Documents published in Scipedia

• Three dimensional analysis of natural convection and entropy generation in a sharp edged finned cavity

  L. Kolsi, H. Oztop, N. Abu-Hamdeh, A. Alghamdi, M. Borjini

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  A computational study has been performed to make a computational analysis of natural convection and entropy generation in a sharp edged finned cavity. Three dimensional analysis has been done by solving governing equations with a written computational code in Fortran. The study is performed for fin inclination angles from −60° to 60°, Ra = 105, Pr = 0.7, Rc (conductivities ratio) changes from 0.01 to 100 and irreversibility coefficient is taken as φ=10-5φ=10-5. It is observed that higher values of thermal conductivity ratio (Rc ⩾ 1) do not affect entropy generation due to heat transfer and Bejan number.

  Abstract
  A computational study has been performed to make a computational analysis of natural convection and entropy generation in a sharp edged finned cavity. Three dimensional analysis [...]

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• Nonlinear throughflow and internal heating effects on vibrating porous medium

  P. Kiran

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The effect of vertical throughflow and internal heating effects on fluid saturated porous medium under gravity modulation is investigated. The amplitude of modulation is considered to be very small and the disturbances are expanded in terms of power series of amplitude of convection. A weakly nonlinear stability analysis is proposed to study stationary convection. The Nusselt number is obtained numerically to present the results of heat transfer while using Ginzburg–Landau equation. The vertical throughflow has dual effect either to destabilize or to stabilize the system for downward or upward directions. The effect of internal heat source enhances or sink diminishes heat transfer in the system. The amplitude and frequency of modulation have the effects of increasing or diminishing heat transport. For linear model Venezian approach suggested that throughflow and internal heating have both destabilizing and stabilizing effects for suitable ranges of  . Further, the study establishes that heat transport can be controlled effectively by a mechanism that is external to the system throughflow and gravity modulation.

  Abstract
  The effect of vertical throughflow and internal heating effects on fluid saturated porous medium under gravity modulation is investigated. The amplitude of modulation is considered [...]

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• Flexural performance of RC beams strengthened with near surface mounted CFRP strips

  A. Khalifa

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The near surface mounted (NSM) fiber reinforced polymer (FRP) reinforcement is emerging as a promising alternative strengthening technique to externally bonded reinforcement (EBR) for increasing the load carrying capacity of reinforced concrete (RC) members. NSM FRP technique has several advantages, in comparison with the EBR method, such as reducing the risk of debonding, and a better protection from the external sources of damage. In this research, the performance and effectiveness of the NSM and EBR techniques for the flexural strengthening of RC beams are compared. In order to achieve this objective, six full-scale, RC beams were strengthened with different carbon FRP (CFRP) schemes and tested. Such beams were designed to fail in a flexural mode. Test results indicated that if the same amount of CFRP is used, beams strengthened with NSM strips achieved higher ultimate load than those strengthened with EBR. Such increase in the ultimate load ratio ranged between 12% and 18%. Furthermore, a design approach for computing the moment capacity of RC flexural members strengthened with NSM CFRP strips is developed and presented in this paper.

  Abstract
  The near surface mounted (NSM) fiber reinforced polymer (FRP) reinforcement is emerging as a promising alternative strengthening technique to externally bonded reinforcement [...]

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• Second law analysis for hydromagnetic couple stress fluid flow through a porous channel

  S. Kareem, S. Adesanya, U. Vincent

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  In this work, the combined effects of magnetic field and ohmic heating on the entropy generation rate in the flow of couple stress fluid through a porous channel are investigated. The equations governing the fluid flow are formulated, non-dimensionalised and solved using a rapidly convergent semi-analytical Adomian decomposition method (ADM). The result of the computation shows a significant dependence of fluid’s thermophysical parameters on Joule’s dissipation as well as decline in the rate of change of fluid momentum due to the interplay between Lorentz and viscous forces. Moreover, the rate of entropy generation in the flow system drops as the magnitude of the magnetic field increases.

  Abstract
  In this work, the combined effects of magnetic field and ohmic heating on the entropy generation rate in the flow of couple stress fluid through a porous channel are investigated. [...]

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• Three-dimensional unsteady natural convection and entropy generation in an inclined cubical trapezoidal cavity with an isothermal bottom wall

  A. Hussein, K. Lioua, R. Chand, S. Sivasankaran, R. Nikbakhti, D. Li, B. Naceur, B. Habib

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  Numerical computation of unsteady laminar three-dimensional natural convection and entropy generation in an inclined cubical trapezoidal air-filled cavity is performed for the first time in this work. The vertical right and left sidewalls of the cavity are maintained at constant cold temperatures. The lower wall is subjected to a constant hot temperature, while the upper one is considered insulated. Computations are performed for Rayleigh numbers varied as 103 ⩽ Ra ⩽ 105, while the trapezoidal cavity inclination angle is varied as 0° ⩽ Φ ⩽ 180°. Prandtl number is considered constant at Pr = 0.71. Second law of thermodynamics is applied to obtain thermodynamic losses inside the cavity due to both heat transfer and fluid friction irreversibilities. The variation of local and average Nusselt numbers is presented and discussed, while, streamlines, isotherms and entropy contours are presented in both two and three-dimensional pattern. The results show that when the Rayleigh number increases, the flow patterns are changed especially in three-dimensional results and the flow circulation increases. Also, the inclination angle effect on the total entropy generation becomes insignificant when the Rayleigh number is low. Moreover, when the Rayleigh number increases the average Nusselt number increases.

  Abstract
  Numerical computation of unsteady laminar three-dimensional natural convection and entropy generation in an inclined cubical trapezoidal air-filled cavity is performed for [...]

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• Study on the effect of alumina nano-fluid on sharp-edge orifice flow characteristics in both cavitations and non-cavitations turbulent flow regimes

  A. Kabeel, M. Abdelgaied

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  In the present study, the effects of alumina nano-fluid concentration on sharp-edge orifice flow characteristics in both cavitations and non-cavitations turbulent flow regimes are numerically investigated. At different concentration of AL2O3 nonmetallic particles (2%, 4%, 6%, 8%, and 10%) volume fractions in pure liquid water as a base fluid. A single-hole orifice pipe is with a small diameter ratio 0.297 and the orifice plate thickness 14 mm. The effects of alumina nano-fluid concentration on sharp-edge orifice flow characteristics have been investigated based on the turbulent kinetic energy, turbulent intensity, turbulent viscosity, and volume fraction of vapor. The results show that for increasing the nonmetallic particle volume fraction from 0.0 to 10%, the turbulent kinetic energy decreases by 20.87% in average downstream the orifice in the whole region, the turbulent intensity decreases by 11.11% in average downstream the orifice in the whole region, the turbulent intensity decreases by 11% in average in the whole region, and the volume fraction of vapor increases by 16.9%. Also, in the separation region downstream the orifice the turbulent kinetic energy increases by 160% in average and the turbulent intensity increases by 74% in average for increasing the nano-fluid concentration from 0.0% to 2%. These are mainly because for using the alumina nano-fluid the separation phenomena decrease due to the increase of the viscosity of the nano-fluid, the total losses in the sharp-edge orifice increase for the increase of the viscosity of the nano-fluid and this causes the increase of the rate of vaporization. In the orifice pipe the total-stress criterion predicts larger cavitating regions in the flow field. However using the nano-fluid with high concentration accelerates the cavitations at the orifice pipe.

  Abstract
  In the present study, the effects of alumina nano-fluid concentration on sharp-edge orifice flow characteristics in both cavitations and non-cavitations turbulent flow regimes [...]

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• Steady fully developed natural convection flow in a vertical annular microchannel having temperature dependent viscosity: An exact solution

  B. Jha, B. Aina, Z. Rilwanu

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  This study is devoted to investigate the steady fully developed natural convection flow in a vertical annular micro-channel having temperature dependent viscosity in the presence of velocity slip and temperature jump at the annular micro-channel surfaces. The governing equations of the motion are a set of ordinary differential equations and their analytical solutions in dimensionless form have been obtained for the temperature field and velocity field. The effect of various flow parameters entering into the problem is discussed with the aid of line graphs. During the course of numerical investigation, it is found that increase in viscosity variation parameter enhances the fluid velocity and velocity slip. Furthermore, an increase in viscosity variation parameter leads to increase in the volume flow rate and skin friction.

  Abstract
  This study is devoted to investigate the steady fully developed natural convection flow in a vertical annular micro-channel having temperature dependent viscosity in the presence [...]

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• A new solution for nonlinear Dual Phase Lagging heat conduction problem

  M. Noroozi, S. Saedodin, D. Ganji

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The application of new methods to solution of non-Fourier heat transfer problems has always been one of the interesting topics among thermal science researchers. In this paper, the effect of laser, as a heat source, on a thin film was studied. The Dual Phase Lagging (DPL) non-Fourier heat conduction model was used for thermal analysis. The thermal conductivity was assumed temperature-dependent which resulted in a nonlinear equation. The obtained equations were solved using the approximate-analytical Adomian Decomposition Method (ADM). It was concluded that the nonlinear analysis is important in non-Fourier heat conduction problems. Significant differences were observed between the Fourier and non-Fourier solutions which stress the importance of non-Fourier solutions in the similar problems.

  Abstract
  The application of new methods to solution of non-Fourier heat transfer problems has always been one of the interesting topics among thermal science researchers. In this paper, [...]

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• An empirical investigation on Cu/Ethylene Glycol nanofluid through a concentric annular tube and proposing a correlation for predicting Nusselt number

  A. Jafarimoghaddam, S. Aberoumand

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The investigation indicates an experimental study on the convective heat transfer of Cu/Ethylene Glycol nanofluid flow inside a concentric annular tube with constant heat flux boundary condition and proposes a novel correlation for the prediction of Nusselt number. For extending the previous study by Jafarimoghaddam et al., we selected the nanoparticles with the average size of 20 nm and also other conditions of the experiment are based on Jafarimoghaddam et al. (2016) [1]. The applied nanofluid was prepared by Electrical Explosion of Wire technique with no accumulation during the experiment. The tube was heated using an electrical heating coil covered it. The effects of different parameters such as flow Reynolds number and nanofluid particle concentration on heat transfer coefficient are studied. The acquired experimental data were used to establish a correlation for predicting Nusselt number of nanofluid flow inside the annular tube. This correlation has been presented by using the exponential regression analysis and least square method. Correlation is valid for Cu/Base Ethylene Glycol nanofluid flow with the volume concentrations between 0.011 and 0.171 in the hydrodynamically fully developed laminar flow regime with Re < 160 which is most applicable in micro heat sinks.

  Abstract
  The investigation indicates an experimental study on the convective heat transfer of Cu/Ethylene Glycol nanofluid flow inside a concentric annular tube with constant heat [...]

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• Protection of DFIG wind turbine using fuzzy logic control

  M. Ismail, A. Bendary

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  In the last 15 years, Double Fed Induction Generator (DFIG) had been widely used as a wind turbine generator, due its various advantages especially low generation cost so it becomes the most important and promising sources of renewable energy. This work focuses on studying of using DFIG as a wind turbine connected to a grid subjected to various types of fault. Crowbar is a kind of protection used for wind turbine generator protection. ANFIS controller is used for protection of DFIG during faults. The fault current under symmetric and asymmetric fault is presented as well as a way to control the increase in rotor current which leads to voltage increase in DC link between wind generator and the grid. ANFIS is used for solving such problem as it is one of the most commonly AI used techniques. Also the current response of DFIG during fault is improved by adapting the parameters of PI controllers of the voltage regulator using fuzzy logics. ANFIS also in this paper is used for detecting and clearing the short circuit on the DC capacitor link during the operation. A simulation study is illustrated using MATLAB/Simulink depending on currents and voltages measurement only for online detection of the faults. The proposed technique shows promising results using the simulation model.

  Abstract
  In the last 15 years, Double Fed Induction Generator (DFIG) had been widely used as a wind turbine generator, due its various advantages especially low generation cost so [...]

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