Possible mechanisms of macrolayer formation

Sadasivan, P.; Chappidi, P.R.; Unal, Cetin; Nelson, Ralph A.

doi:10.1016/0735-1933(92)90016-b

Cited by 27 publications

(16 citation statements)

References 12 publications

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“…The two most important geometries which have been assumed to idealize the liquid-rich "macrolayer" are "vapor stems" as in the model of Dhir et al [15] or "bubbles" as suggested and discussed by Sadasivan et al [20]. Both geometries have been used in subsequent approaches, e.g., [21].…”

Section: Model Geometries For Boiling Processesmentioning

confidence: 97%

“…Eqs. (20), (21)) and is related to the measured contact frequency despite an unknown parameter according to Eq. (26).…”

Section: A New Boiling Heat Transfer Correlationmentioning

confidence: 99%

“…Based on mathematically rigorous definitions of these quantities, a regression problem is formulated and solved in order to correlate unmeasurable relevant geometrical parameters such as the average size of vapor spots and nucleation site density as a function of superheat using measured vapor fractions and interface contact frequency along the entire boiling curve. For this purpose, a simple geometry model of the interfacial structure is employed to capture the underlying geometries of many modeling approaches [15,20] in a unifying manner. This study reveals that many relevant parameters suggested for correlating boiling heat flux are linked to each other by a mathematical model of the interfacial geometry.…”

Section: Objectives and Scopementioning

confidence: 99%

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Towards a unifying heat transfer correlation for the entire boiling curve

Lüttich¹,

Marquardt²,

Buchholz³

et al. 2004

International Journal of Thermal Sciences

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Section: Model Geometries For Boiling Processesmentioning

confidence: 97%

“…Eqs. (20), (21)) and is related to the measured contact frequency despite an unknown parameter according to Eq. (26).…”

Section: A New Boiling Heat Transfer Correlationmentioning

confidence: 99%

Section: Objectives and Scopementioning

confidence: 99%

See 1 more Smart Citation

Towards a unifying heat transfer correlation for the entire boiling curve

Lüttich¹,

Marquardt²,

Buchholz³

et al. 2004

International Journal of Thermal Sciences

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“…where α is the void fraction at the surface, f m is the departure frequency of the mushroom bubble, and an expression for the macrolayer thickness (δ e ) has been proposed by Sadisivian et al (21) :…”

Section: Chf Parametersmentioning

confidence: 99%

Measurement of Key Pool Boiling Parameters in Nanofluids for Nuclear Applications

Bang

Buongiorno

et al. 2008

JPES

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Nanofluids, colloidal dispersions of nanoparticles in a base fluid such as water, can afford very significant Critical Heat Flux (CHF) enhancement. Such engineered fluids potentially could be employed in reactors as advanced coolants in safety systems with significant safety and economic advantages. However, a satisfactory explanation of the CHF enhancement mechanism in nanofluids is lacking. To close this gap, we have identified the important boiling parameters to be measured. These are the properties (e.g., density, viscosity, thermal conductivity, specific heat, vaporization enthalpy, surface tension), hydrodynamic parameters (i.e., bubble size, bubble velocity, departure frequency, hot/dry spot dynamics) and surface conditions (i.e., contact angle, nucleation site density). We have also deployed a pool boiling facility in which many such parameters can be measured. The facility is equipped with a thin indium-tin-oxide heater deposited over a sapphire substrate. An infra-red high-speed camera and an optical probe are used to measure the temperature distribution on the heater and the hydrodynamics above the heater, respectively. The first data generated with this facility already provide some clue on the CHF enhancement mechanism in nanofluids. Specifically, the progression to burnout in a pure fluid (ethanol in this case) is characterized by a smoothly-shaped and steadily-expanding hot spot. By contrast, in the ethanol-based nanofluid the hot spot pulsates and the progression to burnout lasts longer, although the nanofluid CHF is higher than the pure fluid CHF. The presence of a nanoparticle deposition layer on the heater surface seems to enhance wettability and aid hot spot dissipation, thus delaying burnout.

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“…where α is the void fraction at the surface, fm is the departure frequency of the mushroom bubble, and an expression for the macrolayer thickness (δe) has been proposed by Sadisivian et al [19]:…”

Section: Parameters Needed For a Comprehensivementioning

confidence: 99%