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首页> 外文期刊>International Journal of Heat and Mass Transfer >Effect of rainfall transients on thermal and moisture exposure of underground electric cables
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Effect of rainfall transients on thermal and moisture exposure of underground electric cables

机译：降雨瞬变对地下电缆的热和湿气暴露的影响

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摘要

Cable ampacity analysis is generally performed assuming constant worst-state environmental conditions, which often correspond to a dry soil condition or to a condition with uniform ambient soil moisture content. The characteristic time scale of thermal variation in the soil is large, on the order of several weeks, and is similar to the time scale between rainfall events in many geographic locations. Intermittent rainfall events introduce significant transient fluctuations that influence the thermal conditions and moisture content around a buried cable both by increasing thermal conductivity of the soil and by increasing the moisture exposure of the cable insulation. This paper reports on a computational study of the effect of rainfall events on the thermal and moisture transients surrounding a buried cable. The computations were performed with a finite-difference method using an overset grid approach, with an inner polar grid surrounding the cable and an outer Cartesian grid. The thermal and moisture transients observed in computations with periodic rainfall events were compared to control computations with a steady uniform rainfall. Under periodic rainfall conditions, the temperature and moisture fields are observed to approach a limit-cycle condition in which the cable surface temperature and moisture content oscillate in time, but with mean values that are significantly different than the steady-state values.
机译：电缆载流量分析通常是在假设恒定的最坏状态环境条件下进行的，该条件通常对应于干燥土壤条件或环境土壤水分含量均匀的条件。土壤中热变化的特征时间尺度很大，大约数周，并且与许多地理位置降雨事件之间的时间尺度相似。间歇性降雨事件会引起显着的瞬时波动，这既会增加土壤的导热性，又会增加电缆绝缘层的水分暴露量，从而影响埋电缆周围的热状况和水分含量。本文报告了降雨事件对埋电缆周围的热和湿气瞬变影响的计算研究。计算是通过有限差分法使用覆盖网格方法进行的，其中内部极性网格围绕电缆，外部笛卡尔网格。将定期降雨事件的计算中观察到的热和水分瞬变与稳定降雨情况下的控制计算进行了比较。在周期性降雨条件下，观察到温度和湿度场接近极限循环条件，在该条件下，电缆表面温度和水分含量随时间波动，但平均值与稳态值明显不同。

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