Closure to “Discussion of ‘Analysis of Heat Transfer Regulation and Modification Employing Intermittently Emplaced Porous Cavities’ and ‘Analysis of Flow and Heat Transfer Over an External Boundary Covered With a Porous Substrate’” (1995, ASME J. Heat Transfer, 117, p. 554)

1995 ◽  
Vol 117 (2) ◽  
pp. 554-555 ◽  
Author(s):  
K. Vafai ◽  
S. J. Kim
Keyword(s):  
Heat Transfer ◽  
External Boundary ◽  
Porous Substrate ◽  
Flow And Heat Transfer

Analysis of Heat Transfer and Fluid Flow Through a Spirally Fluted Tube Using a Porous Substrate Approach

1994 ◽  
Vol 116 (3) ◽  
pp. 543-551 ◽  
Author(s):  
Vijayaragham Srinivasan ◽  
Kambiz Vafai ◽  
Richard N. Christensen
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Porous Substrate ◽  
The Finite Element Method ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Friction Factors ◽  
Flow Through ◽  
Good Agreement

An innovative approach was opted for modeling the flow and heat transfer through spirally fluted tubes. The model divided the flow domain into two regions. The flutes were modeled as a porous substrate with direction-dependent permeabilities. This enabled modeling the swirl component in the fluted tube. The properties of the porous substrate such as its thickness, porosity, and ratio of the direction-dependent permeabilities were obtained from the geometry of the fluted tube. Experimental data on laminar Nusselt numbers and friction factors for different types of fluted tubes representing a broad range of flute geometry were available. Experimental data from a few of the tubes tested were used to propose a relationship between the permeability of the porous substrate and the flute parameters, particularly the flute spacing. The governing equations were discretized using the Finite Element Method. The model was verified and applied to the other tubes in the test matrix. Very good agreement was found between the numerical predictions and the experimental data.

Symmetric Sink Flow and Heat Transfer Between Two Parallel Disks

2003 ◽  
Author(s):  
Marco Aure´lio dos Santos Bernardes
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Volumetric Flow Rate ◽  
Internal Boundary ◽  
External Boundary ◽  
Radial Coordinate ◽  
Flow And Heat Transfer ◽  
Disk Spacing

The k-ε model are performed to investigate numerically the steady, turbulent, incompressible flow and heat transfer converging radially between two stationary disks, which is as a continuously developing flow problem under the internal boundary layer approximations. The effect of relaminarization was considered. This present study has presented a good agreement with the laminar investigation of Murphy et al [1], where no heat transfer was considered. At large values of the dimensionless radii (>> 1) the velocity profile becomes parabolic and invariant and the friction factor approaches the classic value obtained for fully developed flow between infinite plates, 24/Re0, where Re0 is an overall Reynolds number based on the volumetric flow rate and the disk spacing and is independent of radius. At radii less than one a typical external boundary layer evolves close to the wall with an approximately uniform core region, the boundary layer thickness decreases from one-half the disk spacing to values proportional to the local radii as the flow accelerates and the friction factor approaches the constant 2.17/Re0. A local Nusselt number, Nu = 230(r/R)0.650(1 − r/R)−0.386, where r is radial coordinate and R the radius of the disk, was estimated. A large overall Reynolds number was imposed and a relaminarization of the flow was observed. It was suggested that these results can be applicable for laminar and turbulent flow under Re0 = 106.

Analysis of Surface Enhancement by a Porous Substrate

1990 ◽  
Vol 112 (3) ◽  
pp. 700-706 ◽  
Author(s):  
Kambiz Vafai ◽  
Sung-Jin Kim
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Fluid Layer ◽  
Composite Layer ◽  
Darcy Number ◽  
Temperature Fields ◽  
External Boundary ◽  
Porous Substrate ◽  
Frictional Drag ◽  
Practical Applications

Convective flow and heat transfer through a composite porous/fluid system have been studied numerically. The composite medium consists of a fluid layer overlaying a porous substrate, which is attached to the surface of the plate. The numerical simulations focus primarily on flows that have the boundary layer characteristics. However, the boundary layer approximation was not used. A general flow model that accounts for the effects of the impermeable boundary and inertia is used to describe the flow inside the porous region. Several important characteristics of the flow and temperature fields in the composite layer are reported. The dependence of these characteristics on the governing parameters such as the Darcy number, the inertia parameter, the Prandtl number, and the ratio of the conductivity of the porous material to that of the fluid is also documented. The results of this investigation point out a number of interesting practical applications such as in frictional drag reduction, and heat transfer retardation or enhancement of an external boundary.

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