Nucleate boiling: Microlayer formation, depletion, and contribution to bubble growth

The growth of a vapour bubble at a heated surface involves various fluid mechanics, heat transfer and phase change phenomena. An understanding of the fundamentals of these phenomena on the scale of single bubbles is interesting in its own right from a scientific point of view, and is helpful for the further improvement of macroscopic boiling models. Vapour generation during nucleate boiling at atmospheric pressure conditions is known to occur not only from the curved surface of the bubble, but also from a very thin film of liquid forming between the heated wall and the underside of the bubble, the so-called ‘microlayer’. Microlayers are widely observed in experiments, but theoretical understanding of their formation, behaviour and significance to bubble growth is limited. This thesis presents various studies of the formation, depletion, and contribution to bubble growth of these microlayers. Mechanistic hydrodynamic-only CFD simulations of the formation of such microlayers during the early bubble growth stages, tracking the vapour-liquid interface, are performed. These computational models demonstrate that the balance between inertial and surface tension forces, and the resulting bubble shape, determine the presence and overall extent of microlayers underneath steam bubbles. Their thickness is strongly influenced by viscous effects in the near-wall region. Having identified the underlying physical mechanism behind the formation of microlayers, the thesis then presents CFD simulations of their formation and simultaneous, physically self- consistent evaporative extinction, including the conjugate heat transfer into the solid substrate. Identification of the classes of conditions under which microlayers are likely to be formed is presented, along with an assessment of their relative contribution of vapour to the overall bubble growth.Open Acces

HZDR Multiphase Case Collection for OpenFOAM

HZDR Multiphase Case Collection for OpenFOAM contains simulation setups for the open-source CFD software OpenFOAM extended by the HZDR Multiphase Addon for OpenFOAM. The simulation setups are separated into mono- and polydisperse bubbly flows utilising the HZDR Baseline model set, setups for a hybrid modelling approach (disperse and resolved interfaces) and miscellaneous cases.This work was supported by the Helmholtz European Partnering Program in the project "Crossing borders and scales (Crossing)"

HZDR Multiphase Addon for OpenFOAM

The HZDR multiphase addon contains additional code for the open-source CFD software OpenFOAM, released by The OpenFOAM Foundation. The developments are dedicated to the numerical simulation of multiphase flows, in particular to the multi-field two-fluid model (Euler-Euler method). Within the OpenFOAM library the multiphaseEulerFoam framework is used for this type of simulation. The addon contains a modified multiphaseEulerFoam named HZDRmultiphaseEulerFoam with the full support of the HZDR baseline model set for polydisperse bubbly flows according to Liao et al. (Chem Eng Sci, 2019, Vol. 202, 55-69). In addition a solver dedicated to a hybrid modelling approach (dispersed and resolved interfaces, Meller et al., Int J Numer Meth Fluids. 2020, 1-26) named cipsaMultiphaseEulerFoam is provided with the addon. This solver has an interface to the multiphaseEulerFoam framework and utilizes all available interfacial models of it. General enhancements modified turbulent wall functions of Menter according to Rzehak and Kriebitzsch ( Int J Multiphase Flow, 2015, Vol. 68, 135-152) dynamic time step adjustment via PID controller HZDRmultiphaseEulerFoam bubble induced turbulence model of Ma et al. (Phys Rev Fluids, 2017, Vol. 2, 034301) drag model of Ishii and Zuber (AIChE Journal, 1979, Vol. 25, 843-855) without correction for swarm and/or viscous effects wall lubrication of Hosokawa et al. (ASME Joint US-European Fluids Engineering Division Conference, 2002) additional breakup and coalescence models for class method according to Liao et al. (Chem Eng Sci, 2015, Vol. 122, 336-349) degassing boundary condition (fvOption) configuration files and tutorials for easy setup cipsaMultiphaseEulerFoam morphology adaptive modeling framework for modelling of dispersed and resolved interfaces based on Eulerian multi-field two-fluid model compact interpolation method according to Cubero et al. (Comput Chem Eng, 2014, Vol. 62, 96-107), including virtual mass numerical drag according to Strubelj and Tiselj (Int J Numer Methods Eng, 2011, Vol. 85, 575-590) to describe resolved interfaces in a volume-of-fluid like manner n-phase partial elimination algorithm for momentum equations to resolve strong phase coupling free surface turbulence damping for k-ω SST (symmetric and asymmetric damping, Frederix et al., Nucl Eng Des, 2018, Vol. 333, 122-130) selected tutorial cases: a two-dimensional gas bubble, rising in a liquid, which is laden with micro gas bubbles, and a two-dimensional stagnant stratification of water and oil, sharing a large-scale interface a two-dimensional stratified flow based on the experiment of Fabre et al. (Multiphase Sci Technol, 1987, Vol. 3, 285–301)This work was supported by the Helmholtz European Partnering Program in the project "Crossing borders and scales (Crossing)

HZDR Multiphase Case Collection for OpenFOAM

HZDR Multiphase Case Collection for OpenFOAM contains simulation setups for the open-source CFD software OpenFOAM extended by the HZDR Multiphase Addon for OpenFOAM. The simulation setups are separated into mono- and polydisperse bubbly flows utilising the HZDR Baseline model set, setups for a hybrid modelling approach (disperse and resolved interfaces) and miscellaneous cases.This work was supported by the Helmholtz European Partnering Program in the project "Crossing borders and scales (Crossing)"

HZDR Multiphase Case Collection for OpenFOAM

HZDR Multiphase Case Collection for OpenFOAM contains simulation setups for the open-source CFD software OpenFOAM with the HZDR multiphase addon. The simulation setups are separated into polydisperse bubbly flows utilising the HZDR Baseline model set according to Liao et al. (Chem Eng Sci, 2019, Vol. 202, 55-69), setups for a hybrid modelling approach (disperse and resolved interfaces) according to Meller et al. (Int J Numer Meth Fluids, 2021, Vol. 93, 748–773) and miscellaneous cases. Cases using the HZDR Baseline model set baseline/1998_Liu Reference for experiment: Liu, 3rd Int Conf Multiph Flow (ICMF), Vol. 98, 8-12 Reference for case setup: Rzehak et al., Nucl Eng Des, 2021, Vol. 374, 111079 Kriebitzsch and Rzehak, Fluids, 2016, Vol. 1, 29 baseline/2005_Lucas_et_al Reference for experiment: Lucas et al., Int J Multiph Flow, 2005, Vol. 31, 1304-1328 Reference for case setup: Lehnigk et al., AlChE J (submitted) baseline/2008_Shawkat Reference for experiment: Shawkat et al., Int J Multiph Flow, 2008, Vol. 34, 767-785 Reference for case setup: Kriebitzsch and Rzehak, Fluids, 2016, Vol. 1, 29 baseline/2009_Hosokawa Reference for experiment: Hosokawa and Tomiyama, Chem Eng Science, 2009, Vol. 64, 5308-5318 Reference for case setup: Rzehak et al., Nucl Eng Des, 2021, Vol. 374, 111079 baseline/2013_Hosokawa_and_Tomiyama Reference for experiment: Hosokawa and Tomiyama, Int J Heat Fluid Flow, 2013, Vol. 40, 97-105 Reference for case setup: Kriebitzsch and Rzehak, Fluids, 2016, Vol. 1, 29 Liao et al., Comp Fluids, 2020, Vol. 202, 104496 baseline/2016_Kim_et_al Reference for experiment: Kim et al., Exp Fluids, 2016, Vol. 57, 1432-1114 Reference for case setup: Liao et al., Comp Fluids, 2020, Vol. 202, 104496 Cases using the hybrid modelling approach hybrid/wenka/2D-MP3-23 Reference for experiment: Stäbler, Ph.D. thesis, 2007 Reference for case setup: Tekavčič et al., Nucl Eng Des, 2021, Vol. 379, 111223 hybrid/risingBubbleHysingEtAl2009 References for case setup: Hysing et al., Int J Numer Meth Fluids, 2009, Vol. 60, 1259-1288 Meller et al., Int J Numer Meth Fluids, 2021, Vol. 93, 748–773 Meller et al., Flow Turbul Combust (submitted) hybrid/risingBubbleBalcazarEtAl2015 Reference for experiment: Bhaga and Weber, J Fluid Mech, 1981, Vol. 105, 61-85 Reference for direct numerical simulation: Balcázar et al., Int J Heat Fluid Flow, 2015, Vol. 56, 91-107 References for case setup: Meller et al., Int J Numer Meth Fluids, 2021, Vol. 93, 748–773 hybrid/risingBubbleMellerEtAl2021 Reference for case setup: Meller et al., Flow Turbul Combust (submitted) Miscellaneous cases misc/multiphase/HZDRmultiphaseEulerFoam/1991_Akhtar_et_al Reference for experiment: Akhtar et al., AIChE J, 1991, Vol. 37, 1561–1570 Reference for case setup: Lehnigk et al., AlChE J (submitted)This work was supported by the Helmholtz European Partnering Program in the project "Crossing borders and scales (Crossing)"

Multiphase Cases Repository by HZDR for OpenFOAM Foundation Software

This repository contains simulation setups for the Multiphase Code Repository by HZDR for OpenFOAM Foundation Software. The simulation setups are separated into mono- and polydisperse bubbly flows utilising the Baseline model by HZDR set, setups for a morphology-adaptive multifield two-fluid model (disperse and resolved interfaces) and miscellaneous cases.Acknowledgement: OpenFOAM(R) is a registered trade mark of OpenCFD Limited, producer and distributor of the OpenFOAM(R) software via www.openfoam.com. The Multiphase Cases Repository by HZDR for OpenFOAM Foundation Software is not compatible with the software released by OpenCFD Limited, but is based on the software released by the OpenFOAM Foundation via www.openfoam.orgThis work was supported by the Helmholtz European Partnering Program in the project "Crossing borders and scales (Crossing)"

HZDR Multiphase Addon for OpenFOAM

The HZDR Multiphase Addon is a software publication released by Helmholtz-Zentrum Dresden-Rossendorf according to the FAIR principles (Findability, Accessibility, Interoperability, and Reuseability). It contains experimental research work for the open-source CFD software OpenFOAM, released by The OpenFOAM Foundation. The developments are dedicated to the numerical simulation of multiphase flows, in particular to the multi-field two-fluid model (Euler-Euler method). Within the OpenFOAM library the multiphaseEulerFoam framework is used for this type of simulation. The addon contains a modified solver named HZDRmultiphaseEulerFoam with the full support of the HZDR baseline model set for polydisperse bubbly flows. In addition a solver dedicated to a hybrid modelling approach (dispersed and resolved interfaces, Meller, Schlegel and Lucas, 2021) named cipsaMultiphaseEulerFoam is provided with the addon. This solver has an interface to the multiphaseEulerFoam framework and utilizes all available interfacial models of it. General enhancements modified turbulent wall functions of Menter according to Rzehak and Kriebitzsch (2015) dynamic time step adjustment via PID controller HZDRmultiphaseEulerFoam bubble induced turbulence model of Ma et al. (2017) drag model of Ishii and Zuber (1979) without correction for swarm and/or viscous effects wall lubrication model of Hosokawa et al. (2002) additional breakup and coalescence models for class method according to Kusters (1991) and Adachi et al. (1994) degassing boundary condition (fvModel) lift force correlation of Hessenkemper et al. (2021) lift force correlation of Saffman (1965) as extended by Mei (1992). aspect ratio correlation of Ziegenhein and Lucas (2017) real pressure treatment via explicit turbulent normal stress according to Rzehak et al. (2021) GPU-based accelerated computation of coalescence and breakup frequencies for the models of Lehr et al. (2002) (Petelin et al., 2021) configuration files and tutorials for easy setup of baseline cases according to Hänsch et al. (2021) cipsaMultiphaseEulerFoam morphology adaptive modelling framework for predicting dispersed and resolved interfaces based on Eulerian multi-field two-fluid model compact momentum interpolation method according to Cubero et al. (2014), including virtual mass numerical drag according to Strubelj and Tiselj (2011) to describe resolved interfaces in a volume-of-fluid like manner n-phase partial elimination algorithm for momentum equations to resolve strong phase coupling (Meller, Schlegel and Lucas, 2021) free surface turbulence damping (Frederix et al., 2018) for k-ω SST - symmetric and asymmetric - according to Tekavčič et al. (2021) sub-grid scale modelling framework (Meller, Schlegel and Klein, 2021) additional LES models for the unclosed convective sub-grid scale term closure models for sub-grid surface tension term configuration files and tutorials for easy setup of hybrid casesThis work was supported by the Helmholtz European Partnering Program in the project "Crossing borders and scales (Crossing)

HZDR Multiphase Addon for OpenFOAM

The HZDR Multiphase Addon is a software publication released by Helmholtz-Zentrum Dresden-Rossendorf according to the FAIR principles (Findability, Accessibility, Interoperability, and Reuseability). It contains experimental research work for the open-source CFD software OpenFOAM, released by The OpenFOAM Foundation. The developments are dedicated to the numerical simulation of multiphase flows, in particular to the multi-field two-fluid model (Euler-Euler method). Within the OpenFOAM library the multiphaseEulerFoam framework is used for this type of simulation. The addon contains a modified solver named HZDRmultiphaseEulerFoam with the full support of the HZDR baseline model set for polydisperse bubbly flows. In addition a solver dedicated to a hybrid modelling approach (dispersed and resolved interfaces, Meller, Schlegel and Lucas, 2021) named cipsaMultiphaseEulerFoam is provided with the addon. This solver has an interface to the multiphaseEulerFoam framework and utilizes all available interfacial models of it. General enhancements modified turbulent wall functions of Menter according to Rzehak and Kriebitzsch (2015) dynamic time step adjustment via PID controller HZDRmultiphaseEulerFoam bubble induced turbulence model of Ma et al. (2017) drag model of Ishii and Zuber (1979) without correction for swarm and/or viscous effects wall lubrication model of Hosokawa et al. (2002) additional breakup and coalescence models for class method according to Kusters (1991) and Adachi et al. (1994) degassing boundary condition (fvModel) lift force correlation of Hessenkemper et al. (2021) lift force correlation of Saffman (1965) as extended by Mei (1992). aspect ratio correlation of Ziegenhein and Lucas (2017) real pressure treatment via explicit turbulent normal stress according to Rzehak et al. (2021) GPU-based accelerated computation of coalescence and breakup frequencies for the models of Lehr et al. (2002) (Petelin et al., 2021) configuration files and tutorials for easy setup of baseline cases according to Hänsch et al. (2021) cipsaMultiphaseEulerFoam morphology adaptive modelling framework for predicting dispersed and resolved interfaces based on Eulerian multi-field two-fluid model compact momentum interpolation method according to Cubero et al. (2014), including virtual mass numerical drag according to Strubelj and Tiselj (2011) to describe resolved interfaces in a volume-of-fluid like manner n-phase partial elimination algorithm for momentum equations to resolve strong phase coupling (Meller, Schlegel and Lucas, 2021) free surface turbulence damping (Frederix et al., 2018) for k-ω SST - symmetric and asymmetric - according to Tekavčič et al. (2021) sub-grid scale modelling framework (Meller, Schlegel and Klein, 2021) additional LES models for the unclosed convective sub-grid scale term closure models for sub-grid surface tension term configuration files and tutorials for easy setup of hybrid casesThis work was supported by the Helmholtz European Partnering Program in the project "Crossing borders and scales (Crossing)

HZDR Multiphase Addon for OpenFOAM

The HZDR Multiphase Addon is a software publication released by Helmholtz-Zentrum Dresden-Rossendorf according to the FAIR principles (Findability, Accessibility, Interoperability, and Reuseability). It contains experimental research work for the open-source CFD software OpenFOAM, released by The OpenFOAM Foundation. The developments are dedicated to the numerical simulation of multiphase flows, in particular to the multi-field two-fluid model (Euler-Euler method). Highlights of the provided addon are: HZDR Baseline Model: HZDRMultiphaseEulerFoam solver with full support of the HZDR baseline model set for polydisperse bubbly flows, including configuration files and tutorials for simplified setup of Baseline cases (Hänsch et al., 2021). Population Balance Modelling: A GPU-accelerated population balance method according to Petelin et al. (2021). OpenFOAM-Hybrid cipsaMultiphaseEulerFoam solver featuring a hybrid modelling approach (dispersed and resolved interfaces, Meller et al., 2021) with an interface to the multiphaseEulerFoam framework to utilise all available interfacial models, and configuration files and tutorials for easy setup of hybrid cases. more ...This work was supported by the Helmholtz European Partnering Program in the project "Crossing borders and scales (Crossing)"