On the validity of the adiabatic spreading assumption in droplet impact cooling

Healy, William M.; Hartley, J. G.; Abdel‐Khalik, S. I.

doi:10.1016/s0017-9310(01)00041-2

Cited by 39 publications

(32 citation statements)

References 40 publications

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“…[20], who measured a constant temperature increase along the droplet radius due to the decreased convective heat transfer in the outward fluid direction. However, numerically, a temperature distribution similar to that obtained here was reported for instance by [13]. These discrepancies arising from experimental and numerical studies can be explained by further detailing the fluid dynamics within the droplet, specifically at the lamella and within the rim, in the attempt to relate the fluid dynamic behaviour with the heat transfer process.…”

Section: Resultssupporting

confidence: 76%

“…This approximation is considered valid in the relatively small time scale that is investigated here. This is in agreement with the results reported, for instance by [12][13][19][20]. The Continuum Surface Force (CFS) method proposed in [21] was used to model the surface tension as a volumetric force.…”

Section: Radial Distance R [Mm] = ±200supporting

confidence: 89%

“…In fact, following the pioneering work of [10], who proposed the "Marker and Cell" (MAC) finite difference method to solve the Navier-Stokes equations, other methods have been used to solve numerically the problem of drop impact onto heated surfaces such as the Lagrangian approach [11], the immersed boundary method (IBM) [12] and the Level Set (LS) [13]. In [13], the authors highlight different regions of heat flux along the radial direction of the impacting surface, which can be related with the flow in the lamella. They report that a dip in the heat flux was noticed close to the droplet rim when the film becomes thinner and thus unable to remove as much heat as the other regions of the spreading droplet.…”

Section: Introductionmentioning

confidence: 99%

“…However, efficient cooling can be obtained only from sensible heat [4]. Although droplet spreading on heated surfaces has been extensively studied in the literature [4][5][6], the complex coupling between the fluid dynamics and the heat transfer processes has not yet been completely described. An important limitation in many of the aforementioned studies is that they quantify the heat transfer mainly based on surface temperature measurements at the centre of the impact to the surface, using thermocouples.…”

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confidence: 99%

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Experimental and numerical study on sensible heat transfer at droplet/wall interactions

Teodori

Pontes

Moita

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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The present study addresses a detailed experimental and numerical investigation on the impact of water droplets on smooth heated surfaces. High-speed infrared thermography is combined with high-speed imaging to couple the heat transfer and fluid dynamic processes occurring at droplet impact. Droplet spreading (e.g. spreading ratio) and detailed surface temperature fields are then evaluated in time and compared with the numerically predicted results. The numerical reproduction of the phenomena was conducted using an enhanced version of a VOFbased solver of OpenFOAM previously developed, which was further modified to account for conjugate heat transfer between the solid and fluid domains, focusing only on the sensible heat removed during droplet spreading. An excellent agreement is observed between the temporal evolution of the experimentally measured and the numerically predicted spreading factors (differences between the experimental and numerical values were always lower than 3.4%). The numerical and experimental dimensionless surface temperature profiles along the droplet radius were also in good agreement, depicting a maximum difference of 0.19. Deeper analysis coupling fluid dynamics and heat transfer processes was also performed, evidencing a strong correlation between maximum and minimum temperature values and heat transfer coefficients with the vorticity fields in the lamella, which lead to particular mixing processes in the boundary layer region. The correlation between the resulted temperature fields and the droplet dynamics was obtained by assuming a relation between the vorticity and the local heat transfer coefficient, in the first fluid cell i.e. near the liquid-solid interface. The two measured fields revealed that local maxima and minima in the vorticity corresponded to spatially shifted local minima and maxima in the heat transfer coefficient, at all stages of the droplet spreading. This was particularly clear in the rim region, which therefore should be considered in future droplet spreading models. KeywordsDroplet impact, smooth heated surface, high-speed infrared thermography, VOF, vorticity. IntroductionUnderstanding the fluid dynamic and heat transfer mechanisms of droplet impact on heated surfaces is relevant for a wide range of applications, from fire sprinklers to cooling applications. A popular solution for microprocessors cooling is based on spray impingement [1-2]. The elementary representation of a spray composed by arrays of single droplets impacting onto a heated surface is not straightforward in many of the aforementioned applications, but the complexity of the observed phenomena relays on the study of single droplet impacts to understand the basic governing processes. Such approximation is not so far from the real systems for microelectronics cooling, which actually deal with single droplets or with very sparse sprays [1,3]. In many of these applications, liquid phase change is promoted to take advantage of the latent heat of evaporation. However, efficient cooling can be ...

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Section: Resultssupporting

confidence: 76%

Section: Radial Distance R [Mm] = ±200supporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Experimental and numerical study on sensible heat transfer at droplet/wall interactions

Teodori

Pontes

Moita

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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“…Despite being a pioneer work, the MAC code originally implemented, needed some modifications to account for heat transfer which were further introduced in [25] and [26]. Other methods have been used to solve numerically the problem of drop impact onto heated surfaces such as the Lagrangian approach [27]; the Immersed Boundary Method (IBM) [28,29] and the Level Set (LS) methodology ( [30,31]). In [30], the authors highlight different regions of heat flux along the radial direction of the impacting surface, which can be related with the flow in the lamella (the radial liquid film formed as the droplet spreads) and in the rim, surrounding the lamella.…”

Section: State Of the Artmentioning

confidence: 99%

Sensible Heat Transfer during Droplet Cooling: Experimental and Numerical Analysis

et al. 2017

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This study presents the numerical reproduction of the entire surface temperature field resulting from a water droplet spreading on a heated surface, which is compared with experimental data. High-speed infrared thermography of the back side of the surface and high-speed images of the side view of the impinging droplet were used to infer on the solid surface temperature field and on droplet dynamics. Numerical reproduction of the phenomena was performed using OpenFOAM CFD toolbox. An enhanced volume of fluid (VOF) model was further modified for this purpose. The proposed modifications include the coupling of temperature fields between the fluid and the solid regions, to account for transient heat conduction within the solid. The results evidence an extremely good agreement between the temporal evolution of the measured and simulated spreading factors of the considered droplet impacts. The numerical and experimental dimensionless surface temperature profiles within the solid surface and along the droplet radius, were also in good agreement. Most of the differences were within the experimental measurements uncertainty. The numerical results allowed relating the solid surface temperature profiles with the fluid flow. During spreading, liquid recirculation within the rim, leads to the appearance of different regions of heat transfer that can be correlated with the vorticity field within the droplet.

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Interaction between liquid drop with low impact momentum and heated wall

Liang

Zhang

et al. 2018

Acta Mech

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On the validity of the adiabatic spreading assumption in droplet impact cooling

Cited by 39 publications

References 40 publications

Experimental and numerical study on sensible heat transfer at droplet/wall interactions

Experimental and numerical study on sensible heat transfer at droplet/wall interactions

Sensible Heat Transfer during Droplet Cooling: Experimental and Numerical Analysis

Interaction between liquid drop with low impact momentum and heated wall

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