Recirculating flow and mass transfer in cavities = 공동내에서의 재순환유동과 물질전달

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The recirculating flow in a cavity has been studied numerically and experimentally in relation with mass transfer in small pores. Four models of the cavity are considered: Prototype cavity (which has translating top and bottom walls), top-open cavity at steady state, top-open cavity at unsteady state, and top-and-bottom-open cavity. The visualization experiments have been performed in addition to numerical analysis for both the prototype cavity and the top-and-bottom-open cavity. The mass transfer measurements using the limiting current method have been carried out for the cavities closed or open to a channel. In the prototype cavity with small aspect ratios, the relative direction of the wall movement has a large effect on mass transfer because they influence the rotational direction and the size of the vortices. When $u_B$(x-velocity of the bottom wall) >0, even number of eddies are formed and there is no convective flow across the eddies. When $u_B >0$, the mass or heat transfer between the top and bottom walls is expected to increase because of the enhanced convective flow in the cavity. Therefore the top and bottom walls moving in a opposite directions are more efficient than the walls moving in the same directions either in a creeping flow regime or in a moderate Reynolds number region. Mean Sherwood number increases with both the Reynolds number and the Schmidt number and can be expressed as $Sh_m = 1 + K Re^α Sc^β$ with K, α and β dependent on the respective aspect ratio. The cavity flow patterns from visualization have shown in general good agreement with the numerical solutions except when Ar = 1, $u_B< 0$. The streamlines near the sharp corners are compared with earlier analytical solutions from Moffat and Batchelor. As a result, the region to which the analytical solutions can safely be applied has been identified. In the channel cavity flow, the number of vortices also increases with aspect ratio: The primary and the secondary vortices only are sig...
Chang, Ho-Namresearcher장호남researcher
한국과학기술원 : 화학공학과,
Issue Date
61079/325007 / 000765084

학위논문(박사) - 한국과학기술원 : 화학공학과, 1987.8, [ xiii, 252 p. ]

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