Premium
An experimental study of convective instability in the thermal entrance region of a horizontal parallel‐plate channel heated from below
Author(s) -
Hwang G. J.,
Liu ChengLiung
Publication year - 1976
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450540607
Subject(s) - vortex , mechanics , flow visualization , instability , convection , front (military) , thermal , flow (mathematics) , convective instability , channel (broadcasting) , physics , rayleigh number , optics , meteorology , materials science , natural convection , engineering , electrical engineering
This paper presents results of an experimental investigation on the onset of longitudinal columnar vortices due to buoyant forces in the thermal entrance region of a horizontal parallel‐plate channel heated from below. Channels with width 30 cm and heights h = 2, 3 and 4.5 cm were employed in the experiment. The instability of the convective motion is caused by the effects of temperature gradients in both longitudinal and vertical directions and was observed by a direct flow‐visualization technique using smoke. Photographs of the front and top views of the vortex rolls are presented. Experimental results indicate that the wave number of vortex rolls remains constant along the flow direction and tends to approach the theoretical value as the channel width‐height ratio increases. It was also observed that the critical Rayleigh number from flow visualization is 1.4 to 10 times higher than the critical value from linear theory.