Convective heat transfer to water containing bubbles: Enhancement not dependent on thermocapillarity

Kenning, D. B. R.; Kao, Ying-Chieh

doi:10.1016/0017-9310(72)90099-3

Cited by 37 publications

(10 citation statements)

References 5 publications

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“…Convective heat transfer from BG1 is enhanced. This effect has been shown to be significant by Kenning and Kao [23], who injected nitrogen bubbles into a single phase upward flow past a heated wall and found that the heat transfer coefficient from the wall to the liquid was enhanced by up to 50%.…”

Section: Trend 2: Decrease In F Bg1mentioning

confidence: 96%

Experimental investigation of the thermal interactions of nucleation sites in flow boiling

Baltis

Geld

2014

International Journal of Heat and Mass Transfer

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a b s t r a c tAn experimental setup was designed to perform nucleate boiling experiments in upward saturated flow conditions, in order to investigate the influence of vertically aligned vapor bubble nucleation sites on one another. Experiments were performed by activating two bubble generators, of which the inter-site distance can be varied by steps of 2 mm. Depending on mass flow rate, flow direction and heat fluxes to both bubble generators, nucleation sites have been shown to interact at any nucleation site distance. The results have shown two major trends. The first trend is caused by additional convection (not by bubbles) from the upstream bubble generator, BG2, to the downstream bubble generator, BG1, increasing its nucleation frequency and bubble detachment diameter. The influence of additional convection on bubble frequency and diameter diminishes with increasing inter-site distance, S, and initial bubble nucleation frequency at BG1. The influence of added convective heat is enhanced by increasing the liquid bulk flow rate. The second trend is seen when BG2 initiates its own bubble nucleation. Vapor bubbles that nucleate at BG2 and pass by BG1 in close proximity have an inhibitive effect on bubble nucleation at BG1. The effect of this inhibitive trend diminishes with increasing nucleation frequency at BG1. Because of the significance of the effect of hydrodynamic interaction on the number of active nucleation sites and bubble size at detachment, mechanistic modeling of nucleate flow boiling is expected to benefit from the quantifications presented in this study.

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Section: Trend 2: Decrease In F Bg1mentioning

confidence: 96%

Experimental investigation of the thermal interactions of nucleation sites in flow boiling

Baltis

Geld

2014

International Journal of Heat and Mass Transfer

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“…Soon afterwards, Kenning and Kao [17] reported a limited set of heat flux estimations from their numerical study of Marangoni flow around downward facing bubbles. With regard to the heat transfer rates they concluded that the heat transfer enhancement was confined to a small region along the wall and, for their zero gravity simulations, was dependant on the Marangoni Number.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer near an isolated hemispherical gas bubble: The combined influence of thermocapillarity and buoyancy

O’Shaughnessy

Robinson

2013

International Journal of Heat and Mass Transfer

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Thermal Marangoni convection about a 1 mm radius hemispherical air bubble attached to a heated wall immersed in a silicone oil layer of constant depth of 5 mm was numerically investigated. Tests were performed for a range of Marangoni numbers (145≤Ma≤915) with varying levels of gravitational acceleration between zero gravity and earth gravity in order to quantify the rates of heat transfer. For the zero gravity condition, a thermocapillary-driven vortex develops around the bubble extending the entire height of the channel. This flow structure causes a jet-like flow of heated liquid to emanate from the bubble tip which impinged on the cold wall. With the addition of gravity, a counter rotating secondary buoyancydriven vortex forms which reduces the size of the thermocapillary vortex and disrupts the jet flow from the bubble tip. The wall heat flux profiles indicate that under zero gravity, the peak heat fluxes increase monotonically with Ma with an area of influence that increases asymptotically with Ma. Likewise, under gravity conditions the peak heat flux also increases with Ma and for low Ma is higher than that of 0-g. However, the area of influence is considerably smaller and not sensitive to Ma or the level of gravity. Experimental validation of selected terrestrial gravity numerical results was obtained using particle image velocimetry (PIV) for low to moderate Marangoni numbers. For all experiments, steadystate Marangoni convection was observed. The experimental flow patterns showed good agreement with the numerical solutions.

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“…In order to study the bubble sliding heat transfer enhancement mechanism, the experimental methodology proposed by Kenning and Kao (1972), Thorncroft et al (1998), andOzer et al (2011) is used here. Gas bubbles are injected onto a downward facing heater using a hypodermic needle.…”

Section: Periodic Bubble Slidingmentioning

confidence: 99%

“…They attributed as much as 50% of the heat transfer to sliding bubbles. Experimentally, Kenning and Kao (1972) noticed that bubble injection in an upward flow leads to a 50% increase in the heat transfer coefficient depending on the Reynolds number. They suspected the secondary flow generated by the bubble to be responsible for that increase.…”

Section: Introductionmentioning

confidence: 99%

On the Mechanism of Bubble Induced Forced Convective Heat Transfer Enhancement

Roy¹,

Venuvanalingam²,

Klausner³

et al. 2018

Frontiers in Heat and Mass Transfer

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This article presents both an experimental and numerical study of both stationary and sliding bubbles in a horizontal duct with forced convection heat transfer. An experimental facility was fabricated using a fully transparent, electrically-heated test section in which the bubble dynamics and the thermal field on the heated wall can be acquired using high-speed cameras and Thermochromic Liquid Crystals (TLC). Experiments were conducted using the working fluid HFE 7000 for two different turbulent Reynolds numbers. The experimental temperature field in the span-wise direction is first compared to the numerically calculated temperature field of a bubble sliding near a wall and second to the temperature field calculated for a stationary bubble under the same flow and thermal conditions. In both cases the thermal field influence of the microlayer thickness, bubble shape, and the presence of multiple bubbles is investigated. An important outcome is that, unlike the sliding bubble case, the temperature field calculated in the stationary case is in agreement with the experimental results. The temperature field does not show any significant sensitivity to the micro-layer thickness or the bubble shape. It is concluded that the mechanism of heat transfer enhancement due to growing bubbles in forced convection is due to the flow perturbation induced by the bubble at the growth site or injection site rather than the thermal boundary layer disruption of the sliding bubbles. This is the reason flow boiling superposition correlations have success in predicting heat transfer without considering the bubble sliding process.

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Convective heat transfer to water containing bubbles: Enhancement not dependent on thermocapillarity

Cited by 37 publications

References 5 publications

Experimental investigation of the thermal interactions of nucleation sites in flow boiling

Experimental investigation of the thermal interactions of nucleation sites in flow boiling

Heat transfer near an isolated hemispherical gas bubble: The combined influence of thermocapillarity and buoyancy

On the Mechanism of Bubble Induced Forced Convective Heat Transfer Enhancement

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