scholarly journals Wall-to-liquid mass transfer in fluidized beds and vertical transport of inert particles

2007 ◽  
Vol 72 (11) ◽  
pp. 1103-1113 ◽  
Author(s):  
Nevenka Boskovic-Vragolovic ◽  
Radmila Garic-Grulovic ◽  
Zeljko Grbavcic
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Transfer Factor ◽  
Fluidized Beds ◽  
Liquid Velocity ◽  
Spherical Particles ◽  
Hydraulic Transport ◽  
Transfer Coefficients ◽  
Flowing Fluid ◽  
Inert Particles

Mass transfer coefficients in single phase flow, liquid fluidized beds and vertical hydraulic transport of spherical inert particles were studied experimentally using 40 mm and 25.4 mm diameter columns. The mass transfer data were obtained by studying the transfer of benzoic acid from a tube segment to water using the dissolution method. In all runs, the mass transfer rates were determined in the presence of spherical glass particles 1.2, 1.94 and 2.98 mm in diameter. The influence of different parameters, such as liquid velocity, particles size and voids on mass transfer in fluidized beds and hydraulic transport are presented. The data for mass transfer in all the investigated systems are shown using the Sherwood number (Sh) and mass transfer factor - Colburn factor (jD) - as a function of Reynolds number (Re) for the particles and for the column. The data for mass transfer in particulate fluidized beds and for vertical hydraulic transport of spherical particles were correlated by treating the flowing fluid-particle mixture as a pseudo fluid by introducing a modified mixture Reynolds number (Rem). A new correlation for the mass transfer factor in fluidized beds and in vertical hydraulic transport is proposed.

scholarly journals Mass transfer from the wall of a column to the fluid in a fluidized bed of inert spherical particles

2004 ◽  
Vol 58 (2) ◽  
pp. 69-72
Author(s):  
Danica Brzic ◽  
Nevenka Boskovic-Vragolovic ◽  
Zeljko Grbavcic
Keyword(s):  
Mass Transfer ◽  
Reynolds Number ◽  
Benzoic Acid ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Single Phase ◽  
Spherical Particles ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Transfer Coefficients

Mass transfer in fluidized beds is an important operation for separation processes. Two effects can be achieved by using fluidized beds in mass transfer processes increasing interface area and relative movement between the phases. These effects are both desirable because they lead to greater process rates. This paper presents an experimental investigation regarding mass transfer from the wall of a column to the fluid in a fluidized bed of inert spherical particles. The experiments were conducted in column 40 mm in diameter with spherical particles 0,8-3 mm in diameter and water as one fluidizing fluid. The method of dissolution of benzoic acid was used to provide very low mass flux. The average wall-to-fluid mass transfer coefficients were determined for two systems: single-phase fluid flow and a fluidized bed of inert particles The measurements encompassed a Reynolds number range from 100-4000 for single-phase flow and 600-4000 in fluidized beds. The mass transfer coefficients for both systems were calculated from weight loss of benzoic acid. The effects of superficial liquid velocity and particle diameter on the mass transfer coefficient were investigated. It was found that mass transfer was more intensive in the fluidized bed in comparison with single phase flow. The best conditions for mass transfer were reached at a minimum fluidization velocity, when the mass transfer coefficient had the greatest value. The experimental data were correlated in the form: jd = f(Re), where jd is the dimensionless mass transfer factor and Re the Reynolds number.

scholarly journals Mass transfer between a fluid and an immersed object in liquid-solid packed and fluidized beds

2005 ◽  
Vol 70 (11) ◽  
pp. 1373-1379 ◽  
Author(s):  
Nevenka Boskovic-Vragolovic ◽  
Danica Brzic ◽  
Zeljko Grbavcic
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Benzoic Acid ◽  
Fluidized Beds ◽  
Liquid Velocity ◽  
Spherical Particles ◽  
Flowing Water ◽  
Transfer Rates ◽  
Transfer Data ◽  
Dissolution Method

The mass transfer coefficient between fluid and an immersed sphere in liquid packed and fluidized beds of inert spherical particles have been studied experimentally using a column 40 mm in diameter. The mass transfer data were obtained by studying the transfer of benzoic acid from the immersed sphere to flowing water using the dissolution method. In all runs, the mass transfer rates were determined in the presence of inert glass particles 0.50-2.98 mm in diameter. The influence of different parameters, such as: liquid velocity, particles size and bed void age, on the mass transfer in packed and fluidized beds is presented. The obtained experimental data for mass transfer in the packed and particulate fluidized bed were correlated by a single correlation, thus confirming the similarity between the two systems.

Modeling mass transfer and substrate utilization in the boundary layer of biofilm systems

1998 ◽  
Vol 37 (4-5) ◽  
pp. 139-147 ◽  
Author(s):  
Harald Horn ◽  
Dietmar C. Hempel
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Theory ◽  
Substrate Utilization ◽  
The Other ◽  
Concentration Profiles ◽  
Hydrodynamic Conditions ◽  
Time Axis ◽  
Transfer Coefficients

The use of microelectrodes in biofilm research allows a better understanding of intrinsic biofilm processes. Little is known about mass transfer and substrate utilization in the boundary layer of biofilm systems. One possible description of mass transfer can be obtained by mass transfer coefficients, both on the basis of the stagnant film theory or with the Sherwood number. This approach is rather formal and not quite correct when the heterogeneity of the biofilm surface structure is taken into account. It could be shown that substrate loading is a major factor in the description of the development of the density. On the other hand, the time axis is an important factor which has to be considered when concentration profiles in biofilm systems are discussed. Finally, hydrodynamic conditions become important for the development of the biofilm surface when the Reynolds number increases above the range of 3000-4000.

scholarly journals Highly Resolved Distribution of Heat Transfer for Turbine Leading Edge Film Cooling Including Reynolds Number and Blowing Rate Effects

1998 ◽  
Author(s):  
K. Jung ◽  
D. K. Hennecke
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Heat Mass Transfer ◽  
Leading Edge ◽  
Transfer Coefficients ◽  
Complex Flow ◽  
Long Distance ◽  
Naphthalene Sublimation Technique

The effect of leading edge film cooling on heat transfer was experimentally investigated using the naphthalene sublimation technique. The experiments were performed on a symmetrical model of the leading edge suction side region of a high pressure turbine blade with one row of film cooling holes on each side. Two different lateral inclinations of the injection holes were studied: 0° and 45°. In order to build a data base for the validation and improvement of numerical computations, highly resolved distributions of the heat/mass transfer coefficients were measured. Reynolds numbers (based on hole diameter) were varied from 4000 to 8000 and blowing rate from 0.0 to 1.5. For better interpretation, the results were compared with injection-flow visualizations. Increasing the blowing rate causes more interaction between the jets and the mainstream, which creates higher jet turbulence at the exit of the holes resulting in a higher relative heat transfer. This increase remains constant over quite a long distance dependent on the Reynolds number. Increasing the Reynolds number keeps the jets closer to the wall resulting in higher relative heat transfer. The highly resolved heat/mass transfer distribution shows the influence of the complex flow field in the near hole region on the heat transfer values along the surface.

Volatilization of Packed Beds of Oil Sand Particles

1987 ◽  
Vol 109 (2) ◽  
pp. 71-74
Author(s):  
M. A. Abdrabboh ◽  
G. A. Karim
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Reynolds Numbers ◽  
Spherical Particles ◽  
Packed Beds ◽  
Oil Sand ◽  
Transfer Coefficients ◽  
Simple Analytical Expression ◽  
Low Reynolds Numbers ◽  
Fixed Beds

Based on a quasi-steady system, published experimental data on mass transfer in packed beds of spherical particles at relatively low Reynolds numbers, were employed to estimate the convective mass-transfer coefficients in the bed in terms of the corresponding values for single particles. The average transient fluid concentrations within the bed of particles were also obtained in terms of the corresponding single-particle concentrations using the lumped-heat-capacity system. Thus, experimental data published on volatilization of single oil sand spheres could then be extended to estimate the rates of volatilization of packed beds of oil sand spheres. A simple analytical expression could, therefore, be derived for estimating the transient mass loss from fixed beds of oil sand spheres in terms of the parameters involved.

Dissolution of a Carbon Dioxide Bubble in a Vertical Pipe

2007 ◽  
Author(s):  
Satoru Abe ◽  
Hideaki Okawa ◽  
Shigeo Hosokawa ◽  
Akio Tomiyama
Keyword(s):  
Carbon Dioxide ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Relative Velocity ◽  
Bubble Diameter ◽  
Bulk Liquid ◽  
Vertical Pipe ◽  
Transfer Coefficients ◽  
Mass Transfer Coefficients ◽  
Millipore Water

Dissolution of single carbon dioxide (CO2) bubbles in a vertical pipe of 25 mm in diameter are measured to examine the effects of the ratio λ of sphere–volume equivalent bubble diameter d to pipe diameter D, liquid Reynolds number ReL and surfactants on mass transfer. The bubble diameter d and Reynolds number ReL are varied from 5.0 to 26 mm (λ = 0.20 − 1.0) and from 0 to 3100, respectively. Millipore water, tap water and water contaminated with Triton X–100 are used for the liquid phase. Mass transfer coefficients kL are evaluated from changes in d. The kL decreases with increasing λ for bubbles in stagnant millipore water because of the decrease in bubble rising velocity due to the wall effect. Measured Sherwood numbers Sh do not depend on ReL because a turbulent fluctuation velocity in bulk liquid flow is much smaller than a relative velocity between a bubble and liquid. The mass transfer correlation for a bubble in a stagnant liquid proposed by Johnson et al. is applicable to a bubble in pipe flow, provided that a correct relative velocity between a bubble and liquid is substituted in the correlation. Due to the retardation of capillary wave, mass transfer coefficients for bubbles in contaminated water becomes smaller than those in millipore and tap waters.

Regional Heat Transfer and Pressure Drop in Two-Pass and Three-Pass Flow Passages With 180-Degree Sharp Turns

1989 ◽  
Author(s):  
M. K. Chyu
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Secondary Flows ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Pressure Loss Coefficient ◽  
Single Turn

The heat transfer distributions for flow passing through a two-pass (one-turn) and a three-pass (two-turn) passages with 180-degree sharp turns are studied by using the analogous naphthalene mass transfer technique. Both passages have square cross-section and length-to-height ratio of 8. The passage surface, including top wall, side walls and partition walls, is divided into 26 segments for the two-pass passage and 40 segments for the three-pass passage. Mass transfer results are presented for each segment along with regional and overall averages. The very non-uniform mass transfer coefficients measured around a sharp 180-degree turn exhibit the effects of flow separation, reattachment and impingement, in addition to secondary flows. Results of the three-pass passage indicate that heat transfer characteristics around the second turn is virtually the same as that around the first turn. This may imply that, in a multiple-pass passage, heat transfer at the first turn has already reached the thermally developed (periodic) condition. Over the entire two-pass passage, the heat transfer enhancement induced by the single-turn is about 45% to 65% of the fully developed values in a straight channel. Such a heat transfer enhancement decreases with an increase in Reynolds number. In addition, overall heat transfer of the three-pass passage is approximately 15% higher than that of the two-pass one. This 15% increase appears to be Reynolds number independent. The pressure loss induced by the sharp turns is found to be very significant. Within the present testing range, the pressure loss coefficient for both passages varies significantly with the Reynolds number.

scholarly journals A mass transfer heterogeneous in systems by the adsorption method

2009 ◽  
Vol 15 (1) ◽  
pp. 25-28 ◽  
Author(s):  
Nevenka Boskovic-Vragolovic ◽  
Radmila Garic-Grulovic ◽  
Zeljko Grbavcic ◽  
Rada Pjanovic
Keyword(s):  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Fluidized Beds ◽  
Transfer Coefficients ◽  
Adsorption Method ◽  
Average Mass ◽  
Flow Past ◽  
Column Wall ◽  
Single Sphere

A mass transfer coefficient between: A liquid and single sphere and a liquid And a column wall in packed and fluidized beds of a spherical inert Particle have been studied experimentally using the adsorption method. The experiments were conducted in a column 40 mm in diameter for packed and fluidized beds, and in a two-dimensional column 140 mm?10 mm for the flow past single sphere. In all runs, the mass transfer rates were determined in the presence of spherical glass particles, 3 mm in diameter, for packed and fluidized beds. The mass transfer data were obtained by studying transfer for flow past single sphere, 20 mm in diameter. This paper discusses the possibilities of application of the adsorption method for fluid flow visualization. Local and average mass transfer coefficients were determined from the color intensity of the surface of the foils of silica gel. Correlations, Sh = f(Re) and jD = f(Re), were derived using the mass transfer coefficient data.

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