Secondary flow and enhancement of heat transfer in horizontal parallel-plate and convergent channels heating from below

摘要: Abstract Experimental studies of secondary air flow structure and enhancement heat transfer in horizontal parallel-plate convergent channels have been carried out. The bottom wall is heated uniformly, while the opposite insulated inclined with respect to plate so as create a convergence angel 3° for channel. aspect ratio (width height) channel length height at entrance 6.67 15, respectively. Reynolds number ranges from 100 2000, buoyancy parameter, Gr/Re2, 2.5 907 Pr 0.7. Flow inside visualized by injecting smoke inlet flowing along wall. complete processes formation plumes associated vortices their transformation into longitudinal convection rolls due lateral extension combination are observed. formed much less than those found experiments water. For channel,the favorable pressure gradient causes thinner layer which results later initiation fewer plume produced. interactions between neighboring suppressed acceleration mainstream, ina stable pronounced transfer. Temperature fluctuations different locations measured indicate oscillation flow. effects parameter on Nusselt presented discussed.