Conservative Solute Versus Heat Transport in Porous Media During Push-pull Tests |
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Authors: | A Vandenbohede A Louwyck L Lebbe |
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Institution: | (1) Research Unit Groundwater Modelling, Ghent University, Krijgslaan 281 (S8), 9000 Gent, Oost-Vlaanderen, Belgium |
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Abstract: | Both heat and solute transport in porous media are described by partial differential equations of similar form. Nevertheless,
observing these phenomena in the field on the scale of well tests clearly indicates dissimilar behaviour. This article studies
the aforementioned transport processes by interpreting two push-pull tests of different duration. In both tests, chloride
is applied as a conservative tracer and lower temperature water is injected in higher temperature pristine water at different
flow rates. Simulation and interpretation of the tests are performed by means of ReacTrans, a two-dimensional, axially symmetric,
finite-difference, solute and heat transport model. Since conflicting views exist in literature on the relation between solute
and thermal dispersivity, analysis of field observations focuses on parameters which describe aquifer characteristics affecting
these processes. Parameter estimation is conducted through sensitivity analysis and collinear diagnosis in order to identify
derivable parameters. It is concluded that longitudinal solute dispersivity and thermal diffusivity could be inferred accurately
from chloride and temperature data sampled from the injection/extraction well respectively. Involving supplementary data sampled
from an observation well enables derivation of effective porosity from chloride data and thermal retardation from temperature
data. Moreover, it is inferred that longitudinal solute dispersivity is scale dependent. Thermal diffusivity, however, seems
not to be. This points to dissimilar development of transition zones during solute and heat transport. It is concluded that
conductive transport of heat is much more important than effects of velocity variations through the pore space. |
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Keywords: | Heat transport Conservative solute transport Modelling Parameter identification Dispersivity |
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