Coupled Heat and Water Flows Around Buried Cables

Theoretical and experimental studies of heat flow and moisture movement under thermal gradients are described with particular emphasis on flows around buried electrical transmission cables. A one-dimensional finite difference computer program for analysis of coupled heat and water flows in layered systems based on the Philip and DeVries theory is developed. Theoretical analysis indicate that the most important parameters affecting rate and amount of moisture migration away from buried heat sources are the sources temperature and the soil type. A field test was conducted to evaluate the heat and moisture flow predictive methods. The results showed that water content predictions using the coupled flow computer program match poorly with the actual values, and that predicted values are very sensitive to the soil properties used. A finite element two-dimensional computer program is used to predict the variation of temperature distributions around the buried cable with time after initiation of cable heating. The results show very good agreement between measured and predicted temperature contours.