynamics of a thin liquid film under forced flow and evaporating conditions

Gong

Dinh

2010

Microfluid Nanofluid

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Motivated by quantification of micro-hydrodynamics of a thin liquid film which is present in industrial processes, such as spray cooling, heating (e.g., boiling with the macrolayer and the microlayer), coating, cleaning, and lubrication, we use micro-conductive probes and confocal optical sensors to measure the thickness and dynamic characteristics of a liquid film on a silicon wafer surface with or without heating. The simultaneous measurement on the same liquid film shows that the two techniques are in a good agreement with respect to accuracy, but the optical sensors have a much higher acquisition rate up to 30 kHz which is more suitable for rapid process. The optical sensors are therefore used to measure the instantaneous film thickness in an isothermal flow over a silicon wafer, obtaining the film thickness profile and the interfacial wave. The dynamic thickness of an evaporating film on a horizontal silicon wafer surface is also recorded by the optical sensor for the first time. The results indicate that the critical thickness initiating film instability on the silicon wafer is around 84 lm at heat flux of *56 kW/m 2 . In general, the tests performed show that the confocal optical sensor is capable of measuring liquid film dynamics at various conditions, while the micro-conductive probe can be used to calibrate the optical sensor by simultaneous measurement of a film under quasi-steady state. The microexperimental methods provide the solid platform for further investigation of the liquid film dynamics affected by physicochemical properties of the liquid and surfaces as well as thermal-hydraulic conditions.

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Visualization of a principle mechanism of critical heat flux in pool boiling

Cited by 29 publications

References 12 publications

Numerical prediction of critical heat flux in pool boiling with the two-fluid model

Numerical prediction of critical heat flux in pool boiling with the two-fluid model

Thin Liquid Film Dynamics and Bubble Behavior in Flow Boiling

Diagnostic techniques for the dynamics of a thin liquid film under forced flow and evaporating conditions

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