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Esmail M. A. Mokheimer - One of the best experts on this subject based on the ideXlab platform.

  • Geometry effects on conjugate natural convection heat transfer in vertical eccentric annuli
    International Journal of Numerical Methods for Heat & Fluid Flow, 2007
    Co-Authors: Maged A. I. El-shaarawi, Esmail M. A. Mokheimer, Ahmad Jamal
    Abstract:

    Purpose – To explore the effect of the annulus geometrical parameters on the Induced Flow Rate and the heat transfer under the conjugate (combined conduction and free convection) thermal boundary conditions with one cylinder heated isothermally while the other cylinder is kept at the inlet fluid temperature.Design/methodology/approach – A finite‐difference algorithm has been developed to solve the bipolar boundary‐layer equations for the conjugate laminar free convection heat transfer in vertical eccentric annuli.Findings – Numerical results are presented for a fluid of Prandtl number, Pr=0.7 in eccentric annuli. The geometry parameters of NR2 and E (the fluid‐annulus radius ratio and the eccentricity, respectively) have considerable effects on the results.Practical implications – Applications of the obtained results can be of value in the heat‐exchanger industry, in cooling of underground electric cables, and in cooling small vertical electric motors and generators.Originality/value – The paper presents ...

  • Effect Of Thermal Boundary Conditions OnConjugate Natural Convection Flow In VerticalEccentric Annuli
    Computational Methods and Experimental Measurements XIII, 2007
    Co-Authors: Ahmad Jamal, M.a.i. Ei-shaarawi, Esmail M. A. Mokheimer
    Abstract:

    The effect of thermal boundary conditions on conjugate laminar natural convection heat transfer in vertical eccentric annuli is numerically investigated using the finite-difference technique. Numerical results are presented for a Newtonian fluid of Prandtl number 0.7 in an eccentric annulus. The variation of Induced Flow Rate and total heat absorbed in the annulus are studied for two sets of boundary conditions at different values of geometry parameters (dimensionless annulus eccentricity and radius ratio). In both sets of boundary conditions, one wall is heated isothermally. The other wall is kept at the inlet fluid temperature for the first set of boundary conditions and adiabatic for the second set. The effect of interchanging the wall thermal conditions for each set is also considered. Analysis reveals that heating the outer cylinder wall or keeping one of the annulus walls insulated is more useful for inducing Flow (thermosiphons).

  • maximum possible Induced Flow Rates in open ended vertical eccentric annuli with uniform heat flux
    International Journal of Numerical Methods for Heat & Fluid Flow, 2005
    Co-Authors: Esmail M. A. Mokheimer, Maged A I Elshaarawi
    Abstract:

    Purpose – Obtaining the maximum possible Flow Rates that can be Induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the fourth kind (heating or cooling one of the annulus walls with a uniform heat flux while keeping the other wall at ambient temperature). Obtaining the maximum possible Flow Rates that can be Induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the fourth kind (heating or cooling one of the annulus walls with a uniform heat flux while keeping the other wall at ambient temperature).Design/methodology/approach – The fully‐developed laminar free convection momentum equation has been solved numerically using an analytical solution of the governing energy equation.Findings – Results are presented to show the effect of the annulus radius ratio and the dimensionless eccentricity on the Induced Flow Rate, the total heat absorbed by the fluid, and the fully developed Nussel...

  • Conjugate Effects on Steady Laminar Natural Convection Heat Transfer in Vertical Eccentric Annuli
    International Journal for Computational Methods in Engineering Science and Mechanics, 2005
    Co-Authors: Maged A. I. El-shaarawi, Esmail M. A. Mokheimer, Ahmad Jamal
    Abstract:

    Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically investigated using finite-difference technique. Numerical results are presented for a fluid of Prandtl number 0.7 in an annulus of radius ratio 0.5 and dimensionless eccentricity 0.5. The conjugation effect on the Induced Flow Rate and the total heat absorbed in the annulus is presented for the case of one wall being isothermally heated while the other wall is kept at inlet fluid temperature. The conjugate effects are controlled by solid-fluid conductivity ratio, cylinder walls thickness and dimensionless channel height (i.e. Grashof number). Solid-fluid conductivity ratio is varied over a range that covers practical cases with commonly encountered inner and outer walls thickness. Values of conductivity ratio over which conjugate effect can be neglected have been obtained. *On leave from Ain Shams University, Cairo, Egypt.

  • Maximum possible Induced Flow Rates in open‐ended vertical eccentric annuli with uniform heat flux
    International Journal of Numerical Methods for Heat & Fluid Flow, 2005
    Co-Authors: Esmail M. A. Mokheimer, Maged A. I. El-shaarawi
    Abstract:

    Purpose – Obtaining the maximum possible Flow Rates that can be Induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the fourth kind (heating or cooling one of the annulus walls with a uniform heat flux while keeping the other wall at ambient temperature). Obtaining the maximum possible Flow Rates that can be Induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the fourth kind (heating or cooling one of the annulus walls with a uniform heat flux while keeping the other wall at ambient temperature).Design/methodology/approach – The fully‐developed laminar free convection momentum equation has been solved numerically using an analytical solution of the governing energy equation.Findings – Results are presented to show the effect of the annulus radius ratio and the dimensionless eccentricity on the Induced Flow Rate, the total heat absorbed by the fluid, and the fully developed Nussel...

Maged A. I. El-shaarawi - One of the best experts on this subject based on the ideXlab platform.

  • Geometry effects on conjugate natural convection heat transfer in vertical eccentric annuli
    International Journal of Numerical Methods for Heat & Fluid Flow, 2007
    Co-Authors: Maged A. I. El-shaarawi, Esmail M. A. Mokheimer, Ahmad Jamal
    Abstract:

    Purpose – To explore the effect of the annulus geometrical parameters on the Induced Flow Rate and the heat transfer under the conjugate (combined conduction and free convection) thermal boundary conditions with one cylinder heated isothermally while the other cylinder is kept at the inlet fluid temperature.Design/methodology/approach – A finite‐difference algorithm has been developed to solve the bipolar boundary‐layer equations for the conjugate laminar free convection heat transfer in vertical eccentric annuli.Findings – Numerical results are presented for a fluid of Prandtl number, Pr=0.7 in eccentric annuli. The geometry parameters of NR2 and E (the fluid‐annulus radius ratio and the eccentricity, respectively) have considerable effects on the results.Practical implications – Applications of the obtained results can be of value in the heat‐exchanger industry, in cooling of underground electric cables, and in cooling small vertical electric motors and generators.Originality/value – The paper presents ...

  • Conjugate Effects on Steady Laminar Natural Convection Heat Transfer in Vertical Eccentric Annuli
    International Journal for Computational Methods in Engineering Science and Mechanics, 2005
    Co-Authors: Maged A. I. El-shaarawi, Esmail M. A. Mokheimer, Ahmad Jamal
    Abstract:

    Combined conduction-free convection heat transfer in vertical eccentric annuli is numerically investigated using finite-difference technique. Numerical results are presented for a fluid of Prandtl number 0.7 in an annulus of radius ratio 0.5 and dimensionless eccentricity 0.5. The conjugation effect on the Induced Flow Rate and the total heat absorbed in the annulus is presented for the case of one wall being isothermally heated while the other wall is kept at inlet fluid temperature. The conjugate effects are controlled by solid-fluid conductivity ratio, cylinder walls thickness and dimensionless channel height (i.e. Grashof number). Solid-fluid conductivity ratio is varied over a range that covers practical cases with commonly encountered inner and outer walls thickness. Values of conductivity ratio over which conjugate effect can be neglected have been obtained. *On leave from Ain Shams University, Cairo, Egypt.

  • Maximum possible Induced Flow Rates in open‐ended vertical eccentric annuli with uniform heat flux
    International Journal of Numerical Methods for Heat & Fluid Flow, 2005
    Co-Authors: Esmail M. A. Mokheimer, Maged A. I. El-shaarawi
    Abstract:

    Purpose – Obtaining the maximum possible Flow Rates that can be Induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the fourth kind (heating or cooling one of the annulus walls with a uniform heat flux while keeping the other wall at ambient temperature). Obtaining the maximum possible Flow Rates that can be Induced by free convection in open‐ended vertical eccentric annuli under fundamental thermal boundary conditions of the fourth kind (heating or cooling one of the annulus walls with a uniform heat flux while keeping the other wall at ambient temperature).Design/methodology/approach – The fully‐developed laminar free convection momentum equation has been solved numerically using an analytical solution of the governing energy equation.Findings – Results are presented to show the effect of the annulus radius ratio and the dimensionless eccentricity on the Induced Flow Rate, the total heat absorbed by the fluid, and the fully developed Nussel...

  • Limiting Values for Free-Convection Induced Flow Rates in Vertical Eccentric Annuli with an Isothermal Boundary
    Numerical Heat Transfer Part A: Applications, 2001
    Co-Authors: Maged A. I. El-shaarawi, Esmail M. A. Mokheimer, Habib I. Abulhamayel
    Abstract:

    Fully developed laminar natural convection in vertical eccentric annuli has been investigated under fundamental thermal boundary conditions of the first and third kinds. For conditions of the first kind, numerical solutions are presented showing the effect of eccentricity on the velocity profiles and the local Nusselt number in an annulus of radius ratio 0.5. Limiting values for the Induced Flow Rate and the average Nusselt numbers are presented for a fluid of Pr = 0.7 over wide ranges of eccentricity and annulus radius ratio (0.1-0.9). Closed-form analytical solutions are obtained for fundamental conditions of the third kind and the corresponding variations in the limiting Induced Flow Rates with eccentricity are presented.

  • Unsteady natural convection in open ended vertical concentric annuli
    International Journal of Numerical Methods for Heat & Fluid Flow, 1992
    Co-Authors: Maged A. I. El-shaarawi, M.a. Al‐attas
    Abstract:

    A finite‐difference scheme is developed for solving the boundary layer equations governing the unsteady laminar free convection Flow in open ended vertical concentric annuli. The initial condition considered for the creation of the thermal transient corresponds to a step change in temperature at the inner annulus boundary while the outer wall is maintained adiabatic. Numerical results for a fluid of Pr = 0.7 in an annulus of radius ratio 0.5 are presented. The results show the developing velocity and pressure fields with respect to space and time. Also, the important relationship between the annulus height and the Induced Flow Rate is presented for various values of the time parameter starting from quiescence to the final steady state.

André Zoulalian - One of the best experts on this subject based on the ideXlab platform.

  • Influence of operating conditions and design parameters on hydrodynamics and mass transfer in an emulsion loop–venturi reactor
    Chemical Engineering and Processing: Process Intensification, 2007
    Co-Authors: B. Gourich, N. El Azher, C. Vial, M. Belhaj Soulam, M. Ziyad, André Zoulalian
    Abstract:

    The aim of this paper is first to investigate the influence of operating conditions and design parameters on the hydrodynamics and the mass transfer properties of an emulsion loop–venturi reactor and then to compare its performance to that of the conventional gas–liquid contactors, such as airlift and bubble column reactors or aeRated stirred tanks. The results have shown that emulsion venturi reactors should be preferentially opeRated as gas-inducing devices. In this case, hydrodynamics and mass transfer depend strongly on the clear liquid height. This parameter exhibits an optimum value, as its increase improves mass transfer, but reduces the maximum gas-Induced Flow Rate. Conversely, the respective influences of the tank diameter at constant clear liquid height when D > 0.3 m and of the surface area of the orifices at the venturi throat were not significant in this work. Finally, emulsion loop–venturi contactors appear to be versatile tools able to carry out both fast and slow chemical reactions, which is not the case for the three other kinds of reactors. They are therefore useful when high and quickly adaptable oxygen supply is required, as they avoid also the presence of mechanically moving parts and present lower shear levels than mechanically stirred tanks.

J. Katolicky - One of the best experts on this subject based on the ideXlab platform.

  • Dispersion of pollutants in a street canyon and street intersection under traffic-Induced Flow and turbulence using a low Re κ-ε model
    International Journal of Environment and Pollution, 2002
    Co-Authors: Miroslav Jicha, J. Katolicky, Jiri Pospisil
    Abstract:

    A 3-D Eulerian-Lagrangian approach to moving vehicles is presented that takes into account the traffic-Induced Flow Rate and turbulence. The method is applied to pollutant dispersion in an individual street canyon and a system of two street canyons forming a perpendicular intersection. The approach is based on computational fluid dynamics (CFD) calculations using a Eulerian approach for continuous phase and a Lagrangian approach for moving vehicles. The wind speed was assigned values of 4, 7 and 12 m/s. One-way and two-way traffic with different traffic Rates per lane is considered. In the case of the intersection, a longitudinal wind direction was assumed. Predictions show differences in the pollutant dispersion in the case of one-way and two-way traffic.

  • Dispersion of Pollutants in Street Canyon under Traffic Induced Flow and Turbulence
    Environmental Monitoring and Assessment, 2000
    Co-Authors: Miroslav Jicha, Jiri Pospisil, J. Katolicky
    Abstract:

    A 3-D Eulerian-Lagrangian approach to moving vehicles is presented that takes into account the traffic Induced Flow Rate and turbulence. The method is applied to pollutants dispersion in a street canyon. The approach is based on CFD calculations using Eulerian approach to the continuous phase and Lagrangian approach to the "discrete phase" of moving objects - vehicles. A commercial CFD code StarCD was used into which the Lagrangian model was integRated. As an example a street canyon is taken into consideration. It has the length of 50 m and the aspect ratio of 1.27. The speed of wind was assigned values of 4, 7 and 12 m/s at the altitude of 300 m. The total height of the domain is 115 m. In the study different traffic situations are considered, namely one-way and two-way traffic with different traffic Rates per lane. The predictions show that different traffic situations affect pollutants dispersion in the street canyon and that there are also differences in the pollutants dispersion in case of one- and two-way traffic.

Jiri Pospisil - One of the best experts on this subject based on the ideXlab platform.

  • Dispersion of pollutants in a street canyon and street intersection under traffic-Induced Flow and turbulence using a low Re κ-ε model
    International Journal of Environment and Pollution, 2002
    Co-Authors: Miroslav Jicha, J. Katolicky, Jiri Pospisil
    Abstract:

    A 3-D Eulerian-Lagrangian approach to moving vehicles is presented that takes into account the traffic-Induced Flow Rate and turbulence. The method is applied to pollutant dispersion in an individual street canyon and a system of two street canyons forming a perpendicular intersection. The approach is based on computational fluid dynamics (CFD) calculations using a Eulerian approach for continuous phase and a Lagrangian approach for moving vehicles. The wind speed was assigned values of 4, 7 and 12 m/s. One-way and two-way traffic with different traffic Rates per lane is considered. In the case of the intersection, a longitudinal wind direction was assumed. Predictions show differences in the pollutant dispersion in the case of one-way and two-way traffic.

  • Dispersion of Pollutants in Street Canyon under Traffic Induced Flow and Turbulence
    Environmental Monitoring and Assessment, 2000
    Co-Authors: Miroslav Jicha, Jiri Pospisil, J. Katolicky
    Abstract:

    A 3-D Eulerian-Lagrangian approach to moving vehicles is presented that takes into account the traffic Induced Flow Rate and turbulence. The method is applied to pollutants dispersion in a street canyon. The approach is based on CFD calculations using Eulerian approach to the continuous phase and Lagrangian approach to the "discrete phase" of moving objects - vehicles. A commercial CFD code StarCD was used into which the Lagrangian model was integRated. As an example a street canyon is taken into consideration. It has the length of 50 m and the aspect ratio of 1.27. The speed of wind was assigned values of 4, 7 and 12 m/s at the altitude of 300 m. The total height of the domain is 115 m. In the study different traffic situations are considered, namely one-way and two-way traffic with different traffic Rates per lane. The predictions show that different traffic situations affect pollutants dispersion in the street canyon and that there are also differences in the pollutants dispersion in case of one- and two-way traffic.