Interaction Coefficient Between Ice Particles in Convective Melting of Granular Packed Bed

1999 ◽  
Author(s):  
J. Jiang ◽  
Y.-X. Tao
Keyword(s):  
Stokes Equations ◽  
Volume Fraction ◽  
Particle Interaction ◽  
Packed Bed ◽  
Melting Rate ◽  
Interaction Coefficient ◽  
Solid Particles ◽  
Melting Time ◽  
Ice Volume ◽  
Ice Particles

Abstract To numerically simulate the convective melting of packed bed it is necessary to determine the thermophysical properties or their constitutive equations. One of the most uncertain values among them is the solute interaction coefficient of solid particles, which represents the interaction force between solid particles and is equivalent to the viscosity term in Navier-Stokes equations if the dirty fluid model is applied. It was found from the previous study that the solute (solid particle) interaction coefficient, μs, characterizes the solubility such as the melting rate, the distribution of ice volume fraction, the velocity of ice particle, and the melting time. In this study, a parametric study based on the two-dimensional model for the convective melting of granular packed beds (Jiang et al. 1999) is conducted to determine the sensitivity of interaction coefficient to the model prediction. The packed bed considered here is collection of ice particles of various shapes. Warm water at a constant temperature enters horizontally the bed where melting takes place. Two cases are considered. One is to consider μs as constant, and the other is to consider it as a function of the ice volume fraction. The melting rate, fluid flow velocity and ice volume fraction distribution are discussed for different interaction coefficient values. An “optimal” interaction coefficient between ice particles is determined by comparing the simulation data with experimental data (Tao et al. 1998). It is found that the melting results are most sensitive to the value of constant interaction coefficient rather than to whether it is a constant or as a function of the ice volume fraction.

Experimental Investigation of Convective Melting of Granular Packed Bed Under Microgravity

2000 ◽  
Author(s):  
J. Jiang ◽  
Y. Hao ◽  
Y.-X. Tao
Keyword(s):  
Experimental Investigation ◽  
Average Particle Size ◽  
Particle Diameter ◽  
Vertical Direction ◽  
Packed Bed ◽  
Melting Rate ◽  
Control Flow ◽  
Solid Particles ◽  
Average Particle ◽  
Ice Particles

Abstract To improve the understanding of convective melting of packed solid particles in a fluid, an experimental investigation is conducted to study the melting characteristics of a packed bed by unmasking the buoyancy forces due to the density difference between the melt and solid particles. A close-loop apparatus, named the particle-melting-in-flow (PMF) module, is designed to allow a steady state liquid flow under a specified temperature. The module is on board NASA’s KC-135 reduced gravity aircraft for the experiments. In the test module, water is used as the fluid, and ice particles are fed to the test section at the beginning of the test. As the liquid flows though the bed, the solid grains melt. A perforate plate, through which liquid can flow while the ice particles are retained, bounds the downstream of the packed bed. From the digital video images the local packed bed thickness is measured under control flow rate, and the melting rate is determined. The temperature distribution along the horizontal direction and vertical direction is measured using 19 thermocouples. An infrared camera is mounted to record the local temperature variation between liquid and solid. The melting rates are presented as a function of upstream flow velocity, temperature and initial average particle size of the packed bed. It is found that the melting rate is influenced mainly by the ratio of the Reynolds number (Re, based on the initial particle diameter) to the square of the Froud number (Fr), and me Stefan number (Ste). In general, the dimensionless melting rate decreases as Re/Fr2 increases and increases as Ste increases. With the absence of gravity, i.e., Froud number approaches infinity, a maximum melting rate can be achieved for otherwise the same test conditions. The increase in the melting rate with the increase in Stephan number also becomes more pronounced under the zero gravity condition.

EQUILIBRIUM VELOCITY DISTRIBUTION FUNCTIONS FOR A KINETIC MODEL OF TWO-PHASE FLOWS

1995 ◽  
Vol 05 (02) ◽  
pp. 191-211 ◽  
Author(s):  
LIONEL SAINSAULIEU
Keyword(s):  
Velocity Distribution ◽  
Gas Flow ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Velocity Distribution Function ◽  
Distribution Functions ◽  
Solid Particles ◽  
Navier Stokes ◽  
Two Phase ◽  
Entropy Balance

We consider a cloud of solid particles in a gas flow. The cloud is described by a probability density function which satisfies a kinetic equation. The gas flow is modeled by Navier-Stokes equations. The two phases exchange momentum and energy. We obtain the entropy balance of the gas flow and deduce some bounds for the volume fraction of the gas phase. Writing the entropy balance for the dispersed phase enables one to determine the particles equilibrium velocity distribution function when the gas flow is known.

Experimental Investigation of Convective Melting of Granular Packed Bed Under Microgravity

2002 ◽  
Vol 124 (3) ◽  
pp. 516-524 ◽  
Author(s):  
J. Jiang ◽  
Y. Hao ◽  
Y.-X. Tao
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Froude Number ◽  
Average Particle Size ◽  
Particle Diameter ◽  
Packed Bed ◽  
Melting Rate ◽  
Solid Particles ◽  
Average Particle ◽  
Stefan Number

To improve the understanding of convective melting of packed solid particles in a fluid, an experimental investigation is conducted to study the melting characteristics of a packed bed by unmasking the buoyancy forces due to the density difference between the melt and solid particles. A close-loop apparatus, named the particle-melting-in-flow (PMF) module, is designed to allow a steady-state liquid flow at a specified temperature. The module is installed onboard NASA’s KC-135 reduced gravity aircraft using ice particles of desired sizes and water as the test media. Experimentally determined melting rates are presented as a function of upstream flow velocity, temperature and initial average particle size of the packed bed. It is found that the melting rate is influenced mainly by the ratio of the Reynolds number (Re, based on the initial particle diameter) to the square of the Froude number (Fr), and the Stefan number (Ste). In general, the dimensionless melting rate decreases as Re/Fr2 increases and increases as Ste increases. With the absence of gravity, i.e., as the Froude number approaches infinity, a maximum melting rate can be achieved. The increase in the melting rate proportional to the Stefan number also becomes more pronounced under the zero gravity condition. The trend of average and local Nusselt number of the melting packed bed under microgravity, as a function of Reynolds number and Prandtl number, is discussed and compared with the case of nonmelting packed bed.

Heat Transfer Characteristics in Melting of Granular Packed Bed Subject to Horizontal Forced Convection

2001 ◽  
Author(s):  
Y. L. Hao ◽  
Y.-X. Tao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Packed Bed ◽  
Melting Rate ◽  
Water Velocity ◽  
Flowing Water ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
Ice Particles

Abstract A series of experiments are conducted to investigate the characteristics of melting and heat transfer of a packed bed consisting of melting ice particles subject to horizontal forced convection. The packing pattern of ice particles in horizontally flowing water is recorded using a digital video camcorder and a digital camera at the water velocity of 0.01, 0.05, and 0.10 m/s, respectively, and supply water temperature of 4, 10, 20, and 30 °C, respectively. The mass of ice particles is measured at the desired time interval during the meting process. The volume of packed bed is obtained based on the digital images. The time variation of average melting rate per unit bed volume and average heat transfer coefficient is determined. Within the experimental conditions, the average melting rate per unit bed volume in the packed bed in horizontally flowing water increases during convective melting. The average heat transfer coefficient decreases during convective melting. The effects of water velocity and water temperature on the melting and heat transfer in the melting process are analyzed. The original experimental data and correlations for Nusselt number based on the present results are published.

Simulation of Impaction Between Liquid Droplet and Solid Particles Based on SPH Method

2014 ◽  
Author(s):  
Shuai Meng ◽  
Qian Wang ◽  
Rui Yang
Keyword(s):  
Surface Tension ◽  
Solid Particle ◽  
Liquid Droplet ◽  
Particle Interaction ◽  
Solid Particles ◽  
Seed Particle ◽  
Liquid Droplets ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Spray Granulation

The phenomenon of impaction between liquid droplets and solid particles is involved in many scientific problems and engineering applications, such as impaction between sprayed droplet and solid particles in limestone injection desulfurization system and the collision between a droplet of the liquid to be granulated and a seed particle in fluidized bed spray granulation process. There are a lot of factors affected this phenomenon: droplet and particle size, momentum of both liquid droplet and solid particles, materials, surface conditions of the solid particles and so on. However the experimental or numerical researches have been done mostly pay attention to Specific application or process, so the impaction phenomenon has not been through studied, for example how different factors affected the impaction process with its effect on different applications. This paper focuses on the basic issue of interaction between droplet and solid particles. Three main factors were considered: ratio of diameter between the droplet and solid particle, relative velocity and the surface tension (including the contact angle between droplet and solid particle). All the study is based on simulation using SPH (smoothed particle hydrodynamics) method, and the surface tension is simulated by particle-particle interaction.

Pool Boiling Characteristics of Metallic Nanofluids

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
K. Hari Krishna ◽  
Harish Ganapathy ◽  
G. Sateesh ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boiling Heat Transfer ◽  
Volume Fraction ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Solid Particles ◽  
Heater Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well.

NMR Technique for Multiphase Fluid Study Involving Melting Phenomena

1999 ◽  
Author(s):  
Q. Ni ◽  
J. D. King ◽  
Y.-X. Tao
Keyword(s):  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Melting Rate ◽  
Analysis Method ◽  
Image Analysis Method ◽  
Equilibrium Conditions ◽  
Multiphase Fluid ◽  
Physical Phenomena ◽  
Non Destructive ◽  
Good Agreement

Abstract Nuclear magnetic resonance (NMR) sensors are used to determine the time variation of solid mass for a packed ice bed in an experiment of convective melting under non-thermal equilibrium conditions. The paper describes the basic experimental technique for NAFTM apparatus and feasibility for determining the solid volume fraction and ultimately the melting rate. The NMR technique provides an effective, non-destructive method for multiphase fluid study where phase change is one of the important physical phenomena. The results show a good agreement of data obtained by the NMR method with those from image-analysis method.

Combined Marangoni and buoyancy convection in a porous annular cavity filled with Ag-MgO/water hybrid nanofluid

2021 ◽  
Vol 17 ◽  
Author(s):  
B. Kanimozhi ◽  
M. Muthtamilselvan ◽  
Qasem M. Al-Mdallal ◽  
Bahaaeldin Abdalla
Keyword(s):  
Magnetic Field ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Axial Magnetic Field ◽  
Vertical Wall ◽  
Navier Stokes ◽  
Hybrid Nanofluid ◽  
Radial Magnetic Field ◽  
Navier Stokes Equations ◽  
Buoyancy Convection

Background: This article numerically examines the effect of buoyancy and Marangoni convection in a porous enclosure formed by two concentric cylinders filled with Ag-MgO water hybrid nanofluid. The inner wall of the cavity is maintained at a hot temperature and the outer vertical wall is considered to be cold. The adiabatic condition is assumed for other two boundaries. The effect of magnetic field is considered in radial and axial directions. The Brinkman-extended Darcy model has been adopted in the governing equations. Methods: The finite difference scheme is employed to work out the governing Navier-Stokes equations. The numerically simulated outputs are deliberated in terms of isotherms, streamlines, velocityand average Nusselt number profiles for numerous governing parameters. Results: Except for a greater magnitude of axial magnetic field, our results suggest that the rate of thermal transport accelerates as the nanoparticle volume fraction grows.Also, it is observed that there is an escalation in the profile of average Nusselt numberwith an enhancement in Marangoni number. Conclusion: Furthermore, the suppression of heat and fluid flow in the tall annulus is mainly due to the radial magnetic field whereas in shallow annulus, the axial magnetic field profoundly affects the flow field and thermal transfer.

Comparative Assessment of Turbulence Models for Prediction of Flow-Induced Corrosion Damages

2011 ◽  
Author(s):  
Kaushik Das ◽  
Debashis Basu ◽  
Todd Mintz
Keyword(s):  
Corrosion Rate ◽  
Cross Sections ◽  
Volume Fraction ◽  
Solid Phase ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Continuous Phase ◽  
Comparative Assessment ◽  
Solid Particles ◽  
Protective Film

The present study makes a comparative assessment of different turbulence models in simulating the flow-assisted corrosion (FAC) process for pipes with noncircular cross sections and bends, features regularly encountered in heat exchangers and other pipeline networks. The case study investigates material damage due to corrosion caused by dissolved oxygen (O2) in a stainless steel pipe carrying an aqueous solution. A discrete solid phase is also present in the solution, but the transport of the solid particles is not explicitly modeled. It is assumed that the volume fraction of the solid phase is low, so it does not affect the continuous phase. Traditional two-equation models are compared, such as isotropic eddy viscosity, standard k-ε and k-ω models, shear stress transport (SST) k-ω models, and the anisotropic Reynolds Stress Model (RSM). Computed axial and radial velocities, and turbulent kinetic energy profiles predicted by the turbulence models are compared with available experimental data. Results show that all the turbulence models provide comparable results, though the RSM model provided better predictions in certain locations. The convective and diffusive motion of dissolved O2 is calculated by solving the species transport equations. The study assumes that solid particle impingement on the pipe wall will completely remove the protective film formed by corrosion products. It is also assumed that the rate of corrosion is controlled by diffusion of O2 through the mass transfer boundary layer. Based on these assumptions, corrosion rate is calculated at the internal pipe walls. Results indicate that the predicted O2 corrosion rate along the walls varies for different turbulence models but show the same general trend and pattern.

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