Secondary flow in Horizontal Convergent or Divergent channel heated from below

• Main Authors: Liu, Chien-Wei, 劉建惟
• Other Authors: Gau Chi
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/57959211671653115775

碩士 === 國立成功大學 === 航空太空工程學系 === 85 === Experiments were performed to study the heat transfer behavior of secondaryflow in horizontal convergent or divergent channel heated from below for airflow. The experiment is devised for two parts. The first one is wall heat transfer distribution measurement, the other is flow visualization.Both of them can provide an understanding to the physical phenomenon.One of the side walls which maintains horizontal is heated uniformly and the opposite wall which has a convergent or divergent angle of 3 is insulated. During the experiment, the Reynolds number of the main forced flow ranges from 105 to 1000 and the buoyancy parameter varies from 1.5 to 907.In horizontal channel, the buoyancy induced secondary flow can produce plume and mushroom- like vortices which can significantly increase the heattransfer in the channel. In the divergent channel, the adverse pressure gradient causes a thicker bottom heated layer as well as a much earlier initiation of plumes and earlier interaction between neighboring vortices and plumes which become unsteady in the downstream. In convergent channel,the favorable pressure gradient causes a thinner bottom heated layer and amuch later initiation of secondary flow. The effect of buoyancy is reducedin the downstream regime where the flow acceleration is significant.