Laminar natural convection heat transfer is numerically investigated in convergent and divergent vertical channels with a single obstruction. The channel walls are maintained at a uniform temperature which exceeds the ambient temperature using air as the working fluid. The dimensionless parameters of interest in the problem are six, namely, the Rayleigh number (Ra), the aspect ratio (AR), the dimensionless distance of the obstruction centerline above the entrance of the channel, the dimensionless obstruction width, the angle (γ) and the Prandtl number (Pr). The effect of the first four parameters on the average Nusselt number has been studied by the authors for γ = 0 (parallel-walled channel) and will serve as a baseline against which to compare results for positive angle (i.e. convergent channel) and for negative angle (i.e. divergent channel). The results show that the average Nusselt number for both convergent and divergent channels deviates significantly at low Rayleigh numbers (Ra < 500) when compared with the ones for parallel-walled channel (γ = 0) and the deviation is not significant (around 5%) at high Rayleigh numbers (Ra > 500). The Rayleigh number and the average Nusselt number are based on Smin (Smin being the width of the exit for the convergent channel and the width of the entrance for the divergent channel). A complete discussion of the results based on the flow field, average Nusselt number, velocity and temperature profiles will be presented in the paper.
|Number of pages
|Published - 1992
ASJC Scopus subject areas
- Geotechnical Engineering and Engineering Geology