Flow dynamics and heat transfer of wavy condensate film

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20030466

Miyara, Akio

Wave evolution and heat transfer behavior of a wavy condensate film down a vertical wall have been investigated by a finite different method, in which the algorithm is based on the HSMAC method, and a staggered grid fixed on a physical space is employed. For the moving interface, newly proposed methods are used. A random perturbation of the film thickness is generated near the leading edge. The perturbation quickly diminishes once and small-amplitude long waves are propagated downstream. Then the amplitude of the wave increases rapidly at a certain position, and the wave shape changes from a sinusoidal wave to a pulse-like solitary wave which is composed of a large-amplitude wave and capillary waves. Figure A-1 shows an instantaneous stream line of the pulse-like solitary waves. The stream line is obtained for moving coordinates with the wave velocity. A circulation flow occurs in the large waves, and it disappears in the interacting wave at downstream. In the capillary waves, no circulation flow generates. The circulation flow affects the temperature field. Temperature contour lines are deformed by the convection effect of the circulation flow. On the other hand, the temperature contour is dense in the wave toughs and substrates because of the film thinning effect. These facets imply that the heat transfer is enhanced by two kinds of effects: the convection and the local film thinning. Figure A-3 shows the comparison of the present simulation results with the Chun-Seban equation for wavy film and the Nusselt equation for laminar film with smooth surface. Nu of the present results departs from Nusselt equation because of the wave generation. The pint of the departure depends on Prandtl number. Lower Prandtl number departs at higher Reynolds number. In the fully developed wave region, the simulation result of Pr = 5 reasonably agrees to the Chun-Seban equation. For Pr = 10, however, the simulation result is fairly higher. Because of limitation of calculation scheme, the developed wavy region of Pr = 1 could not be obtained.

• Research Organization: Saga Univ. (JP)
• OSTI ID: 20030466
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
FILM CONDENSATION
FILM FLOW
FINITE DIFFERENCE METHOD
HEAT TRANSFER
THICKNESS