Pore Scale Investigation of Heat Conduction of High Porosity Open-Cell Metal Foam/Paraffin Composite

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Heat Conduction ◽  
Pore Size ◽  
Metal Foam ◽  
Volume Fraction ◽  
Experimental Studies ◽  
Scale Model ◽  
Small Scale ◽  
High Porosity ◽  
Pore Scale ◽  
Open Cell

In this paper, a numerical model employing an approximately realistic three-dimensional (3D) foam structure represented by Weaire–Phelan foam cell is developed to study the steady-state heat conduction of high porosity open-cell metal foam/paraffin composite at the pore-scale level. The conduction problem is considered in a cubic representative computation unit of the composite material with a constant temperature difference between one opposite sides of the cubic unit (the other outer surfaces of the cubic unit are thermally insulated). The effective thermal conductivities (ETCs) of metal foam/paraffin composites are calculated with the developed pore-scale model considering small-scale details of heat conduction, which avoids using adjustable free parameters that are usually adopted in the previous analytical models. Then, the reason why the foam pore size has no evident effect on ETC as reported in the previous macroscopic experimental studies is explored at pore scale. Finally, the effect of air cavities existing within solid paraffin in foam pore region on conduction capacity of metal foam/paraffin composite is investigated. It is found that our ETC data agree well with the reported experimental results, and thus by direct numerical simulation (DNS), the ETC data of different metal foam/paraffin composites are provided for engineering applications. The essential reason why pore size has no evident effect on ETC is due to the negligible interstitial heat transfer between metal foam and paraffin under the present thermal boundary conditions usually used to determine the ETC. It also shows that overlarge volume fraction of air cavity significantly weakens the conduction capacity of paraffin, which however can be overcome by the adoption of high conductive metal foam due to enhancement of conduction.

Numerical Study of Heat Conduction of High Porosity Open-Cell Metal Foam/Paraffin Composite at Pore Scale

2016 ◽  
Author(s):  
Yuanpeng Yao ◽  
Huiying Wu ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Pore Size ◽  
Metal Foam ◽  
Foam Cell ◽  
High Porosity ◽  
Pore Scale ◽  
Thermal Equilibrium State ◽  
Foam Structure ◽  
Open Cell

In this paper, a numerical model employing 3D foam structure represented by Weaire-Phelan foam cell is developed to study the steady heat conduction of high porosity open-cell metal foam/paraffin composite at the pore-scale level. Two conduction problems are considered in the cubic representative computation unit of the composite material: one with constant temperature difference between opposite sides of the cubic unit (that can be used to determine the effective thermal conductivity (ETC)) and the second with constant heat flux at the interface between metal foam and paraffin (that can be used to determine the interstitial conduction heat transfer coefficient (ICHTC)). The effects of foam pore structure parameters (pore size and porosity) on heat conduction are investigated for the above two problems. Results show that for the first conduction problem, the effect of foam structure on heat conduction (i.e. the ETC) is related to porosity rather than pore size. The essential reason is due to the thermal equilibrium state between metal foam and paraffin indicated by the negligible interstitial heat transfer. While for the second conduction problem with inherent thermal non-equilibrium effect, it shows that both porosity and pore size significantly influence the interstitial heat conduction (i.e. the ICHTC). Furthermore, the present ETC and ICHTC data are compared to the results in the published literature. It shows that our ETC data agree well with the reported experimental results, and are more accurate than the numerical predications based on body-centered-cubic foam cell in literature. And our ICHTC data are in qualitative agreement with the published numerical results, but the present results are based on a more realistic foam structure.

scholarly journals Development of a numerical workflow based on <i>μ</i>-CT imaging for the determination of capillary pressure–saturation-specific interfacial area relationship in 2-phase flow pore-scale porous-media systems: a case study on Heletz sandstone

Solid Earth ◽  
2016 ◽  
Vol 7 (3) ◽  
pp. 727-739 ◽  
Author(s):  
Aaron Peche ◽  
Matthias Halisch ◽  
Alexandru Bogdan Tatomir ◽  
Martin Sauter
Keyword(s):  
High Resolution ◽  
Pore Size ◽  
Capillary Pressure ◽  
Interfacial Area ◽  
Scale Model ◽  
Phase Flow ◽  
Pore Scale ◽  
Pore Size Distributions ◽  
Phase Saturation

Abstract. In this case study, we present the implementation of a finite element method (FEM)-based numerical pore-scale model that is able to track and quantify the propagating fluid–fluid interfacial area on highly complex micro-computed tomography (μ-CT)-obtained geometries. Special focus is drawn to the relationship between reservoir-specific capillary pressure (pc), wetting phase saturation (Sw) and interfacial area (awn). The basis of this approach is high-resolution μ-CT images representing the geometrical characteristics of a georeservoir sample. The successfully validated 2-phase flow model is based on the Navier–Stokes equations, including the surface tension force, in order to consider capillary effects for the computation of flow and the phase-field method for the emulation of a sharp fluid–fluid interface. In combination with specialized software packages, a complex high-resolution modelling domain can be obtained. A numerical workflow based on representative elementary volume (REV)-scale pore-size distributions is introduced. This workflow aims at the successive modification of model and model set-up for simulating, such as a type of 2-phase problem on asymmetric μ-CT-based model domains. The geometrical complexity is gradually increased, starting from idealized pore geometries until complex μ-CT-based pore network domains, whereas all domains represent geostatistics of the REV-scale core sample pore-size distribution. Finally, the model can be applied to a complex μ-CT-based model domain and the pc–Sw–awn relationship can be computed.

Experimental Studies of Hydrodynamic Properties and Screening of Riser Fairing Concepts for Deep Water Applications

2015 ◽  
Author(s):  
Rolf Baarholm ◽  
Kjetil Skaugset ◽  
Halvor Lie ◽  
Henning Braaten
Keyword(s):  
Experimental Studies ◽  
Real Life ◽  
Cross Flow ◽  
Free Vibrations ◽  
The Body ◽  
Scale Model ◽  
Small Scale ◽  
Structural Fatigue ◽  
And Performance ◽  
Set Up

The VIV oscillations of marine risers are known to increase drag, and lead to structural fatigue. One proven method of suppressing this vibration is the use of fairings and strakes. These coverings essentially modify the flow along the cylinder, tripping the production of Karman vortices so that they act less coherently or far enough downstream so they interact less with the body. The Norwegian Deepwater Programme (NDP) has conducted a project with the objective to develop and qualify effective low drag fairing concepts with respect to VIV mitigation and galloping. Furthermore, emphasis is put on easy handling and installation. This paper describes the work and findings in an early phase of the development. This includes small scale model test campaigns. In addition to the bare riser for reference, the behaviour and performance of a total of 10 different fairing concepts are evaluated. Free oscillation tests are performed in a towing tank, where 2D fairings were tested in a pendulum set-up. The set-up enables free vibrations in up to 3 DOF (in-line and cross-flow vibrations and yaw). Fix tests with the purpose of establishing hydrodynamic coefficients for the various fairings have been performed in a large cavitation tunnel. Clear differences in performance have been noticed; particular for drag and galloping responses. Based on the results from the 2D tests, a screening of the fairing designs has been performed and the findings have set the course for further development of the most promising candidates for real life applications.

scholarly journals Numerical Simulation on Enhanced Heat Transfer of Metal Foam Based on LBM

2021 ◽  
Vol 2085 (1) ◽  
pp. 012028
Author(s):  
Zhongli Li ◽  
Peng Hu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Nusselt Number ◽  
Metal Foam ◽  
Metal Structure ◽  
Heat Transfer Process ◽  
Solid Particles ◽  
Distribution Model ◽  
High Porosity ◽  
Open Cell

Abstract Open cell foam metal has the characteristics of high porosity and large specific surface area. And it has developed rapidly in the related research of heat exchanger. Aiming at the convective heat transfer process of open cell metal structure with high porosity, a two-dimensional stochastic distribution model is established. Numerical simulation is carried out using the single-relaxation-time dual-distribution-function lattice-Boltzmann-method (BGK-DDF-LBM). For the non-ideal solid particles with unequal diameter and incomplete circular structure, the flow field is analyzed by taking the porosity of 0.964 as an example, and the dimensionless permeability is calculated. When the porosity is constant, the Nusselt number of the porous section increases with the increases of Reynolds number in the range of 10 to 100, which shows heat transfer performance. In addition, the Nusselt number of the porous section increases with the increase of porosity in the range of porosity from 0.900 to 0.980.

scholarly journals Numerical study of pore-scale flow and noise of an open cell metal foam

2018 ◽  
Vol 82-83 ◽  
pp. 185-198 ◽  
Author(s):  
Chen Xu ◽  
Yijun Mao ◽  
Zhiwei Hu
Keyword(s):  
Metal Foam ◽  
Numerical Study ◽  
Pore Scale ◽  
Open Cell

scholarly journals Development of a numerical workflow based on μ-CT-imaging for the determination of capillary pressure-saturation-specific interfacial area relationship in two-phase flow pore-scale porous media systems: A case study on Heletz sandstone

2016 ◽  
Author(s):  
Aaron Peche ◽  
Matthias Halisch ◽  
Alexandru Bogdan Tatomir
Keyword(s):  
High Resolution ◽  
Pore Size ◽  
Capillary Pressure ◽  
Two Phase Flow ◽  
Interfacial Area ◽  
Scale Model ◽  
Phase Flow ◽  
Pore Scale ◽  
Two Phase

Abstract. In this case study, we present the implementation of a FEM-based numerical pore-scale model that enables to track and quantify the propagating fluid-fluid interfacial area on highly complex μ-CT obtained geometries. Special focus is drawn to the reservoir specific capillary pressure (pc)- wetting phase saturation (Sw)- interfacial area (awn)- relationship. The basis of this approach are high resolution μ-CT images representing the geometrical characteristics of a georeservoir sample. The successfully validated two-phase flow model is based on the Navier-Stokes equations, including the surface tension force in order to consider capillary effects for the computation of flow and the phase field method for the emulation of a sharp fluid-fluid interface. In combination with specialized software packages, a complex high resolution modeling domain could be obtained. A numerical workflow based on REV-scale pore size distributions is introduced. This workflow aims at the successive modification of model and model setup for simulating such a type of two-phase problem on asymmetric μ-CT-based model domains. The geometrical complexity is gradually increased starting from idealized pore geometries until complex μ-CT-based pore network domains, whereas all domains represent geostatistics of the REV-scale core sample pore size distribution. Finally, the model could be applied on a complex μ-CT-based model domain and the pc-Sw-awn relationship could be computed.

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