A Correlation for Nusselt Number of Slip Gas Flow in Confined Porous Media

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Ammar Tariq ◽  
Peng Li ◽  
Anyi Xu ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Nusselt Number ◽  
Gas Flow ◽  
Velocity Slip ◽  
Clear Understanding ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Multiple Relaxation Time ◽  
Microporous Media

Abstract A clear understanding of flow and heat transfer at pore-scale level in microporous media is a topic of concern in microcooling/heating systems. In this work, a multiple-relaxation-time lattice Boltzmann method (LBM) is employed to study flow and heat transfer of gas in microporous media. Curved boundaries are treated using an effective boundary condition, which is formed by combining nonequilibrium extrapolation with counterextrapolation methods. The method also incorporates velocity slip and temperature jump on gas–solid interface. A two-dimensional (2D) porous domain composed of microcylinders, is considered from a representative element volume (REV) for the simulation. Porosity of the domain is variated by altering diameter of microcylinders. Nusselt number is calculated by varying Knudsen number (0.0–0.1), Reynolds number (5–50) and porosity (0.4–0.8). Based on the obtained numerical predictions, a new Nusselt number correlation is proposed for the first time in this work which can accurately predict the heat transfer for slip gas flow in confined porous media.

Slip Gas Flow and Heat Transfer in Confined Porous Media With Different Shape Cylinders

2021 ◽  
Author(s):  
Ammar Tariq ◽  
Zhenyu Liu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Gas Flow ◽  
Velocity Slip ◽  
Heat Transfer Analysis ◽  
Variable Boundary ◽  
Flow And Heat Transfer ◽  
Multiple Relaxation Time ◽  
Permeability Increase ◽  
Boltzmann Method

Abstract With the recent advances in micro devices, an accurate gas flow and heat transfer analysis become more relevant considering the slip effect. A micro-scale, multiple-relaxation-time (MRT) lattice Boltzmann method with double distribution function approach is used to simulate flow and heat transfer through circular- and diamond-shaped cylinders at the porescale level. The velocity slip and temperature jump are captured at the boundaries using a non-equilibrium extrapolation scheme with the counter-extrapolation method. A pore-scale domain of micro-cylinders comprised of circle and diamond shape are studied. It is found that the permeability increases linearly with an increase in Knudsen number for both circular- and diamond-shaped cylinders. However, the permeability increase for circular obstacle is larger than that of the diamond one. A larger surface area for diamond cylinder will offer more resistance to flow, hence resulting in lower values. For heat transfer, the Nusselt number shows an increase with increasing Reynolds number, however, it decreases with the increase in porosity. Nusselt number values are found to be higher for a circular obstacle. A variable boundary gradient for circular obstacle could be a possible explanation for this difference.

Nusselt Number Prediction for Slip Flow in Confined Porous Media Based on Lattice Boltzmann Method

2019 ◽  
Author(s):  
Ammar Tariq ◽  
Zhenyu Liu ◽  
Zhiyu Mu ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Nusselt Number ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Slip Flow ◽  
Flow And Heat Transfer ◽  
Prime Concern ◽  
Multiple Relaxation Time ◽  
Boltzmann Method

Abstract Understanding flow and heat transfer in porous media is a matter of prime concern for micro devices. In this work, slip flow and heat transfer of gaseous fluid through the confined porous media is numerically simulated using a multiple-relaxation-time lattice Boltzmann method. The method is employed using an effective curved boundary treatment based on non-equilibrium extrapolation and counter-extrapolation methods. Nusselt number prediction for varying porosity, Knudsen and Reynolds number are studied. Based on the obtained numerical results, it is proved that the current technique can be used to effectively model slip flow and heat transfer at pore-scale.

scholarly journals A Non-Newtonian Magnetohydrodynamics (MHD) Nanofluid Flow and Heat Transfer with Nonlinear Slip and Temperature Jump

Mathematics ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 1199 ◽  
Author(s):  
Jing Zhu ◽  
Yaxin Xu ◽  
Xiang Han
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Temperature Jump ◽  
Thin Sheet ◽  
Velocity Slip ◽  
Skin Friction Coefficient ◽  
Slip Condition ◽  
Physical Parameters ◽  
Nanofluid Flow ◽  
Flow And Heat Transfer

The velocity and thermal slip impacts on the magnetohydrodynamics (MHD) nanofluid flow and heat transfer through a stretched thin sheet are discussed in the paper. The no slip condition is substituted for a new slip condition consisting of higher-order slip and constitutive equation. Similarity transformation and Lie point symmetry are adopted to convert the derived governed equations to ordinary differential equations. An approximate analytical solution is gained through the homotopy analysis method. The impacts of velocity slip, temperature jump, and other physical parameters on flow and heat transfer are illustrated. Results indicate that the first-order slip and nonlinear slip parameters reduce the velocity boundary layer thickness and Nusselt number, whereas the effect on shear stress is converse. The temperature jump parameter causes a rise in the temperature, but a decline in the Nusselt number. With the increase of the order, we can get that the error reaches 10 − 6 from residual error curve. In addition, the velocity contours and the change of skin friction coefficient are computed through Ansys Fluent.

Magnetogasdynamic Flow and Heat Transfer in a Microchannel

2011 ◽  
Author(s):  
Huei Chu Weng
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Joule Heating ◽  
Electromagnetic Force ◽  
Gas Flow ◽  
Velocity Slip ◽  
Flow And Heat Transfer ◽  
Electric And Magnetic Field ◽  
Flow Through ◽  
Flow Drag

The presence of current flow in an electric and magnetic field results in electromagnetic force and joule heating. It is desirable to understand the roles of electromagnetic force and joule heating on gas microflow and heat transfer. In this study, a mathematical model is developed of the pressure-driven gas flow through a long isothermally heated horizontal planar microchannel in the presence of an external electric and magnetic field. The solutions for flow and thermal field and characteristics are derived analytically and presented in terms of dimensionless parameters. It is found that an electromagnetic driving force can be produced by a combined non-zero electric field and a negative magnetic field and results in an additional velocity slip and an additional flow drag. Also, a joule heating can be enhanced by an applied positive magnetic field and therefore results in an additional temperature jump and an additional heat transfer.

Comparison of Fluid Flow and Heat Transfer Through Metal Foams and Wire Mesh by Using CFD

2019 ◽  
Vol 12 (3) ◽  
pp. 220-226
Author(s):  
Banjara Kotresha ◽  
Nagarajan Gnanasekaran
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Numerical Simulations ◽  
Metal Foam ◽  
Metal Foams ◽  
Wire Mesh ◽  
Flow And Heat Transfer ◽  
The Wire

Background: The unique structural characteristics of the metal foams, such as low density, large surface area, ability to increase turbulence, and increased heat transfer efficiency, are the advantages associated with thermal applications such as electronics cooling, refrigeration air conditioning, etc. The porous metal foam structures are extensively used to enhance heat transfer. Objective: This paper discusses the numerical simulations of a vertical channel filled with metal foam and wire mesh. The fluid flow and heat transfer phenomena of a wire mesh are compared with two different types of metal foams. Metal foams are made of aluminium and copper while the wire mesh is made of brass. The porosity of the metallic porous structures varies from 0.85 to 0.95. Methods: A Darcy extended Forchheirmer model is considered for solving fluid flow through the porous media while the heat transfer through the porous media is predicted using local thermal non-equilibrium model. Results: Initially, the results obtained using the proposed numerical procedures are compared with experimental results available in the literature. The numerical simulations suggest that the pressure drop increases as the velocity of the fluid increases and decreases as the porosity increases. The heat transfer coefficient and Nusselt number are determined for both the metal foams and the wire mesh. Conclusion: The Nusselt number obtained for wire mesh shows almost 90% of the copper metal foam in the same porosity range. The numerical results suggest that the brass wire mesh porous medium can also be used for enhancement of heat transfer. In this article, patents have been discussed.

Numerical Modeling of Slip Flow and Heat Transfer Over Microcylinders With Lattice Boltzmann Method

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Zhenyu Liu ◽  
Zhiyu Mu ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Lattice Boltzmann ◽  
Gas Flow ◽  
Temperature Jump ◽  
Slip Flow ◽  
Velocity Slip ◽  
Curved Boundary ◽  
Slip Regime ◽  
Flow And Heat Transfer ◽  
Boltzmann Method

In this paper, a lattice Boltzmann (LB) model is established to simulate the gaseous fluid flow and heat transfer in the slip regime under the curved boundary condition. A novel curved boundary treatment is proposed for the LB modeling, which is a combination of the nonequilibrium extrapolation scheme for the curved boundary and the counter-extrapolation method for the macroscopic variables on the curved gas–solid interface. The established numerical model can accurately predict the velocity slip and temperature jump of the microscale gas flow on the curved surface, which agrees well with the analytical solution for the microcylindrical Couette flow and heat transfer. Then, the slip flow and the heat transfer over the single microcylinder are numerically studied in this work. It shows that the velocity slip and the temperature jump are obviously influenced by the Knudsen number and the Reynolds number, and the local Nusselt number depends on which gas rarefaction effect (velocity slip or temperature jump) is dominant. An increase in the Prandtl number leads to a decrease in the temperature jump, which enhances the heat transfer on the microcylinder surface. The numerical simulation of the flow and heat transfer over two microcylinders in tandem configuration are carried out to investigate the wake interference effect. The results show that the slip flow and heat transfer characteristics of the downstream microcylinder are influenced by the wake region behind the upstream cylinder as the spacing is small.

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