Characterizing the Two‐Dimensional Thermal Conductivity Distribution in a Sand and Gravel Aquifer

Abstract

Both hydrologic and thermal transport properties play a significant role in the movement of heat through permeable sedimentary material; however, the thermal conductivity is rarely characterized in detailed spatial resolution. As part of a study of the movement of thermal plumes through a sand and gravel aquifer, we have constructed a twodimensional profile of thermal conductivity. This work consisted of: (i) measuring the thermal conductivity of the soil solids, l s , for the main stratigraphic units using the steady-state divided-bar apparatus and estimating conductivity from mineral composition; (ii) measuring the volumetric water content and porosity using crosshole groundpenetrating radar; (iii) evaluating four models used to predict the apparent thermal conductivity, l, of variably saturated soils and selecting the best model using the information-theoretic approach, (iv) calculating the l field on a 0.25-m square cell grid using measured data and the selected model, and (v) simulating thermal transport within the two-dimensional domain using a finite element numerical model. The apparent thermal conductivity in the saturated aquifer ranges from 2.14 to 2.69 W m 21 K 21 with a mean of 2.42 W m 21 K 21. Numerical simulations show that the heterogeneous thermal conductivity field results in increased thermal dispersion that is most pronounced at the plume front. Our values for l and l s may be used for glacial soils with similar mineralogy and texture. Our methods may also be used at other sites to construct the thermal conductivity distribution.

Hydraulic characterization of aquifers by thermal response testing: Validation by large-scale tank and field experiments

“…For example, Markle et al . [] analyzed the evolution of a thermal plume in a glacial‐outwash aquifer of the Tricks Creek wetland complex in southwest Ontario, Canada. Their main objective was to assess the impact of thermal disturbances on the subsurface, and therefore, a detailed characterization of the hydraulic and thermal properties was performed.…”

Thermal transport modelling in a fully integrated surface/subsurface framework

“…Thermal conductivities of the solids (k s ) assigned to each subsurface material type are consistent with measured saturated thermal conductivity values of Schmidt et al (2007) (Table VI). Other thermal properties are taken from Markle et al (2006) and Verseghy (1991). A constant temperature was assigned below the water table for the lateral boundaries of the domain as well as to the bottom of the domain.…”

Simple determination of the thermal conductivity of the solid phase of particulate materials

“…[14,19,20,33]). One of the reasons for this observation may be that the thermal conductivity probe, which makes localised measurements, has the potential for a bias towards the continuous phase of a mixture which, in this case, is the fluid phase which has lower thermal conductivity than the solid.…”

“…The measurement and prediction of the thermal conductivity of porous media in general [1][2][3][4][5][6][7][8][9][10][11] and soils, sands and rocks in particular [12][13][14][15][16][17][18][19] have occupied a substantial portion of literature and continue to do so. Typically the modelling approach is to treat the porous medium as a two-phase (solid-fluid) or three-phase (solid-waterair) material and predict the thermal conductivity based on the amounts and thermal conductivities of the components.…”