论文标题
在辐射和自然对流中的半透明壁上热绝热边界条件的研究
Investigation of Thermal Adiabatic Boundary Condition on Semitransparent Wall in Combined Radiation and Natural Convection
论文作者
论文摘要
由于半透明窗口是否允许能量通过热传递的辐射模式离开系统，因此在半透明窗口上出现了两个热绝热边界条件。假定是半透明材料的低电导率，能量不会通过传热模式离开。这确实意味着半透明窗口可能仅是导电的绝热（QC = 0），或者是导电和辐射绝热的（QC + QR = 0）。在目前的工作中，已经在雷利数（RA）10^5的自然对流问题中研究了上述两个热绝热边界条件，而腔体中的prandtl数量（pr）为0.71，其左垂直壁已分为4：6的左垂直壁为上下部分。上部分是半透明窗口，而下部则是在296K的温度下等温壁。在半透明窗口上以45^0的角度在半透明窗口上以不同的值（0、100、500和1000 w/m2）照射准直的光束。通过对流温度为305K，对流加热和热传递系数为50 W/m2k，而右壁在与左下壁的同一温度下也等温度，而上壁是等等的，并且上壁是绝热的。除半透明窗口外，所有墙壁都是不透明的辐射。结果表明，腔体内的两个涡流的动力学随照射值以及半透明窗口的边界条件发生了巨大变化。与半透明窗口上唯一的无动性绝热状况相比，用于连接和辐射绝热条件的腔内多胎内温度和努塞尔的数量增加。
Two thermal adiabatic boundary conditions arise on the semitransparent window owing to the fact that whether semitransparent window allows the energy to leave the system by radiation mode of heat transfer. It is assumed that being low conductivity of semitransparent material, energy does not leave by conduction mode of heat transfer. This does mean that the semitransparent window may behave as only conductively adiabatic (qc = 0) or combinedly conductively and radiatively adiabatic (qc + qr = 0). In the present work, the above two thermal adiabatic boundary conditions have been investigated in natural convection problem for the Rayleigh number (Ra) 10^5 and Prandtl number(Pr) 0.71 in a cavity, whose left vertical wall has been divided into upper and lower parts in the ratio of 4:6. The upper section is semitransparent window, while lower section is isothermal wall at a temperature of 296K. A collimated beam is irradiated with different value (0, 100, 500 and 1000 W/m2) on the semitransparent window at an angle of 45^0 . The cavity is heated from the bottom by convective heating with free stream temperature of 305K and heat transfer coefficient of 50 W/m2K while right wall is also isothermal at same temperature as of lower left wall and upper wall is adiabatic. All walls are opaque for radiation except semitransparent window. The results reveal that the dynamics of both the vortices inside the cavity change drastically with irradiation value and also with the boundary conditions on the semitransparent window. The temperature and Nusselt number increase inside the cavity multifold for combinedly conductively and radiatively adiabatic condition than the only conductively adiabatic condition on the semitransparent window.
