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首页> 外文期刊>International Journal of Heat and Mass Transfer >Flow condensation pressure oscillations at different orientations
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Flow condensation pressure oscillations at different orientations

机译：冷凝水在不同方向上的振荡

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Investigation of two-phase flow dynamic behavior and instabilities has traditionally centered on phenomena present in boiling flows due to the safety critical nature of boiling in a variety of cooling applications. Analysis of pressure signals in condensing systems reveal the presence of relevant oscillatory phenomena during flow condensation as well, which may impact performance in applications concerned with precise system control. Towards this end, the present study presents results for oscillatory behavior observed in pressure measurements during flow condensation of FC-72 in a smooth circular tube in vertical upflow, vertical downflow, and horizontal flow orientations. Dynamic behavior observed within the test section is determined to be independent of other components within the flow loop, allowing it to be isolated and interpreted as resulting from physical aspects of two-phase flow with condensation. The presence of a peak oscillatory mode (one of significantly larger amplitude than any others present) is seen for 72% of vertical upflow test cases, 61% of vertical downflow, and 54% of horizontal flow. Relative intensities of this peak oscillatory mode are evaluated through calculation ofQFactor for the corresponding frequency response peak. Frequency and amplitude of peak oscillatory modes are also evaluated. Overall, vertical upflow is seen to exhibit the most significant oscillatory behavior, although in its maximum case amplitude is only seen to be 7.9% of time-averaged module inlet pressure, indicating there is little safety risk posed by oscillations under current operating conditions. Flow visualization image sequences for each orientation are also presented and used to draw parallels between physical characteristics of condensate film behavior under different operating conditions and trends in oscillatory behavior detected in pressure signals.
机译：传统上，对两相流动力学行为和不稳定性的研究主要集中在沸腾流中的现象，这是由于在各种冷却应用中沸腾的安全性至关重要。对冷凝系统中压力信号的分析也揭示了在冷凝过程中也存在相关的振荡现象，这可能会影响与精确系统控制有关的应用程序的性能。为此，本研究提出了在光滑的圆形管中，在垂直向上流动，垂直向下流动和水平流动方向上，在FC-72流动凝结期间压力测量中观察到的振荡行为的结果。测试部分内观察到的动态行为被确定为独立于流环路内的其他组件，从而可以将其隔离和解释为由两相流在冷凝条件下的物理状态产生的结果。对于72％的垂直上流测试案例，61％的垂直下流测试案例和54％的水平流，可以看到峰值振荡模式（幅度明显大于其他任何一种）。通过计算相应频率响应峰的QFactor来评估此峰振荡模式的相对强度。还评估了峰值振荡模式的频率和幅度。总的来说，尽管在最大情况下，振幅仅被视为平均时间模块进口压力的7.9％，但垂直向上流动表现出最显着的振荡行为，这表明在当前工作条件下，由振动引起的安全风险很小。还介绍了每个方向的流动可视化图像序列，并将其用于在不同操作条件下冷凝膜行为的物理特征与压力信号中检测到的振荡行为趋势之间绘制相似度。

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