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1.
Effects of Viscous Dissipation and Flow Work on Forced Convection in a Channel Filled by a Saturated Porous Medium 总被引:1,自引:3,他引:1
Fully developed forced convection in a parallel plate channel filled by a saturated porous medium, with walls held either at uniform temperature or at uniform heat flux, with the effects of viscous dissipation and flow work included, is treated analytically. The Brinkman model is employed. The analysis leads to expressions for the Nusselt number, as a function of the Darcy number and Brinkman number. 相似文献
2.
A perturbation approach is used to obtain analytical expressions for the velocity, temperature distribution, and transient
Nusselt number for the problem of forced convection, in a parallel-plates channel or a circular tube occupied by a saturated
porous medium modeled by the Brinkman equation, produced by an applied pressure gradient that fluctuates with small amplitude
harmonically in time about a non-zero mean. It is shown that the fluctuating part of this Nusselt number alters in magnitude
and phase as the dimensionless frequency increases. The magnitude increases from zero, goes through a peak, and then decreases
to zero. The height of the peak decreases as the modified Prandtl number increases. The phase (relative to that of the steady
component) decreases from π/2 to − π/2. The height of the peak at first increases, goes through a maximum, and then decreases
as the Darcy number decreases. 相似文献
3.
A two-velocity two-temperature model for bi-dispersed porous media is formulated. Using the model, an analytic solution is obtained for the problem of forced convection in a channel between parallel plane walls that are held either at uniform temperature or uniform heat flux. In each case, Nusselt number values are given as functions of a conductivity ratio, a velocity ratio, a volume fraction, and an internal heat exchange parameter. 相似文献
4.
An analytic solution is obtained for forced convection flow in a parallel-plates channel or a circular duct occupied by a
hyper-porous medium saturated with a rarefied gas in the slip-flow regime, for the case of uniform flux boundary conditions.
As expected, it is found that velocity slip leads in general to increased heat transfer and temperature slip leads to reduced
heat transfer. 相似文献
5.
Buoyant flow is analysed for a vertical fluid saturated porous layer bounded by an isothermal plane and an isoflux plane in
the case of a fully developed flow with a parallel velocity field. The effects of viscous dissipation and pressure work are
taken into account in the framework of the Oberbeck–Boussinesq approximation scheme and of the Darcy flow model. Momentum
and energy balances are combined in a dimensionless nonlinear ordinary differential equation solved numerically by a Runge–Kutta
method. Both cases of upward pressure force (upward driven flows) and of downward pressure force (downward driven flows) are examined. The thermal behaviour for upward driven flows and downward driven flows is quite different. For upward driven
flows, the combined effects of viscous dissipation and pressure work may produce a net cooling of the fluid even in the case
of a positive heat input from the isoflux wall. For downward driven flows, viscous dissipation and pressure work yield a net
heating of the fluid. A general reflection on the roles played by the effects of viscous dissipation and pressure work with
respect to the Oberbeck–Boussinesq approximation is proposed. 相似文献
6.
A.V. Kuznetsov 《Flow, Turbulence and Combustion》1998,60(2):173-192
In this paper, the problem of fully developed forced convection in a parallel-plate channel partly filled with a homogeneous porous material is considered. The porous material is attached to the walls of the channel, while the center of the channel is occupied by clear fluid. The flow in the porous material is described by a nonlinear Brinkman–Forchheimer-extended Darcy equation. Utilizing the boundary-layer approach, analytical solutions for the flow velocity, the temperature distribution, as well as for the Nusselt number are obtained. Dependence of the Nusselt number on several parameters of the problem is extensively investigated. 相似文献
7.
An adaptation of the classical Graetz methodology is applied to investigate the thermal development of forced convection in
a parallel plate channel or a circular tube filled by a porous medium saturated by a rarefied gas, with walls held at constant
heat flux. The Brinkman model is employed. The analysis leads to expressions for the local Nusselt number Nu as functions of the dimensionless longitudinal coordinate and the Darcy number. It is found that an increase in the velocity
slip coefficient generally increases Nu by a small or moderate amount (but the circular tube at large Darcy number is an exception) while an increase in the temperature
slip coefficient reduces Nu by a more substantial amount. These trends are uniform as the longitudinal coordinate varies. 相似文献