ARPN Journal of Engineering and Applied Sciences                         ISSN 1819-6608
   
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ARPN Journal of Engineering and Applied Sciences                    May 2013 | Vol. 8  No. 5
   
Title:

Numerical simulation of nozzle flow with chemical equilibrium

Author (s):

Mohamed A. Al Kady and Farouk M. Owis

Abstract:

The compressible two-dimensional planar and axisymmetric Navier-Stokes equations are solved in generalized curvilinear coordinates to simulate non-reacting and chemical equilibrium nozzle flows. A zonal turbulence model of  is used in the simulations to compute the eddy viscosity. A numerical method is developed to discretize the governing equations using the finite difference technique. The convective terms in the governing equations are solved numerically using a second order flux difference splitting method of Roe while a second order central difference is used for the viscous terms. The discretized equations are integrated implicitly in time to increase the stability of the numerical scheme. The flow solver is coupled with a chemical equilibrium module to compute the composition of gas mixture of known enthalpy and pressure. Few test cases are performed to illustrate the capabilities of the flow solver to predict nozzle flow with and without chemical equilibrium. The results are compared with the published data and the results are in good agreement with those published simulations of the same test cases.

 
 
 
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Title:

Effect of green inhibitor on the corrosion behaviour of reinforced carbon steel in concrete

Author (s): Eyu D.G, Chukwuekezie C, Esah H, Idris J. and Mohammad I.
Abstract:

The effect of inhibitors on the corrosion behaviour of carbon steel reinforced in concrete exposed to 3.5% NaCl solution has been studied by electrochemical and weight loss tests. The corrosion potential and concrete resistivity were determined during the immersion time of the concrete specimens. The results show that calcium nitrite and vernonia amygdalina extract reduced corrosion rate compared to sodium nitrite. However, vernonia amygdalina inhibition was more effective in the immersed concrete in simulated seawater. The weight loss results demonstrated that 2% sodium nitrite was more effective with efficiency of 96% in comparison with 2% calcium nitrite and 6% vernonia amygdalina with efficiency of 92% and 75% respectively. From the results, it is evident that the extract from vernonia amygdalina (bitter leaf) acts as an excellent corrosion inhibitor for rebar steel, efficiency increases with increase in dosage, and the inhibition mechanism was by physical adsorption which is responsible for shielding the specimen from corrosive environment.

 
 
 
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Title:

Optimization of water distribution networks path

Author (s):

Ioan Sarbu and Emilian Stefan Valea

Abstract:

The determination of pipe network optimal path is important for an effective modeling and optimization of water-distribution systems. A principal application of the branched network optimal path is to evaluate the hydraulic performance of the distribution system based on selected schemes for many types of network analysis (e.g., design, operation, calibration). Already known algorithms for solving this problem usually determine a sole solution which in some cases proves to be suboptimal. This paper is a mathematical approach of the branched pipe network path optimization for water distribution. It is developed an algorithm based on graph-theory which generates all minimal trees of the graph comprising nodes where consumers are placed and links (pipes) between them and is implemented in a computer program for PC microsystems. Thus, can be determined all optimal solutions, for a given criterion. The optimization model is applicable to design of the distribution networks for hydro-urban and hydro-amelioration systems. Numerical example will be presented to demonstrate the accuracy and efficiency of the proposed optimization model. These show a good performance of the new model.

 
 
 
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Title: Investigating the effects of some parameters on hydrogen sulphide stripping column using aspen hysys
Author (s): Saidat Olanipekun Giwa, Abdulwahab Giwa and Hale Hapoglu
Abstract:

This work has been carried out to investigate the effects of fresh water volumetric flow rate, column tray number, wastewater feed tray number and boilup ratio on the stripping column used for the purification of wastewater containing hydrogen sulphide as the main impurity. The stripping column was modelled with the aid of Aspen HYSYS using Electrolyte NRTL as the Fluid Package. The wastewater feed and the stripping liquid (fresh water) feed were passed into the stripping column at a temperature of 25 oC and a pressure of 1 atm. From the results obtained from the investigations carried out, it was revealed that pure water was obtained as the bottom product of the stripping column used for the purification of the wastewater but the mass fractions of the hydrogen sulphide and the purified water in the top product was found to vary with the changes in the parameters considered. So, it is recommended that the values of the parameters should be chosen for the treatment of the wastewater containing hydrogen sulphide based on whether hydrogen sulphide is expected to be in low or high concentration in the top product of the column.

 
 
 
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Title: A comprehensive survey on multi-port bidirectional dc-dc converters for renewable energy systems
Author (s): Venmathi. M and Ramaprabha. R

Abstract:

Renewable energy sources such as fuel cells, photovoltaic (PV) arrays are increasingly being used in automobiles, residential and commercial buildings. For stand-alone systems energy storage devices are required for backup power and fast dynamic response. A power electronic converter interfaces the sources with the load along with energy storage. Existing converters for such applications use a common dc link. High frequency ac-link based systems have recently been explored due to its advantages of reduced part count, reduced size and centralized control. Such a high frequency ac link based converter is termed as a multi-port converter in which ports are connected with the energy sources, energy storage devices and the load. It is desirable to have bi-directional, isolated power flow between energy storage devices and the sources. This paper deals about the multi-port bidirectional converters with different topologies either with voltage fed or current fed structure. Bidirectional power flow between the load port and the energy storage devices are achieved in order to maintain the power balance in the system. The power flow between ports can be controlled by suitable control strategy and phase-shifting the square wave outputs of the bridges in combination with pulse width modulation (PWM) control scheme. Moreover the converter also has high efficiency due to soft-switching operation in all the ports. This paper deals about an elaborate review on bidirectional multi-port dc-dc converters for interfacing the renewable sources.

 
 
 
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Title:

Magnetic susceptibility, remanent magnetization and coercivity variations along soil profile

Author (s):

N. D. Nurgalieva and P.G. Yassonov

Abstract:

The determination of magnetic susceptibility χ, remanent magnetization Jr and coercivity Bcr variations along Glifada automorphic soil profile has been carried out using χ - meter MS2-B and unique lab coercivity spectrometer permitting to distinguish paramagnetic magnetization and saturation remanent magnetization and to determine Jr and coercivity Bcr. These parameters give the consideration of soils components in terms of paramagnetic, ferromagnetic, ferrimagnetic, or antiferromagnetic states. The results have revealed that investigated soil profile was recorded in magnetic parameters variations and controlled by environmental factors.

 
 
 
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Title:

Assessment of carbon emissions under the uncertainty of the energy using for the production of pig meat

Author (s):

Prayong Keeratiurai

Abstract:

Carbon is an important element for humans because it is the primary element of both plants and animals and it cycles through living and non-living components. Pigs are energy using animals that are raised for their meat, and produce emissions of CO2. The carbon footprint is also the alternative for consumers to choose products with the least release of greenhouse gases into the environment. Therefore it is important to study and understand the relationship between the carbon emissions and carbon transfer to pig energy use to develop carbon footprints for meat production. The focus of this study was to develop carbon footprints for pig meat production. To accomplish this we studied the rate of the carbon emissions from electricity, petroleum, LPG used during meat production. The results shown that the carbon emission were 0.210.05, 1.220.13 and 0.240.05 kg.C/head/day from the using of electricity energy, transportation energy, and LPG, respectively. The carbon emission from the using of transportation energy was quite high in terms of energy using but low in the using of electricity and LPG activities. The results also shown that the carbon emission of the energy using from farms and slaughterhouses were 1.980.17 and 1.110.04 kg.C/head/day, respectively. The carbon footprint from energy using were 26.330.33 kg.CO2.eq./1 kg.meat. Therefore, farmers should reduce emissions from energy consumption such as reduce electricity utilization in farms, slaughterhouses and reduce distance for animal feed transportation to farms, animals to farms and slaughterhouses. It is suggested that the use of fuel for transportation should be reduced because it creates the highest carbon emission.

 
 
 
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Title:

Coordination of PSS and facts devices for power system stability enhancement: a review of the state-of-the-art

Author (s):

J. Usman, M.W. Mustafa and G. Aliyu

Abstract:

Power systems stability has been a concern and it will continue to be the major concern in power system operations due to power system oscillations caused by complex interconnections. Efforts have been attracted towards damping the power system oscillations for enhancing stability in power systems. The instability that has been affected by the complex interconnections is the small signal stability. Power system stabilizers (PSS) are promising in damping small signal stability. Although, PSS are confronted with some drawbacks of serious variation in the voltage profiles and it may also results in leading power factor operations which may cause reduction of system stability under heavy disturbances. In large multimachine power systems, the application of only conventional PSS may cease to provide adequate damping for inter-area oscillations and effect of variation in voltage profile. However, power electronic device known as Flexible Alternating Current Transmission System (FACTS) devices are effective in damping the inter-area oscillations and capable of handling the variations in voltage profile. Therefore this paper presents a comprehensive review and evaluation of PSS and FACTS power oscillation damping (POD) controllers in mitigating low frequency oscillations based on computational intelligence methods. Technical paper publications on design, optimal location and optimal parameter tuning associated with PSS and FACTS based controllers are highlighted. Finally the potential future research directions for novel PSS and FACTS devices is proposed as a reference for interested researchers.

 
 
 
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Title:

Effects of chemical reaction and radiation absorption on the unsteady MHD free convective flow past an infinite vertical moving plate with constant heat source

Author (s):

A.G. Vijaya Kumar, K. Raveendra Babu, B. Reddappa  and S.V.K. Varma

Abstract:

An analysis has been carried out to investigate the effects of the heat source, chemical reaction and radiation absorption on unsteady MHD flow with heat and mass transfer of an incompressible, viscous, electrically conducting fluid past an infinite vertical moving plate with constant temperature in the presence of transverse applied magnetic field. An exact solution for the flow problem has been obtained by solving the governing equations using Laplace-transform technique. At time ť > 0, the plate is given an impulsive motion with a constant velocity 0. At the same time, the plate temperature and concentration levels near the plate are raised to T́ ww and Cw, respectively. The velocity, temperature, concentration and the rate of mass transfer are discussed through graphs while the numerical values of Nusselt number are presented in a table.

 
 
 
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Title: Methyl acetate reactive distillation process modeling, simulation and optimization using aspen plus
Author (s): Abdulwahab GIWA

Abstract:

The modeling, simulation, and optimization of the reactive distillation esterification process used for the production of methyl acetate have been carried out in this work with the aid of Aspen PLUS. The Aspen PLUS reactive distillation process model was developed and simulated using Rad Frac packed column, the rectification and the stripping sections of which was filled with Raschig Type packing of dimension 25 mm and the reaction section of which was filled with Sigma Type packing material of 10 mm dimension. In addition, Non-Random Two-Liquid property method, volumetric feed rates of both acetic acid and methanol of 0.03 L/min, feed temperature and pressure of 25 oC and 1 atm respectively were used. The optimization of the process was accomplished using the Optimization Section of Model Analysis Tools of Aspen PLUS. The good convergence obtained from the simulation of the developed Aspen PLUS model of the reactive distillation process has shown the versatility of Aspen PLUS in successfully representing the behavior of the complex reactive distillation process used for methyl acetate production. Furthermore, the achievement of the value of the objective function given by the optimization of the process when the estimated optimum values of reflux ratio and reboiler duty were used to run the developed model revealed that the optimum values obtained from Aspen PLUS were valid ones.

 
 
 
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Title: Effects of slip condition and multiple constrictions on couple stress fluid flow through a channel of non uniform cross section
Author (s): Gurju Awgichew and G. Radhakrishnamacharya

Abstract:

Steady incompressible couple stress fluid flow through a non-uniform channel with two stenoses is investigated. Assuming the stenoses to be mild and using the slip boundary condition, the equations governing the flow of the proposed model are solved and closed form expressions for the flow characteristics (resistance to flow and wall shear stress) are derived. Both the resistance to flow and the wall shear stress increase with the heights of the stenoses and slip parameter but decrease with Darcy number. The effects of wall exponent parameter on the flow characteristics also have been studied.

 
 
 
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