7 results on '"partial wetting"'
Search Results
2. Evaporation of an isolated liquid plug moving inside a capillary tube.
- Author
-
Srinivasan, Vyas, Marty-Jourjon, Victor, Khandekar, Sameer, Lefèvre, Frederic, and Bonjour, Jocelyn
- Subjects
- *
EVAPORATION (Chemistry) , *CAPILLARY tubes , *METHANOL , *VELOCITY , *ADIABATIC flow - Abstract
The paper reports an experimental study to understand the evaporation mechanism of a partially wetting isolated liquid plug (methanol) of length L moving inside a long, dry, horizontal circular glass capillary tube (ID = 1.5 mm). The plug (with specified range of non-dimensional L / D ratios) is pushed from rest by controlled injection of air from one side, till a quasi-steady terminal plug velocity is achieved in the adiabatic section (non-heated length) of the capillary tube. Under such conditions, the drainage of thin-film occurring at the receding interface and its subsequent dewetting is well predicted by existing literature. The plug is then allowed to move through the heated section maintained at constant wall temperature (lesser than the saturation temperature of methanol). The drained film now starts evaporating rapidly, drastically affecting the bulk transport behavior. High resolution videography, coupled with laser confocal microscopy provides vital bulk as well as local information, including time-varying plug length, film thickness and local dewetting behavior near the contact line. Experimental results obtained for different wall temperatures and different initial L / D ratios of liquid plug suggests that the Taylor’s law for predicting drainage characteristics under adiabatic flow conditions is valid, even for cases where there is a continuous evaporation of thin-film. The study thus provides a framework for modeling evaporative flux based on simple hydrodynamic theory of film drainage. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
3. 1D and 2D simulations of partially wetted catalyst particles: A focus on heat transfer limitations
- Author
-
Bazer-Bachi, Frédéric, Augier, Frédéric, and Santos, Bruno
- Subjects
- *
HEAT transfer , *HYDRODYNAMICS , *MASS transfer , *EVAPORATION (Chemistry) , *CATALYSTS , *TRICKLE bed reactors , *BOUNDARY value problems , *MATHEMATICAL models - Abstract
Abstract: Hydrodynamics and transport phenomena inside Trickle Bed Reactors are strongly modified when superficial liquid velocity is not sufficient to insure a perfect wetting of catalyst particles. For this reason, the impact of partial wetting on catalyst effectiveness has been widely studied in past, in case of isothermal reactions. Heat transfer limitations, inside or outside catalyst particles, have also been investigated, but only in case of total wetting. In the present study, the effect of partial wetting is quantified numerically for various kinetics, mass and heat transfer limitations. When possible, an analogy is proposed between 1D and 2D models of particles. Robust rules are proposed to take into account for partial wetting in 1D-radial models of particles. The case of partial evaporation inside catalyst pores is also studied. Evaporation phenomena is approximated following a simple approach. Performed calculations show that the effect of partial wetting can affect very strongly catalyst effectiveness factors, especially in case of evaporation in the pores. The use of 1D approximations gives a good prediction of the global catalyst efficiency, as far as boundary conditions are symmetric between heat and mass transfer. Otherwise, 1D models are not relevant anymore. [Copyright &y& Elsevier]
- Published
- 2011
- Full Text
- View/download PDF
4. Modeling of critical phenomena for liquid/vapor–gas exothermic reaction on a single catalyst pellet
- Author
-
Shigarov, A.B., Kulikov, A.V., Kuzin, N.A., and Kirillov, V.A.
- Subjects
- *
MATHEMATICAL models , *HYDROCARBONS , *HYDROGENATION - Abstract
Physical mechanisms are discussed and crude mathematical models with lumped parameters are developed, which explain the authors recent experimental data , concerning temperature hysteresis and multiplicity phenomena for α-methylstyrene (AMS) liquid–vapor hydrogenation on a single catalyst pellet. The interplay between endothermic vaporization and exothermic vapor phase reaction is elucidated. The results of this study may help to develop more sophisticated models and theory of hot spots formation and runaway phenomena in trickle-bed reactors. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
- View/download PDF
5. Evaporation of an isolated liquid plug moving inside a capillary tube
- Author
-
Victor Marty-Jourjon, Vyas Srinivasan, Jocelyn Bonjour, Sameer Khandekar, Frédéric Lefèvre, Indian Institute of Technology Kanpur (IIT Kanpur), Centre d'Energétique et de Thermique de Lyon (CETHIL), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), and Department of Mechanical Engineering [Kanpur]
- Subjects
Fluid Flow and Transfer Processes ,Plug flow ,Materials science ,Capillary action ,Dewetting ,Mechanical Engineering ,Evaporation ,Thin-film drainage ,Mechanics ,Taylor’s law ,Partial wetting ,Condensed Matter Physics ,law.invention ,Taylor plug flow ,Condensed Matter::Soft Condensed Matter ,Physics::Fluid Dynamics ,law ,[SPI.MECA.THER]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph] ,Wetting ,Spark plug ,Adiabatic process ,Hydrodynamic theory - Abstract
International audience; The paper reports an experimental study to understand the evaporation mechanism of a partially wetting isolated liquid plug (methanol) of length L moving inside a long, dry, horizontal circular glass capillary tube (ID = 1.5 mm). The plug (with specified range of non-dimensional L/D ratios) is pushed from rest by controlled injection of air from one side, till a quasi-steady terminal plug velocity is achieved in the adiabatic section (non-heated length) of the capillary tube. Under such conditions, the drainage of thin-film occurring at the receding interface and its subsequent dewetting is well predicted by existing literature. The plug is then allowed to move through the heated section maintained at constant wall temperature (lesser than the saturation temperature of methanol). The drained film now starts evaporating rapidly, drastically affecting the bulk transport behavior. High resolution videography, coupled with laser confocal microscopy provides vital bulk as well as local information, including time-varying plug length, film thickness and local dewetting behavior near the contact line. Experimental results obtained for different wall temperatures and different initial L/D ratios of liquid plug suggests that the Taylor’s law for predicting drainage characteristics under adiabatic flow conditions is valid, even for cases where there is a continuous evaporation of thin-film. The study thus provides a framework for modeling evaporative flux based on simple hydrodynamic theory of film drainage.
- Published
- 2015
6. Evaporation at microscopic scale and at high heat flux
- Author
-
Janecek, Vladislav, Physique et mécanique des milieux hétérogenes (UMR 7636) (PMMH), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Service des Basses Températures (SBT ), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Pierre et Marie Curie - Paris VI, and Vadim Nikolayev(vadim.nikolayev@espci.fr)
- Subjects
analyisis asymptotiques ,partial wetting ,angle de contact ,ligne de contact ,boiling crisis ,crise d'ébullition ,singularity ,[SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] ,asymptotic analysis ,mouillage partial ,[PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other] ,[PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph] ,[SPI.MECA.THER]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph] ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,contact angle ,contact line ,évaporation - Abstract
This thesis theoretically investigates the transport processes in the vicinity of the triple gas-liquid-solid contact line and its impact on macroscopic evaporation. In the first part of the thesis, the hydrodynamics close to the contact line at partial wetting is studied. Specifically, evaporation into the atmosphere of pure vapor driven by heating of the substrate is considered. The question of singularity relaxation is addressed. The main finding of the thesis is that the Kelvin effect (dependence of saturation temperature on pressure) is sufficient by itself to relax the hydrodynamic contact line singularity. The proposed microregion (the contact line vicinity) model for small interface slopes is solved numerically. Asymptotic solutions are found for some specific cases. The governing length scales of the problem are identified and the multiscale nature of the phenomenon is addressed. Parametric studies revealing the role of the thermal resistance of vapor-liquid interface, slip length, thermocapillary term, the vapor recoil and surface forces are also performed. An extension of the lubrication approximation for high slopes of the gas-liquid interface at evaporation is discussed. In the second part of the thesis, the previously established microregion model is coupled to a simplified single vapor bubble growth numerical simulation. The bubble departure from the heater at boiling is also studied. It was proposed in the thesis, that under high heat loads, the increase of the apparent contact angle causes the vapor bubble to spread over the heated substrate. Such a behavior may cause the heater dry-out that occurs during the boiling crisis.; Cette thèse étudie théoriquement les processus de transport au voisinage de la ligne triple de contact liquide-gaz-solide et leur impact sur l'évaporation macroscopique. Dans la première partie de la thèse, l'hydrodynamique au voisinage de la ligne de contact est étudiée sous les conditions de mouillage partiel. L'évaporation induite par le chauffage du substrat dans l'atmosphère de vapeur du même fluide est considérée. La relaxation de la singularité hydrodynamique de la ligne triple est considérée. La principale conclusion de la thèse est que l'effet Kelvin (dépendance de la température de saturation de la pression) est suffisant en soi, pour faire disparaitre la singularité des variables hydrodynamiques. La microrégion (le voisinage de la ligne de contact) est résolue numériquement et analytiquement pour de faibles pentes de l'interface liquide-vapeur. Les échelles de longueur caractéristiques du problème sont identifiées et la nature multi-échelle du phénomène est prise en compte. Les études paramétriques effectuées révèlent le rôle de la résistance thermique de l'interface vapeur-liquide, de la longueur de glissement, du terme thermocapillaire, du recul de vapeur et ainsi que des forces de surface. Une extension de l'approximation de lubrification pour de pentes élevées de l'interface gaz-liquide à l'évaporation est discutée. Dans la seconde partie de la thèse, le modèle précédemment établi pour la microrégion est couplé à des simulations numériques de la croissance d'une bulle de vapeur. Le départ de la bulle de vapeur de la paroi chauffante pendant l'ébullition a également été étudiée. Il a été proposé dans la thèse, que sous des charges thermiques élevées, l'augmentation de l'angle de contact apparent provoque l'étalement de la bulle de vapeur sur la paroi chauffante. Ce phénomène peut conduire, au séchage de la paroi observé pendant la crise d'ébullition.
- Published
- 2012
7. Evaporation à l'échelle microscopique et à haut flux thermique
- Author
-
Janecek, Vladislav, Physique et mécanique des milieux hétérogenes (UMR 7636) (PMMH), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Service des Basses Températures (SBT ), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Pierre et Marie Curie - Paris VI, Vadim Nikolayev(vadim.nikolayev@espci.fr), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
- Subjects
analyisis asymptotiques ,partial wetting ,angle de contact ,ligne de contact ,boiling crisis ,crise d'ébullition ,singularity ,[SPI.MECA.MEFL]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Fluids mechanics [physics.class-ph] ,asymptotic analysis ,mouillage partial ,[PHYS.COND.CM-GEN]Physics [physics]/Condensed Matter [cond-mat]/Other [cond-mat.other] ,[PHYS.MECA.THER]Physics [physics]/Mechanics [physics]/Thermics [physics.class-ph] ,[SPI.MECA.THER]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Thermics [physics.class-ph] ,[PHYS.MECA.MEFL]Physics [physics]/Mechanics [physics]/Fluid mechanics [physics.class-ph] ,contact angle ,contact line ,évaporation - Abstract
This thesis theoretically investigates the transport processes in the vicinity of the triple gas-liquid-solid contact line and its impact on macroscopic evaporation. In the first part of the thesis, the hydrodynamics close to the contact line at partial wetting is studied. Specifically, evaporation into the atmosphere of pure vapor driven by heating of the substrate is considered. The question of singularity relaxation is addressed. The main finding of the thesis is that the Kelvin effect (dependence of saturation temperature on pressure) is sufficient by itself to relax the hydrodynamic contact line singularity. The proposed microregion (the contact line vicinity) model for small interface slopes is solved numerically. Asymptotic solutions are found for some specific cases. The governing length scales of the problem are identified and the multiscale nature of the phenomenon is addressed. Parametric studies revealing the role of the thermal resistance of vapor-liquid interface, slip length, thermocapillary term, the vapor recoil and surface forces are also performed. An extension of the lubrication approximation for high slopes of the gas-liquid interface at evaporation is discussed. In the second part of the thesis, the previously established microregion model is coupled to a simplified single vapor bubble growth numerical simulation. The bubble departure from the heater at boiling is also studied. It was proposed in the thesis, that under high heat loads, the increase of the apparent contact angle causes the vapor bubble to spread over the heated substrate. Such a behavior may cause the heater dry-out that occurs during the boiling crisis.; Cette thèse étudie théoriquement les processus de transport au voisinage de la ligne triple de contact liquide-gaz-solide et leur impact sur l'évaporation macroscopique. Dans la première partie de la thèse, l'hydrodynamique au voisinage de la ligne de contact est étudiée sous les conditions de mouillage partiel. L'évaporation induite par le chauffage du substrat dans l'atmosphère de vapeur du même fluide est considérée. La relaxation de la singularité hydrodynamique de la ligne triple est considérée. La principale conclusion de la thèse est que l'effet Kelvin (dépendance de la température de saturation de la pression) est suffisant en soi, pour faire disparaitre la singularité des variables hydrodynamiques. La microrégion (le voisinage de la ligne de contact) est résolue numériquement et analytiquement pour de faibles pentes de l'interface liquide-vapeur. Les échelles de longueur caractéristiques du problème sont identifiées et la nature multi-échelle du phénomène est prise en compte. Les études paramétriques effectuées révèlent le rôle de la résistance thermique de l'interface vapeur-liquide, de la longueur de glissement, du terme thermocapillaire, du recul de vapeur et ainsi que des forces de surface. Une extension de l'approximation de lubrification pour de pentes élevées de l'interface gaz-liquide à l'évaporation est discutée. Dans la seconde partie de la thèse, le modèle précédemment établi pour la microrégion est couplé à des simulations numériques de la croissance d'une bulle de vapeur. Le départ de la bulle de vapeur de la paroi chauffante pendant l'ébullition a également été étudiée. Il a été proposé dans la thèse, que sous des charges thermiques élevées, l'augmentation de l'angle de contact apparent provoque l'étalement de la bulle de vapeur sur la paroi chauffante. Ce phénomène peut conduire, au séchage de la paroi observé pendant la crise d'ébullition.
- Published
- 2012
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