Experimental Observations of the Microlayer in Vapor Bubble Growth on a Heated Solid

Koffman, Larry D.; Plesset, Milton S.

doi:10.1115/1.3245631

Cited by 107 publications

(63 citation statements)

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“…The observed temperature drop was due to surface cooling resulting from microlayer evaporation, as suggested in pioneering studies on the subject of microlayer evaporation (e.g. in [22][23][24][42][43][44][45]). The beginning of the microlayer evaporation at each sensor is marked on the temperature profiles shown in Fig.…”

Section: Analysis Of the Temperature Resultsmentioning

confidence: 88%

Physical mechanisms of heat transfer during single bubble nucleate boiling of FC-72 under saturation conditions-I. Experimental investigation

Moghaddam

Kiger

2009

International Journal of Heat and Mass Transfer

106

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Section: Analysis Of the Temperature Resultsmentioning

confidence: 88%

Physical mechanisms of heat transfer during single bubble nucleate boiling of FC-72 under saturation conditions-I. Experimental investigation

Moghaddam

Kiger

2009

International Journal of Heat and Mass Transfer

106

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“…The thickness further increases with an increase in flow velocity. Koffman and Plesset, (1983) measured a thickness of 1-3 μm in pool boiling. The microlayer contribution therefore is expected to be lower in microchannel flow boiling because of the increase in the film thickness.…”

Section: Figmentioning

confidence: 99%

“…The microlayer thickness is ~ 1-3 μm (Koffman and Plesset, 1983). The high frequency in the bubble ebullition cycle limits the occurrence, extent and duration of dry patches from microlayer depletion from evaporation at high heat fluxes.…”

Section: Microlayermentioning

confidence: 99%

Similarities and Differences Between Flow Boiling in Microchannels and Pool Boiling

Kandlikar

2010

Heat Transfer Engineering

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Recent literature indicates that under certain conditions the heat transfer coefficient during flow boiling in microchannels is quite similar to that under pool boiling conditions. This is rather unexpected as microchannels are believed to provide significant heat transfer enhancement under single-phase as well as flow boiling conditions. This paper explores the underlying heat transfer mechanisms and illustrates the similarities and differences between the two processes. Formation of elongated bubbles and their passage over the microchannel walls have similarities to the bubble ebullition cycle in pool boiling. During the passage of elongated bubbles, the longer duration between two successive liquid slugs leads to wall dryout and a critical heat flux that may be lower than that under pool boiling conditions. A clear understanding of the similarities and differences will help in overcoming some of these limiting factors and in developing strategies for enhancing heat transfer during flow boiling in microchannels.

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“…Since this occurs first at its inner radius, where the initial thickness of the film was least, there is an associated progressive increase in the radius of the dry patch around the nucleation site [9]. Figure 2 Current understanding of the micro-layer [10].…”

Section: Figurementioning

confidence: 99%

Evaporative thermal resistance and its influence on microscopic bubble growth

Giustini

Jung

Kim

et al. 2016

International Journal of Heat and Mass Transfer

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Simulations of the formation of small steam bubbles indicate that the rate of growth of bubbles is very sensitive to the rate of evaporation of the micro-layer of liquid beneath the bubble. Such evaporation is rapid, and is modelled as being driven by the large heat flux through the thin liquid layer caused by the difference in temperature between the solid-liquid interface, and the saturation temperature in the interior of the bubble. However, application of this approach to recent experimental measurements of Jung and Kim generated anomalous results. In this paper we demonstrate that a model of the micro-layer heat flux that includes an allowance for the finite evaporative thermal resistance is able to eliminate these anomalies. This evaporative thermal resistance is a consequence of near-interface molecular dynamics, characterised by a quantity termed 'evaporation coefficient'. Whilst in most engineering applications evaporative thermal resistance is small compared to conductive resistance, here, with the micro-layer thickness ranging from a few microns down to zero, it becomes of considerable importance. Selection of a molecular 'evaporation coefficient' to restore consistency to the anomalous measurements allows a plausible numerical value to be inferred. For the several times and multiple locations studied, a fairly consistent value of between 0.02 and 0.1 is indicated, (for saturated water in laboratory conditions), which itself is consistent with earlier literature values of this rather difficult quantity. It is shown that the evaporative resistance always represents a large fraction of the conductive resistance, and for important phases of the process dominates it. The need for inclusion of this phenomenon in the microlayer models used in bubble analysis is clear.

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Experimental Observations of the Microlayer in Vapor Bubble Growth on a Heated Solid

Cited by 107 publications

References 0 publications

Physical mechanisms of heat transfer during single bubble nucleate boiling of FC-72 under saturation conditions-I. Experimental investigation

Physical mechanisms of heat transfer during single bubble nucleate boiling of FC-72 under saturation conditions-I. Experimental investigation

Similarities and Differences Between Flow Boiling in Microchannels and Pool Boiling

Evaporative thermal resistance and its influence on microscopic bubble growth

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