Numerical Back-Analysis of Geothermal Laboratory Tests with Forced Groundwater flow

Abstract

The influence of groundwater flow velocity on the increase of the effective thermal conductivity of water saturated sediments has not been determined sufficiently. Common literature (VDI 4640) distinguishes between effective thermal conductivities for dry, moist and water saturated sands. The influence of the Darcy velocity is not considered in these recommendations. Therefore, extensive experimental investigations of groundwater dominated geothermal systems have been conducted in field tests, as presented on the geothermal workshop in 2012 (Huber & Arslan 2012a) as well as in laboratory tests. A geothermal laboratory device has been developed. With the help of this conduction and convection laboratory device the performance of geothermal systems under forced groundwater flow can be determined. The different types of heat transport processes in geothermal systems can be characterized clearly. All the results gathered in the experimental investigations were verified and extrapolated by numerical back analysis. After all, recommendations for the increase of the effective thermal conductivity of groundwater dominated geothermal systems depending on the Darcy velocity were given in addition to (VDI 4640).