The hydrodynamics of microlayer formation beneath vapour bubbles

Hänsch, Susann; Walker, S.P.

doi:10.1016/j.ijheatmasstransfer.2016.07.026

Cited by 26 publications

(29 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand performing a fully resolved Direct Numerical Simulation of Nucleate Boiling when a microlayer will develop seems to be a more feasible task, since the range of scales involved in the overall physical phenomenon is not as large as in the case involving a micro-region. Recent studies have presented first results on such a configuration by using a very refined grid in the vicinity of the wall in [14], or by using a subgrid model to describe this micro-layer in [49].…”

Section: Methodsmentioning

confidence: 99%

Direct numerical simulation of nucleate pool boiling at large microscopic contact angle and moderate Jakob number

Huber

Tanguy

Sagan

et al. 2017

International Journal of Heat and Mass Transfer

View full text Add to dashboard Cite

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 17968 a b s t r a c tIn this paper, we present Direct Numerical Simulations of Nucleate Boiling on a single site in configurations involving both a large microscopic contact angle, a moderate Jakob number (less than 50) and a high density ratio between the two phases. A detailed study on the validation of the numerical simulations is presented. Several issues about the numerical modelling of the contact line are addressed in order to define a global strategy to perform accurate and predictive simulations. Benchmarks from pioneering studies (Son et al., 1999) have been reproduced with more recent numerical methods and thinner grids in order to define the most relevant strategy for successful simulations. In particular, the grid sensitivity of the solution is thoroughly investigated by performing simulations with four successive grids. The numerical results are compared favorably with experimental data, since the discrepancy between the numerical solutions and the experimental data is always less than 10% whether the departure diameter or the departure frequency are considered. The influence on the numerical solution of the thermal conduction in the solid heater is also assessed and we report that this parameter has no influence in the configurations of thick and highly conductive materials that have been considered in this study. We also present clarifications about the requirement of a specific modelling in the contact line region in order to account for a possible impact of the micro-region. Finally, based on the results of this analysis of our numerical simulations, we formulate the following unusual conclusion: the implementation of a micro-region model and an additional coupling between the overall solver and such a model is not required to perform well-resolved and accurate numerical simulations in the case of high density ratio, high microscopic contact angle (up to 30°) and moderate Jakob number. Next, we present some comparisons on the bubble shape evolution between the numerical simulations and a static force balance model, in order to investigate the mechanisms leading to the bubble detachment. Finally, we conclude this paper by presenting a parametric study, by varying the Jakob number, in order to propose a new correlation on the bubble detachment radius depending on the latter dimensionless number.

show abstract

Section: Methodsmentioning

confidence: 99%

Direct numerical simulation of nucleate pool boiling at large microscopic contact angle and moderate Jakob number

Huber

Tanguy

Sagan

et al. 2017

International Journal of Heat and Mass Transfer

View full text Add to dashboard Cite

show abstract

“…More recently, there have been attempts to model microlayers by means of CFD analyses. Hänsch and Walker (2016) studied the hydrodynamics of microlayer formation using detailed interface-tracking computations. The work of Guion et al (2018) focused on the hydrodynamic microlayer formation during the very early inertial bubble growth regime.…”

Section: 'Physically-based' Predictionsmentioning

confidence: 99%

“…An initial report of modelling the hydrodynamics of the microlayer formation has been presented earlier (Hänsch and Walker, 2016). Validation of these initial results will be given in 4.1, and an extension of these results to model up to the point of bubble departure, will be presented in Section 5.1.…”

Section: Hydrodynamic Formation Of a Microlayermentioning

confidence: 99%

See 1 more Smart Citation

Microlayer formation and depletion beneath growing steam bubbles

Hänsch

Walker

2019

International Journal of Multiphase Flow

Self Cite

View full text Add to dashboard Cite

Microlayers, the few-microns-thick layers of liquid that sometimes remain beneath bubbles growing on a heated substrate, are widely observed in experiments, but theoretical understanding of their formation, behaviour and role in bubble growth is limited. In this paper we present detailed interface-tracking simulations of the formation and depletion of such microlayers. Validation of our results is presented to the degree that available measurements of such a rapid and microscopic phenomenon allow. The work extends previous mechanistic hydrodynamic-only CFD simulations of early microlayer formation up to typical bubble departure times. These calculations confirm the understanding that the bubble growth rate and the resulting bubble shape determine the presence and overall extent of microlayers underneath steam bubbles. Their thickness is strongly influenced by viscous effects and surface tension. We then present coupled, physically self-consistent CFD simulations of the formation and evaporative depletion of such microlayers. This modelling suggests strongly that the evaporation process itself constitutes a significant fraction of the small resistance to heat and mass transfer presented by the very thin liquid layer. Inclusion of representations of evaporative thermal resistance, consistent with those suggested in the literature, is seen to promote the prediction of microlayer formation. Identification of the classes of conditions under which microlayers seem likely to be formed is presented, along with an assessment of their relative contributions to bubble growth. Comparisons of the predictions with recent detailed microlayer measurements indicate good agreement.

show abstract

“…Further details are available in a conference paper (Hänsch and Walker, 2016b), and in a recent journal submission (Hänsch and Walker, 2016a).…”

Section: Introductionmentioning

confidence: 99%