About a correlating equation for predicting pressure drops through packed beds of spheres in a large range of Reynolds numbers

2007 ◽  
Vol 46 (4) ◽  
pp. 329-333 ◽  
Author(s):  
A. Montillet ◽  
E. Akkari ◽  
J. Comiti
Keyword(s):  
Large Range ◽  
Reynolds Numbers ◽  
Packed Beds ◽  
Pressure Drops ◽  
Correlating Equation

URANS Calculations for Smooth Circular Cylinder Flow in a Wide Range of Reynolds Numbers: Solution Verification and Validation

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Guilherme F. Rosetti ◽  
Guilherme Vaz ◽  
André L. C. Fujarra
Keyword(s):  
Large Range ◽  
Reynolds Numbers ◽  
Uncertainty Estimation ◽  
Wide Range ◽  
Modeling Errors ◽  
Solution Verification ◽  
Sst Turbulence Model ◽  
Validation Procedure ◽  
Cylinder Flow ◽  
Fixed Cylinder

The flow around circular smooth fixed cylinder in a large range of Reynolds numbers is considered in this paper. In order to investigate this canonical case, we perform CFD calculations and apply verification & validation (V&V) procedures to draw conclusions regarding numerical error and, afterwards, assess the modeling errors and capabilities of this (U)RANS method to solve the problem. Eight Reynolds numbers between Re = 10 and Re=5×105 will be presented with, at least, four geometrically similar grids and five discretization in time for each case (when unsteady), together with strict control of iterative and round-off errors, allowing a consistent verification analysis with uncertainty estimation. Two-dimensional RANS, steady or unsteady, laminar or turbulent calculations are performed. The original 1994 k-ω SST turbulence model by Menter is used to model turbulence. The validation procedure is performed by comparing the numerical results with an extensive set of experimental results compiled from the literature.

Pressure Drops and Dryout Heat Fluxes of Packed Beds with Cylindrical Particles

2019 ◽  
Vol 41 (12) ◽  
pp. 1014-1025
Author(s):  
Liangxing Li ◽  
Shuangbao Zhang ◽  
Kailin Wang ◽  
Huasheng Wang
Keyword(s):  
Heat Fluxes ◽  
Packed Beds ◽  
Pressure Drops ◽  
Cylindrical Particles

Experimental Investigation of Pressure Drop Characteristics of Viscous Fluid Flow Through Small Diameter Orifices

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Lalit Kumar Bohra ◽  
Leo M. Mincks ◽  
Srinivas Garimella
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Viscous Fluid ◽  
Euler Number ◽  
Small Diameter ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Operating Conditions ◽  
Turbulent Regime ◽  
Pressure Drops

Abstract An experimental study on the flow of a highly viscous fluid through small diameter orifices was conducted. Pressure drops were measured for each of nine orifices, including orifices of nominal diameter 0.5, 1, and 3 mm and three different orifice thicknesses, over wide ranges of flow rates and temperatures. The fluid under consideration exhibits steep dependence of the properties (changes of several orders of magnitude) as a function of temperature and pressure and is also non-Newtonian at the lower temperatures. At small values of Reynolds number, an increase in aspect ratio (length/diameter ratio of the orifice) causes an increase in Euler number. It was also found that at extremely low Reynolds numbers, the Euler number was very strongly influenced by the Reynolds number, while the dependence becomes weaker as the Reynolds number increases toward the turbulent regime, and the Euler number tends to assume a constant value determined by the aspect ratio and the diameter ratio. A two-region (based on Reynolds number) model was developed to predict Euler number as a function of diameter ratio, aspect ratio, viscosity ratio, and generalized Reynolds number. It is shown that for such a highly viscous fluid with some non-Newtonian behavior, accounting for the shear rate through the generalized Reynolds number results in a considerable improvement in the predictive capabilities of the model. Over the laminar, transition, and turbulent regions, the model predicts 86% of the data within ±25% for the geometry and operating conditions investigated in this study.

Numerical Investigation on the Effect of Transversal Septa on Forced Convection in Circular Tubes

2009 ◽  
Author(s):  
O. Manca ◽  
S. Nardini ◽  
D. Ricci
Keyword(s):  
Heat Transfer ◽  
Numerical Investigation ◽  
Forced Convection ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Circular Tubes ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer

Conventional sources of energy have been depleting at an alarming rate, which makes future sustainable development of energy use very difficult. Thus, heat transfer enhancement technology plays an important role and it has been widely applied to many applications as in refrigeration, automotive, process industry, solar energy heater, etc. Convective heat transfer can be enhanced passively by changing flow geometry, boundary conditions or by increasing thermal conductivity of the fluid. Another possibility for increasing heat transfer with gas is to employ extended surfaces. In this paper a numerical investigation is carried out on forced convection in circular tubes with septa heated by constant fluxes and characterized by different shapes. When gas flows in a tube, septa with one or more openings can be used as fins. Furthermore, when the openings are arranged to give a spiral motion around the cylinder axis wall-fluid contact area increases. As a consequence the presence of the septa may significantly augment pressure drops. The fluid is air and properties are function of temperature. Septa of the same material of the tube are introduced and several shapes and arrangements are analyzed as well as different Reynolds numbers, baffle spacings and heat fluxes applied on the external surface. The investigation is accomplished by means of the commercial code Fluent. A k-e turbulence model is used with enhanced wall treatment options. Results are presented in terms of temperature and velocity fields, local and average heat transfer coefficients, friction factors and pressure drops for different values of heat flux, Reynolds numbers and baffle spacings. The aim of this study is to find the shape and arrangement of septa such to give high heat transfer coefficients and low pressure drops.

scholarly journals Heat Transfer Enhancement by Detached S-Ribs for Twin-Pass Parallelogram Channel

Inventions ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 50 ◽  
Author(s):  
Shyy Chang ◽  
Wei-Ling Cai ◽  
Ruei-Jhe Wu
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Reynolds Numbers ◽  
Test Channel ◽  
Pressure Drops ◽  
Transfer Rates ◽  
Performance Factors ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Measured Pressure

Detached S-ribs are proposed to arrange in the stagger manner along two parallelogram straight channels interconnecting with a 180° smooth-walled sharp bend for heat transfer enhancements. The detailed Nusselt number distributions over the two opposite channel endwalls at Reynolds numbers of 5000, 7500, 10,000, 12,500, 15,000 and 20,000 are measured using the steady-state infrared thermography method. The accompanying Fanning friction factors are evaluated from the measured pressure drops across the entire test channel. Having acquired the averaged heat transfer properties and Fanning friction factors, the thermal performance factors are determined under the criterion of constant pumping power consumptions. With the regional accelerated flows between the detached S-ribs and the channel endwall, the considerable heat transfer elevations from the Dittus–Boelter correlation levels are achieved. The comparative thermal performances between the two similar twin-pass parallelogram channels with detached 90° and S-ribs disclose the higher regional heat transfer rates over the turning region and the larger Fanning frictions factors, leading to the lower thermal performance factors, for present test channel with the detached S-ribs. To assist design applications, two sets of empirical correlations evaluating the regionally averaged Nusselt numbers and Fanning friction factors are devised for present twin-pass parallelogram channel with the detached S-ribs.

Flow Measurements in an Atherosclerotic Curved, Tapered Femoral Artery Model of Man

1988 ◽  
Vol 110 (4) ◽  
pp. 310-319 ◽  
Author(s):  
L. H. Back ◽  
E. Y. Kwack ◽  
D. W. Crawford
Keyword(s):  
Flow Simulation ◽  
Reynolds Numbers ◽  
Flow Measurements ◽  
Pressure Drops ◽  
Physiological Conditions ◽  
Curvature Effects ◽  
Smooth Model ◽  
Lesion Localization ◽  
Flow Resistances

Flow visualization and pressure measurements were made for physiological conditions in a model derived from a femoral angiorgram of a patient with lesion localization on the inner curvature wall and with vessel taper. Effects of curvature and taper were evaluated separately in other curved, tapered, smooth and straight, tapered, smooth models. Double helical secondary flow patterns were modified by plaque on the inner wall, and flow separations were observed between plaques at higher flow rates and Reynolds numbers. Pressure drop data for the plaque simulation model were similar in trend with Reynolds number as for the smooth model, but flow resistances were 25 to 40 percent higher. Significant pressure drops were measured due to the mild taper which could be estimated from momentum considerations, and smaller increased pressure drops were found due to curvature effects at the higher Dean numbers. Flow resistances for in vivo pulsatile flow simulation were about 10 percent higher than for steady flow for the plaque model, whereas no differences were observed for the smooth model.

URANS Calculations for Smooth Circular Cylinder Flow in a Wide Range of Reynolds Numbers: Solution Verification and Validation

2012 ◽  
Author(s):  
Guilherme F. Rosetti ◽  
Guilherme Vaz ◽  
André L. C. Fujarra
Keyword(s):  
Large Range ◽  
Reynolds Numbers ◽  
Data Repository ◽  
Wide Range ◽  
Solution Verification ◽  
Sst Turbulence Model ◽  
Validation Procedure ◽  
Unsteady Rans ◽  
Cylinder Flow ◽  
Fixed Cylinder

The flow around circular smooth fixed cylinder in a large range of Reynolds numbers is considered in this paper. In order to investigate this canonical case, we perform CFD calculations and apply Verification & Validation (V&V) procedures to draw some conclusions regarding numerical error, and afterwards, assess the modelling errors and capabilities of URANS method to solve this problem. Eight Reynolds numbers between Re = 10 and Re = 5×105 will be presented with five geometrically similar grids and five time steps for each case, together with strict control of iterative and round-off errors, allowing a consistent verification analysis with uncertainty estimation. In these calculations, two-dimensional Unsteady RANS calculations were performed making use of the k–ω SST turbulence model. The Validation procedure is performed by comparing the numerical results with an extensive set of experimental results compiled from the literature and also made available in the VIV Data Repository website (http://oe.mit.edu/VIV/).

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.

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