DNS of turbulent heat transfer through two-dimensional slits

2008 ◽  
Vol 8 (7/8) ◽  
pp. 397 ◽  
Author(s):  
S. Makino ◽  
K. Iwamoto ◽  
H. Kawamura
Keyword(s):  
Heat Transfer ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Two Dimensional

Turbulent Heat Transfer Augmentation Using Microscale Disturbances Inside the Viscous Sublayer

1992 ◽  
Vol 114 (2) ◽  
pp. 348-353 ◽  
Author(s):  
H. Kozlu ◽  
B. B. Mikic ◽  
A. T. Patera
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Heat Removal ◽  
Channel Flows ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Two Dimensional ◽  
Optimal Position ◽  
Heat Transfer Augmentation ◽  
Near Wall

We report here on an experimental study of heat transfer augmentation in turbulent flow. Enhancement strategies employed in this investigation are based on the near-wall mixing processes induced in the sublayer through appropriate wall and near-wall streamwise-periodic disturbances. Experiments are performed in a low-turbulence wind-tunnel with a high-aspect-ratio rectangular channel having either (a) two-dimensional periodic microgrooves on the wall, or (b) two-dimensional microcylinders placed in the immediate vicinity of the wall. It is found that micro-disturbances placed inside the sublayer induce favorable heat-transport augmentation with respect to the smooth-wall case, in that near-analogous momentum and heat transfer behavior are preserved; a roughly commensurate increase in heat and momentum transport is termed favorable in that it leads to a reduction in the pumping power penalty at fixed heat removal rate. The study shows that this favorable performance of microcylinder-equipped channel flows is achieved for microcylinders placed inside y+ ≃20, implying a dependence of the optimal position and size on Reynolds number. For microgrooved channel flows, favorable augmentation is obtained for a wider range of Reynolds numbers; however, optimal enhancement still requires a matching of geometric perturbation with the sublayer scale.

Heat Transfer Enhancement to the Drag-Reducing Flow of Surfactant Solution in Two-Dimensional Channel With Mesh-Screen Inserts at the Inlet

2000 ◽  
Vol 123 (4) ◽  
pp. 779-789 ◽  
Author(s):  
Peiwen Li ◽  
Yasuo Kawaguchi ◽  
Hisashi Daisaka ◽  
Akira Yabe ◽  
Koichi Hishida ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Surfactant Solution ◽  
Wire Mesh ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Two Dimensional ◽  
Transfer Enhancement ◽  
High Reynolds

The heat transfer enhancement of drag-reducing flow of high Reynolds number in a two-dimensional channel by utilizing the characteristic of fluid was studied. As the networks of rod-like micelles in surfactant solution are responsible for suppressing the turbulence in drag-reducing flow, destruction of the structure of networks was considered to eliminate the drag reduction and prevent heat transfer deterioration. By inserting wire mesh in the channel against the flow, the drag-reducing function of the micellar structure in surfactant aqueous solution was successfully switched off. With the Reynolds number close to the first critical Reynolds number, the heat transfer coefficient in the region downstream of the mesh can be improved significantly, reaching the same level as that of water. The region with turbulent heat transfer downstream of the mesh becomes smaller as the concentration of surfactant in the solution increases. Three types of mesh of different wire diameter and opening space were evaluated for their effect in promoting heat transfer and the corresponding pressure loss due to blockage of the mesh. The turbulent intensities were measured downstream from the mesh by using a Laser Doppler Velocimetry (LDV) system. The results indicated that the success of heat transfer enhancement is due to the strong turbulence promoted by the mesh which destroys the network of rod-like micelles by applying high shear stress and thus relaxing the shear induced state (SIS).

Sign in / Sign up

Export Citation Format

Share Document