Determination of thermal conductivity in the subsurface using laboratory and field experiments and theoretical models

Menberg, Kathrin; Steger, Hagen; Zorn, Roman; Reuß, Manfred; Pröll, Markus; Bayer, Peter; Blum, Philipp

Determination of thermal conductivity in the subsurface using laboratory and field experiments and theoretical models | Bestimmung der Wärmeleitfähigkeit im Untergrund durch Labor- und Feldversuche und anhand theoretischer Modelle

2013

For the planning and design of borehole heat exchangers systems, the knowledge of the thermophysical ground parameters is essential. In this study, several methods for the determination of thermal conductivity were used on a borehole for a ground source heat pump system. Thermal conductivity was measured on core samples using laboratory tests and likewise a Thermal Response Test (TRT) was carried out. In addition, several ground parameters, such as water content and carbonate content, were determined by laboratory tests. With these parameters the thermal conductivity was then calculated using different theoretical models. The best agreement between measured and calculated values for thermal conductivities was obtained using the geometric mean. The mean error of these calculations in this study is about 12 %. Thus, the accuracy of the calculation of thermal conductivity is lower than the accuracy of the laboratory tests or TRTs, but it nevertheless represents a simple and more accurate method than parameter estimations based on published values.

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