Latest issue

by S. Maalej, M. C. Zaghdoudi, R. Ramzi

Vol. 7. n. 1, pp. 1-9

Abstract - In this work, we present an experimental study of the thermal performance of a Heat Pipe Solar Collector (HPSC). The HPSC has 12 copper heat pipes filled with water and having a capillary structure made of helicoidal and trapezoidal capillary grooves, and Compound Parabolic Concentrator (CPC) type reflectors are used. The tests were performed under the meteorological conditions of Tunis during spring and summer 2009, and several operating parameters such as the solar irradiation, the mass flow rate, and the temperature of water flowing through the HPSC are considered. For fixed operating conditions, the experimental results show that the instantaneous efficiency of the HPSC increases during the day and reaches 80 % in late afternoon. However, it decreases when water mass flow rate and temperature increase. The experimental thermal performance curves (instantaneous efficiency vs. reduced temperature) allow for the determination of the optical efficiency as well as the solar collector heat losses coefficient.

Keywords: Heat Pipes, Vacuum Solar Collector, Efficiency, Solar Cooling.

by Marcos Corrêa de Carvalho, João Maurício Rosário, Liz Katherine Rincón Ardila, Almiro Franco da Silveira Junior

Vol. 7. n. 1, pp. 10-23

Abstract - Current technological trends have inspired the use of automation concepts to improve life quality, energy consumption, accessibility and comfort in environments where persons tend to spend time, be it at work, home or leisure spaces. Assistive Domotics is oriented in developing solutions to assist persons with reduced capacity, and disabled and elderly persons, using technological devices, automation systems and more adequate environments. The goal of this paper is to present a Structured Methodology for Assistive Domotics as an Integrated Automation Solution based on the diagnostic of needs to assist persons, and the analysis and design of environments with technological integration and universal design concept. The methodology considers the involvement of various devices to create scalable, friendly and accessible systems. To validate the proposed methodology some cases studies are presented.

Keywords: Assistive Domotics, Technological Integration, Design of Environments, Structured Methodology.

by H. Z. Hassan

Vol. 7. n. 1, pp. 24-37

Abstract - In this study, an investigation of the influence of the adsorption refrigeration system parameters, within their limiting range, on the system performance and operation is introduced. A thermodynamic differential model is developed to analyze the system components and processes of the thermodynamic operating cycle. The analysis is based on a clear fundamental approach which is based on the energy conservation principle and dynamic equilibrium of the adsorption process. Activated carbon‎‎‎–‎methanol as working pair is used in this work. The effect of condensation, evaporator, ambient, and the maximum cycle temperatures on the adsorption cooling system behavior are explained and clarified. Moreover, the influences of the heat capacity of the metallic casing of the adsorption reactor as well as the total bed porosity variations are studied as well.

Keywords: Refrigeration, Adsorption, Thermodynamic Model, Parametric Analysis.

by Adnan Abbas, Mohamad Minhat, Md. Nizam

Vol. 7. n. 1, pp. 38-45

Abstract - The high temperature which occurs in metal cutting operations as a result of heat directly or indirectly influencing the cutting tool and work piece properties. The major part of the energy is converted into heat in primary heat zone which also call shear zone. This paper studies minimization of shear zone temperature during cutting a mild steel work piece by carbide insert cutting tool in computerized numerical control (cnc) turning operation using dry cutting machining. Genetic Algorithm and Direct Search Toolbox methodology is used as optimization method for this purpose. The ideal cutting parameters which help in decreasing the shear zone temperature are obtained. The upper and lower boundaries of cutting parameters will be used as operation constraints. There are many cutting parameters have a huge effect on the shear zone temperature while another have a low.

Keywords: Cnc Turning Machine, Carbide Insert Cutting Tool, Genetic Algorithm Tool Box, Ideal Cutting Parameters, Mild Steel Work Piece, Shear Zone Temperature.

by Azuwir Mohdnor., M. Z. Abdulmuin , A. H. Adom

Vol. 7. n. 1, pp. 46-52

Abstract - In this paper, nonlinear mathematical models for an automotive engine fuelled with palm biodiesel (Palm Oil Methyl Ester) are developed. Assuming a discrete time form for the system model, a polynomial Nonlinear Autoregressive exogenous (NARX) with a linear-in-parameter model structure is selected in this work. Real-time data obtained using a computer-based data acquisition system from a 2.0L automotive diesel engine test-bed unit is used for parameter estimation. The orthogonal least squares (OLS) algorithm together with the Error Reduction Ratio (ERR) criteria are used to select the significant terms in the NARX models in order to determine a parsimonious model and estimate the parameters of nonlinear model. Finally, the models are validated by plotting the output predicted by the models and comparing it with the measured output. The modelling error of both models is examined.

Keywords: Orthogonal Least Squares; System Identification; Non-Linear Modeling; Biodiesel; Palm Methyl Ester.

by M. A. A. Mohd Salleh, A. M. Mustafa Al Bakri, Flora Somidin, H. Kamarudin

Vol. 7. n. 1, pp. 53-59

Abstract - This review paper discusses on the recent lead-free composite solders developed using powder metallurgy (PM) routes. However, the review will focus on the sintering part in the powder metallurgy techniques which the application of microwave technology can be utilized in the development of robust lead-free composite solders. Comprehensive reviews of the published literatures were carried out to understand the requirements and problems in fabricating the lead-free composite solder by using microwave-assisted sintering PM route. This paper describes the improvement of the recent development of lead-free composite solders using microwave-assisted sintering application. It can be summarized that by adding appropriate amounts of a third element as reinforcement in lead-free base matrix system has mostly improved mechanical properties of the monolithic solder. Nevertheless, the review discovered with microwave-assisted sintering, most lead-free bulk samples exhibited a superior microstructural feature which has brought to surprisingly a better mechanical properties in the solder compared to conventionally sintered samples. With microwave-assisted sintering application, the issues related to the implementation of microwave-assisted sintering in lead-free solder development based solder system reinforced with ceramic particulates are also introduced. Furthermore, with the implementation of new hybrid microwave sintering technique which arises from the coalition of conventional and microwave sintering, will yield a staggering advancement in lead-free nanocomposite solder development.

Keywords: Lead-Free Composite Solder, Powder Metallurgy, Conventional Sintering, Microwave-Assisted Sintering, Mechanical Properties.

by Chaouki Ali, Rached Nciri, Kamel Rabhi, Faouzi Nasri, Habib Ben Bacha

Vol. 7. n. 1, pp. 60-66

Abstract - This paper presents a new conception of air conditioning prototype powered by solar energy. The installation, composed of four compartments, consists of three functioning modes according to the season of the year and the climatic conditions. The summer-mode with pre-cooling of air is studied. Mathematical models based on heat and mass transfer behaviors in the solar collector, storage tank, humidifier and desiccant wheel have been developed. The system of equations is numerically resolved using a finite volume method to study the behavior of the prototype.

Keywords: Air Conditioning, Solar Energy, Desiccant Wheel, Numerical Simulation.

by W. I. Wan Mastura, H. Kamarudin, I. Khairul Nizar, A. M. Mustafa Al Bakri, M. BnHussain

Vol. 7. n. 1, pp. 67-71

Abstract - The influence of curing time and curing temperature on properties of fly ash-based geopolymer bricks has been studied. The compressive strength and water absorption of geopolymer bricks were investigated which are produced by applying heat treatments between the ranges of room temperature to 80°C at several period of time for curing (1 – 24) hours. In this research, the fly ash-based geopolymer bricks showed that the curing system have a significant effect to the properties of fly ash-based geopolymer bricks. It was observed that prolonged curing time enhanced the geopolymerization reaction resulting increase in compressive strength. The highest compressive strength of geopolymer bricks for different curing temperature given by bricks sample cured at 70°C for 24 hours at the ageing of 7 days.

Keywords: Geopolymer, Fly Ash, Bricks, Mechanical Properties.

by I. Golshokouh, S. Syahrullail, F. N. Ani, H. H. Masjuki

Vol. 7. n. 1, pp. 72-80

Abstract - Lubricant oils have an important role in manufacturing processes for reducing friction and wear between in-contact rotational pieces with different speeds. Vegetable oils are known as new, clean and renewable sources. Palm Fatty Acid distillate (PFAD) is sourced from the vegetable oil family and is potential as an alternative source of mineral lubricant/Hydraulic oils. This study was performed utilizing various speeds (800, 1000, 1200, 1400 and 1600rpm) and according to the American Society for Testing and Materials (ASTM) with number D 4172 (speed 1200 rpm, load 392N, temperature 75°C and in one hour) using a four ball wear machine tester. To evaluate the PFAD results, similar experiments were done using Engine and Hydraulic oil and the results were compared mutually. The results showed that, the anti-friction and anti -wear ability of PFAD were higher than those of Engine and Hydraulic mineral oils. Also, the value of flash temperature parameter of PFAD oil was higher than other test oils. However, the amount of viscosity oil for PFAD was less than Engine oil.

Keywords: PFAD Oil, Four-Ball Tribotester, Wear Scar Diameter, Friction, Flash Temperature Parameter, Viscosity.

by Mahmoud H. Salem, M. N. Anany , M. El-Habrouk , Sohair F. Rezeka

Vol. 7. n. 1, pp. 81-90

Abstract - This paper investigates the control of a dynamic vibration absorber with a magneto-rheological fluid damper. The approaches include Linear Quadratic Regulator (LQR) and adaptive Feed Forward Control with Linear Quadratic Regulator as a feedback controller (LQR+FF). The responses of the controlled semi-active dynamic absorber system are evaluated with external sinusoidal inputs and compared to the optimally-tuned passive vibration absorber system using viscous dampers. The simulation results show that integrating controlled MR dampers in vibration absorber system is feasible and effective. The linear quadratic control is shown to improve the dynamic absorber performance over a substantial range of excitation frequencies and force levels. The LQR control method with the feed forward control is more effective than the LQR control alone and even more effective than the passive control in suppressing the vibration of the main mass and reducing the transmitted forces at resonant machine frequency and at higher external frequencies.

Keywords: Dynamic Vibration Absorber, MR Damper, Optimum-Tuned-Absorber, LQR Control, Adaptive Feed-Forward Control.

by Slimen Attyaoui,, Said Mlik

Vol. 7. n. 1, pp. 91-95

Abstract - The aim of this paper is to investigate the possibilities to use experimental model test to look the influence in concentration between commercially lubricant only and the same lubricant with solid additives in internal combustion engine. The tests were performed in a bus and tractor engines. The influences of different additives are studied. This study proved that the use of additives like Sn and Pb can cause decreased concentration in metal in internal combustion engine, and make it operate in a better condition. It was also seen that the solid additives package appears not to be enough as a lubricant concentration data, at least not in the tribological conditions.

Keywords: Tribo Catalytic, Regeneration, Lubricant.

by Chaouki Ali, Kamel Rabhi, Rached Nciri, Faouzi Nasri, Habib Ben Bacha

Vol. 7. n. 1, pp. 96-104

Abstract - This research focuses on the development of new adsorption air conditioning system powered by solar energy. The new system uses humidifier, heat exchanger, rotary desiccant and silica gel/water adsorption chiller. This unit is introduced to allow the production heat or cold with a good indoor air quality, and controls hygrometry. This system is powered by solar energy and does not “abuse” nature. The new design is made of five sections which are: the Pre-cooling / pre-heating, the drying, the energy recovery, the water adsorption chiller and the brewing. It permits three working modes according to the climatic conditions and to the season of the year. This work focuses on the design, modelling and numerical simulation of the air conditioning system working in winter mode. The simulation uses ambient temperature and solar flux for Gafsa city conditions to predict the behaviour of the system. Moreover, we present the evolution temperature during 24 hours in the building, the storage tank and at some point on the new system. This work includes a study of the building relative humidity, vs respectively, relative humidity at the outlet air of the humidifier and temperature of the water used for humidification.

Keywords: Air Conditioning, Solar Energy, Adsorption Chiller, Indoor Air Quality, Desiccant Wheel.

by Pramod S. Purandare, Mandar M. Lele, Rajkumar Gupta

Vol. 7. n. 1, pp. 105-109

Abstract - Helical coil heat exchangers are popular because of compact structure with enhanced heat transfer coefficient by passive heat transfer enhancement technique. Due to these advantages helical coil tube heat exchangers are widely used in various applications like power plants, nuclear reactors, refrigeration and air-conditioning systems, heat recovery systems, chemical processing and food industries. The analysis of the helical coil heat exchanger with different operating and geometric parameters is presented in this paper. The analysis shows that both operating and geometric parameters are having influence on heat transfer characteristic. The analysis of heat transfer coefficient and Nusselt Number with respect to Reynolds number with different correlations and its signifence is discussed in this paper. The effect of geometric parameter on performance of helical coiled tube heat exchanger is also presented in this paper.

Keywords: Shell and Coiled Tube, Heat Exchanger, Thermal Performance, Laminar, Turbulent, Heat Transfer Coefficient.

by S. Ramesh, N. Natarajan

Vol. 7. n. 1, pp. 110-114

Abstract - Nowadays the usage of composite materials increased rapidly in all applications. The main problem in choosing composite material for a particular application is the machining. The composite materials cannot be machined easily due to its mechanical properties. In this paper an attempt has been made for machining of hybrid metal matrix composite (MMC) material by achieving best Material Removal Rate and surface roughness by using Wire Electrical Discharge Machining. Taguchi method is used to design the experiments for machining and the optimized set of parameters that produce best output is determined. Finally ANOVA is used to determine the influence of parameters that affects the output of the machining.

Keywords: Taguchi Method, WEDM, ANOVA, Material Removal Rate, Surface Roughness, Hybrid MMC.

by P. Suresh, K. Marimuthu, S. Ranganathan

Vol. 7. n. 1, pp. 115-125

Abstract - The utilization of metal matrix composite materials are increased enormously in many engineering fields because of many beneficial properties. Consequently, the need for precise machining of composites has also been improved. In this present study, efforts are made to investigate the effect of various parameters on multi-performance characteristics in turning of Al-SiC-Gr metal matrix composites. Taguchi design method was used to conduct experiments. The influence of cutting speed, feed rate, depth of cut and combined equal weight fraction of SiC-Gr on the response variable of surface finish, material removal rate of the work piece and flank wear of the tool are established. The significance of the parameters and its optimum level is determined for each individual response by using analysis of variance (ANOVA). The optimum machining parameters for multi-performance characteristics are also obtained by weighted grey relational approach. The confirmation experiment revealed that the selected optimal combination of process parameters is able to achieve desired performance characteristics.

Keywords: Al-SiC-Gr Hybrid Composite, Turning, Optimization, ANOVA, Weighted Grey Relational Approach.

by G. Mylsami, N. Nedunchezhian

Vol. 7. n. 1, pp. 126-133

Abstract - Automotive exhaust systems give a major contribution to the sound quality of a vehicle. The principal sources of noise in automotive engines are intake noise, radiator noise, combustion noise, exhaust noise etc. Out of these exhaust noise is predominant and it is to be controlled. Computational Fluid Dynamics is the current trend on automotive field in reducing the cost effect for the analysis of various models. The suitable design and development of exhaust muffler will help to reduce the noise level, at the same time performance of the engine should not be affected. Mechanical performance of the perforated muffler can be controlled by the porosity and distribution of holes. Three different types of new reactive perforated tube mufflers have been modelled and pressure and velocity boundary input has been given and outputs are taken this output are compared with experimental measurements the reactive perforated tube muffler1 considerably reduce the exhaust noise of internal combustions engine.

Keywords: Muffler, Perforated, Noise.

by W. Rahman, J. B. Shamsul, M. N. Mazlee

Vol. 7. n. 1, pp. 134-139

Abstract - The application of microwave sintering to metallic materials offers better mechanical properties over conventional sintering method. In this paper, the effect of heating rate on the microstructure and properties of the sintered 84Fe-11Cr-5Al₂O₃ composite was investigated. Sintering was carried out in a tubular microwave furnace HAMiLab-V3 under N₂ atmosphere. The heating rates were selected between 10°C/min to 60°C/min with increment of 10°C/min. A study of microstructure and physical properties was carried out on sintered samples. The results showed that the optimum heating rate was 20°C/minute. It was observed that, relative density, porosity and hardness decreased as heating rate higher than 20°C/minute.

Keywords: Microwave Sintering, Heating Rate, Relative Density, Porosity, Hardness.

by Z. Yahya, Ch. Mbow, A. O. M. Mahmoud, M. L. Sow

Vol. 7. n. 1, pp. 140-146

Abstract - The authors examine numerically a flow of interaction plume - thermosiphon unsteady, two-dimensionally in a vertical cylinder; this flow of natural convection assumed laminar is generated by the presence of a generating source at the input of the cylinder. To bypass the speed-pressure coupling of the Navier - Stokes equations, a method of projection type Predictor - corrector is used. Numerical integration is done in a field variable mesh with the Patankar control volume method. The discretized equations are then solved by the iterative method of relaxation line by line. The influence of the Rayleigh number and radius of the heat source on the dynamic and thermal fields, the local Nusselt numbers are analyzed and the phenomena of entry are discussed.

Keywords: Cylinder, Interaction, Numerical Modeling, Plume, Source, Thermosiphon.

by Ali Jebelli, Mustapha C. E. Yagoub, Ruzairi bin H. J. Abdul Rahim, Hossein Kazemi

Vol. 7. n. 1, pp. 147-153

Abstract - In this paper, an efficient design control system for autonomous underwater robots is presented. It uses an on-chip RAM rather than a lateral control system for more robustness and a microcontroller-based fuzzy logic controller to better stabilize the robot balancing while moving forward. It was implemented along with a fuzzy proportional integral controller as supervisor and demonstrated through experiments.

Keywords: Autonomous Underwater Robot (AUV), Fuzzy logic controller (FLC), PWM, PID.

by A. Khadraoui, C. Mahfoudi, A. Zaatri, K. Djouani

Vol. 7. n. 1, pp. 154-160

Abstract - In this paper we present a methodology for determining the optimal force distribution in case of multiple manipulators system grasping an object. The force distribution problem is formulated in terms of a nonlinear programming problem under equality and inequality constraints. The friction constraints are transformed from non linear inequalities into a combination of linear equalities and linear inequalities. The original non linear constrained programming problem is then transformed into a quadratic optimization problem. Some simulation results are given and the generalization of the approach to multiple manipulators system grasping an object is discussed.

Keywords: Multi-Robots Cooperation, Grasping, Optimal Force Distribution, Dynamic Modeling, Friction Constraints, Quadratic Programming.

by M. T. Muhammad Faheem, A. M. Mustafa Al Bakri, H. Kamarudin, C. M. Ruzaidi, M. Binhussain, A. M. Izzat

Vol. 7. n. 1, pp. 161-166

Abstract - The strength of geopolymer depends on the nature of source materials. For example, geopolymer produced with calcined source material such as calcined kaolin, fly ash, ground granulated blastfurnace slag (GGBS) and others produce a higher compressive strength compared to geopolymer produced with non-calcined source material such as kaolin. This paper studied the effect of various ratios of Na₂SiO₃/NaOH ratio, kaolin/alkaline activator ratio and sand/kaolin ratio to the strength of clay - based geopolymer brick. The samples had been tested to determine their compressive strength, density, and water absorption properties. Compression tests were conducted at seventh day of testing of all specimens. Tests were carried out on standard size of geopolymer brick according to British Standard (BS 3921).

Keywords: Geopolymers, Bricks, Clay, Kaolin, Compressive Strength, Masonry Brick, Non Load Bearing.

by U. Arunachalam, P. Veeramani, N. Shenbaga Vinnayaga Moorthi

Vol. 7. n. 1, pp. 167-175

Abstract - The recent developments in aerospace, missiles, rockets, automobile engines necessitate the development of thermal barrier coating to protect the costly, precious base structural components from the heat load. Because of the intermediate heat loads, the base materials explode due to high temperature corrosion, alterations in grains etc. Hence, it becomes a major concern to provide a thermal barrier coating which has the property of being easily applied, economical cost and durable life to protect the base materials. This review paper provides a detailed survey on the nickel - tungsten alloy coating by various processes viz electro-deposition, plasma spray, coating behavioural aspects, its mechanical properties, thermal properties and surface topography.

Keywords: Nickel Tungsten Alloy Coating, Thermal Barrier, Electro Deposition, Heat Load.

by A. B. Sanuddin, H. Azmi, M. S. Hussin, K. L. Chuan, Z. A. Zailani, M. F. M. A. Hamzas

Vol. 7. n. 1, pp. 176-180

Abstract - This paper presents the investigation of the effect of sintering temperature on mechanical properties of Al/SiC composites. The composites were produced via conventional powder metallurgy processing. The particle size of Al and SiC powders are 63 µm and 37 µm respectively. The sintering temperatures exerted on the samples were 550, 570, 590, 610, 630 and 650°C at a fixed time of 1 h. The compressive, hardness and impact tests were performed on the sintered samples to characterize their mechanical properties. It was found that as the sintering temperature increase, the mechanical properties of the samples were also increased at earlier temperature and show a decrease trend thereafter. Similarly, this trend was also observed in the density test. Furthermore, microscopic observations showed that the porosity level decrease as the sintering temperature increase excluding at the temperature of 650oC.

Keywords: Aluminium Based Composite, Sintering Temperature, Powder Metallurgy, Mechanical Property.

by Vijay W. Bhatkar, V. M. Kriplani, G. K. Awari

Vol. 7. n. 1, pp. 181-188

Abstract - In recent years, microchannel heat exchangers are intensively used in refrigeration and air conditioning systems as they are super efficient. This paper introduces a microchannel condenser for domestic air conditioners with a simulated model to evaluate its performance using MATLAB results. The model was used to obtain the optimal geometrical, operating and performance parameters for different number of microchannels with various no of passes with different number of tubes per pass for one ton of refrigeration system using R134a as the refrigerant. In this paper simulated results of two phase heat transfer coefficient and two phase pressure drop using the selected correlations are plotted against mass flux, dryness fraction, number of microchannels, number of passes in the condenser, saturation temperature and overall conclusions are made.

Keywords: Correlations, Microchannel, Multiphase, Numerical Simulation, MATLAB.

by Atul P. Kulkarni, Girish G. Joshi, Amit Karekar, Vikas G. Sargade

Vol. 7. n. 1, pp. 189-197

Abstract - This study presents analytical and experimental results of cutting force and chip-tool interface temperature developed during turning of AISI 304 austenitic stainless steels using nano-crystalline AlTiCrN coated cemented carbide insert. The work-tool thermocouple calibration set-up based on the novel concept was developed. Inconel air heater of 1 KW capacity was used as a heating element at the work-tool junction for heating the junction steadily up to 1000 °C. The turning tests were conducted at cutting speeds in the range of 140 to 320 m/min, feed in the range of 0.08 to 0.26 mm/rev keeping depth of cut constant at 1 mm. The influence of cutting parameters and tool coating were investigated on the average chip-tool interface temperature and cutting force. A regression model for chip-tool interface temperature was developed considering the effect of cutting parameters. In addition, the experimental results were validated using the 'Boothroyd temperature model'. Experimentally an interface temperature of 979°C was observed whereas the model predicted 988°C temperature at 260 m/min cutting speed and 0.14 mm/rev feed. The interface temperature in turning is strongly dependent on the cutting speed followed by feed. The AlTiCrN coated shows excellent thermal stability due to the formation of stable Cr₂O₃ or and dense α(Al,Cr)₂O₃ mixed oxide scales. The developed interface model shows excellent fit and could be used effectively for predicting the interface temperature for the given tool and work material and cutting conditions.

Keywords: AlTiCrN, AISI304, Temperature, Boothroyd-Model, Inconel-heater.

by M. Tabarki, S. Ben Mabrouk

Vol. 7. n. 1, pp. 198-206

Abstract - This present survey aims to obtain a bioclimatic building, made from a double external envelope in straws, with natural cooling and heating. The building is designed with double walls, double terraces and double floors in straws bullets. The doors and the windows are supposed insulating, using the polystyrene. The three-dimensional modelling of heat and mass transfers is led, in transient response and simultaneously, within the air of the cell, considered at the instruction temperature, and through its internal partitions. To model the building, considered in laminar regime, the Navier Stokes equations, the coupling between the three modes of thermal transfers and the method of the average radiant temperature, are adopted. The numerical values of model when compared to the results of experiences appeared very satisfactory. The theoretical and experimental survey proved that buildings with double envelope in straws bullets are bioclimatic and with homogeneous distribution in temperature and in humidity.

Keywords: Modelling, Straws, Double envelope, Heating, Cooling, Bioclimatic.

by H. P. Rani, G. Janardhana Reddy

Vol. 7. n. 1, pp. 207-216

Abstract - A numerical study has been carried out for the conjugate heat transfer on unsteady natural convection boundary layer flow of a viscous incompressible fluid over a vertical slender hollow cylinder. A Crank-Nicolson type of implicit method is used to solve the governing unsteady, non-linear and coupled equations. The resulting system of equations are solved by using the Thomas algorithm. The computations are carried out for different values of Prandtl number Pr and conjugate-conduction parameter P.

Keywords: Conjugate Heat Transfer, Natural Convection, Vertical Slender Hollow Cylinder, Finite Difference Method.

by N. U. Korde, A. T. Pise, Rahul H. Salunkhe

Vol. 7. n. 1, pp. 217-223

Abstract - The objective of the study is to numerically investigate falling film thickness over horizontal tubes. Commonly used six fluids are selected for this study, with modified Galileo number Ga*in the range of 36 to 500. Efforts are made to study variation in geometrical parameters i.e. tube diameter and spacing between the tubes. Commercial CFD code (FLUENT version 13.0.0) for 2D configurations is used for simulation over two horizontal tubes. Model of coupled volume-of-fluid and level-set method are used for the numerical investigation. Results obtained are discussed by comparing the present available data in terms of effect of modified Galileo number, Ga* on film thickness. It is observed that the nature of film thickness over the tubes is similar to available experimental and numerical data. An attempt is made to propose a numerical correlation for film thickness in terms of non-dimensional numbers and tube angle.

Keywords: Falling Film Thickness, Horizontal Tubes, Volume of Fluid, Level Set Method.

by A. Elaoud, S. Chehaibi, M. Ben Amor, E. Hajtaieb

Vol. 7. n. 1, pp. 224-230

Abstract - Potable water in Tunisia has well defined characteristics. Thus, the Water researches and Technologies Centre-Borj Cedria mainly processing Natural Waters Laboratory, has worked on the physic-chemical quality of the water. As the Higher Institute of Agronomy-chott mariem have studied the phenomena associated with flows. For this work shows that natural water flows that can be generated in a pipeline. During operation of agricultural pumps (centrifugal pumps), the speed of the electric motor increases from zero to the permanent regime speed. This change in regime influences the flow of the hydraulic installation and forced it to follow the starting dynamic law of the motor. Under the effect of the friction force, due to the fluid viscosity, the transient regime is dumped until reaching the normal operating conditions. In this work, we study this phenomenon and see the influence of the pump startup on the hydraulic behaviour of one dimensional flow throw a cylindrical pipe of linear elastic behaviour. The pipe is connected to constant level reservoir at the downstream end. The problem is governed by a two coupled linear hyperbolic partial differential equations which are the equations of continuity and motion. The mathematical model is solved by the method of characteristics where at the upstream end, that is, at the pump station, the boundary condition is given by the differential equation for speed change of the pump motor. A theoretical relationship is introduced to express the motor torque in terms of the time. At the downstream end the discharging reservoir is assumed to be at a constant level. The computed head and discharge time curves, caused by the starting of the pump, are plotted at some cross sections of the pipe. The results show that the evolution of the hydraulic variables is well influenced by the applied motor torque.

Keywords: Transient Flow, Pipe, Method of Characteristics, Boundary Condition, Motor Torque.

by Ahmed Jassim Shkarah, Mohd Yusoff Bin Sulaiman, Md Razali bin Hj Ayob

Vol. 7. n. 1, pp. 231-237

Abstract - The micro channel heat sink (MCHS) is the most widely used heat sink. It is continuously studied by different researchers and companies who improve the effectiveness and efficiency with which it removes heat from devices. This review paper focuses on two-phase flow in MCHS and includes the mathematical and numerical analysis of the two-phase flow in MCHS. It also provides an overview of the types of MCHS with respect to the arrangement of the fins. These types include rectangular, circular, and other types of MCHS. It includes some applications in which the MCHS is preferably used. In addition to these applications of the MCHS, this review paper includes a brief explanation of the fluids used in the MCHS to increase its effectiveness.

Keywords: Micro Channel Heat Sink, Two-phase flow in MCHS, Analysis of MCHS.

by Z. Yahya, Ch. Mbow, A. O. M. Mahmoud, M. L. Sow

Vol. 7. n. 1, pp. 238-242

Abstract - In this work, we present a numerical study of natural convection laminar flow resulting from the interaction of a thermal plume with a vertical thermosiphon. The thermal plume is generated by the presence of a heat source. We study, among other, the effects of different positions of the generating source on the overall structure of the flow, the authors study numerically the influence of the vertical location of the generating source to the input of the cylinder, with a volume of control of Patankar method and from the full Navier Stokes equations. A mesh of variable steps was chosen. The pressure is calculated using a projection-type Predictor-corrector method. The numerical solution of the discretized equations was made by the iterative method of relaxation line-by-line, and calculations are stopped when the convergence conditions are met.

Keywords: Interaction, Heat Source, Position, Thermal Plume, Thermosiphon.

by S. Sathyanarayanan, A. Vimala Juliet

Vol. 7. n. 1, pp. 243-247

Abstract - This paper presents the Finite Element Analysis (FEA) of MEMS based capacitive pressure sensor to monitor intraocular pressure. The sensor composed of a square Polysilicon diaphragm that deflects in response to applied pressure. Applied pressure deflects the 2 µm diaphragm, changing the capacitance between the Polysilicon diaphragm and the bottom electrode Si substrate. The square diaphragm produces highest induced stress resulting in high sensitivity. Intellisuite FEA modeling software was used to predict sensor actuation, capacitance output and the avoidance of material failure. The FEA modeling and simulated data results is generated. The simulation of the MEMS capacitive pressure sensor achieves good linearity in the intraocular pressure range. The geometry and dimensions are selected to produce optimal performance of the sensor.

Keywords: MEMS, Biosensor, Glaucoma, Square Diaphragm, Finite Element Analysis.

by Rajiv Kaul, S. N. Sapali

Vol. 7. n. 1, pp. 248-260

Abstract - Turbulent flows are commonly encountered in practical applications such as water turbine, Centrifugal pump etc. It is the time-mean behavior of the flows that is usually of practical interest. Therefore, the equations for unsteady laminar flow are converted into the time-averaged equations for turbulent flow by an averaging operation in which it is assumed that there are rapid and random fluctuations about the mean value. The additional terms arising from this operation are the Reynolds stresses, turbulent heat flux, turbulent diffusion flux etc. The transition from unstable to fully turbulent flow has until now been accessible by direct numerical simulation. Experimental investigations are very difficult because the flow is particularly sensitive to unavoidable and often unknown disturbing influences which can decisively change the transition behavior. The widespread use of turbo-machinery calls for the design of more efficient and more reliable machines, which directly translates into cost savings and better productivity. Centrifugal pump technology involves a wide spectrum of flow phenomenon and various methods of impellers design, fabrication and degree of impellers surface finishing, which has a profound impact on its performance. Numerical simulations can provide quite accurate information on the complicated fluid behavior inside the machine for various designs (blades angles) necessary for performance evaluation of a particular design. The current investigation is aimed to simulate the complex internal water flow in a centrifugal pump impeller for low specific speed (6-blades semi-shrouded) by using a (3-D) Navier-Stokes equation with various (k-ω, SST) turbulence models. The numerical solution of the deiscretized (3-D), incompressible Navier-Stokes equations over a structured/unstructured grid is accomplished with CFD package Ansys-CFX.

Keywords: Centrifugal Pump, Impeller, Model, Blade Angle, CFD, Turbulent Flow.

by A. M. Senthil Anbazhagan, M. Dev Anand

Vol. 7. n. 1, pp. 261-268

Abstract - The objective of this work is to find out the stress intensity and load confrontation of the axially cracked ASME pressure vessels so that the condition of the vessel will be branded how much more the life of the vessel wall would come if the crack is generated during operating conditions. The background of this work is based on the failures often occurring in the oil, gas and chemical plant industries. Process equipments are having its own standard design procedures and operating life’s according to its material properties. Some of the equipments need frequent refurbishment as well as proper maintenance during operations due to the various working conditions. The code practices that process equipments need to be designed for time span of 20 to 25 years. However failures occurring during operations are unpredictable but it is diagnosable. It may be due to various reasons such as malfunctioning of components and wrong operations. In this paper the work is such that if the crack is generated axially inside due to load or corrosion, how much more operation the vessel would sustain. If the cracks grow continuously due to frequent loads how long the un-cracked thicknesses would withstand the internal pressure loads. ASME based designed pressure vessel has been considered for this study. The typical pressure vessel crack has been modeled internally in axial directions. The operating load has been applied and the behavior of cracks and its load confrontations were simulated using finite element technology and the results were presented.

Keywords: ASME, Crack Propagation, Finite Element Analysis, Load Confrontation, Stress Intensity Factor, Failures Vessels. Linear Elastic Fracture Mechanics, Elastic Plastic Regions, Yielding Fracture Mechanics, Crack Tip Opening Displacement.