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International Heat Transfer Conference 11

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

MIXED CONVECTION FLOW AND HEAT TRANSFER IN A HORIZONTAL DIVERGENT CHANNEL WITH BOTTOM WALL HEATED

C. Gau
Institute of Aeronautics and Astronautics National Cheng Kung University Taiwan, CHINA

M. Huang
Institute of Aeronautics and Astronautics National Cheng Kung University Taiwan, CHINA

C. W. Liu
Institute of Aeronautics and Astronautics National Cheng Kung University Taiwan, CHINA

Win Aung
International Network for Engineering Education and Research, Potomac, MD, USA, National Science Foundation, Arlington, VA, USA

DOI: 10.1615/IHTC11.3140
pages 257-262

Abstract

Experimental studies of the secondary (low structure and its enhancement on the heat transfer in a horizontal divergent channel have been carried out. The bottom wall is horizontal and is heated uniformly, and while the opposite wall is insulated and inclined with respect to the horizontal plane so as to create a divergence angle of 3°. The aspect ratio (width to height) and the ratio of channel length to height at the entrance of the channel is 6.67 and 15. The Reynolds number ranges from 100 to 2000 and the buoyancy parameter, Gr/Re2, from 0 to 405. flow structure inside the channel is visualized by injecting smoke at the inlet flowing along the bottom wall. Secondary How appearing as mushroom-shaped plumes associated with vortices is also found in the divergent channel. The adverse pressure gradient in the divergent channel causes a thicker heated layer in the bottom and earlier initiation of secondary flow. The interaction between neighboring vortices and plumes becomes highly unstable. This causes an earlier and larger enhancement of the heat transfer than the case of die parallel-plate channel. The highly unstable interaction between neighboring plumes in the downstream precludes the formation of steady two-dimensional longitudinal vortex rolls. Temperature fluctuations at different locations are measured to indicate the flow structure and oscillation of the secondary flow. The effects of the buoyancy parameter and the divergence of the channel on the secondary flow structure and the Nusselt number are presented and discussed.

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