The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform

Khalid N. Alammar - One of the best experts on this subject based on the ideXlab platform.

  • Flow and heat transfer characteristics downstream of a porous sudden expansion: A numerical study
    Thermal Science, 2011
    Co-Authors: Khalid N. Alammar
    Abstract:

    Incompressible, axisymmetric laminar flow downstream of a porous expansion is simulated. Effect of the Darcy number and Inertia Coefficient on flow and heat transfer characteristics downstream of the expansion is investigated. The simulation revealed circulation downstream of the expansion. Decreasing the Darcy number is shown to decrease the circulation region. The Nusselt number, friction Coefficient, and pressure drop are shown to increase, while reattachment and location of maximum heat transfer move upstream with decreasing Darcy number. Similar effects are observed with increasing Inertia Coefficient.

  • Flow and Heat Transfer Characteristics Downstream of A Porous Sudden Expansion
    10th AIAA ASME Joint Thermophysics and Heat Transfer Conference, 2010
    Co-Authors: Khalid N. Alammar
    Abstract:

    Incompressible, axisymmetric laminar flow downstream of a porous expansion is simulated. Effect of the Darcy number and Inertia Coefficient on flow and heat transfer characteristics downstream of the expansion is investigated. The simulation revealed circulation downstream of the expansion. Decreasing the Darcy number is shown to decrease circulation. The Nusselt number, friction Coefficient, and pressure drop are shown to increase, while reattachment and location of maximum heat transfer move upstream with decreasing Darcy number. Similar effects are observed with increasing Inertia Coefficient.

  • Flow and heat transfer characteristics downstream of a porous sudden expansion: A numerical study
    Thermal Science, 2010
    Co-Authors: Khalid N. Alammar
    Abstract:

    Original scientific paper UDC: 532.546:536.22:519.872 DOI: 10.2298/TSCI1102389A Incompressible, axisymmetric laminar flow downstream of a porous expansion is simulated. Effect of the Darcy number and Inertia Coefficient on flow and heat transfer characteristics downstream of the expansion is investigated. The simulation revealed circulation downstream of the expansion. Decreasing the Darcy number is shown to decrease the circulation region. The Nusselt number, friction Coefficient, and pressure drop are shown to increase, while reattachment and location of maximum heat transfer move upstream with decreasing Darcy number. Similar effects are observed with increasing Inertia Coefficient.

Frederic Topin - One of the best experts on this subject based on the ideXlab platform.

  • Micro-structural Impact of Different Strut Shapes and Porosity on Hydraulic Properties of Kelvin-Like Metal Foams
    Transport in Porous Media, 2014
    Co-Authors: Prashant Kumar, Frederic Topin
    Abstract:

    Various ideal periodic isotropic structures of foams (tetrakaidecahedron) with constant ligament cross section are studied. Different strut shapes namely circular, square, diamond, hexagon, star, and their various orientations are modeled using CAD. We performed direct numerical simulations at pore scale, solving Navier–Stokes equation in the fluid space to obtain various flow properties namely permeability and Inertia Coefficient for all shapes in the porosity range, $$0.60

  • Micro-structural Impact of Different Strut Shapes and Porosity on Hydraulic Properties of Kelvin-Like Metal Foams
    Transport in Porous Media, 2014
    Co-Authors: Prashant Kumar, Frederic Topin
    Abstract:

    Various ideal periodic isotropic structures of foams (tetrakaidecahedron) with constant ligament cross section are studied. Different strut shapes namely circular, square, diamond, hexagon, star, and their various orientations are modeled using CAD. We performed direct numerical simulations at pore scale, solving Navier-Stokes equation in the fluid space to obtain various flow properties namely permeability and Inertia Coefficient for all shapes in the porosity range, for wide range of Reynolds numbers, . We proposed an analytical model to obtain pressure drop in metallic foams in order to correlate the resulting macroscopic pressure and velocity gradients with the Ergun-like approach. The analytical results are fully compared with the available numerical data, and an excellent agreement is observed.

  • Investigation of fluid flow properties in open cell foams: Darcy and weak Inertia regimes
    Chemical Engineering Science, 2014
    Co-Authors: Prashant Kumar, Frederic Topin
    Abstract:

    Knowledge of flow properties induced by open cell foams is essential to the successful design and operation of high performance industrial systems. Flow properties are strongly dependent on the geometry of foams, but these relationships are not still fully characterized. This paper investigates the impact on flow properties of the geometrical characteristics of metal foams in the porosity range of 80-95%. An analytical model is proposed to characterize the foam matrix fully. 3-D direct numerical simulations at pore scale have been performed, and the Navier-Stokes equation has been solved for various Reynolds numbers (10(-5) < Re < 500) in the fluid space. We determine permeability in the Darcy regime and distinguish it from permeability obtained in the Inertia regime (Forchheimer Equation). The Inertia Coefficient is determined using both the Darcy and Inertia regimes. The two approaches are fully discussed and the critical importance of the permeability of the Darcy regime to the friction factor is shown. We further derive an analytical solution determining fluid flow characteristics in order to incorporate the resulting macroscopic pressure and velocity gradients in the Ergun-like equation. The analytical results are thoroughly compared with the numerical and experimental data and an excellent agreement is observed. (C) 2014 Elsevier Ltd. All rights reserved.

  • Influence of Pore and Strut Shape on Open Cell Metal Foam Bulk Properties
    2012
    Co-Authors: Prashant Kumar, Frederic Topin, Jean-michel Hugo, Jerome Vicente
    Abstract:

    The thermo-physical behavior of open-celled metal foams depends on their microscopic structure. An ideal periodic isotropic structure of tetrakaidecahedron shape i.e. Kelvin cell is studied. We have proposed an analytical model in order to obtain geometrical parameters correctly as they have substantial influence on thermal and hydraulic phenomena, where strut geometry is of prime importance. Various relationships between different geometrical parameters and porosities are presented. Consequently, empirical correlations are proposed to determine permeability and Inertia Coefficient using Ergun like model for computing pressure drop.

Haibo Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Tailor-making thermocouple junction for flame temperature measurement via dynamic transient method
    Proceedings of the Combustion Institute, 2017
    Co-Authors: Xin Tian, Haibo Zhao
    Abstract:

    Abstract Traditional dynamic method for temperature measurement is generally based on the assumption that the thermal Inertia Coefficient of a thermocouple junction is invariable (time constant) within the whole measuring process. Furthermore, the effect of heat conduction and heat radiation on the temperature response of the thermocouple is simply neglected under certain conditions. In this study, a new concept is proposed for improvement of the traditional dynamic method. The key point of the newly-proposed method is to tailor-make a thermocouple junction diameter to realize accurate compensation for radiation heat loss and specific heat capacity rising with the heat conduction from wires to the junction, which eventually makes the temperature response curve of the thermocouple still comply with the first-order response equation. The proposed method can be used for temperature measurement of high temperature flame, fine particle-laden flame as well as lab-scale small flame. Heat sink at the thermocouple junction due to heat conduction from neighboring wires to the junction is observed via numerical calculation, which can compensate the temperature rise lag of the junction caused by the radiation heat loss and the increase of specific heat capacity. Thus, there is no need to neglect the effect of heat conduction, heat radiation and thermal Inertia Coefficient variation on temperature measurement as in the traditional dynamic method. A thermocouple with the junction diameter of 0.7 mm can retain relatively long time (ca. 2 s) of steady apparent thermal Inertia Coefficient. The tailor-made thermocouple is applied to measure the temperature of TiO2 aerosol flame and sooting flame. The temperature measurement results agree well with both simulation results and benchmark experimental results, which indicates that the improved dynamic method and the tailor-made thermocouple can be employed to measure the temperature of fine particle-laden flame in a relatively straightforward manner.

Prashant Kumar - One of the best experts on this subject based on the ideXlab platform.

  • Micro-structural Impact of Different Strut Shapes and Porosity on Hydraulic Properties of Kelvin-Like Metal Foams
    Transport in Porous Media, 2014
    Co-Authors: Prashant Kumar, Frederic Topin
    Abstract:

    Various ideal periodic isotropic structures of foams (tetrakaidecahedron) with constant ligament cross section are studied. Different strut shapes namely circular, square, diamond, hexagon, star, and their various orientations are modeled using CAD. We performed direct numerical simulations at pore scale, solving Navier–Stokes equation in the fluid space to obtain various flow properties namely permeability and Inertia Coefficient for all shapes in the porosity range, $$0.60

  • Micro-structural Impact of Different Strut Shapes and Porosity on Hydraulic Properties of Kelvin-Like Metal Foams
    Transport in Porous Media, 2014
    Co-Authors: Prashant Kumar, Frederic Topin
    Abstract:

    Various ideal periodic isotropic structures of foams (tetrakaidecahedron) with constant ligament cross section are studied. Different strut shapes namely circular, square, diamond, hexagon, star, and their various orientations are modeled using CAD. We performed direct numerical simulations at pore scale, solving Navier-Stokes equation in the fluid space to obtain various flow properties namely permeability and Inertia Coefficient for all shapes in the porosity range, for wide range of Reynolds numbers, . We proposed an analytical model to obtain pressure drop in metallic foams in order to correlate the resulting macroscopic pressure and velocity gradients with the Ergun-like approach. The analytical results are fully compared with the available numerical data, and an excellent agreement is observed.

  • Investigation of fluid flow properties in open cell foams: Darcy and weak Inertia regimes
    Chemical Engineering Science, 2014
    Co-Authors: Prashant Kumar, Frederic Topin
    Abstract:

    Knowledge of flow properties induced by open cell foams is essential to the successful design and operation of high performance industrial systems. Flow properties are strongly dependent on the geometry of foams, but these relationships are not still fully characterized. This paper investigates the impact on flow properties of the geometrical characteristics of metal foams in the porosity range of 80-95%. An analytical model is proposed to characterize the foam matrix fully. 3-D direct numerical simulations at pore scale have been performed, and the Navier-Stokes equation has been solved for various Reynolds numbers (10(-5) < Re < 500) in the fluid space. We determine permeability in the Darcy regime and distinguish it from permeability obtained in the Inertia regime (Forchheimer Equation). The Inertia Coefficient is determined using both the Darcy and Inertia regimes. The two approaches are fully discussed and the critical importance of the permeability of the Darcy regime to the friction factor is shown. We further derive an analytical solution determining fluid flow characteristics in order to incorporate the resulting macroscopic pressure and velocity gradients in the Ergun-like equation. The analytical results are thoroughly compared with the numerical and experimental data and an excellent agreement is observed. (C) 2014 Elsevier Ltd. All rights reserved.

  • Influence of Pore and Strut Shape on Open Cell Metal Foam Bulk Properties
    2012
    Co-Authors: Prashant Kumar, Frederic Topin, Jean-michel Hugo, Jerome Vicente
    Abstract:

    The thermo-physical behavior of open-celled metal foams depends on their microscopic structure. An ideal periodic isotropic structure of tetrakaidecahedron shape i.e. Kelvin cell is studied. We have proposed an analytical model in order to obtain geometrical parameters correctly as they have substantial influence on thermal and hydraulic phenomena, where strut geometry is of prime importance. Various relationships between different geometrical parameters and porosities are presented. Consequently, empirical correlations are proposed to determine permeability and Inertia Coefficient using Ergun like model for computing pressure drop.

Raed Abed Mahdi - One of the best experts on this subject based on the ideXlab platform.

  • review of convection heat transfer and fluid flow in porous media with nanofluid
    Renewable & Sustainable Energy Reviews, 2015
    Co-Authors: Raed Abed Mahdi, Kannan M. Munisamy, H A Mohammed, Nawaf H. Saeid
    Abstract:

    There are two advantages of using porous media. First, its dissipation area is greater than the conventional fins that enhances the heat convection. Second is the irregular motion of the fluid flow around the individual beads which mixes the fluid more effectively. Nanofluids result from the mixtures of base fluid with nanoparticles having dimensions of (1–100) nm, with very high thermal conductivities; as a result, it would be the best convection heat transfer by using two applications together: porous media and nanofluids. This article aims to summarize the published articles in respect to porosity, permeability (K) and Inertia Coefficient (Cf) and effective thermal conductivity (keff) for porous media, also on the thermophysical properties of nanofluid and the studies on convection heat transfer in porous media with nanofluid.