Numerical Prediction of Evaporation Processes in Porous Media Combustors

2007 ◽  
Author(s):  
C. Periasamy ◽  
A. Saboonchi ◽  
S. R. Gollahalli
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Numerical Study ◽  
Mean Value ◽  
Pollutant Emissions ◽  
Fuel Spray ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Computational Domain ◽  
The Mean

This paper presents a numerical study of evaporation characteristics of liquid fuel spray in porous media. A two-energy equation model was employed to predict solid and gas phase temperatures. Governing equations were solved on a two-dimensional axisymmetric computational domain of 2.15 × 20 cm. An air-blast atomizer model was used to inject kerosene fuel spray on to the porous medium. Combustion in porous media was simulated by using a uniform volumetric heat source in the porous region. Numerical results were obtained with a commercial code Fluent 6.0. For a heat feedback rate of 1% of average heat input, the porous medium attained a temperature of 465 K. This data agreed well with experimental data obtained by infrared imaging. With an increase in heat feedback rate, the porous medium temperature also increased. Surface temperature distribution in porous media for different heat feedback rates was predicted. Results indicate that the transverse distribution was uniform within 1.5% of the mean value. Droplet diameter was smaller in spray core upstream of porous medium and increased radially due to the swirling action imparted to the atomizing air. Transverse vapor concentration results downstream of porous medium show that the distribution was uniform within 5% of the mean value, which demonstrates that porous medium uniformly distributes the fuel vapor-air mixture. The spatially homogeneous reactant mixture is important to achieve good combustion, reduce pollutant formation, and minimize instabilities in practical combustors. Effects of equivalence ratio and flame temperature on transverse vapor concentration profiles were also numerically studied. Porous media combustors could be used in gas turbine and industrial burner applications to reduce pollutant emissions.

Modeling Liquid Spray Evaporation in Heated Porous Media With a Local Thermal Non-Equilibrium Model

2004 ◽  
Author(s):  
Chendhil Periasamy ◽  
Sathish K. Sankara Chinthamony ◽  
S. R. Gollahalli
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Porous Media ◽  
Equation Model ◽  
Vapor Concentration ◽  
Computational Domain ◽  
Equilibrium Models ◽  
Radial Profiles ◽  
Energy Equations ◽  
Non Equilibrium

The situations such as rapid evaporation, and significant heat generation/convective heat transfer, typically encountered in liquid-fueled porous media combustors, warrant the use of local thermal non-equilibrium models. Knowledge of fuel vaporization and mixing is important to understand the combustion characteristics. In this paper, a two-energy equation model is presented to account for the non-equilibrium between the solid and liquid phases. In this approach, two energy equations for solid and gas phases were solved. Kerosene fuel, issued from an air-blast atomizer, was injected on to a heated porous medium. Governing equations were applied on a 2-D axisymmetric, computational domain of 20.3 cm × 2.5 cm. Computer simulations were conducted using a commercial code Fluent 6.0. Heat transfer from combustion porous medium was simulated by setting a volumetric heat source in the porous region. Accordingly, the peak temperatures in porous media varied from 473 K to 590 K. Axial temperature profiles within the porous media were obtained with equilibrium and non-equilibrium models. Results indicated that the equilibrium models slightly underpredicted the peak temperature. Using non-equilibrium models, radial profiles of kerosene vapor concentration were obtained at different axial locations and the results showed that the thermal effects of the porous medium dominated in the evaporation process. Numerical results were also compared with available data and the agreement was found to be good.

scholarly journals Numerical Study of Suspension Filtration Model in Porous Medium with Modified Deposition Kinetics

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 696
Author(s):  
Bekzodjon Fayziev ◽  
Gafurjan Ibragimov ◽  
Bakhtiyor Khuzhayorov ◽  
Idham Arif Alias
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Chemical Engineering ◽  
Numerical Study ◽  
Kinetic Equations ◽  
Sufficient Conditions ◽  
Computational Mathematics ◽  
Deposition Kinetics ◽  
Dynamic Factors ◽  
Suspension Filtration

Filtration is one of the most used technologies in chemical engineering. Development of computer technology and computational mathematics made it possible to explore such processes by mathematical modeling and computational methods. The article deals with the study of suspension filtration in a porous medium with modified deposition kinetics. It is suggested that deposition is formed in two types, reversible and irreversible. The model of suspension filtration in porous media consists of the mass balance equation and kinetic equations for each type of deposition. The model includes dynamic factors and multi-stage deposition kinetics. By using the symmetricity of porous media, the higher dimensional cases are reduced to the one-dimensional case. To solve the problem, a stable, effective and simple numerical algorithm is proposed based on the finite difference method. Sufficient conditions for stability of schemes are found. Based on numerical results, influences of dynamic factors on solid particle transport and deposition characteristics are analyzed. It is shown that the dynamic factors mainly affect the profiles of changes in the concentration of deposition of the active zone.

Numerical Study on the Performance of a Tube With Inserted Porous Media of Various Thermal Conductivities

2016 ◽  
Author(s):  
Tariq Amin Khan ◽  
Wei Li
Keyword(s):  
Thermal Conductivity ◽  
Porous Medium ◽  
Porous Media ◽  
Velocity Profile ◽  
Fluid Transport ◽  
Energy Transport ◽  
Numerical Study ◽  
Darcy Number ◽  
Local Thermal Equilibrium ◽  
Working Fluid

Numerical study is performed on the effect of thermal conductivity of porous media (k) on the Nusselt number (Nu) and performance evaluation criteria (PEC) of a tube. Two-dimensional axisymmetric forced laminar and fully developed flow is assumed. Porous medium partially inserted in the core of a tube is investigated under varied Darcy number (Da), i.e., 10−6 ≤ Da ≤ 10−2. The range of Re number used is 100 to 2000 and the conductivity of porous medium is 1.4 to 202.4 W/(m.K) with air as the working fluid. The momentum equations are used to describe the fluid flow in the clear region. The Darcy-Forchheimer-Brinkman model is adopted for the fluid transport in the porous region. The mathematical model for energy transport is based on the one equation model which assumes a local thermal equilibrium between the fluid and the solid phases. Results are different from the conventional thoughts that porous media of higher thermal conductivity can enhance the performance (PEC) of a tube. Due to partial porous media insertion, the upstream parabolic velocity profile is destroyed and the flow is redistributed to create a new fully develop velocity profile downstream. The length of this flow redistribution to a new developed laminar flow depends on the Da number and the hydrodynamic developing length increases with increasing Da number. Moreover, the temperature profile is also readjusted within the tube. The Nu and PEC numbers have a nonlinear trend with varying k. At very low Da number and at a lower k, the Nu number decreases with increasing Re number while at higher k, the Nu number first increases to reach its peak value and then decreases. At higher Re number, the results are independent of k. However, at a higher Da number, the Nu and PEC numbers significantly increases at low Re number while slightly increases at higher Re number. Hence, the change in Nu and PEC numbers neither increases monotonically with k, nor with Re number. Investigation of PEC number shows that at very low Da number (Da = 10−6), inserting porous media of a low k is effective at low Re number (Re ≤ 500) while at high Re number, using porous material is not effective for the overall performance of a tube. However, at a relatively higher Da number (Da = 10−2), high k can be effective at higher Re number. Moreover, it is found that the results are not very sensitive to the inertia term at lower Da number.

Oscillatory forcing of flow through porous media. Part 2. Unsteady flow

2002 ◽  
Vol 465 ◽  
pp. 237-260 ◽  
Author(s):  
D. R. GRAHAM ◽  
J. J. L. HIGDON
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Pressure Gradient ◽  
Flow Rate ◽  
Flow Through Porous Media ◽  
Mean Flow ◽  
Two Fluids ◽  
Mean Pressure ◽  
Flow Through ◽  
The Mean

Numerical computations are employed to study the phenomenon of oscillatory forcing of flow through porous media. The Galerkin finite element method is used to solve the time-dependent Navier–Stokes equations to determine the unsteady velocity field and the mean flow rate subject to the combined action of a mean pressure gradient and an oscillatory body force. With strong forcing in the form of sinusoidal oscillations, the mean flow rate may be reduced to 40% of its unforced steady-state value. The effectiveness of the oscillatory forcing is a strong function of the dimensionless forcing level, which is inversely proportional to the square of the fluid viscosity. For a porous medium occupied by two fluids with disparate viscosities, oscillatory forcing may be used to reduce the flow rate of the less viscous fluid, with negligible effect on the more viscous fluid. The temporal waveform of the oscillatory forcing function has a significant impact on the effectiveness of this technique. A spike/plateau waveform is found to be much more efficient than a simple sinusoidal profile. With strong forcing, the spike waveform can induce a mean axial flow in the absence of a mean pressure gradient. In the presence of a mean pressure gradient, the spike waveform may be employed to reverse the direction of flow and drive a fluid against the direction of the mean pressure gradient. Owing to the viscosity dependence of the dimensionless forcing level, this mechanism may be employed as an oscillatory filter to separate two fluids of different viscosities, driving them in opposite directions in the porous medium. Possible applications of these mechanisms in enhanced oil recovery processes are discussed.

scholarly journals Numerical Investigation of Oil Gas Separation with the Use of VOF CFD

2021 ◽  
Vol 11 (6) ◽  
pp. 7841-7845
Author(s):  
S. Tomescu ◽  
I. O. Bucur
Keyword(s):  
Porous Media ◽  
Numerical Investigation ◽  
Gas Turbines ◽  
Computer Aided Design ◽  
Volume Fraction ◽  
Numerical Study ◽  
Computational Domain ◽  
Two Phase ◽  
Volume Porosity ◽  
Set Up

In this research paper, a numerical study regarding gas-oil separation is presented. Employing the geometry of a classic separator used by the NRDI for Gas Turbines COMOTI and a Computer-Aided Design (CAD) software, the computational domain was defined. To perform the Computational Fluid Dynamics (CFD) investigation, the mesh was created with the ANSYS Meshing tool, and the ANSYS CFX was employed as a solver. The computational domain was split into 5 subdomains, 3 were fluid and 2 were defined as porous media. The volume porosity, loss model, and permeability were set up. In terms of turbulence flow, the standard k–ε model was adopted. The results of the numerical calculations in terms of oil volume fraction and streamline profiles were used to analyze the separator configuration. The results show that the numerical investigation with the VOF (Volume of Fluid Method) - CFD model is capable of analyzing the performance of a two-phase separator equipped with two demisters-porous media.

Considerations on Water, Oil and Air in Porous Media

1985 ◽  
Vol 17 (4-5) ◽  
pp. 467-476 ◽  
Author(s):  
H. O. Schiegg
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Scale Factor ◽  
Groundwater Table ◽  
Saturation Curve ◽  
Observation Well ◽  
Capillary Fringe ◽  
Phreatic Aquifer ◽  
The Mean ◽  
The Relationship

Oil, a hydrocarbon spilled above a phreatic aquifer, initially percolates primarily vertically until it reaches the capillary fringe. Subsequently, the oil migrates within the capillary fringe parallel to the groundwater table thereby creating an oil-polluted layer parallel to the groundwater table. The mean thickness of such an oil-polluted layer is denoted by . The objective of this paper is to describe as a function of the thickness of oil in an observation well and of the oil potential, respectively. For oil to enter a porous medium, a minimum value of is necessary and will be determined. The paper starts by explaining the relationship between the water-air saturation curve and the saturation curves for water-oil and oil-air as expressed by the scale factor Ω. Subsequently, the phenomenon of capillary pollution is described. The influence of hysteresis in capillarity on the above considerations is shown at the end of the paper.

Kinematical measurement of hydraulic tortuosity of fluid flow in porous media

2015 ◽  
Vol 26 (02) ◽  
pp. 1550017 ◽  
Author(s):  
Y. Jin ◽  
J. B. Dong ◽  
X. Li ◽  
Y. Wu
Keyword(s):  
Porous Media ◽  
Flow Direction ◽  
Estimation Method ◽  
Mean Value ◽  
Calculation Model ◽  
Flow In Porous Media ◽  
Porous Media Flow ◽  
Average Value ◽  
The Mean ◽  
The Impact

It is hard to experimentally or analytically derive the hydraulic tortuosity (τ) of porous media flow because of their complex microstructures. In this work, we propose a kinematical measurement method for τ by introducing the concept of local tortuosity, which is defined as the ratio of fluid particle velocity to its component along the macro flow. And then, the calculation model of τ is analytically deduced in terms of that τ is the mean value of the local tortuosity. To avoid the impact from the singularity of local tortuosity, the velocity is normalized, and τ is then approximated by the ratio of the mean normalized velocity to the average value of its component along the macro-flow direction. The new estimation method is verified by flow through different types of porous media via the lattice Boltzmann method, and the relationships between permeabilities and tortuosities obtained by different methods are examined. The numerical results show that tortuosity by the novel approach is in good agreement with the existing theory, and the kinematic definition of hydraulic tortuosity is also proven.

Spray Impingement and Evaporation Through Porous Media

2004 ◽  
Author(s):  
Sathish K. Sankara Chinthamony ◽  
Chendhil Periasamy ◽  
S. R. Gollahalli
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Flow Rate ◽  
Mass Flux ◽  
Ceramic Foam ◽  
Vapor Concentration ◽  
Combustion Heat ◽  
Liquid Mass ◽  
Spray Impingement ◽  
Carbon Ceramic

This paper presents an experimental study on spray impingement and fuel evaporation processes in porous media. Aviation-type kerosene (Jet-A) was used as the fuel and an open-cell, silicon carbide coated, carbon-carbon ceramic foam was used as the porous medium. The fuel was sprayed into a coflowing, preheated air environment using an air-blast atomizer. A Phase Doppler Particle Analyzer (PDPA) was used to measure Sauter mean diameter (SMD), liquid mass flux, and axial velocity of the droplets. The porous medium was resistively heated to simulate heat feedback from the combustion zone. An organic vapor analyzer, based on catalytic oxidation, was used to measure the concentration of kerosene vapor downstream of the porous medium. The temperature and flow rate of coflow air were held constant, while the fuel flow rate, and hence, the overall equivalence ratio, was varied from 0.3 to 0.6. Higher liquid mass flux was recorded away from the spray core region, due to the swirling action of atomizing air. Surface temperature measurements of porous media revealed the uniformity of thermo-electrical properties of the medium. Vapor concentration measurements with combustion heat feedback (a heat input of 33 kW/m2) increased the average vapor concentration by 63% and 43% than that of no heat feedback case for 0.3 and 0.6 equivalence ratios respectively.

scholarly journals Numerical Study of the Effect of Magnetic Field on Nanofluid Heat Transfer in Metal Foam Environment

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Hamid Shafiee ◽  
Elaheh NikzadehAbbasi ◽  
Majid Soltani
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Porous Medium ◽  
Porous Media ◽  
Fluid Flow ◽  
Volume Fraction ◽  
Numerical Study ◽  
Computational Simulation ◽  
Thermodynamic Efficiency ◽  
Two Phase

The magnetic field can act as a suitable control parameter for heat transfer and fluid flow. It can also be used to maximize thermodynamic efficiency in a variety of fields. Nanofluids and porous media are common methods to increase heat transfer. In addition to improving heat transfer, porous media can increase pressure drop. This research is a computational simulation of the impacts of a magnetic field induced into a cylinder in a porous medium for a volume fraction of 0.2 water/Al2O3 nanofluid with a diameter of 10 μm inside the cylinder. For a wide variety of controlling parameters, simulations have been made. The fluid flow in the porous medium is explained using the Darcy-Brinkman-Forchheimer equation, and the nanofluid flow is represented utilizing a two-phase mixed approach as a two-phase flow. In addition, simulations were run in a slow flow state using the finite volume method. The mean Nusselt number and performance evaluation criteria (PEC) were studied for different Darcy and Hartmann numbers. The results show that the amount of heat transfer coefficient increases with increasing the number of Hartmann and Darcy. In addition, the composition of the nanofluid in the base fluid enhanced the PEC in all instances. Furthermore, the PEC has gained its highest value at the conditions relating to the permeable porous medium.

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