An experimental study of non-Darcian effects in free convection in a saturated porous medium

Preliminary experimental results for the investigation of non-Darcy effects in free convection in a porous medium are reported in this paper. In comparison with experimental results, it is found that the Plumb and Huenefeld theory for non-Darcy flow in a porous medium overestimates the heat transfer rate while underestimates the temperature distribution by a substantial amount.     

Thermal convection and boiling in a porous medium

Experimental observations of boiling in a water-saturated porous medium are reported. The porous medium is contained in a vertical circular cylinder of diameter D and height H which is heated from below and cooled from above. Single-cell thermal convection occurs prior to the onset of boiling. With the onset of boiling, an isothermal two-phase zone forms above the bottom in regions of ascending convection. The size of the two-phase zone increases with increasing heat flux. At high heat fluxes the cellular convertion flow disappears; a horizontal water layer is then observed to overlie a two-phase layer. A vertical countercurrent flow of liquid and vapor dominates heat transfer in the two-phase layer. In the layered state, an oscillatory boiling mode can develop which is attributed to the periodic formation of a vapor layer at the heating surface.     

A multi-domain spectral method for non-Darcian mixed convection flow in a power-law fluid with viscous dissipation

The purpose of this study is to investigate non-Darcian mixed convection flow, heat and mass transfer in a non-Newtonian power-law fluid over a flat plate embedded in porous medium with suction and viscous dissipation and also is to demonstrate the application and utility of a recently developed multi-domain bivariate spectral quasi-linearisation method (MD-BSQLM) in finding the solutions of highly nonlinear differential equations. The flow is subject to, among other source terms, internal heat generation, thermal radiation and partial velocity slip. The coupled system of nonlinear partial differential equations are solved using a MD-BSQLM to find the fluid properties, the skin friction, as well as the heat and mass coefficients. We have presented selected results that give the significance of some system parameters on the fluid properties. This MD-BSQLM has not been used before in the literature to find the nature of the solutions of power-law fluids. Indeed, validation of this numerical method for general fluid flows, heat and mass transfer problems has not yet been done. This study presents the first opportunity to evaluate the accuracy and robustness of the MD-BSQLM in finding solutions of non-Newtonian fluids.     

Free convection and mass transfer flow through a porous medium bounded by an infinite vertical limiting surface with constant suction

Steady two-dimensional free convection and mass transfer flow, of an incompressible viscous fluid through a porous medium bounded by a vertical infinite limiting surface (plane wall) is considered. Expressions for the velocity, temperature, concentration and the rate of heat transfer are obtained. Effects of Gr (Grashof number), Gm (modified Grashof number) and permeability K of the porous medium on the velocity and rate of heat transfer are discussed when the surface is subjected to a constant suction velocity.     

Convection in a porous medium with non-linear density effects

Effect of non-linear density-temperature relation on convective stability in a porous medium has been studied using normal mode technique. Computations have been made for both Brinkman and Darcy models. The analysis is an extension of that by Wu and Cheng [5] to Porous media.     

Mixed convection in a nanofluid-filled sloshing porous cavity including inner heated rose

Journal of Thermal Analysis and Calorimetry - In this paper, study of the heat transfer by mixed convection in sloshing enclosures heated from inside by an inner rose and filled with a porous...     

Applications of nanofluids in porous medium

Journal of Thermal Analysis and Calorimetry - This investigation provides a review on the applications of nanofluids in porous media. The transport phenomena in porous media have been of continuing...     

Microbial control of hydrogen sulfide production in a porous medium

Applied Biochemistry and Biotechnology - The ability of a sulfide- and glutaraldehyde-tolerant strain ofThiobacillus denitrificans (strain F) to control sulfide production in an experimental system...     

Numerical investigation of nanofluid laminar forced convection heat transfer between two horizontal concentric cylinders in the presence of porous medium

Journal of Thermal Analysis and Calorimetry - In this paper, the finite volume method is used to investigate the laminar forced convection of water–copper nanofluid between two porous...     

Nucleation of CO2-hydrate in a porous medium

Experiments designed to crystallize gas hydrate from dissolved CO₂ in natural porous media are used to study nucleation under varying thermodynamic conditions. We recover quantitative information from these experiments using a stochastic model for the nucleation process. Estimates of the model parameters are used to determine the average time for nucleation as a function of temperature and composition.     

Mixed convection heat transfer of a nanofluid in a lid-driven enclosure with two adherent porous blocks

Journal of Thermal Analysis and Calorimetry - Convective flow and heat transfer in an alumina/water nanofluid enclosure having two centered adherent porous blocks under the effect of moving upper...     

Unsteady double-diffusive convection in a water-based Al2O3-nanofluid in a two-sided lid-driven porous cavity

A numerical investigation of the flow and behaviour of properties of a water-based Al₂O₃-nanofluid inside a two-sided lid-driven inclined non-uniformly heated and concentrated porous cavity is made in this paper. The focus of the study is on determining how the buoyancy ratio and the inclination angles influence the unsteady double-diffusive natural convection in a cavity filled with a porous medium, and with non-uniform boundary conditions. We further consider different nanoparticle volume fractions of the nanofluid. It is assumed that the left and right vertical walls are insulated, while the bottom wall is heated and concentrated non-uniformly and the top wall maintained at a constant cold temperature. The top and bottom walls move from left to right and right to left with constant speed, respectively. The governing equations are solved numerically using a staggered grid finite-difference method for streamlines, isotherms, iso-concentrations, average Nusselt number and average Sherwood number for various values of nanoparticle volume fraction, inclination angle and buoyancy ratio. The change in the flow, temperature and concentration profile patterns with respect to time is depicted and described. The results are compared with previously published work and excellent agreement has been obtained.     

Thermodynamics of magnetohydrodynamic Brinkman fluid in porous medium

This research article investigates that how heat flow changes versus temperature or time on the rheology of magnetohydrodynamic Brinkman fluid embedded in porous medium for the oscillations of heated plate. A fractional approach namely Caputo–Fabrizio fractional operator is applied for developing the governing partial differential equations of Brinkman fluid flow. The fractional governing partial differential equations have been modeled for temperature distribution, mass concentration and velocity field along with imposed initial and boundary conditions. The solutions are obtained by integral transforms and presented in special and elementary functions. In the limiting sense, the analytical solutions are particularized in the presence and absence of heat and mass transfer, magnetic field and porous medium. The parametric graphs have been depicted for the influence of different embedded rheological parameters on fluid flow. The results show few interesting differences and similarities by comparative analysis for fractional and ordinary Brinkman fluid flow, such as physically higher Prandtl (Pr) number that leads to decay thermal diffusivity which results in the reduction in thermal field; this means that better quality of production can be achieved through proper choice of Prandtl (Pr) and Schmidt (Sc) numbers.

     

The critical gas saturation in a porous medium in the presence of gravity

The critical gas saturation, S(gc), denotes the volume fraction of the gas phase at the onset of bulk gas flow during the depressurization of a supersaturated liquid in a porous medium. In the absence of gradients due to viscous or gravity forces, S(gc) is controlled by nucleation, capillary forces, and the rate of decline of the supersaturation. In this paper we address one important additional effect, that of buoyancy. We use 2-D pore-network simulations, based on invasion percolation in a gradient (IPG), and corresponding scaling relations to obtain the dependence of S(gc) on the gravity Bond number, B, under conditions of slow growth, namely when mass transfer is sufficiently fast. The critical gas saturation approaches two plateau values at low and high Bond numbers. In the in-between region it scales as a power law of B, which for a 2-D lattice is S(gc) approximately B(-0.91).     

Simultaneous derivative spectrophotometric determination of thorium and uranium in a micellar medium

Derivative photometric methods for trace analysis of Th(IV) and UO₂(II), and their simultaneous determination in mixtures using 5,8-dihydroxy-1,4-naphthoquinone in a micellar medium are reported. Molar absorptivity and Sandell's sensitivity of 1:2 Th(IV) and 1:1 UO₂(II) complexes at their λ_max, 614.5 nm and 637.0 nm are, 1.19 × 10⁴ 1/mol/cm and 1.12 × 10⁴ 1/mol/cm and 1.95 × 10⁻² μg/cm² and 2.13 × 10⁻² μg/cm² μg/cm², respectively. Calibration graph is linear over the range 9.28 × 10⁻²−18.56 μg/ml of Th(IV) and 9.52 × 10⁻²−19.04 μg/ml of UO₂(II). Though presence of Th(IV) and UO₂(II) causes interference in each others determination, 9.28 × 10⁻¹−9.28 μg/ml Th(IV) and 9.52 × 10⁻¹−9.52 μg/ml UO₂(II) when present together, can be simultaneously determined using derivative spectra.