Permeability (K) and form coefficient (C) are the characteristic hydraulic properties of any porous medium. They are determined simultaneously, for known fluid thermo-physical properties by using the Hazen-Dupuit-Darcy model (HDD) to curve-fit the longitudinal global pressure-drop versus average fluid speed data from an isothermal, steady flow, hydraulic experiment across a test section of the porous medium. The K and C thus measured are global parameters, i.e., valid for the entire porous medium and universal provided the flow throughout the porous medium is of plug flow nature. We report here experimental evidence on the influence of non-plug flow velocity profiles at the inlet, on the simultaneous determination of K and C of fissure- and rod bundle-type porous inserts. Although variation in K is minimal, as much as 12.1% variation in C is observed, when going from a fully developed velocity profile to a plug flow profile at the inlet. Copyright © 2006 by ASME.

Arunn Narasimhan

Department of Mechanical Engineering

Curve fitting

Hydraulics

Parameter estimation

Porous materials

Pressure drop

Steady flow

Velocity control

DARCY MODEL

HAZEN DUPUIT DARCY MODEL (HDD)

PLUG FLOW

POROUS INSERTS

Mechanical permeability

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Permeability and Form Coefficient Measurement of Porous Inserts With Non-Darcy Model Using Non-Plug Flow Experiments

Journal of Fluids Engineering, Transactions of the ASME

Stacks of parallel plates modeled as a standard fissure-type anisotropic porous medium are filled inside a rectangular channel up to half the cross section height. The interface slip coefficient α for the isothermal laminar incompressible flow exiting this partially filled porous-medium channel is then determined using particle image velocimetry (PIV) experiments and numerical simulations. Required measurements of the Darcy velocity uD on the porous-medium (PM) side, the local velocity uf, and its gradient ∂uf/∂y on the clear-fluid (CF) side are performed across different length scales. The fissure-type porous-medium parameters are systematically varied in the porosity range 0.2≤φ≤0.95 and flow direction permeability 10-6 &lt; K, m2 &lt; 10 -9. From the exit-velocity profile, the empirical slip coefficient α is determined using a generalized relationship. When the measurements across the PM-CF interface are performed across a length scale equal to the representative elemental length (REL) of the porous media considered (i.e., equal to the sum of plate thickness (a) and gap (b)), the determined α value is found to remain invariant. Copyright © 2014 by ASME.

Experimental and numerical determination of interface slip coefficient of fluid stream exiting a partially filled porous medium channel

In this article, heat transfer enhancement of line focus solar collector with porous disc receiver is studied with water and therminol oil. A three dimensional (3-D) numerical simulation of porous disc enhanced receiver is carried out using commercial CFD software Fluent 6.3 to evolve the optimum configuration. The 3-D numerical model is solved by renormalization-group based k-e turbulent model associated with standard wall function. The effect of porous disc receiver configurations (solid disc at bottom; porous disc at bottom; porous disc at top; and alternative porous disc) on performance of the trough concentrator is investigated. The effect of porous disc geometric parameters (φ, θ, W, H and t) and fluid parameters (Pr and m) on heat transfer enhancement of the receiver is also studied. The numerical simulation results show that the flow pattern around the solid and porous discs are entirely different and it significantly influences the local heat transfer coefficient. The porous disc receiver experiences low pressure drop as compared to that of solid disc receiver due to less obstruction. The optimum configuration of porous disc receiver enhances the heat transfer rate of 221 W m -1 and 13.5% with pumping penalty of 0.014 W m -1 for water and for therminol oil-55, heat transfer rate enhances of 575 W m -1 and 31.4% with pumping penalty of 0.074 W m -1 as compared to that of tubular receiver at the mass flow rate of 0.5 kg s -1. The Nusselt number and friction factor correlations are proposed for porous disc receiver to calculate heat transfer characteristics. The porous disc receiver can be used to increase the performance of solar parabolic trough concentrator. © Springer-Verlag 2011.

Heat and Mass Transfer/Waerme- und Stoffuebertragung

Effect of porous disc receiver configurations on performance of solar parabolic trough concentrator

The experimental determination of permeability K and form coefficient C, two hydraulic properties necessary to characterize a porous medium, is beset with undesired secondary effects, which augment the uncertainties in their determination. This study sets forth a new measuring protocol, with derived model equations, to guide the design of experiments for accurate determination of K and C, using Darcy's law of flow through a porous medium and Newton's law of flow around a bluff body as constitutive equations defining K and C, respectively. The analysis shows that the model equation for measuring C requires the separation between the viscous-drag effect imposed by the porous medium and the viscous effect of the boundary walls on the measured pressure drop when defining K. Furthermore, the model equations suggest large aspect ratio channels and laminar flow with maximum Re as the best choice for measuring K and C (contrary to prevailing belief). The protocol is applicable to either individual or concurrent determination of K and C. © 2005 American Institute of Physics.

Fulltext

Physics of Fluids

Protocol for measuring permeability and form coefficient of porous media

Hydrodynamic experiments measuring longitudinal pressure-drop versus flow rate are conducted for turbulent flow of air (channel hydraulic diameter based Reynolds number range of 2300 to 6860) through near-compact heat exchanger models with rod bundles having aligned (inline) arrangement. Effects of the flow (Re), the geometry parameters, and number of rods of the test models on the nondimensional pressure-drop ξ are studied in detail. Treating the near compact heat exchanger model as a porous medium, a dimensional pressure-drop (ΔP/L) versus average velocity of flow (U) model similar in content to a non-Darcy porous medium model, is shown to fit the experimental data with fair accuracy. Variation in form drag related to, and induced by the flow and geometric parameters are shown to be the reason for the pressure-drop variations of different models. The relation between the porous medium type model (ΔP/L versus U) and the "ξ versus Re" model is discussed with careful attention to the differences in the two transitions viz. laminar to turbulent and viscous-drag to form-drag dominated flow inside the models. A proposed correlation for predicting ξ, ably capturing all of the form effects induced by the flow and geometric parameters, is found to give predictions with ±20% accuracy Copyright © 2004 by ASME.

Turbulent flow hydrodynamic experiments in near-compact heat exchanger models with aligned tubes

Journal of Fluids Engineering

The Effects of Compression and Pore Size Variations on the Liquid Flow Characteristics in Metal Foams

A computational evaluation of the Ergun and Forchheimer equations for fibrous porous media

Journal of Heat Transfer

Modified Hazen-Dupuit-Darcy Model for Forced Convection of a Fluid With Temperature-Dependent Viscosity

Permeability and form coefficient measurement of porous inserts with non-darcy model using non-plug flow experiments

Journal	Journal of Fluids Engineering, Transactions of the ASME
ISSN	00982202
Open Access	No