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International Review of Mechanical Engineering - Papers
Capillary
Adhesive Forces in Woven Textile Fabrics
by Ben Amar Sami,
Ben Marzoug Imed, Halimi Mohamed-Taher, Maatoug Sameh
Vol. 5 n. 1, pp. 1-6
Abstract - One of the basic principles of wetting and diffusive phenomenon in woven textile fabrics is that the media geometrical should be understood by studying the capillary adhesive force. In this work, a model based on Laplace formulation was proposed; it uses the geometrical parameters recovered by image processing in order to determine the capillary diffusive drop in woven textile fabric and the wetting force between meniscus and solid. Measurements of capillary adhesive force in solid and woven textile fabric are taken using a microbalance with high degree. Critical initial drop volume for woven textile fabric was determined. Theoretical and experimental comparison of results permitted us to propose a model for capillary adhesive force between meniscus and woven textile fabric according to the initial drop volume and woven technical parameters. model coefficients are estimated using double last square method. The results shows the capillary adhesive force refers to the wetting and diffusive force. Wetting force depends on the specific surface, form and cover factors of woven fabric. Diffusive force depends on the solid fraction, thickness and specific surface of woven fabric.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Drop Spreading; Meniscus; Capillary Adhesive; Wetting; Textile Porous Media.
Evaluation
of Notch Stress Intensity Factor in Pipe with External Oriented Defect
by B. El Hadim, H.
El Minor, M. El Hilali
Vol. 5 n. 1, pp. 7-11
Abstract - The
problem of pipelines subjected to external defects caused by foreign
scratch objects or gouges is treated. The external oriented defect
represented by a blunt notch in the pipe under internal pressure has
been considered and an elastic-plastic finite element method is applied
to this survey.
The notch stress intensity factor is evaluated for various notch radii
and various notch defect orientations. The results exhibit that the
notch stress intensity factor increases with the notch radius and
decreases when the notch orientation moves away of the longitudinal
direction parallel to the pipe axis.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: External Oriented Defect, Pipe, Notch Stress Intensity Factor.
Agitator
Shaft’s Fatigue Design Verification using Finite Element Method
by Makarand R. Gurav,
Barun Chakrabarti, Vilas R. Kalamkar
Vol. 5 n. 1, pp. 12-20
Abstract -
This paper discusses an approach for performing fatigue analysis of an
agitator shaft of a large mixing vessel used in process plant. The
analysis is carried out to estimate fatigue life under high-cycle
fatigue criterion. The shaft is subjected to vibration due to
multi-axial forces resulting from bending and torsional loading imposed
by the mixing operation. The approach followed in this work involves:
(1) Measurement of actual vibration of shaft during test (2) Stress
analysis of agitator shaft for unit displacement using FE method (3)
Estimation of stress amplitude variation using vibration data obtained
from the test (4) Estimation of stress cycle by Rain-flow counting
method and (5) Fatigue analysis and life estimation based on cumulative
damage rule. The paper also discusses an alternative approach for
estimating stress amplitude variation through dynamic stress analysis.
The fatigue life estimation results obtained from both approaches are
then compared.
The paper concludes that the approach followed in this work is effective
and can be adopted as a generic methodology for design and analysis of
agitator systems.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Agitator System, Fatigue Life, Stress Analysis, Vibration Fatigue, Rain Flow Counting Method.
The
Metal Flow Evaluation of Billet Extruded With RBD Palm Stearin
by S. Syahrullail,
C.S.N. Azwadi, Tiong Chiong Ing
Vol. 5 n. 1, pp. 21-27
Abstract - Today, the development of bio-lubricants, which are biodegradable, has become one of the most urgent research projects all over the world. In Malaysia, palm oil has shown promise as a bio-lubricant. Palm oil is eco-friendly and has a high production rate, which could fulfill the demand for a vegetable base lubricating oil. In this research, the possibility of RBD palm stearin to be used as a cold work forward extrusion was investigated with plane strain extrusion experiments. Billet material used in the present experiment was Aluminum Alloy AA5083. The metal flow of billet in the deformation area was analyzed with the visioplasticity method. From the results, we confirmed that the lubrication performance of RBD palm stearin is as effective as paraffinic mineral oil in its ability to reduce frictional constraint in a cold work extrusion.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Extrusion, Palm Olein, Paraffinic Mineral Oil, Surface Roughness, Visioplasticity.
Finite-Element
Analysis of Gas Tungsten Arc Plasma with Anode (SUS304) Melting
by Ali Moarrefzadeh
Vol. 5 n. 1, pp. 28-33
Abstract - In this paper, the plasma arc welding is studied and SUS304 temperature field is gained in this process. In order to clarify the formative mechanism of penetration geometry of anode in an arc melting process by using gas tungsten arc plasma, a numerical model is useful to understand quantitative values of the balances of mass, energy and force in the melting phenomena. In the present paper, the whole region of arc melting process, namely tungsten cathode, arc plasma and anode is treated in a unified numerical model to take into account the close interaction between the arc plasma and the liquid anode. Calculations are made for the time-dependent development of the penetration of the anode for the arc plasma in different gaseous atmosphere at a current of 150 A. The anode penetration geometry as a function of time is predicted in the arc melting process in argon and also helium.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Finite-Element, Arc Plasma, Anode, Melting, Welding, Shielding Gas; Argon, Helium.
Gas-Liquid
U-Tube Reactor for Drinking Water Treatment by Ozone Disinfection and
Oxidation
by Ashraf S. Ismail
Vol. 5 n. 1, pp. 34-51
Abstract - A
mathematical modeling of the gas-liquid flow in U-tube reactor, used for
drinking water disinfection by ozone, has been described. The simplified
Eulerian two-fluid model along with homogenous two-phase model has been
utilized to calculate flow field, gas holdup, and energy dissipation
rate. Then, the population balance model including breakage and
coalescence of bubbles due to turbulent eddies, has been solved
numerically through iteration procedure to calculate the bubble size
distribution. The bubble size distribution is used to calculate the
volumetric liquid-side mass transfer coefficient, KLa. The calculation
of Ozone concentration in the gas phase and liquid phase was developed
through the simulation of the U-tube reactor by dividing it into simple
principle reactors forms, plug flow reactor (PFR) and continuous stirred
tank reactor (CSTR). The calculated holdup, and volumetric mass transfer
coefficient have been compared with the experimental results in the
literature, with good agreement.
The effect of the gas-phase and liquid-phase superficial velocities, and
the reactor dimensions, on the holdup , volumetric mass transfer
coefficient, ozone absorption efficiency, ozone concentration in
gas-phase and liquid-phase, and concentration of ozone consuming
substances in water have been studied. As both the residence time and
interfacial area increase, the mass transfer process will be more
efficient. The residence time can be controlled by controlling the
gas-phase and liquid-phase velocities, in addition to reactor dimensions
such as its height and diameters. The interfacial area is controlled by
controlling the bubble size distribution through the hydrodynamics and
energy dissipation rate, to encourage bubble breakage and inhibit bubble
coalescence.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Water treatment, U-tube reactor, Gas-liquid flow, Water Ozonation, Water disinfection.
Neural
Network Based Wear Monitoring of Single Point Cutting Tool using Acoustic
Emission Techniques
by P.Kulandaivelu,
S.Sundaram, P.Senthil Kumar
Vol. 5 n. 1, pp. 52-58
Abstract - This paper investigate flank and crater wear characteristics of coated carbide tool inserts during dry turning of steel workpieces. A brief review of tool wear mechanisms is presented together with new evidence showing that wear of the TiC layer on both flank and rake faces is dominated by discrete plastic deformation, which causes the coating to be worn through to the underlying carbide substrate when machining at high cutting speeds and feed rates. Wear also occurs as a result of abrasion, as well as cracking and attrition, with the latter leading to the wearing through of the coating on the rake face under low speed conditions. When moderate speeds and feeds are used, the coating remains intact throughout the duration of testing. Wear mechanism maps linking the observed wear mechanisms to machining conditions are presented for the first time. These maps demonstrate clearly that transitions from one dominant wear mechanism to another may be related to variations in measured tool wear rates. Comparisons of the present wear maps with similar maps for uncoated carbide tools show that TiC coatings dramatically expand the range of machining conditions under which acceptable rates of tool wear might be experienced. However, the extent of improvement brought about by the coatings depends strongly on the cutting conditions, with the greatest benefits being seen at higher cutting speeds and feed rates. Among these methods, tool condition monitoring using Acoustic Emission Techniques (AET) is an emerging one. Hence, the present work carried out to study the stability, applicability and relative sensitivity of AET in tool condition monitoring in turning. Attempt were made using Neural Network tool to predict the possibilities of establishing the correlation between the crater wear and the variation of Acoustic Emission parameters like Average value, RMS value and Area or Energy of the signal.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Acoustic Emission Parameters, Crater wear, Stress wave, Back Propagation Neural Network.
Inhibition
of Corrosion of Mild Steel in Hydrochloric Acid by Bambusa Arundinacea
by A. S.
Abdulrahman, Mohammad Ismail, Mohammad Sakhawat Hussain
Vol. 5 n. 1, pp. 59-63
Abstract -
The inhibitive property of green plant inhibitor (Bambusa Arundinacea) on
the corrosion of mild steel strip in 1M HCl were studied using weight
loss technique. Inhibition efficiency of 72.84% at 10% v/v of extract
concentration for 72 hours exposed time for Bambusa arundinacea was
achieved. Adsorption of the inhibitor molecules on mild steel strip
surfaces was consistent with Langmuir adsorption isotherm.
Copyright © 2011 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords: Acid Solutions, Mild Steel, Weight Loss, Acid Inhibition, Acid Corrosion.
Three
Dimensional Dynamic Contact of Spur Gear by Using Finite Element Technique
by Ali Kamil
Jebur, I.A.Khan, Y.Nath
Vol. 5 n. 1, pp. 64-70
Abstract -
This template represents the basic guidelines and desired layout final
manuscript of Tooth contact stresses are often calculated with the Hertz
formula when the tooth load are known. Since the Hertz formula was
deduced from two symmetric elastic cylinders, so it is not precise
enough for contact stress calculation of gear teeth, also Hertz formula
cannot calculate correct stress values of contact teeth. It is widely
agreed that the theoretical analysis (FEM by using ANSYS) of spur gears
can be performed using 2D approach (point to point). This paper
investigates the characteristics of an Involutes gear system including
contact stresses between pair of the gears (surface to surface
contact)(2D and 3D) for polyimide materials. To enable the investigation
of contact problems with Finite Element Method (FEM), the stiffness
relationship between the two contacts areas is usually established
through a spring placed between the two contacting areas. The results of
the two and three dimensional FEM analyses from ANSYS (surface to
surface contact) are presented. These stresses are compared between two
and three dimensional. Both results agree very well. This indicates that
the (FEM) model (surface to surface contact) is accurate more than
(point to point) and (Hertz's equations) results because it is very near
to the facts. Also the different of the results between two and three
dimension are very small and equal (3.95%).
Copyright © 2011 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords: Contact Stress, Finite Element Method, Spur Gear, Hertz.
Analysis
Free Vibration of FGM Cylindrical Shells under Clamped-Simply Support Boundary
Conditions
by
M.R.Isvandzibaei
Vol. 5 n. 1, pp. 71-78
Abstract -
In the present work, study of the vibration of thin cylindrical shells
made of a functionally gradient material (FGM) composed of stainless
steel and nickel is presented. Material properties are graded in the
thickness direction of the shell according to volume fraction power law
distribution. The objective is to study the natural frequencies, the
influence of constituent volume fractions and the effects of boundary
conditions on the natural frequencies of the FG cylindrical shell. The
study is carried out using third order shear deformation shell theory.
The analysis is carried out using Hamilton’s principle. The governing
equations of motion of FG cylindrical shells are derived based on shear
deformation theory. Results are presented on the frequency
characteristics, influence of constituent volume fractions and the
effects of clamped-simply boundary conditions.
Copyright © 2011 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords: Vibration FGM Cylindrical Shell, Hamilton’s Principle.
The
Effect of the Thermal Behavior of a Machine Tool on the Dimensional
Accuracy of Parts
by Yuxia Lu, M. N.
Islam
Vol. 5 n. 1, pp. 79-87
Abstract - The thermal behavior of machine tools can profoundly affect the dimensional accuracy of manufactured parts; yet no publications have explored the relationship between dimensional accuracy of workpieces and the thermal status of machine tools. This paper investigates the thermal behavior of a three-axis CNC machine tool by machining several workpieces at different thermal conditions, analyzing the dimensional accuracy of the machined workpiece using a coordinate measuring machine (CMM) and directly showing the relationship between the dimensional accuracy of the workpiece and the machine tool’s thermal status.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Dimensional accuracy, Flatness, Positioning accuracy, Thermally stable stage, Warm-up period.
Cognitive
optimization of mechanical structures
by J. L. Marcelin
Vol. 5 n. 1, pp. 88-91
Abstract - This work focuses on the mechanical structure optimization field. The optimization deals with cognitive methods and shows a good efficiency thanks to calculation rapidity and implementation facility. In this paper, we manipulate the most recently methods used to process mechanical problems like genetic algorithms and neural networks. An example illustrates the efficiency of coupling these algorithms.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Structural optimization, genetic algorithms, neural networks.
Aerodynamic
Study of Combustor Using Axial Swirler
by Mohammad Nazri
Mohd Jaafar, Mohd Khairul Firdaus Mohd Nor, Mohd Shaiful Ashrul Ishak
Vol. 5 n. 1, pp. 92-99
Abstract
- A study has been conducted to investigate the flow pattern in a gas
turbine combustion chamber by simulation and experimental approaches.
Flow pattern inside a combustor is important to self sustain the flame,
increase mixing of air and fuel and combustion intensity.
Aerodynamically curved vanes allow the incoming axial flow to turn
gradually. This inhibits flow separation on the suction side of the
vane. Thus, more complete turning and higher swirl and radial-velocity
components can be generated at the swirler exit, with the added
advantage of lower pressure loss. The swirl number was varied from 0.48,
0.83 and 1.43. The highest swirl number of 1.43 for axial swirler is
capable to create a clear reversal mass flow rate zone.
Copyright © 2011 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords: Axial Swirlers, Recirculation Zone, Swirl Number, Combustor Flow Pattern, CFD Simulation.
Catalytic
Combustion System for use in Malaysia Small Gas Turbine: a Feasibility Study
by Mohammad Nazri
Mohd Jaafar, Ahmad Huzairi Hussain, Mohd Shaiful Ashrul Ishak
Vol. 5 n. 1, pp. 100-105
Abstract -
Nowadays, the rates of air pollutant produced by small gas turbine in
manufacturing and automobile industries increased continuously. Besides
that, the uncontrolled rate of emissions released into the ambient air
could pollute the air environment and harm human life. Normally, the
emissions produced from fuel oxidation inside the combustor of the gas
turbine are nitrogen oxides (NOx), carbon monoxide (CO) and unburned
hydrocarbon. Most of the produced emissions could harm our environment
such as greenhouse effect and could deplete the ozone layer and allow
increased of radiation. The effects from these situations gradually
endanger the human life in general. Realizing the importance of
controlled emission, this feasibility study is conducted to propose a
new combustor for use in Malaysia small gas turbine. The proposed
combustor satisfies the objective as more effective, greener and able to
operate at optimum level. Catalytic combustor was chosen based on its
performance, capital cost, rate of emission, feasibility and durability.
Copyright © 2011 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords: Catalytic Combustor, Nitrogen Oxides (Nox), Carbon Monoxide (CO), Unburned Hydrocarbon Emissions, Small Gas Turbine.
Development
of Gas Turbine Spray Test Rig for Biofuel
by Noor Nadia
Raupeeh, Mohammad Nazri Mohd Jaafar, Mohd Amirul Amin Arizal, Mohd Shaiful
Ashrul Ishak
Vol. 5 n. 1, pp. 106-112
Abstract - The design of the fuel supply system to be used for biofuel is one of the systems that are complicated to design. As this system involves a lot of components, all the components in this design play an important role to ensure that the objective of the system achieved. The purpose of the fuel supply system for gas turbine combustor is to apply the fuel to the combustion chamber through an atomizer to burn and produce 100kW of power. The hollow cone fine spray nozzle, 1.1 mm in diameter was chosen as the atomizer. To evaluate the atomization behavior of palm biofuel blends as an alternative fuels, the physical properties of biofuel blends were determined. These parameters were used to compare the Sauter Mean Diameter (SMD) and the spray cone angle of the various fuel blends. The spray angle of this fuel is around 70 to 84 degrees at pressure around 7 to 9 bars. The main components such as fuel tank, pumps, filters, valves, fuel piping and flow meter had been chosen systematically. This method is used to analyze the components by simulating the real flow process in the fuel system works. Besides that, to test the fuel supply system performance, tests had been conducted using the PDA and the spray characteristics of biofuel was observed. Therefore the characteristics of biofuel such as fuel droplet velocity and size had been obtained from this experimental.
Keywords: Fuel Supply System, Atomizer, Biofuel, Pressure-Swirl.
Development
and Application of Artificial Dissipation Schemes
by H. Bagheri-Esfe,
M. Malek-Jafarian, M.R. Mohaghegh
Vol. 5 n. 1, pp. 113-119
Abstract -
The SCalar Dissipation Scheme (SCDS-1) and MAtrix Dissipation Scheme
(MADS-1) are two common artificial dissipation schemes that have been
used for several years. Two new artificial dissipation schemes are
introduced by using the QUICK scheme in this paper (SCDS-2, MADS-2). The
capability of these four artificial dissipation schemes is compared for
two different problems. First for the channel flow problem and then for
the moving vortex problem. The results of two problems show that the
accuracy of these new artificial dissipation schemes (SCDS-2, MADS-2)
are almost equal to two other schemes (SCDS-1, MADS-1). The
implementation of the boundary conditions is more convenient in the new
schemes. Also the new artificial dissipation schemes don’t need any
sensor.
Copyright © 2011 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords: Accuracy, Artificial Dissipation Scheme, QUICK Scheme, Shock Waves.
Numerical
Analysis of Laminar Forced Convection Flow of a Radiating Gas over an
Inclined Forward Facing Step
by A. B. Ansari,
S. A. Gandjalikhan Nassab
Vol. 5 n. 1, pp. 120-127
Abstract - In the present work, forced convection laminar flow of a radiating gas over a forward facing step (FFS) in a duct is analyzed. The fluid is treated as a gray, absorbing, emitting and scattering medium. The two-dimensional Cartesian coordinate system is used to simulate flow over inclined surface by considering the Blocked-off region in regular grid. The Navier-stokes and energy equations are solved numerically by the CFD techniques to obtain the velocity and temperature fields. Discretized forms of these equations are obtained by the finite volume method and solved using the SIMPLE algorithm. Since the gas is considered as a radiating medium, all of the convection, conduction and radiation heat transfer mechanisms take place simultaneously in the gas flow. For computation of the radiative term, the radiative transfer equation (RTE) is solved numerically by the discrete ordinate method (DOM) to find the radiative heat flux distribution inside the radiating medium. By this numerical approach, the velocity, pressure and temperature are calculated. The effects of optical thickness, albedo coefficient and the radiation-conduction parameter on heat transfer behavior of the system are also investigated. The numerical results are compared with the available data published in open literature and good agreement was obtained.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Forward Facing Step, Laminar Convection Flow, Radiation Heat Transfer, Blocked-Off Method.
Thermal
Energy Losses in Pressure Reducer Valve of City Gate Station
by N.Etemadee,
S.Saedodin
Vol. 5 n. 1, pp. 128-133
Abstract - Reducing the pressure of natural gas in city gate station will cause cooling around pressure reducer valve and so this help to formation gas hydrate in pipeline. In fact low temperature, existing water in pipeline and the presence of hydrate ingredients such as methane, ethane, and carbon dioxide cause this process. Gas hydrate in gas transmission pipelines will prevent transmission of gas and the pipeline will be blocked. So we should prevent the formation of gas hydrate, because the costs of pipeline blockages due to hydrate formation are high. One method for preventing hydrate formation is temperature control that with heating gas can be prevented from reaching the point of hydrate formation. In this paper the temperature changes during the process of reducing gas pressure are calculated. Compressibility factor of natural gas are calculated according to the temperature of natural gas and assumption that the natural gas is real gas and with equation of state. Then the enthalpy of natural gas and heat losses are calculated with this information. For calculating the enthalpy of the gas mixture, we developed a numerical method and a computer program. We have run program for a CGS regulator. Finally the results are presented as graphs.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Pressure Reducer Valve, Temperature, Compressibility Factor, Enthalpy, Natural Gas.
Design
and Fabrication of Thermal Conductivity Measuring Equipment
by H. U. Ugwu, S.
N. Ojobor
Vol. 5 n. 1, pp. 134-142
Abstract - Engineering education would be purposeful if only engineering and basic sciences can be applied to practical situations without the drudgery of memorizing the formula or imagining what a particular scientific equipment looks like. This will be desirable if our technical institutions, schools and universities start applying theory in practice. It is with this basic conceptual ideology that this equipment is designed due to unavailability of these modern facilities in our schools’ laboratories for simple practical demonstration. In this paper, thermal conductivity equipment was designed using low cost and readily available industrial materials. This is done with a view to encouraging indigenous local ingenuity derived from the knowledge of basic classroom physics theory and its adaptability to science and technological training. The insulator in the system was a combination of clay and saw dust as fibre which formed the composite material. The effectiveness of the insulation was found to be 49.65%. The electrical system was most simple with a control On-Off switch. A light battery-operated digital temperature indicator was used to record temperatures at various locations in the equipment. The designed and constructed conductivity measuring equipment was used to determine the thermal conductivity of brass and mild steel. The conductivity of mild steel specimen at 100°C was 50.2W/mK, and the measured conductivity of brass at the same temperature was found to be 120W/mK. This compared favourably well with literature value of 109-159W/mK. The equipment performed as commercially available ones and could measure the thermal conductivity of metal to the range of ±10% error.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Composite Material, Critical Radius of Insulation, Efficiency of Insulation, Moisture Content of Insulation, Steady State Conditions of Heat Flow, Thermal Conductivity, Thermal Insulations.
Energy
Losses of Oil-in-Water Emulsions Flow through Pipe Fittings using Image
Processing
by Mohamed F.
Khalil, Sadek Z. Kassab, Ashraf S. Ismail, Ibrahim S. Elazab
Vol. 5 n. 1, pp. 143-163
Abstract - The
present study deals with the micro as well as macro experimental
investigation of the behavior of the flow of oil-in-water (o/w)
emulsions through pipe fitting. In the first stage, energy losses for
the flow of stable and unstable oil-in-water (o/w) emulsions through 90°
short elbow, sudden enlargement, sudden contraction, and gate valve,
were determined. Three pipes of different diameter are used. The
experimental work was carried out using three sets of o/w emulsions. The
first is stabilized o/w emulsion using Sodium dodeycl sulfate (SDS)
emulsifier. The second is stabilized o/w emulsion using fatty acid and
amine (FAA) emulsifier. The third is unstable o/w emulsion at different
holdup values. The dispersed phase holdup changed from 15% up to 65%.
The energy losses for each piping element are based on detailed
measurements of the axial pressure distributions along the element
including that along upstream and downstream tangent lines. Correlations
for resistance coefficients (K) were established for all these elements.
The flow in 90° short elbow exhibit the higher values in energy loss
coefficient, then the fully open gate valve comes in the second stage,
and the energy loss coefficient in sudden enlargement comes in the third
stage. The sudden contraction exhibits the lower values for energy loss
coefficient. For sudden contraction, as the area ratio, Ad/Au, increases
from 0.56 to 0.64, the energy loss coefficient decreases. For sudden
enlargement, as the area ratio, Au/Ad, increases from 0.56 to 0.64, the
energy loss coefficient decreases. The resistance coefficients for
stable and unstable o/w emulsions were lower than that for water. The
unstable o/w exhibits lower values in loss coefficient compared with
that for stable o/w. The stable o/w emulsion with SDS emulsifier shows
lower values for loss coefficient than that for stable o/w emulsion with
FAA emulsifier. The energy loss coefficient is found to be inversely
proportional to the generalized Reynolds number for laminar flow, and to
approach constant asymptotic values for turbulent flow, which is in
agreement with literature. The energy loss coefficient increases as the
holdup increases and the flow rate decreases.
In the second stage of the present study a photographic and subsequent
image analysis technique was used to determine upstream and downstream
droplet size distribution in unstable oil-in-water emulsion flowing
through the 25mm 90° short elbow, and gate valve, at different holdup
and velocities. The images were automatically treated, analyzed and
several object descriptors obtained for each droplet using a Matlab
software. The upstream and downstream mean droplet diameter, calculated
from the droplet size distribution resulting from image analysis, at
different velocities is presented. The downstream mean droplet diameter
is smaller than the upstream one, due to breakup of droplets passing
through the pipeline. The droplet breakup increases as the emulsion
velocity increase. As the holdup increases from 0.3 to 0.55, the mean
droplet diameter increases, and this attributed to the droplet
coalescence process.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Secondary Losses, Droplet Size Distribution, Emulsion, Droplet Break-up, Image Processing, Pipe Fittings.
Analysis
of Laminar Film Condensation on the Porous Wall of a Vertical Tube
by Lazhar
Merouani, Azeddine Belhamri
Vol. 5 n. 1, pp. 164-172
Abstract - A numerical study of laminar film condensation by forced convection of steam-air mixtures in a vertical tube is presented. The internal face of the tube wall is coated with a thin porous layer. A set of complete boundary layer equations governing the conservation of momentum, heat and mass is used to describe the transfers in the liquid film and the mixture. The flow field in the porous medium is described by the Darcy-Brinkman-Forchheimer model. These three phases are related with the continuity of velocity, shear stress, temperature, heat and mass flux at the interfaces. The dimensionless transfer equations are discretized using an implicit finite difference scheme. The liquid film thickness is determined by solving the liquid mass balance equation. Results were obtained for a saturated steam-air mixture. Profiles of velocity, temperature in the three media and vapor mass fraction in the mixture are presented. The effects of main properties of the porous layer such as thickness and Darcy number are highlighted. Additionally, the influence of the inlet Reynolds number and inlet vapor mass fraction of the mixture on the evolution of heat flux and condensate flow rate is also investigated.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Condensation, Forced Convection, Liquid Film, Porous Layer, Steam-Air Mixture.
Influence
of Vertical Primary Suspension Stiffness Parameter on Dynamic Response
of Railway Bogie
by Karim H. Ali
Abood, R. A. Khan
Vol. 5 n. 1, pp. 173-179
Abstract - A mathematical model of a railway carriage moving on tangent tracks is constructed by deriving the equations of motion concerning the model in which single-point and two-point wheel-rail contact is considered. The presented railway carriage model comprises of carbody and front and rear simple conventional bogie with two leading and trailing wheelets attached to each bogie. The railway carriage is modeled by 31 degrees of freedom which govern vertical displacement, lateral displacement, roll angle and yaw angle dynamic response of wheelset whereas vertical displacement, lateral displacement, roll angle, pitch angle and yaw angle dynamic response of carbody and each of the two bogies. Linear stiffness and damping parameters of longitudinal, lateral and vertical primary and secondary suspensions are provided to the railway carriage model. Combination of linear Kalker's theory and nonlinear Heuristic model is adopted to calculate the creep forces in which introduced at wheel and rail contact patch area. Computer aided-simulation is constructed to solve the governing differential equations of the mathematical model using Runge-Kutta fourth order method. Principle of limit cycle and phase plane approach is applied to realize the stability and to evaluate the concerning critical hunting velocity at which railway carriage starts to hunt. Numerical simulation model is used to study the dynamic responses of a railway carriage bogie subjected to specific parameters of wheel conicity and primary suspension characteristics. A comparison to study the sensitivity of railway carriage bogie to dynamic responses is also presented at different vertical primary suspension stiffness parameters.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Railway Carriage, Railway Bogie, Tangent Tracks, Wheel Conicity, Suspension Stiffness, Critical Hunting Velocity.
Experimental
and Theoretical Analysis on Enhanced Flat Miniature Heat Pipes With
Axial Capillary Grooves and Screen Meshes
by S. Maalej, J.
Mansouri, M. C. Zaghdoudi
Vol. 5 n. 1, pp. 180-195
Abstract - Combined experimental and analytical studies are realized in order to determine the thermal performance of a Flat Mini Heat Pipe (FMHP) including a mixed capillary system, which is composed of screen meshes and mini-channels. In the analytical study, a model of FMHP with mixed capillary structure is developed, and it is capable to simulate the FMHP thermal performance for different operating conditions. The optimal geometrical characteristics of the meshes are also identified. In the experimental study, different FMHP prototypes are manufactured and tested. The number of screen meshes is kept the same for the different tested configurations; however different meshing sizes are used. The heat transfer improvement, obtained by comparing the heat pipe thermal resistance to the heat conduction thermal resistance of a copper plate having the same dimensions as the tested heat pipes, is demonstrated for the different prototypes. The heat transfer enhancement depends on the input heat flux rate, the screen mesh porosity, and the FMHP orientation in respect to gravity. The comparison between the analytical and experimental results shows a good agreement in predicting both the maximum capillary limit and the FMHP thermal resistance.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Electronics Cooling, Capillary Structures, Mini Heat Pipes, Capillary Limit.
Experimental
Study On The Thermal Performance Of Enhanced Flat Miniature Heat Pipes
by J. Mansouri, S.
Maalej, M. B. H. Sassi, M. C. Zaghdoudi
Vol. 5 n. 1, pp. 196-208
Abstract - An experimental study is realized in order to verify the Mini Heat Pipe (MHP) concept for cooling high power dissipation electronic components and determines the potential advantages of constructing mini channels as an integrated part of a flat heat pipe. Three Flat Mini Heat Pipe (FMHP) prototypes including a capillary structure composed of parallel rectangular microchannels, a combined capillary structure composed of parallel microchannels and protrusions, and a capillary structure composed of protrusions, are manufactured and a filling apparatus is developed in order to charge such FMHPs. The heat transfer improvement obtained by comparing the heat pipe thermal resistance to the heat conduction thermal resistance of a copper plate having the same dimensions as the tested FMHP is demonstrated for different heat input flux rates. Moreover, the heat transfer in the evaporator and condenser sections are analyzed for the different capillary structures and heat transfer laws are proposed.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Electronics cooling, Miniature Heat Pipes, Microchannels, Capillary structure.
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