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首页> 外文期刊>International Journal of Heat and Fluid Flow >Observations on braided thin wire nucleate boiling in microgravity
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Observations on braided thin wire nucleate boiling in microgravity

机译:微重力下编织细线核沸腾的观察

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A microgravity experiment was conducted on the Space Shuttle Endeavor (STS-108) to observe sustained nucleate boiling of water. Subcooled water was boiled with a single strand and a braid of three 0.16 mm diameter and 80 mm long Nichrome resistive wires. A CCD video camera recorded the experiment while six thermistors recorded the temperature of the fluid at various distances from the heating element. This paper reports experimental results in observations, measurements, and data analysis. Bubble explosions were found to take place shortly after the onset of boiling for both the single and braid of wires. The explosion may produce a high heat transfer rate, as it generates a cloud of microbubbles. The number, size, and departure rate of the bubbles from the heater wire were measured and compared with theoretical models as a function of time. The temperature measurements revealed a complex temperature distribution in the fluid chamber due to bubbles ejected from the wire that carried thermal energy close to the temperature sensors. Drag forces on departing bubbles were calculated based on bubble movement and used to predict bubble propagation. Results from this experiment provided further understanding of nucleate boiling dynamics in microgravity for the eventual design and implementation of two-phase heat transfer systems in space applications.
机译:在航天飞机(STS-108)上进行了微重力实验,观察到水持续成核沸腾。用单股线和三根直径为0.16 mm的编织物和80 mm长的Nichrome电阻丝将过冷的水煮沸。 CCD摄像机记录了实验,而六个热敏电阻记录了距加热元件不同距离的流体温度。本文在观察,测量和数据分析中报告了实验结果。发现单根和编织线沸腾后不久都发生气泡爆炸。爆炸可能会产生很高的传热速率,因为它会产生一团微气泡。测量了气泡从加热丝中的数量,大小和离开率,并将其与理论模型进行了时间比较。温度测量结果表明,由于从电线喷射的气泡携带的热能接近温度传感器,因此在流体腔室内温度分布复杂。基于气泡的移动来计算离开气泡的阻力,并用于预测气泡的传播。该实验的结果为最终在空间应用中设计和实现两相传热系统提供了对微重力下核沸腾动力学的进一步理解。

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