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首页> 外文期刊>International Journal of Heat and Mass Transfer >Flow Instability (FI) for subcooled flow boiling through a narrow rectangular channel under transversely uniform and non-uniform heat flux
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Flow Instability (FI) for subcooled flow boiling through a narrow rectangular channel under transversely uniform and non-uniform heat flux

机译：在横向均匀和非均匀热通量下通过狭窄矩形通道沸腾的过冷流的流动不稳定性（FI）

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Transversely non-uniform heating enforces high local heat fluxes at a few areas on the heated surface and low local heat fluxes at others. Differences in the heat flux distribution may generate differences in the boiling behavior when compared with that under uniform heating. Thus, the present experiments investigate the influence of transverse heat flux distribution on the flow instability through a narrow rectangular channel (2.35 mm × 54.0 mm × 566 mm). A wide range of experimental operation conditions, such as inlet temperatures (35–65 °C), thermal power (500–6250 W), and mass flow rates (0.03–0.13 kg/s), are applied to the upward flow channel. The working fluid corresponds to demineralized water under atmospheric pressure. The channel is heated from a side, and the other side is a transparent polycarbonate window from which the bubble behavior is visualized by using a high-speed camera. The heating surface is composed of aluminum with a width of 50 mm and a length of 300 mm. The experiments are performed by using two different procedures to achieve the flow instability, namely (1) constant mass flow rate with power increases and (2) constant power with mass flow rate decreases. The results show that the flow instability occurs at similar thermal power and similar mass flow rates for both uniform and non-uniform heating conditions. However, the pressure drop and wall temperature curves exhibit differences in the trends between the two heating conditions, especially after the fluctuation in the inlet pressure. In the uniform case, bubbles are generated uniformly on the whole transverse direction of the heated surface. In the non-uniform case, more bubbles are generated at the higher local heat flux, which disturbs the velocity profile in the transverse direction. The differences in bubble generation in the transverse direction leads to differences in the flow instability in a narrow rectangular channel.
机译：横向不均匀加热会在被加热表面的一些区域强制产生较高的局部热通量，而在其他区域则会产生较低的局部热通量。与均匀加热相比，热通量分布的差异可能会导致沸腾行为的差异。因此，本实验研究了横向热通量分布对通过狭窄矩形通道（2.35×mm××54.0×mm××566×mm）的流动不稳定性的影响。向上流动通道应用了各种各样的实验操作条件，例如入口温度（35–65 C），热功率（500–6250 W）和质量流率（0.03–0.13 kg / s）。工作流体对应于大气压下的软化水。通道从一侧加热，另一侧是透明的聚碳酸酯窗口，可通过使用高速摄像机从中观察到气泡行为。加热表面由铝制成，宽度为50 mm，长度为300 mm。通过使用两种不同的过程来进行实验，以实现流动的不稳定性，即（1）随着功率增加的恒定质量流量和（2）随着质量流量减小的恒定功率。结果表明，对于均匀和不均匀的加热条件，在相似的热功率和相似的质量流率下都会发生流动不稳定性。但是，压降和壁温曲线在两种加热条件之间的趋势上显示出差异，尤其是在入口压力波动之后。在均匀的情况下，在加热表面的整个横向上均匀地产生气泡。在非均匀情况下，在较高的局部热通量下会产生更多的气泡，这会干扰横向的速度分布。横向气泡产生的差异导致狭窄矩形通道内流动不稳定性的差异。

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