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Effective diffusivity in partially-saturated carbon-fiber gas diffusion layers: Effect of through-plane saturation distribution
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Two-phase flow distribution of saturated refrigerants in microchannel heat exchanger headers
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Effective diffusivity in partially-saturated carbon-fiber gas diffusion layers: Effect of local saturation and application to macroscopic continuum models
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Modeling oil saturation evolution in residual oil zones: Implications for CO2 EOR and sequestration
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Ignition characteristics of a bio-derived class of saturated and unsaturated furans for engine applications
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Analysis of combined HERA data in the impact-parameter dependent saturation model
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Pore saturation model for capillary imbibition and drainage pressures
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Uncertainty quantification of CO₂ saturation estimated from electrical resistance tomography data at the Cranfield site
A parametric bootstrap approach is presented for uncertainty quantification (UQ) of CO₂ saturation derived from electrical resistance tomography (ERT) data collected at the Cranfield, Mississippi (USA) carbon sequestration site. There are many sources of uncertainty in ERT-derived CO₂ saturation, but we focus on how the ERT observation errors propagate to the estimated CO₂ saturation in a nonlinear inversion process. Our UQ approach consists of three steps. We first estimated the observational errors from a large number of reciprocal ERT measurements. The second step was to invert the pre-injection baseline data and the resulting resistivity tomograph was used as the prior information for nonlinear inversion of time-lapse data. We assigned a 3% random noise to the baseline model. Finally, we used a parametric bootstrap method to obtain bootstrap CO₂ saturation samples by deterministically solving a nonlinear inverse problem many times with resampled data and resampled baseline models. Then the mean and standard deviation of CO₂ saturation were calculated from the bootstrap samples. We found that the maximum standard deviation of CO₂ saturation was around 6% with a corresponding maximum saturation of 30% for a data set collected 100 days after injection began. There was no apparent spatial correlation between the mean and standard deviation of CO₂ saturation but the standard deviation values increased with time as the saturation increased. The uncertainty in CO₂ saturation also depends on the ERT reciprocal error threshold used to identify and remove noisy data and inversion constraints such as temporal roughness. Five hundred realizations requiring 3.5 h on a single 12-core node were needed for the nonlinear Monte Carlo inversion to arrive at stationary variances while the Markov Chain Monte Carlo (MCMC) stochastic inverse approach may expend days for a global search. This indicates that UQ of 2D or 3D ERT inverse problems can be performed on a laptop or desktop PC.
Pyroclast cooling and saturation in water
In the submarine setting pyroclast cooling and saturation, by controlling the buoyancy of individual clasts and surrounding fluid, exert fundamental controls on the dispersal and fate of volcanic material. Here, we use laboratory experiments to understand and quantify how hot and air-filled pyroclasts cool and saturate in liquid water. By measuring internal temperature and clast submerged weight in over thirty experiments, we find that pumice cools and saturates in two stages. We observe that the first stage is marked by much higher rates of cooling and saturation than the second stage and that the transition between stages is sharp. We propose conceptual and quantitative models for each stage of pyroclast cooling and saturation. Specifically we argue that the first stage is defined by the presence of internal steam. That is, hot pyroclasts ingest liquid water and generate steam. Once a clast's internal pore space is filled with steam, heat loss to the surroundings causes condensation of internal vapor and clast saturation. Stage 1 ends when all internal steam has condensed. We test this idea with a Stefan Model with advection and conclude that heat loss, rather than permeability, controls the saturation of pyroclasts above the boiling temperature. We find that permeability matters for air-filled clasts with initial temperatures below the boiling point. Stage 2 begins after all internal vapor has condensed and we propose that stage 2 cooling and saturation are controlled by heat conduction and thermal contraction of trapped gas, respectively. From our understanding of the processes that govern the stage 1 to 2 transition, we derive an empirical average pyroclast cooling rate of q = 7.5 ± 0.5 W cm -2 . Finally, we develop quantitative models for cooling-controlled porous clast saturation and for buoyant clast rise to the ocean surface. We find that meter size clasts stay buoyant for more than 10 min - long enough to reach the surface from a depth of 1000 m. Lastly, the models developed here test our understanding of clast-scale processes and demonstrate that - in hot and porous clasts - the details of internal texture do not matter because clast saturation, and thus buoyancy and fate in the water column, are governed by heat transfer.
Impact of gravity on hydrate saturation in gas‐rich environments
Abstract We extend a one‐dimensional analytical solution by including buoyancy‐driven flow to explore the impact of gravity on hydrate formation from gas injection into brine‐saturated sediments within the hydrate stability zone. This solution includes the fully coupled gas and liquid phase flow and the associated advective transport in a homogeneous system. We obtain the saturations assuming Darcy flow under combined pressure and gravity gradients; capillary forces are neglected. At a high gas supply rate, the overpressure gradient (gradient of water pressure deviation from the hydrostatic pressure) dominates the gas flow, and the hydrate saturation is independent of the flow rate and flow direction. At a low gas supply rate, the buoyancy (the drive for gas flow induced by the density difference between gas and liquid) dominates the gas flow, and the hydrate saturation depends on the flow rate and flow direction. Hydrate saturation is highest for upward flow, and lowest for downward flow. Hydrate saturation decreases with flow rate for upward flow, and increases with flow rate for downward flow. In all cases, hydrate saturation is constant behind the hydrate solidification front. Gas saturation is homogeneous and close to the residual value for upward flow at a low rate; gas flows at the rate it is supplied. Gas saturation is much greater than the residual value, and decreases from the gas inlet to the hydrate solidification front for downward flow at a very low rate. The effect of gravity is usually negligible in laboratory experiments, yet is significant in natural hydrate systems.
Hydrogen and oxygen stable isotope dynamics of hyper-saline and salt-saturated aqueous solutions
An attractive tracer of water-surface interactions in humidity exposure experiments are the stable hydrogen and oxygen isotopes in water vapor, though the conventional method of using salt saturated aqueous solutions to control humidity is likely to exert strong effects on the H and O stable isotope composition of the vapor. The magnitude of these effects are virtually unknown for hyper-saline solutions near salt saturation and beyond. Here we explore the hydrogen and oxygen stable isotope effects of salt-water mixtures from dilute to the salt saturation point and beyond for BaCl 2 , CaCl 2 , KCl, K 2 SO 4 , MgCl 2 , NaBr, NaCl, and NaI salts, of which the O isotope results on BaCl 2 , K 2 SO 4 , and NaBr are the first to be reported, and the first for H with BaCl2. We find that vapor humidity levels, and hydrogen and oxygen isotope effects in the vapor generated from dilute solutions to salt-saturated mixtures increase in magnitude by predictable linear trends. In the case of hydrogen isotope salt effects, the cation identity matters, as the effect becomes stronger with decreasing size and increasing charge (increasing ionic potential) in the sequence of: K < Na < Ba < Ca < Mg. For oxygen, the cation effect becomes stronger with increasing ionic potential, in the order of Na < Ba < K < Ca < Mg (irrespective of sign). Hydrogen and oxygen isotope effects in vapor from salt concentrations greater than the salt saturation point do not behave as systematically, with some of the salts displaying no increase in isotope effects beyond saturation, while others show an increase in isotope effects beyond salt saturation, especially in the case of hydrogen. We make specific recommendations on the salts that exert hydrogen and oxygen isotope effects with the least magnitude and most predictability for humidity levels from 26% to 92%. The use of salt solutions to create vapor at less than 100% and with specific δ 2 H and δ 18 O values that differ from that defined by the global meteoric water relationship also seems possible. Hyper-saline surface waters can exist at and above saturation, and thus these isotope effects may be present in them, as well as in minerals that form from these waters.