Effect of Eddy Formation on Transient Phenomena of Free Convection in an Enclosure

在考虑冷却条件的情况下，研究了涡流的形成对换热的影响。由于发汗流体是空气，因此测量了铝表面的发射率。发射率被确定为0.44的值。采用高1 m、宽0.5m、两壁间距0.05- 0.25m的垂直封闭，用烟雾法观测涡动。在导电壁的每一侧上检测运动。在热壁面上，频率为1.2 ~ 2.1Hz，波长约为70 mm，通过分析边界层方程得出结论：边界层外前缘的压力偏差引起了发展流动的时间，而在边界层中观察到了小的波动运动。在热壁上，频率为4 ~ 6 Hz，波长为30-40 mm，振幅为5-15 mm，这种弱湍流使流动发展有一段时间，并使边界层有所增厚。

Effects of eddy formation on heat transfer were studied by making account of cooling condition. Becouse of transpiration fluid as air, emissivity of aluminum surface was measured. The emissivity was determined as a value of 0.44. Employed vertical enclosure was that the height = 1 m, the width = 0.5 m and the distance of two walls = 0.05-0.25 m.Vortex motions are observed by a smoke method. The motion is detected on each side of conducting wall. On the hot wall, the frequency is ranging from 1.2 to 2.1 Hz and wave length is almost 70 mm. A concluding remark is given by analyzing boundary layer equation that a pressure deviation at the outer leading edge of boundary layer gives rise a time elapsing to developed flow.Small undulatory motion, on the other hand, is observed in the boundary layer. On the hot wall, the frequency is ranging from 4 to 6 Hz and the wave length is 30-40 mm with the amplitude of 5-15 mm. This weak turbulence gives a time elapsing to developed flow and some thickening of the boundary layer.As a result of flow simulation on a computer, in a case of air flow, it is suggested that the distance of two walls should be chosen as the suitable characteristic length.