Flow pattern and heat transfer of low-speed upward flow between uniformly heated vertical plates

Low-speed upward flow in an uniformly heated vertical flat duct was studied experimentally. The flow pattern was visualized by the dye injection method. The flow was laminar throughout the entire channel when the effect of buoyancy was relatively small. However, the streak line of dye began to oscillate sinusoidally halfway through the channel when the effect of buoyancy became large, and then the flow transited to a turbulent one. The wall temperature oscillated sinusoidally at the transition point, and fluctuated randomly in the turbulent region. The heat transfer coefficient increased rapidly with the flow transition. The effects of Reynolds number and modified Grashof number upon the condition under which flow transition occurred and upon the heat transfer coefficient in the turbulent region were clarified. (author)