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다공성 매질내 유체의 자연대류 개시에 미치는 열손실의 영향

Effect of Lateral Heat Loss on the Onset of Natural Convection in a Box of Fluid-Saturated Porous Medium

HWAHAK KONGHAK, April 1983, 21(2), 79-88(10), NONE
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Abstract

다공성 매질내 유체의 자연대류 개시에 미치는 벽면에서의 열손실 효과를 열 및 유동경계면 조건에 따라 포괄적으로 규명하기 위하여 상층면은 등온의 투수성 또는 불투수성이고, 바닥은 등온 또는 일정한 열플럭스로 가열되는 불투수성 경계면인 상자를 모델로 안정성 해석을 행하였다. 상기 연구의 결과 자연대류가 시작되는 임계 Rayleigh 수와 이때의 대류유동의 셀모오드(cellular mode)를 상자의 기하구조, 주위온도, 전열 계수 및 경계 조건들의 함수로 표시하였으며, 벽면에서 열손실이 있는 경우 임계 Rayleigh 수는 증가하고, 경계 조건들이 Dirichlet형으로 주어질 때 열적 안정성이 가장 증가한다는 사실을 확인하였다.
The onset of natural convection has been examined for a fluid-saturated porous material contained within a thin box under the influence of lateral heat losses. Thermal boundary conditions consist of an isothermal upper surface and either prescribed temperature or prescribed heat flux at the lower boundary. Both permeable and impermeable upper boundaries are considered.
Critical Rayleigh numbers and the preferred convective cellular modes at the onset of convection have been determined analytically as functions of the box geometry, ambient temperature and heat transfer coefficient. The results show that the critical Rayleigh number for a box with lateral heat loss is higher than thet predicted in the limit of no heat loss except for extremely small aspect ratios. And the case with no Neumann boundary condition has been found the most stable.

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