共查询到20条相似文献,搜索用时 15 毫秒
1.
Irfan Anjum Badruddin N. J. Salman Ahmed Abdullah A. A. A. Al-Rashed Jeevan Kanesan Sarfaraz Kamangar H. M. T. Khaleed 《Transport in Porous Media》2012,91(2):697-715
The present study is intended to study heat and mass transfer in a vertical annular cylinder embedded with saturated porous
medium. The inner surface of cylinder is maintained at uniform wall temperature and uniform wall concentration. The governing
partial differential equations are non-dimensionalised and solved by using finite element method (FEM). The porous medium
is discritised using triangular elements with uneven element size. Large number of smaller-sized elements are placed near
the walls of the annulus to capture the smallest variation in solution parameters. The results are reported for both aiding
and opposing flows. The effects of various non-dimensional numbers such as buoyancy ratio, Lewis number, Rayleigh number,
aspect ratio, etc on heat and mass transfer are discussed. The temperature and concentration profiles are presented. 相似文献
2.
C. Y. Wang 《Transport in Porous Media》2011,90(2):321-332
The fully developed flow and H1 heat transfer in a polygonal duct filled with a Darcy–Brinkman medium is studied. The efficient
method of boundary collocation is used. The problem is governed by the duct shape and a non-dimensional parameter s which characterizes the inverse square root of permeability. Asymptotic formulas for small and large s are derived. 相似文献
3.
利用数值计算方法研究了旋转矩形截面螺旋管内的粘性流动,分析了在离心力,科氏力共同作用下曲线管道中的二次流动结构、轴向流速分布、截面温度分布、摩擦系数比以及管道Nusselt数比随各参数的变化情况。计算结果表明:当旋转方向和主流方向相同时,旋转的作用与增大Dean数的作用相同,使得管道摩擦系数变大,管道换热效果增强,而当旋转方向和主流方向相反时,管道内流动结构变化十分明显,当F≈-1.2时(F为科氏力与离心力之比),二次流出现类似于直扭管内的鞍状流动结构,轴向速度类似于静止直管内的流动结构,管道内的摩擦系数与静止直管内的摩擦系数大约相等,换热效果减至最弱;挠率对流动结构以及摩擦系数比和Nusselt系数比的影响效果与F有关。 相似文献
4.
In this article, free convection heat transfer over a vertical cylinder with variable surface temperature distributions in a porous medium is analyzed. It is assumed that the fluid and solid phases are not in local thermal equilibrium and, therefore, a two-temperature model of heat transfer is applied. The coupled momentum and energy equations are presented and then they are transformed into ordinary differential equations. The similarity equations are solved numerically. The resulting velocity, streamlines, temperature distributions for fluid and solid phases are shown for different values of parameters entering into the problem. The calculated values of the local Nusselt numbers for both solid and fluid phases are also shown. 相似文献
5.
Results of a numerical study of a laminar separated flow behind a rectangular step on a porous surface with uniform injection
or suction are described. Two cases are considered: an unconfined flow past a step and flow evolution in a confined channel
(duct). It is shown that mass transfer on the surface causes strong changes in the flow structure and substantially affects
the position of the reattachment point, as well as friction and heat transfer. More intense injection leads first to an increase
in the separation-zone length and then to its rapid vanishing due to boundary-layer displacement. Vice versa, suction at high
Reynolds numbers Re
s
> 100 reduces the separation-zone length. The duct flow has a complicated distribution of friction and heat-transfer coefficients
along the porous surface owing to the coupled effect of the transverse flow of the substance and changes in the main flow
velocity due to mass transfer.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 1, pp. 18–28, January–February, 2006. 相似文献
6.
Heat and Mass Transfer in MHD Micropolar Flow Over a Vertical Moving Porous Plate in a Porous Medium
Youn J. Kim 《Transport in Porous Media》2004,56(1):17-37
An analysis is presented for the problem of free convection with mass transfer flow for a micropolar fluid via a porous medium bounded by a semi-infinite vertical porous plate in the presence of a transverse magnetic field. The plate moves with constant velocity in the longitudinal direction, and the free stream velocity follows an exponentially small perturbation law. A uniform magnetic field acts perpendicularly to the porous surface in which absorbs the micropolar fluid with a suction velocity varying with time. Numerical results of velocity distribution of micropolar fluids are compared with the corresponding flow problems for a Newtonian fluid. Also, the results of the skin-friction coefficient, the couple stress coefficient, the rate of the heat and mass transfers at the wall are prepared with various values of fluid properties and flow conditions. 相似文献
7.
Yu-Shu Wu Bitao Lai Jennifer L. Miskimins Perapon Fakcharoenphol Yuan Di 《Transport in Porous Media》2011,88(2):205-223
Recent laboratory studies and analyses (Lai et al. Presented at the 2009 Rocky Mountain Petroleum Technology Conference, 14–16
April, Denver, CO, 2009) have shown that the Barree and Conway model is able to describe the entire range of relationships between flow rate and
potential gradient from low- to high-flow rates through porous media. A Buckley and Leverett type analytical solution is derived
for non-Darcy displacement of immiscible fluids in porous media, in which non-Darcy flow is described using the Barree and
Conway model. The comparison between Forchheimer and Barree and Conway non-Darcy models is discussed. We also present a general
mathematical and numerical model for incorporating the Barree and Conway model in a general reservoir simulator to simulate
multiphase non-Darcy flow in porous media. As an application example, we use the analytical solution to verify the numerical
solution for and to obtain some insight into one-dimensional non-Darcy displacement of two immiscible fluids with the Barree
and Conway model. The results show how non-Darcy displacement is controlled not only by relative permeability, but also by
non-Darcy coefficients, characteristic length, and injection rates. Overall, this study provides an analysis approach for
modeling multiphase non-Darcy flow in reservoirs according to the Barree and Conway model. 相似文献
8.
Fethi Kamışlı 《Transport in Porous Media》2009,80(2):345-371
The flow of an incompressible Newtonian fluid confined in a planar geometry with different wall temperatures filled with a
homogenous and isotropic porous medium is analyzed in terms of determining the unsteady state and steady state velocities,
the temperature and the entropy generation rate as function of the pressure drop, the Darcy number, and the Brinkman number.
The one-dimensional approximate equation in the rectangular Cartesian coordinates governing the flow of a Newtonian fluid
through porous medium is derived by accounting for the order of magnitude of terms as well as accompanying approximations
to the full-blown three-dimensional equations by using scaling arguments. The one-dimensional approximate energy and the entropy
equations with the viscous dissipation consisting of the velocity gradient and the square of velocity are derived by following
the same procedure used in the derivation of velocity expressions. The one-dimensional approximate equations for the velocity,
the temperature, and the entropy generation rate are analytically solved to determine the velocity, the temperature, and the
entropy distributions in the saturated porous medium as functions of the effective process parameters. It is found that the
pressure drop, the Darcy number, and the Brinkman number affect the temperature distribution in the similar way, and besides
the above parameters, the irreversibility distribution ratio also affects the entropy generation rate in the similar way. 相似文献
9.
Yi Xiong Jinbiao Yu Hongxia Sun Jiangru Yuan Zhaoqin Huang Yu-shu Wu 《Transport in Porous Media》2017,117(3):367-383
The pore and pore-throat sizes of shale and tight rock formations are on the order of tens of nanometers. The fluid flow in such small pores is significantly affected by walls of pores and pore-throats. This boundary layer effect on fluid flow in tight rocks has been investigated through laboratory work on capillary tubes. It is observed that low permeability is associated with large boundary layer effect on fluid flow. The experimental results from a single capillary tube are extended to a bundle of tubes and finally to porous media of tight formations. A physics-based, non-Darcy low-velocity flow equation is derived to account for the boundary layer effect of tight reservoirs by adding a non-Darcy coefficient term. This non-Darcy equation describes the fluid flow more accurately for tight oil reservoir with low production rate and low pressure gradient. Both analytical and numerical solutions are obtained for the new non-Darcy flow model. First, a Buckley–Leverett-type analytical solution is derived with this non-Darcy flow equation. Then, a numerical model has been developed for implementing this non-Darcy flow model for accurate simulation of multidimensional porous and fractured tight oil reservoirs. Finally, the numerical studies on an actual field example in China demonstrate the non-negligible effect of boundary layer on fluid flow in tight formations. 相似文献
10.
Ahmed A. Afify 《Transport in Porous Media》2007,66(3):391-401
An analysis is presented to investigate the effects of temperature-dependent viscosity, thermal dispersion, Soret number and
Dufour number on non-Darcy MHD free convective heat and mass transfer of a viscous, incompressible and electrically conducting
fluid past a vertical isothermal surface embedded in a saturated porous medium. The governing partial differential equations
are transferred into a system of ordinary differential equations, which are solved numerically using a fourth order Runge–Kutta
scheme with the shooting method. Comparisons with previously published work by Hong and Tien [Hong, J. T. and Tien, C. L.:
1987, Int. J. Heat Mass Transfer
30, 143–150] and Sparrow et al. [Sparrow, E. M. et al.: 1964, AIAA J. 2 652–659] are performed and good agreement is obtained. Numerical results of the skin friction coefficient, the local Nusselt
number and the local Sherwood number as well as the velocity, temperature and concentration profiles are presented for different
physical parameters. 相似文献
11.
12.
The lattice Boltzmann method is carried out to investigate the heat transfer enhancement in a U-turn duct which is partially filled with a porous media. The porous layer is inserted at the core of the duct and is modeled using the Brinkman–Forchheimer assumptions. In order to validate the results, first a channel flow problem without any porous layer is compared with available data. Second, the porous Couette flow and partially porous channel flow are successfully compared with the studies of other researchers. Then, fluid flow in a clear U-turn duct is studied looking carefully at the velocity, curvature and rotation effects. Finally, the effects of porous layer thickness on the rate of heat transfer and pressure drop are investigated. Parametric studies are conducted to evaluate the effects of various parameters (i.e., Reynolds number, Darcy number, rotation number), highlighting their influences on the thermo-hydrodynamics behavior of the flow. The optimum values of porous layer thickness are presented for specific flow parameters. 相似文献
13.
V. I. Terekhov N. I. Yarygina R. F. Zhdanov 《Journal of Applied Mechanics and Technical Physics》2003,44(4):522-531
Results of an experimental study of heat transfer in a separated flow behind a step and a rib are presented. The influence of the obstacle height (H = 6–30 mm) on heat and mass transfer and the structure of the thermal boundary layer is studied. The features of heat transfer in recirculation and relaxation zones of the separated flow are analyzed, and the effect of separation on intensification and suppression of turbulent heat transfer is determined. 相似文献
14.
E. A. Chinnov I. A. Sharina O. A. Kabov 《Journal of Applied Mechanics and Technical Physics》2004,45(5):705-711
Heat transfer in a film flow of the FC-72 dielectric liquid down a vertical surface with an embedded 150×150 mm heater is experimentally examined in the range of Reynolds numbers Re = 5–375. A chart of liquid-film flow modes is constructed, and characteristic heat-transfer regions are identified. Data on the dependence of heater-wall temperature and local heat flux at the axis of symmetry of the heater on the longitudinal coordinate are obtained. Local and mean heat-transfer coefficients are calculated. It is shown that enhanced heat transfer is observed in the region where rivulets starts forming in the low-Reynolds-number liquid-film flow. 相似文献
15.
16.
A numerical study is performed to analyze steady laminar forced convection in a channel in which discrete heat sources covered
with porous material are placed on the bottom wall. Hydrodynamic and heat transfer results are reported. The flow in the porous
medium is modeled using the Darcy–Brinkman–Forchheimer model. A computer program based on control volume method with appropriate
averaging for diffusion coefficient is developed to solve the coupling between solid, fluid, and porous region. The effects
of parameters such as Reynolds number, Prandtl number, inertia coefficient, and thermal conductivity ratio are considered.
The results reveal that the porous cover with high thermal conductivity enhances the heat transfer from the solid blocks significantly
and decreases the maximum temperature on the heated solid blocks. The mean Nusselt number increases with increase of Reynolds
number and Prandtl number, and decrease of inertia coefficient. The pressure drop along the channel increases rapidly with
the increase of Reynolds number. 相似文献
17.
Effects of Chemical Reaction and Double Dispersion on Non-Darcy Free Convection Heat and Mass Transfer 总被引:1,自引:0,他引:1
In this article, the effects of chemical reaction and double dispersion on non-Darcy free convection heat and mass transfer
from semi-infinite, impermeable vertical wall in a fluid saturated porous medium are investigated. The Forchheimer extension
(non-Darcy term) is considered in the flow equations, while the chemical reaction power–law term is considered in the concentration
equation. The first order chemical reaction (n = 1) was used as an example of calculations. The Darcy and non-Darcy flow, temperature and concentration fields in this study
are observed to be governed by complex interactions among dispersion and natural convection mechanisms. The governing set
of partial differential equations were non-dimensionalized and reduced to a set of ordinary differential equations for which
Runge–Kutta-based numerical technique were implemented. Numerical results for the detail of the velocity, temperature, and
concentration profiles as well as heat transfer rates (Nusselt number) and mass transfer rates (Sherwood number) are presented
in graphs. 相似文献
18.
Combined, forced, and free flow in a vertical circular duct filled with a porous medium is investigated according to the Darcy–Boussinesq
model. The effect of viscous dissipation is taken into account. It is shown that a thermal boundary condition compatible with
fully developed and axisymmetric flow is either a linearly varying wall temperature in the axial direction or, only in the
case of uniform velocity profile, an axial linear-exponential wall temperature change. The case of a linearly varying wall
temperature corresponds to a uniform wall heat flux and includes the uniform wall temperature as a special case. A general
analytical solution procedure is performed, by expressing the seepage velocity profile as a power series with respect to the
radial coordinate. It is shown that, for a fixed thermal boundary condition, i.e., for a prescribed slope of the wall temperature,
and for a given flow rate, there exist two solutions of the governing balance equations provided that the flow rate is lower
than a maximum value. When the maximum value is reached, the dual solutions coincide. When the flow rate is higher than its
maximum, no axisymmetric solutions exist.
E. Magyari is on leave from the Institute of Building Technology, ETH—Zürich. 相似文献
19.
Fluid Dynamics - Free internal waves in a two-dimensional vertically inhomogeneous stratified flow are considered in the Boussinesq approximation with account of the Earth’s rotation. The... 相似文献
20.
A. B. Gorshkov 《Fluid Dynamics》2001,36(1):139-146
Supersonic perfect-gas flow past a sphere and a cylinder at a constant surface temperature is investigated on the basis of a numerical solution of the Navier-Stokes equations. The Re-dependence of the Nusselt number and the recovery coefficient is calculated for the Reynolds numbers ranging from 1 to 1000 and Mach numbers 3 (cylinder) and 5 (sphere) and compared with the experimental data. The influence of slip and no-slip conditions imposed on the body surface on the heat transfer parameters and the base flow is analyzed. 相似文献