Macrodispersion and Recovery of Solutes and Heat in Heterogeneous Aquifers

Tang, D. W. S.; Zee, S.E.A.T.M. van der

doi:10.1029/2021wr030920

Cited by 7 publications

(4 citation statements)

References 94 publications

(175 reference statements)

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“…Although the fluid velocities and pore sizes simulated in these additional scenarios may be rather large for typical environmental flows in soil matrices, they are relevant to flow in fractures, macropores, and high-conductivity conduits. If such preferential flow zones are present, the advection of contaminants may be routed primarily through them (Tang & Van Der Zee, 2022).…”

Section: Hydrodynamic Liftmentioning

confidence: 99%

Colloid Transport and Retention in Constricted Tube Pore Spaces With Diverse Geometries and Orientations

Tang,

Raoof

2024

Water Resources Research

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Colloidal contaminants infiltrate and can be attached onto grain surfaces of soils and aquifers, where they may persist. In this study, Lagrangian particle tracking is used to investigate particle trajectories and attachment in pore and fracture spaces modeled as three‐dimensional constricted tubes with diverse geometries and orientations relative to gravity. A comprehensive force balance arising from hydrodynamic drag and lift, gravitational settling, Brownian motion, and attractive DLVO interactions is simulated. Results show that the collection efficiency η is primarily governed by the dimensionless settling number 𝑆, representing the relative dominance of gravitational over hydrodynamic forces experienced by the particles. High‐𝑆 scenarios have larger η and are more sensitive to pore orientation, while low‐𝑆 scenarios are more sensitive to pore geometry. For all scenarios but especially low‐S scenarios, the majority of colloid attachment occurs near pore extremities, where fluid velocities are low, such that mechanical remobilization of particles attached is improbable. In low‐𝑆 scenarios, particles may spread and become immobilized at greater distances from the contamination source owing to lower η, are harder to mechanically remobilize as they attach more disproportionately at pore extremities, and have trajectories more sensitive to minor forces, rendering their environmental fates complex. Characterizing the collection efficiency and deposition morphology for various pore space geometries and orientations is crucial in understanding particle fate and developing continuum‐scale models of colloid transport in real soils, where pore spaces are heterogeneous and advection paths are tortuous.

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Section: Hydrodynamic Liftmentioning

confidence: 99%

Colloid Transport and Retention in Constricted Tube Pore Spaces With Diverse Geometries and Orientations

Tang,

Raoof

2024

Water Resources Research

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“…'s “effective thermal conductivity,” which has till now been empirical in nature. As macrodispersion due to aquifer heterogeneity may be considered a form of mechanical dispersion with a space‐dependent mechanical dispersion coefficient, it would also be possible to include the effects of macrodispersion into k eff , if the macrodispersion parameters are known (Tang & van der Zee, 2022).…”

Section: Theorymentioning

confidence: 99%

“…When ATES systems are operated for multiple cycles, the recovery efficiency increases with the number of cycles, according to the expression

\begin{align*}{F}_{n}=1-(1-F){n}^{z-1},\end{align*}

where n refers to the n th cycle, F n = 1 − M n is the recovery efficiency of the n th cycle, and z is an empirical parameter that is negatively correlated with F and analytically bounded in the range

\frac{1}{2}\le z\le 1

(Tang & van der Zee, 2021a). Extensive numerical simulations show that although the value of z is highly positively correlated with M (Tang & van der Zee, 2021a, 2022). However, the value of z is also affected by the duration of the rest phase, which refers to the period of time between an extraction phase and the injection phase of the subsequent cycle.…”

Section: Theorymentioning

confidence: 99%

“…One is thermal diffusion due to heat diffusion through the aquifer matrix, in the liquid as well as solid phase (Almeida et al., 2022; Bloemendal & Hartog, 2018; Paz et al., 2017). Another is the mixing of water, which occurs as a result of processes such as mechanical dispersion due to pore‐scale mixing between the injected water and native groundwater (Tang & van der Zee, 2021a), macrodispersion driven by hydraulic heterogeneities in the aquifer (Tang & van der Zee, 2022), and free convection driven by density gradients between the warm and cold groundwater (Sheldon et al., 2021). Most studies on the thermal recovery efficiency of ATES invoke numerical modeling to capture these relevant processes, but such models require detailed data on (heterogeneous) aquifer composition and properties, and water injection and extraction rate timeseries, which may be unavailable or very costly to obtain from field characterization, while also requiring intensive model construction and simulation time.…”

Section: Introductionmentioning

confidence: 99%

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Dimensionless Thermal Efficiency Analysis for Aquifer Thermal Energy Storage

Tang,

Rijnaarts

2023

Water Resources Research

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Seasonal warm and cold water storage in groundwater aquifers is a cost‐effective renewable energy technology for indoor heating and cooling. Simple dimensionless analytical solutions for the thermal recovery efficiency of Aquifer Thermal Energy Storage (ATES) systems are derived, subject to heat losses caused by thermal diffusion and mechanical dispersion. The analytical solutions pertain to transient pumping rates and storage durations, and multiple cycles of operation, and are applicable to various well configurations and thermal plume geometries. Heat losses to confining layers, its implications for optimizing plume geometries and aspect ratios, and heat spreading due to free convection are also discussed. This provides a general tool for broad and rapid assessment of aquifers and ATES systems. We show that if heat exchange with the confining layers is negligible, the thermal recovery efficiency of thermal plumes with cylindrical geometry is independent of the aquifer porosity and heat capacity C0. Therefore, if mechanical dispersion is negligible as is often the case, the only aquifer property that affects the recovery efficiency is the aquifer thermal conductivity. The field‐scale aquifer thermal conductivity λ can therefore be inferred from the recovery efficiency of a push‐pull heat recovery test. Remarkably, an increase in C0 could either increase, decrease, or not affect the recovery efficiency, depending on the thermal plume geometry. Hence, the analytical solutions reveal that the recovery efficiency is affected by complex interactions between the thermal plume geometry and aquifer properties. Approximate analytical solutions for subsurface temperature profiles over an entire ATES cycle are also derived.

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