A numerical study on droplet-particle collision dynamics

Malgarinos, Ilias; Νikolopoulos, Nikos; Gavaises, Manolis

doi:10.1016/j.ijheatfluidflow.2016.06.010

Cited by 67 publications

(36 citation statements)

References 33 publications

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“…Using this technique, the grid is refined close to the liquid-gas interface and follows its motion dynamically, while the computational cost is decreased compared to a uniform grid having the same resolution [33]. The current model, has been validated for droplet impact onto solid flat and spherical surfaces under isothermal conditions [33,34]; in this work it is extended to account for heat transfer, phase change and surface "cracking" reactions, as will be presented in the following sections.…”

Section: Fluid Flow and Volume Of Fluid Methodsmentioning

confidence: 99%

“…It was observed that as the temperature of the catalyst increases or the initial drop kinetic energy decreases, the gas layer is formed more easily, and therefore the possibility of liquid pore blockage decreases. Another way to estimate solid-liquid contact would be to measure the percentage of wall area which is actually covered in liquid as in [34]. Finally, the best/worst case scenarios refer only to the operating conditions investigated.…”

Section: Dtp=2mentioning

confidence: 99%

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Numerical investigation of heavy fuel droplet-particle collisions in the injection zone of a Fluid Catalytic Cracking reactor, Part I: Numerical model and 2D simulations

Malgarinos

Νikolopoulos

Gavaises

2017

Fuel Processing Technology

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This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractThe present paper investigates the collisions between heavy gasoil droplets and solid catalytic particles taking place at conditions realized in Fluid Catalytic Cracking reactors (FCC). The computational model utilizes the Navier-Stokes equations along with the energy conservation and transport of species equations. The VOF methodology is used in order to track the liquid-gas interface, while a dynamic local grid refinement technique is adopted, so that high accuracy is achieved with a relative low computational cost. Phase-change phenomena (evaporation of the heavy gasoil droplet), as well as catalytic cracking surface reactions are taken into account. Physical properties of heavy and light molecular weight hydrocarbons are modeled by representative single component species, while a 2-lump scheme is proposed for the catalytic cracking reactions. The numerical model is firstly validated for the case of a single liquid droplet evaporation inside a hot gaseous medium and impingement onto a flat wall for droplet heating and film boiling conditions. Afterwards, it is utilized for the prediction of single droplet-catalyst collisions inside the FCC injection zone. The numerical results indicate that droplets of similar size to the catalytic particles tend to be levitated more easily by hot catalysts, thus resulting in higher cracking reaction rates/cracking product yield, and limited possibility for liquid pore blocking. For larger sized droplets, the corresponding results indicate that the production of cracking products is not favored, while solid-liquid contact increases. Hotter catalysts promote catalytic cracking reactions and droplet levitation over the catalytic particle, owed to the formation of a thin vapour layer between the liquid and the solid particle.

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Section: Fluid Flow and Volume Of Fluid Methodsmentioning

confidence: 99%

Section: Dtp=2mentioning

confidence: 99%

Numerical investigation of heavy fuel droplet-particle collisions in the injection zone of a Fluid Catalytic Cracking reactor, Part I: Numerical model and 2D simulations

Malgarinos

Νikolopoulos

Gavaises

2017

Fuel Processing Technology

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“…The liquid film was easily to splash during the coating process when the impact velocity was high. The liquid film splashed at some point and the inner part of the liquid film retracted under the surface tension while the outer part of the liquid film continued to spread and gathered in the bottom as a long strip [27].…”

Section: The Effect Of Impact Velocitymentioning

confidence: 99%

“…If the spherical diameter was much larger than the droplet diameter, the impact effect was similar to the impact on a plate [30]. Malgarinos et al [27] indicated that coating would take place when the droplet initial kinetic energy was equal or higher than the surface energy needed to spread the film past the particle equator. Besides the rate of film thinning became slower with decreasing curvature ratio (the ratio of the initial droplet diameter to the surface diameter).…”

Section: The Effect Of Curvature Ratiomentioning

confidence: 99%

Research progress of droplet impact on dry curve surfaces

Liu

Chen

Shi

et al. 2018

AIP Conference Proceedings

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“…For the latter cases, the bubble density obeys a polytropic gas equation of state ( ), where the constant parameter κ is set according to a reference state for gas pressure and density. The thermal VOF model has been extensively used in a number of studies from the authors' group in deforming droplet simulations such as in [10][11][12] and in [13][14][15], but also in cases with polytropic bubble dynamics as in [16,17]. The model equations have been presented in detail in the aforementioned works and thus they are not repeated here.…”

Section: Mathematical Modelsmentioning

confidence: 99%

Numerical investigation of the role of heat transfer in bubble dynamics

Fostiropoulos¹,

Malgarinos²,

Strotos³

et al. 2017

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

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Bubble dynamics is generally described by the well-known Rayleigh-Plesset (R-P) equation in which the bubble pressure (or equivalently the bubble density) is predefined by assuming a polytropic gas equation of state with common assumptions to include either isothermal or adiabatic bubble behaviour. The present study examines the applicability of this assumption by assuming that the bubble density obeys the ideal gas equation of state, while the heat exchange with the surrounding liquid is estimated as part of the numerical solution. The numerical model employed includes the solution of the Navier-Stokes equations along with the energy equation, while the liquidgas interface is tracked using the Volume of Fluid (VOF) methodology; phase-change mechanism is assumed to be insignificant compared to bubble heat transfer mechanism. To assess the effect of heat transfer and gas equation of state on bubble behaviour, simulations are also performed for the same initial conditions by using a polytropic equation of state for the bubble phase without solving the energy equation. The accuracy of computations is enhanced by using a dynamic local grid refinement technique which reduces the computational cost and allows for the accurate representation of the interface for the whole duration of the phenomenon in which the bubble size changes significantly. A parametric study performed for various initial bubble sizes and ambient conditions reveals the cases for which the bubble behaviour resembles that of an isothermal or the adiabatic one. Additional to the CFD simulations, a 0-D model is proposed to predict the bubble dynamics. This combines the solution of a modified R-P equation assuming ideal gas bubble content along with an equation for the bubble temperature based on the 1 st law of thermodynamics; a correction factor is used to represent accurately the heat transfer between the two phases. KeywordsBubble dynamics, heat transfer, CFD-VOF model, 0-D model. IntroductionThe need for the inclusion of thermal effects in bubble dynamics was first addressed in [1] among others; it was shown that the polytropic gas assumption may provide inaccurate predictions of the bubble behaviour when thermal processes are taken into consideration. Since then, the effect of heat and mass transfer on bubble dynamics were examined in a large number of studies, either by CFD numerical models that are capable of solving the complex equations that characterize the physical processes of the bubble motion, or by reduced order models which include various assumptions but are computationally more efficient. In the framework of the CFD studies, the effect of heat transfer by solving the equation of gas-vapour bubble including variation of liquid temperature and assuming liquid incompressibility was examined in [2]. The main assumption in this study, was that the temperature distribution inside the bubble to be uniform, which allowed the authors to integrate analytically the continuity and momentum equations inside the bubble. In [3], the motion ...

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A numerical study on droplet-particle collision dynamics

Cited by 67 publications

References 33 publications

Numerical investigation of heavy fuel droplet-particle collisions in the injection zone of a Fluid Catalytic Cracking reactor, Part I: Numerical model and 2D simulations

Numerical investigation of heavy fuel droplet-particle collisions in the injection zone of a Fluid Catalytic Cracking reactor, Part I: Numerical model and 2D simulations

Research progress of droplet impact on dry curve surfaces

Numerical investigation of the role of heat transfer in bubble dynamics

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