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首页> 外文期刊>International Journal of Heat and Mass Transfer >Natural convection heat transfer characteristics in vertical cavities with active and inactive top and bottom disks
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Natural convection heat transfer characteristics in vertical cavities with active and inactive top and bottom disks

机译：带有主动和非主动顶盘和底盘的垂直腔中的自然对流传热特性

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摘要

Natural convection heat transfer was investigated in vertical cavities where either all surfaces were active, or only the vertical surface was active for four different geometries, which were varied by placing a disk at the top and/or bottom of the cavity. A cupric acid-copper sulfate electroplating system was employed for mass transfer experiments exploiting the analogy with heat transfer. The Rayleigh number was varied in the range 4.55 × 10~9 ≤ Ra_(Lw) ≤ 3.79 × 10~(13). Preliminary tests for a vertical pipe, upward-and downward-facing horizontal disks showed good agreement with existing correlations. The measured Nusselt numbers in the vertical cavities with all surfaces active were always greater than those with only the vertical surface active, which is attributed to greater hydrodynamic interaction of the flows generated by different surfaces. When all surfaces were active, the bottom-closed cavity exhibited the largest heat transfer rates, followed by both-closed, top-closed, and both ends open cavities; this trend was observed with laminar and turbulent flows. With only the vertical surface active, similar trends were observed except that the heat transfer rates were almost identical for both-open and top-closed cavities, which is attributed to the weak influence of the top disk on the heat transfer characteristics. Using these results, empirical correlations were derived for both laminar and turbulent flow conditions.
机译：在垂直空腔中研究了自然对流传热，在垂直空腔中，对于四个不同的几何形状，所有表面都是活动的，或者只有垂直表面才是活动的，这是通过在空腔的顶部和/或底部放置一个圆盘来改变的。利用与传热类似的方法，将铜酸-硫酸铜电镀系统用于传质实验。瑞利数在4.55×10〜9≤Ra_（Lw）≤3.79×10〜（13）的范围内变化。垂直管，向上和向下的水平盘的初步测试显示与现有的相关性很好。所有表面均处于活动状态的垂直腔中测得的Nusselt数始终大于仅垂直表面为活动的腔中的Nusselt数，这归因于不同表面产生的流的更大的流体动力相互作用。当所有表面都处于活动状态时，底部封闭的腔体表现出最大的传热速率，其次是两个封闭的，顶部封闭的和两端开放的腔体。在层流和湍流中观察到了这种趋势。仅在垂直表面处于活动状态时，观察到类似的趋势，不同的是，开孔和顶孔腔的传热速率几乎相同，这是由于顶盘对传热特性的影响较弱。利用这些结果，得出了层流和湍流条件的经验相关性。

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