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International Review of Mechanical Engineering - January 2011 (Vol. 5 N. 1) - Papers

 

 

   

 

 


 

 

International Review of Mechanical Engineering - Papers

 

go to top   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.

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Keywords: Drop Spreading; Meniscus; Capillary Adhesive; Wetting; Textile Porous Media.

 


 

go to top   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.

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Keywords: External Oriented Defect, Pipe, Notch Stress Intensity Factor.

 


 

go to top   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
.

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Keywords: Agitator System, Fatigue Life, Stress Analysis, Vibration Fatigue, Rain Flow Counting Method.

 


 

go to top   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.

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Keywords: Extrusion, Palm Olein, Paraffinic Mineral Oil, Surface Roughness, Visioplasticity.

 


 

go to top   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.

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Keywords: Finite-Element, Arc Plasma, Anode, Melting, Welding, Shielding Gas; Argon, Helium.

 


 

go to top   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.

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Keywords: Water treatment, U-tube reactor, Gas-liquid flow, Water Ozonation, Water disinfection.

 


 

go to top   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.

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Keywords: Acoustic Emission Parameters, Crater wear, Stress wave, Back Propagation Neural Network.

 


 

go to top   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.
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Keywords: Acid Solutions, Mild Steel, Weight Loss, Acid Inhibition, Acid Corrosion.

 


 

go to top   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%).
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Keywords: Contact Stress, Finite Element Method, Spur Gear, Hertz.

 


 

go to top   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.
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Keywords: Vibration FGM Cylindrical Shell, Hamilton’s Principle.

 


 

go to top   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.

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Keywords:  Dimensional accuracy, Flatness, Positioning accuracy, Thermally stable stage, Warm-up period.

 


 

go to top   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.

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Keywords: Structural optimization, genetic algorithms, neural networks.

 


 

go to top   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.
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Keywords: Axial Swirlers, Recirculation Zone, Swirl Number, Combustor Flow Pattern, CFD Simulation.

 


 

go to top   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.
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Keywords: Catalytic Combustor, Nitrogen Oxides (Nox), Carbon Monoxide (CO), Unburned Hydrocarbon Emissions, Small Gas Turbine.

 


 

go to top   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.
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Keywords: Fuel Supply System, Atomizer, Biofuel, Pressure-Swirl.

 


 

go to top   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.
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Keywords: Accuracy, Artificial Dissipation Scheme, QUICK Scheme, Shock Waves.

 


 

go to top   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.

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Keywords:  Forward Facing Step, Laminar Convection Flow, Radiation Heat Transfer, Blocked-Off Method.

 


 

go to top   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.

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Keywords:  Pressure Reducer Valve, Temperature, Compressibility Factor, Enthalpy, Natural Gas.

 


 

go to top   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.

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Keywords:  Composite Material, Critical Radius of Insulation, Efficiency of Insulation, Moisture Content of Insulation, Steady State Conditions of Heat Flow, Thermal Conductivity, Thermal Insulations.

 


 

go to top   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.

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Keywords:  Secondary Losses, Droplet Size Distribution, Emulsion, Droplet Break-up, Image Processing, Pipe Fittings.

 


 

go to top   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.

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Keywords:  Condensation, Forced Convection, Liquid Film, Porous Layer, Steam-Air Mixture.

 


 

go to top   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.

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Keywords:  Railway Carriage, Railway Bogie, Tangent Tracks, Wheel Conicity, Suspension Stiffness, Critical Hunting Velocity.

 


 

go to top   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.

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Keywords:  Electronics Cooling, Capillary Structures, Mini Heat Pipes, Capillary Limit.

 


 

go to top   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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