DA-00-13-3 -- Field Test of a New Method for Determining Soil Formation Thermal Conductivity and Borehole Resistance PDF

A new method of determining soil thermal properties from in-situ tests has been developed. Based on a one-dimensional numerical heat transfer model, the method uses parameter estimation techniques to determine soil thermal conductivity and borehole resistance from field-collected data. This paper presents the results of analysis of data from three tests performed in Lincoln, Nebraska, in order to validate the method. The one-dimensional method was found to agree well with line source and cylindrical source thermal conductivity estimates derived from the same data sets. The method was also able to measure the resistance of the three borehole heat exchangers. The measured resistances lie within the expected range of resistances for the given grouting materials. A further benefit of our method is its relative insensitivity to changes in power input caused by short-term voltage fluctuations.

Units: I-P