Non-isothermal flow in low permeable porous media: a comparison of Richards’ and two-phase flow approaches
The present work compares the performance of two alternative flow models for the simulation of thermal-hydraulic coupled processes in low permeable porous media: non-isothermal Richards’ and two-phase flow concepts. Both models take vaporization processes into account: however, the Richards’ model neglects dynamic pressure variations and bulk flow of the gaseous phase. For the comparison of the two approaches first published, data from a laboratory experiment are studied involving thermally driven moisture flow in a partially saturated bentonite sample. Then a benchmark test of longer-term thermal-hydraulic behavior in the engineered barrier system of a geological nuclear waste repository is analyzed (DECOVALEX project). It was found that both models can be used to reproduce the vaporization process if the intrinsic permeability is relative high. However, when a thermal-hydraulic coupled problem has the same low intrinsic permeability, only the two-phase flow approach provides reasonable results.
KeywordsNon-isothermal two-phase flow Richards’ approximation Porous media CTF1 experiment DECOVALEX task D
The development of the numerical models was conducted in the framework of the international DECOVALEX project. The funding from the Federal Institute for Geosciences is highly acknowledged (Dr. Shao). This work is part of the PoF research initiative of the Helmholtz Association within the Environmental Engineering and Geothermal Technology programs. Funding from the Swedish Radiation Safety Authority (SSM) through the US Department of Energy Contract No. DE-AC02-05CH11231 is greatly appreciated.
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