Theoretical Leidenfrost point (LFP) model for sessile droplet

Cai, Chang; Mudawar, Issam; Liu, Hong; Si, Chao

doi:10.1016/j.ijheatmasstransfer.2019.118802

Cited by 26 publications

(13 citation statements)

References 43 publications

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“…8. In fact, the wall rewetting température for 2.2 kg/h is approximately 220 °C, which is close usual values of the Leidenfrost temperature found in the literature with sessile droplets onto smooth metallic hot surfaces [30][31][32]. Then, once one droplet wets the wall, the temperature close to this location decreases to values 245 below the Leidenfrost temperature and the rewetting front quickly spreads over the surface.…”

Section: Irt Results: Internai Heat Dissipation and Wall Rewettingsupporting

confidence: 83%

Experimental study of dispersed flow film boiling at sub-channel scale in LOCA conditions: Influence of the steam flow rate and residual power

Oliveira

Carrillo

Labergue

et al. 2020

Applied Thermal Engineering

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Reflooding experiments with rod bundles at Loss Of Coolant Accident (LOCA) conditions usually use intrusive methods with limited access and, consequently, their data are not always adequate and comprehensive to validate simulation codes. For this reason, sub-channel scale experiments are useful to obtain detailed data in a more controlled environment for an accurate thermal-hydraulics investigation. In this study, we present experiments of the cooling phase with an internal steam-droplets flow in a vertical pipe simulating an undamaged sub-channel in a nuclear reactor. Simultaneous measurements were performed of the wall temperature and droplets characteristics (velocity, diameter and temperature) using only optical techniques. An analysis is made on how the steam flow rate and maintained heating power during the cooling phase affect the wall heat dissipation, wall rewetting and droplets dynamics. Results show that wall rewetting normally occurs from bottom to top, and the temperature at minimum heat flux is highly affected by the droplets dynamics. Furthermore, droplets are accelerated when passing through the heated tube, especially at higher wall temperatures, and their temperature is nearly the same up-and downstream of the test section. Results with heating during the cooling phase show that wall rewetting takes place at higher wall temperatures and advances slower with the increase in the maintained heating power. Moreover, for the time period and flow conditions used in this work, wall rewetting does not occur for maintained powers higher than 1.5 kW/m.

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Section: Irt Results: Internai Heat Dissipation and Wall Rewettingsupporting

confidence: 83%

Experimental study of dispersed flow film boiling at sub-channel scale in LOCA conditions: Influence of the steam flow rate and residual power

Oliveira

Carrillo

Labergue

et al. 2020

Applied Thermal Engineering

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“…According to the wetting layer evolution taken by the high-speed camera and the surface temperatures solved by the inverse heat transfer program, the finish temperatures of the dry surface layer (the onset temperatures of the wetting layer) for the samples with the initial temperature 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, and 900℃ are approximately 424℃, 410℃, 408℃, 402℃, 395℃, 387℃, and 369℃, respectively. This temperature is LFP [10], as shown in Fig. 7.…”

Section: Wetting Layer Evolution Of Cooling Surfacementioning

confidence: 83%

“…Compared with other quenching processes, spray cooling technology has the characteristics of high heat exchange capacity, good uniformity of heat removal, no pollution to the environment, and no contact thermal resistance with overheat surface [5][6][7]. Spray cooling has a broad application prospect in heat dissipation with high heat flux [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Wetting layer evolution and interfacial heat transfer in water-air spray cooling process of hot metallic surface

Ning

Zou

et al. 2022

THERM SCI

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Spray cooling experiments on the hot metallic surfaces with different initial temperatures were performed. This paper adopts a self-developing program which is based on the inverse heat transfer algorithm to solve the interfacial heat transfer coefficient and heat flux. The temperature-dependent interfacial heat transfer mechanism of water-air spray cooling is explored according to the wetting layer evolution taken by a high-speed camera and the surface cooling curves attained by the inverse heat transfer algorithm. Film boiling, transition boiling, and nucleate boiling stages can be noticed during spray cooling process of hot metallic surface. When the cooled surface?s temperature drops to approximately 369?C - 424?C; the cooling process transfers into the transition boiling stage from the film boiling stage. The wetting regime begins to appear on the cooled surface, the interfacial heat transfer coefficient and heat flux begin to increase significantly. When the cooled surface?s temperature drops to approximately 217?C - 280?C, the cooling process transfers into the nucleate boiling stage. The cooled surface was covered by a liquid film, and the heat flux begins to decrease significantly.

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“…In the transition boiling regime, liquid contact occurs with portions of the surface, resulting in a significant improvement in heat transfer compared to film boiling. To predict the LFP, several models and correlations have been proposed [2][3]. These are based in several hypotheses including a Taylor-like hydrodynamic instability that can disrupt vapor pockets, or an explosive boiling caused by homogeneous nucleation.…”

Section: Introductionmentioning

confidence: 99%

The Leidenfrost transition of liquid droplets impinging onto a superheated surface

Caballina

Collignon

Srivastava

et al. 2021

ICLASS

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Heat transfer during the impact of a droplet on a sapphire substrate is investigated by means of infrared thermography. For that, the sapphire is coated with a very thin layer of TiAlN having a high emissivity in the IR domain. Spatially and time resolved measurements of the temperature at the front face of the solid wall are obtained. Results obtained for water droplets show that the dynamic Leidenfrost point (LFP) is close to 450°C and coincides with the onset of a fingering pattern. Approaching the dynamic LFP, despite the cooling by the droplet, the wall surface temperature never decreases below 310°C which is about the temperature of the spinodal for water, i.e. the maximum temperature at which water can still exist in the liquid state. Considering that a wetting contact is taking place below the dynamic LFP, wall temperature measurements demonstrate that the drop impact comes with a very strong superheating of the liquid. The liquid touching the wall is heated up to the spinodal temperature. Based on the idea that the dynamic LFP could correspond to the wall temperature, for which the contact temperature at a solid/liquid interface is equal to the spinodal temperature, a model is proposed for the dynamic LFP. This model considers the thermal effusivities of the liquid and the wall, as well as the liquid flow in the spreading lamella.

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Theoretical Leidenfrost point (LFP) model for sessile droplet

Cited by 26 publications

References 43 publications

Experimental study of dispersed flow film boiling at sub-channel scale in LOCA conditions: Influence of the steam flow rate and residual power

Experimental study of dispersed flow film boiling at sub-channel scale in LOCA conditions: Influence of the steam flow rate and residual power

Wetting layer evolution and interfacial heat transfer in water-air spray cooling process of hot metallic surface

The Leidenfrost transition of liquid droplets impinging onto a superheated surface

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