الفهرس 
AbstractOnly 14 pages are availabe for public view
 |  | from | 162 |  |  |
| | | from | 162 | | |
Abstract
Liquid flow and heat transfer in microchannels were studied. Deviations of flow and heat transfer from those of normal size channels were reviewed. A critical analysis was made of previously advanced hypotheses to explain deviations of liquid flow. A hypothesis relying on surface roughness [Sabry (2000)] was reviewed. In order to give an additional decisive argument to this hypothesis, detailed finite element simulations have been conducted in the immediate vicinity of tiny roughness elements of different regular shapes (half circular, rectangular and triangular) placed at the wall of a twodimensional channel. In all cases, three consecutive and similar roughness elements were placed separated by a distance equal to the roughness width. Results show that separation takes place between roughness elements for all shapes and regardless of the value of Reynolds number. Both wall shear stress and wall heat flux nearly vanish between roughness elements, with a negative peak for the pressure. Flow separation and negative pressure will tend to free dissolved gases (whether from the liquid or from the walls) in this zone.