Unsteady Laminar Pulsating Flow in a Saturated Porous Microchannel in the Presence of Electrical Double-Layer Effects

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Muhammad Dilawar Khan Niazi ◽  
Hang Xu
Keyword(s):  
Angular Velocity ◽  
Forced Convection ◽  
Double Layer ◽  
Analytical Solutions ◽  
Electrical Double Layer ◽  
Darcy Number ◽  
Pulsating Flow ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Periodic Pressure

Abstract The forced convection of a pulsating flow in a saturated porous parallel-plates microchannel driven by a periodic pressure in the presence of an electrical double layer is investigated. Such configuration is very important but seldom considered in literature. Analytical solutions for electrical, momentum, and temperature fields are obtained by means of a substitution approach. The results show that the flow fields depend highly on the electro-osmotic parameter κ, the angular velocity parameter Ω, as well as the Darcy number Da.

On Combined Free and Forced Convection in Channels

1960 ◽  
Vol 82 (3) ◽  
pp. 233-238 ◽  
Author(s):  
L. N. Tao
Keyword(s):  
Forced Convection ◽  
Rectangular Channel ◽  
Complex Function ◽  
Vertical Channel ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Free And Forced Convection ◽  
Energy Equations ◽  
Helmholtz Wave Equation ◽  
Transfer Problems

The heat-transfer problems of combined free and forced convection by a fully developed laminar flow in a vertical channel of constant axial wall temperature gradient with or without heat generations are approached by a new method. By introducing a complex function which is directly related to the velocity and temperature fields, the coupled momentum and energy equations are readily combinable to a Helmholtz wave equation in the complex domain. This greatly reduces the complexities of the problems. For illustrations, the cases of flows between parallel plates and in a rectangular channel are treated. It shows that this method is more direct and powerful than those of previous investigations.

Optimization of Parallel, Horizontal, and Laminar Forced Air-Cooled Heat Generating Boards

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
M. O. Özdemir ◽  
H. Yüncü
Keyword(s):  
Forced Convection ◽  
Heat Dissipation ◽  
Rectangular Channel ◽  
Numerical Procedure ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Constant Property ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Optimal Spacing

The objective of this study is to predict numerically the optimal spacing between parallel heat generating boards. The isothermal boards are stacked in a fixed volume of electronic package enclosed by insulated lateral walls, and they are cooled by laminar forced convection of air with prescribed pressure drop. In the numerical procedure, governing equations for the solution of forced convection of constant property incompressible flow through one rectangular channel are solved. Resulting flow and temperature fields in each rectangular channel yield the optimal board-to-board spacing by which maximum heat dissipation rate from the package to the air is achieved. Next, generalized correlations for the determination of the maximum heat transfer rate from the package and optimal spacing between boards are derived in terms of prescribed pressure difference, board length, and density and kinematic viscosity of air. Finally, corresponding correlations are compared with the available two-dimensional studies in literature for infinite parallel plates.

HOMOTOPY ANALYSIS OF TRANSIENT MAGNETO-BIO-FLUID DYNAMICS OF MICROPOLAR SQUEEZE FILM IN A POROUS MEDIUM: A MODEL FOR MAGNETO-BIO-RHEOLOGICAL LUBRICATION

2012 ◽  
Vol 12 (03) ◽  
pp. 1250051 ◽  
Author(s):  
O. ANWAR BÉG ◽  
M. M. RASHIDI ◽  
T. A. BÉG ◽  
M. ASADI
Keyword(s):  
Magnetic Field ◽  
Porous Medium ◽  
Angular Velocity ◽  
Differential Equations ◽  
Darcy Number ◽  
Squeeze Film ◽  
Squeezing Flow ◽  
Parallel Plates ◽  
Viscosity Parameter ◽  
Homotopy Analysis

The transient squeezing flow of a magneto-micropolar biofluid in a noncompressible porous medium intercalated between two parallel plates in the presence of a uniform strength transverse magnetic field is investigated. The partial differential equations describing the two-dimensional flow regime are transformed into nondimensional, nonlinear coupled ordinary differential equations for linear and angular momentum (micro-inertia). These equations are solved using the robust Homotopy Analysis Method (HAM) and also numerical shooting quadrature. Excellent correlation is achieved. The influence of magnetic field parameter (Ha) , micropolar spin gradient viscosity parameter (Γ) and unsteadiness parameter (S) on linear and angular velocity (micro-rotation) are presented graphically, for specified values of the micropolar vortex viscosity parameter (R), Darcy number (Da i.e. permeability parameter) and medium porosity parameter (ε). Increasing magnetic field (Ha) serves to decelerate both the linear and angular velocity i.e. enhances lubrication. The excellent potential of HAM in bio-lubrication flows is highlighted.

Optimal Spacings for Mixed Convection

2004 ◽  
Vol 126 (6) ◽  
pp. 956-962 ◽  
Author(s):  
T. Bello-Ochende ◽  
A. Bejan
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Mixed Convection ◽  
Forced Convection ◽  
Geometry Optimization ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Dimensionless Groups ◽  
Drop Number ◽  
Single Formula

This paper completes the description of geometry optimization in stacks of parallel plates that generate heat. The spacing between plates, or the number of plates in a fixed volume, has been maximized in two limits: pure natural convection and pure forced convection. In this paper, the in-between regime of mixed convection is modeled numerically. After simulating the flow and temperature fields in configurations with a variety of spacings, this paper reports the optimal spacings and the dimensionless groups that govern them (Rayleigh number, pressure drop number, mixed convection ratio). It shows that the numerical results match the results in the limits of natural convection and forced convection. The paper constructs a correlation that bridges the gap between the two limits, and provides a single formula for optimal spacings covering the entire domain, from natural convection to forced convection.

Local Thermal Equilibrium in Forced Convection Through Porous Media

2010 ◽  
Author(s):  
A. Nouri-Borujerdi
Keyword(s):  
Porous Medium ◽  
Pressure Gradient ◽  
Forced Convection ◽  
Thermal Equilibrium ◽  
Fluid Transport ◽  
Convection Heat Transfer ◽  
Darcy Number ◽  
Equation Model ◽  
Temperature Fields ◽  
Local Thermal Equilibrium

Forced convection heat transfer through a channel filled with a porous medium is investigated using perturbation method. Two-energy equation model is utilized to represent the assumption of local thermal non-equilibrium which exists between the solid and fluid phases. The Brinkman-Forchheimer extension of the Darcy model is used to represent the fluid transport within the porous medium. Analytical solution is obtained for both fluid and solid temperature fields incorporating the effects of various pertinent parameters such as the Darcy number, the Biot number, the thermal conductivity and the pressure gradient. It is found that the Darcy number and the pressure gradient have significant effects on the local thermal equilibrium assumption.

Modeling the Electrical Double Layer to Understand the Reaction Environment in a CO2 Electrocatalytic System

2019 ◽  
Author(s):  
Divya Bohra ◽  
Jehanzeb Chaudhry ◽  
Thomas Burdyny ◽  
Evgeny Pidko ◽  
wilson smith
Keyword(s):  
Electric Field ◽  
Double Layer ◽  
Electrical Double Layer ◽  
Surface Reaction ◽  
Catalyst Surface ◽  
Local Reaction ◽  
Reaction Diffusion ◽  
Alkali Metal Cations ◽  
Applied Potential ◽  
Critical Aspect

<p>The environment of a CO<sub>2</sub> electroreduction (CO<sub>2</sub>ER) catalyst is intimately coupled with the surface reaction energetics and is therefore a critical aspect of the overall system performance. The immediate reaction environment of the electrocatalyst constitutes the electrical double layer (EDL) which extends a few nanometers into the electrolyte and screens the surface charge density. In this study, we resolve the species concentrations and potential profiles in the EDL of a CO<sub>2</sub>ER system by self-consistently solving the migration, diffusion and reaction phenomena using the generalized modified Poisson-Nernst-Planck (GMPNP) equations which include the effect of volume exclusion due to the solvated size of solution species. We demonstrate that the concentration of solvated cations builds at the outer Helmholtz plane (OHP) with increasing applied potential until the steric limit is reached. The formation of the EDL is expected to have important consequences for the transport of the CO<sub>2</sub> molecule to the catalyst surface. The electric field in the EDL diminishes the pH in the first 5 nm from the OHP, with an accumulation of protons and a concomitant depletion of hydroxide ions. This is a considerable departure from the results obtained using reaction-diffusion models where migration is ignored. Finally, we use the GMPNP model to compare the nature of the EDL for different alkali metal cations to show the effect of solvated size and polarization of water on the resultant electric field. Our results establish the significance of the EDL and electrostatic forces in defining the local reaction environment of CO<sub>2</sub> electrocatalysts.</p>

Sign in / Sign up

Export Citation Format

Share Document