Measurement of Film Thickness for Continuous Fluid Flow Within a Spinning Cone

2014 ◽  
Author(s):  
Digby D. Symons ◽  
Arnaud F. M. Bizard
Keyword(s):  
Fluid Flow ◽  
Angular Velocity ◽  
Film Thickness ◽  
Industrial Process ◽  
Vertical Axis ◽  
Experimental Results ◽  
Analytical Theory ◽  
Thin Film Flow ◽  
Thickness Measurements ◽  
Good Agreement

This paper reports experimental measurements of film thickness for continuous fluid flow within a spinning cone. The results are compared to analytical theory for thin film flow and found to be in good agreement. Spinning cones are used in various industrial process machines, including spinning cone distillation columns, centrifugal film evaporators and continuous centrifugal filters. In each case a fluid is fed continuously into the centre of a conical vessel which spins about a vertical axis with the cone apex pointing downwards. The fluid acquires the angular velocity of the cone and migrates up the internal wall of the cone under centrifugal force. Knowledge of the film thickness and flow velocity is often important in order to understand other performance parameters of the process such as evaporation or filtration rates. This paper aims to aid the design of new process machines by providing a mathematical model for film thickness that is validated by experimental results. Experiments have been conducted in which the angle of cone, angular velocity and input flow rate were all varied. Film thickness measurements were obtained via a novel optical method based on photographing the displacement of a projected grid on the surface of the flow within the cone. The method has the advantages of not disturbing the flow in any way and can provide thickness measurements over the whole cone depth. Measurements are also made insensitive to any transients by use of relatively long photographic exposures. Measurements are compared to analytical theory for axisymmetric, steady state, free-surface laminar flow of a Newtonian fluid in a spinning cone. The theory assumes the flow is thin but takes account of gravity. The theoretical model is found to be in good agreement with the experimental results.

Some Limitations in Applying Classical EHD Film Thickness Formulas to a High-Speed Bearing

1981 ◽  
Vol 103 (2) ◽  
pp. 295-301 ◽  
Author(s):  
J. J. Coy ◽  
E. V. Zaretsky
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Heating Effects ◽  
Theoretical Predictions ◽  
Traction Fluid ◽  
Shear Heating ◽  
Thickness Measurements ◽  
Inner Race ◽  
Maximum Stresses ◽  
Good Agreement

Elastohydrodynamic film thickness was measured for a 20-mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N (20, 100, and 175 lb). The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa (185,000, 303,000, and 356,000 psi). Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (a) synthetic paraffinic, (b) synthetic paraffinic with additives, (c) neopentylpolyol (tetra) ester meeting MIL-L-23699A specifications, and (d) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions using the formulae of Grubin, Archard and Cowking, Dowson and Higginson, and Hamrock and Dowson. There was good agreement with theory at low dimensionless speed, but the film was much smaller than theory predicts at higher speeds. This was due to kinematic starvation and inlet shear heating effects. Comparisons with Chiu’s theory on starvation and Cheng’s theory on inlet shear heating were made.

Temperature Distribution in a Turbulent Flow in the Heat Pollution Phenomena

2020 ◽  
Author(s):  
Victorita Radulescu
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Fluid Flow ◽  
Temperature Distribution ◽  
Prandtl Number ◽  
Experimental Results ◽  
Turbulent Heat ◽  
Fluid Viscosity ◽  
Solid Walls ◽  
Good Agreement

Abstract The thermal pollution, with major effects on the water quality degradation by any process involving the temperature transfer, represents nowadays a major concern for the entire scientific world. The turbulent heat and the mass transfer have an essential role in the processes of thermal pollution, mainly in problems associated with the transport of hot fluids in long heating pipes, thermal flows associated with big thermo-electric power plants, etc. In the last decades, the problems of the turbulent heat and mass transfer were analyzed for different dedicated applications. The present paper, in the first part, estimates the universal law of the velocity distribution near a solid wall, with a specific interpretation of the fluid viscosity, valid for all types of flows. Most of the scientific researches associate nowadays both the turbulent heat and the mass transfer with the Prandtl number. In the turbulent fluid flow near a solid and rigid surface, there are three flowing domains, laminar, transient, and fully turbulent, each one with its characteristics. In this paper, it is assumed that the friction effort at the wall remains valid at any distance from the wall, but with different forms associated with the dynamic viscosity. By using the superposition of the molecular and turbulent viscosity and by creating the interdependence between the molecular and turbulent transfer coefficients is estimated the mathematical model of the velocity profile for the fluid flow and temperature distribution. Three supplementary hypotheses have been assumed to estimate the dependence between the laminar and thermal sub-layer and the hydrodynamic sub-layer. The theoretical obtained distribution was compared with some experimental results from the literature and it was observed there is a good agreement between them; the differences are smaller than 3%. In the second part of the paper is determined the temperature field for a fluid flowing also in presence of the solid surfaces with different temperatures, associated not only with the Prandtl number but also with the fluid viscosity and its dependence with the temperature, correlated with the Grashoff number. In the next paragraph is used the concept of the laminar substrate with different thicknesses for the hydrodynamic flows with thermal transfer to the solid walls, and also the inverse transfer from the solid walls affecting the fluid flow and the mass transfer. The obtained mathematical model is correlated with the semi-empirical data from the literature. By numerical modeling, the obtained results were compared with the experimental measurements and it was determined the dependence between the Stanton number and the Prandtl number. The numerical results demonstrate a good agreement with the experimental results in a wide range of the Prandtl numbers from 0.5 to 3000. Finally, are mentioned some conclusions and references.

A Duct Optimization Study for a Vertical Axis Hydro-current Turbine Model

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
M. Alidadi ◽  
V. Klaptocz ◽  
G. W. Rawlings ◽  
Y. Nabavi ◽  
S. Calisal
Keyword(s):  
Power Output ◽  
Numerical Optimization ◽  
Vertical Axis ◽  
Experimental Results ◽  
Maximum Power Output ◽  
Numerical Predictions ◽  
Optimization Study ◽  
Current Turbine ◽  
Turbine Model ◽  
Good Agreement

A numerical optimization study is used to design a duct for a model of vertical axis hydro-current turbine. The effects of this duct on the power output and torque fluctuations of the turbine model are then examined numerically and experimentally. Relatively good agreement was obtained between the experimental results and numerical predictions especially at higher tip speed ratios. Experimental results show an 85% increase in the maximum power output when the turbine is placed inside the duct. The numerical and experimental torque curves for the turbine also show substantial reductions in the torque fluctuations as a result of ducting.

Measurement of Fluid Flow Thickness Within a Rotating Cone

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Digby D. Symons ◽  
Arnaud F. M. Bizard
Keyword(s):  
Fluid Flow ◽  
Free Surface ◽  
Steady State ◽  
Theoretical Model ◽  
Laminar Flow ◽  
Internal Surface ◽  
Vertical Axis ◽  
Experimental Measurements ◽  
Rotating Cone ◽  
Good Agreement

This paper reports experimental measurements of film thickness for continuous fluid flow on the internal surface of a cone rotating about a vertical axis. Measurements were obtained via an optical method based on photographing the displacement of a grid projected onto the surface of the flow within the cone. Results are compared to analytical theory for axisymmetric, steady state, free-surface laminar flow of a Newtonian fluid in a spinning cone. The theory assumes that the flow is thin but takes account of gravity. The theoretical model is found to be in good agreement with the experimental results.

Refined Models for Hydrodynamic Lubrication in Axisymmetric Stretch Forming

1994 ◽  
Vol 116 (1) ◽  
pp. 101-109 ◽  
Author(s):  
Tze-Chi Hsu ◽  
William R. D. Wilson
Keyword(s):  
Film Thickness ◽  
Hydrodynamic Lubrication ◽  
The Other ◽  
Lubricant Film Thickness ◽  
Stretch Forming ◽  
Sheet Bending ◽  
Membrane Stiffness ◽  
Thickness Measurements ◽  
Sheet Deformation ◽  
Good Agreement

Two mathematical models for axisymmetric stretch forming with a spherical punch are developed. The models combine a finite element representation of the sheet deformation with a hydrodynamic lubrication model. In one model the influence of sheet bending stiffness is taken into account while in the other only the membrane stiffness is considered. Comparison of the predictions of the models with the film thickness measurements of Hector and Wilson indicates that the inclusion of elastic effects is important in predicting lubricant film thickness. The results of the bending model are in particularly good agreement with the experimental data. A useful analytical method for predicting the film thickness at the center of the conjunction at the onset of yield is also developed.

Numerical and Experimental Investigation of Thermodynamic Behavior of Positive Displacement Compressor

2010 ◽  
Author(s):  
Morad Paknezhad ◽  
Tooraj Yousefi ◽  
Sajjad Sadeghi ◽  
Mehran Ahmadi
Keyword(s):  
Experimental Investigation ◽  
Numerical Model ◽  
Angular Velocity ◽  
Thermodynamic Analysis ◽  
Experimental Results ◽  
Thermodynamic Behavior ◽  
Outlet Pressure ◽  
Positive Displacement ◽  
Fluent Software ◽  
Good Agreement

A numerical model, based on dynamic mesh, has been developed by FLUENT software, to simulate behavior of a positive displacement compressor. Only first compression stage of compressor was modeled. Modeling was done, by dividing the domain to three areas with different type meshes. Some relations were presented for volumetric, mechanical, isothermal, and overall isothermal performance, and thermodynamic analysis has been performed in term of these relations. Effects of outlet pressure and crankshaft’s angular velocity have been investigated on work, polytropic factor of compression, and efficiency. Numerical and experimental results have been compared, and a good agreement was seen between them.

scholarly journals Rotary Wheel Atomizer Study Using Computational Fluid Dynamics and Full-Scale Testing

2018 ◽  
Author(s):  
Frank Vinther ◽  
Tórstein Vincent Joensen ◽  
Maximilian Kuhnhenn ◽  
Mads Reck ◽  
Cameron Tropea
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Flow ◽  
Drop Size ◽  
Volume Of Fluid ◽  
Experimental Results ◽  
Atomization Process ◽  
Internal Fluid ◽  
Internal Fluid Flow ◽  
Good Agreement

This study models the internal fluid flow from the center to the edge of a rotary atomizer wheel, the flow out of the atomizer, including the film, rivulet and ligament formation, as well as the subsequent atomization process associated with the atomizer outflow using computational fluid dynamics with a volume of fluid approach. The model shows how fluid exits through the overflow and not through the bushing at high inlet fluxes and can reproduce experimental results of power consumption. Furthermore, the drop-size distribution at a given distance from the bushing exit is in good agreement with experimental results. Keywords: Spray drying; Rotary Atomizer; CFD; Droplet size; Volume of Fluid.

Magnetorheological Fluid Flow in Microchannels

2010 ◽  
Vol 77 (4) ◽  
Author(s):  
Joseph Whiteley ◽  
Faramarz Gordaninejad ◽  
Xiaojie Wang
Keyword(s):  
Magnetic Field ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Dynamic Pressure ◽  
Magnetorheological Fluid ◽  
Fused Silica ◽  
Experimental Results ◽  
Microchannel Flow ◽  
Roughness Effects ◽  
Good Agreement

This study presents experimental results on the flow of magnetorheological grease (MRG) through microchannels. MR materials flowing through microchannels create microvalves. The flow is controlled by injecting the MRG through microchannels with controlled adjustable rates. To study the effect of different channel diameters and surface roughnesses, microchannels made of stainless steel, PEEK, and fused silica materials with nominal internal diameters ranging from 1 mm to 0.075 mm (75 μm) are tested. A magnetic field is applied perpendicular to the microchannel flow and is controlled by an input electric current. The pressure drop of the flow is measured across the length of the microchannels. The dynamic pressure drop range and surface roughness effects are also discussed. The Herschel–Bulkley model for non-Newtonian fluid flow is employed to the experimental results with good agreement. The results show a significant pressure drop for different magnetic field strengths.

An Investigation of Self-Acting Foil Bearings

1965 ◽  
Vol 87 (4) ◽  
pp. 837-846 ◽  
Author(s):  
J. T. S. Ma
Keyword(s):  
Film Thickness ◽  
Experimental Results ◽  
Capacitive Sensors ◽  
Exit Region ◽  
Empirical Expressions ◽  
Foil Bearings ◽  
Minimum Film Thickness ◽  
Theoretical Predictions ◽  
Predicted Values ◽  
Thickness Measurements

Experimental results on the interior and the exit region film-thickness measurements of self-acting foil bearings are presented and discussed. These measurements were made with capacitive sensors and conductive foils. The measured and predicted values agree very well within the range of nondimensional parameters, h0/R, from 10−4 to 10−3 and, T/μU, from 105 to 106. The agreement deviates for values beyond these ranges. Empirical expressions for predicting the constant and minimum film thickness applicable beyond these ranges are also presented. They are valid within the range of h0/R from 5(10)−5 to 10−2 and T/μU from 104 to 105. Growing sinusoidal film thickness in the exit region was also observed, measured, and checked with theoretical predictions.

Enhanced Photoyield with Decreasing Film Thickness on Metal-Semiconductor Structures

1996 ◽  
Vol 448 ◽  
Author(s):  
V. Hoffmann ◽  
M. Brauer ◽  
M. Schmidt
Keyword(s):  
Quantum Yield ◽  
Film Thickness ◽  
Layer Thickness ◽  
Experimental Results ◽  
Experimental Result ◽  
Model Calculations ◽  
Hot Carrier ◽  
Semiconductor Structures ◽  
Carrier Scattering ◽  
Good Agreement

AbstractExperimental results of the internal quantum yield Yi associated with the internal photoemission on Au/n-Si structures are presented. The samples were prepared on Si(100) and Si(111) substrates with photoemitter layer thicknesses ranging from 5 nm to 50 nm. The Yi was measured at temperatures between 165 K and 300 K with the photoexciting energy varying from 0.72 eV to 1.07 eV. It was found that the Yi increases with decreasing Au layer thickness with a strong enhancement (40 times) in regard to the conventional Fowler theory. This experimental result is in good agreement with model calculations taking account of hot carrier scattering in the photoemitter layer. Barrier energies are larger than deduced from the Fowler plot.

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