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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Hydrodynamics of countercurrent flows in a structured packed column: effects of initial wetting and dynamic contact angle

The structured packed column has gained considerable attention as a prospective technology to mitigate carbon dioxide emissions from thermal power plants. The computational flow investigation of such systems is a multiscale problem, and local hydrodynamics plays a key role in overall column efficiency. Accordingly, multiphase flow studies in the representative elementary unit (REU) of a packed column can offer insights into the local flow behavior such as flow pattern, interfacial area, etc. The interfacial area plays a key role in the overall interphase mass transfer and thereby in separation efficiency. The predicted effective area matches well with corresponding ones in experiments for Mellapak 250.Y packings. The contact angle (i.e., solid substrate behavior) is one of the critical factors that dictates wettings, and thereby the interfacial area. The dynamic contact angle (DCA) was considered in order to explore the effects of contact angle hysteresis on the interfacial area. DCA has more pronounced impact on the interfacial area for a solvent possessing a higher value of surface tension and equilibrium contact angle. The interfacial area shows temporal undulation and does not achieve a pseudo steady state due to the capillary force. In contrary, the interfacial area gets a net value for a solvent having low surface tension value. Further, specification of the static contact angle at the solid substrate shows the least value of the interfacial area. We also extensively studied the effect of the initial sheet condition (dry vs wet) on the interfacial area. The initially wetted sheets show slightly higher value of the interfacial area as compared to the initially dry sheets at a fixed flow rate for a solvent having high surface tension value. Wetting hysteresis decreases with increasing liquid loads. On the other hand, wetting hysteresis does not occur for a solvent having value of low surface tension and equilibrium contact angle.

structured packings, dynamic contact angle, interf↗
DOE OSTI2020

Coupled confined phase behavior and transport of methane in slit nanopores

The proximity of the order of magnitude molecular mean free path and pore sizes in nanopores leads to remarkable interactions between molecules and walls. In such systems, the thermodynamic property and the transport behavior of fluids deviate from those at bulk conditions. Molecular dynamics (MD) simulation may be used to investigate the effects of confinement on fluid physics in nanosize pores. However, translating these subscale observations into a larger scale of interest remains a challenging task. In this work, we propose a modified extension of Peng-Robinson equation of state (PR-EOS) motivated and guided by MD simulation results. The shift of critical properties, i.e., pressure and temperature, are evaluated independently. A temperature dependent parameter is introduced to account for the existence of capillary pressure in the two-phase region. Here, this formulation is capable of capturing the shift in critical properties as well as density phase diagrams under various confinement scenarios. We incorporate the proposed EOS in the lattice Boltzmann method (LBM) to study coupled confined phase behavior and transport of methane in nano-size slit pores. Adsorptive strength is determined such that the resulting density ratio matches that from MD simulation. Results indicate that the use of the proposed EOS leads to smaller fluid velocities compared to PR-EOS. This effect is due to stronger interactions between fluid particles under confinement. Also, results show that transport characteristics are impacted by the pressure of the system: in systems with a relatively low pressure, transport seems to be dominated by Knudsen diffusion; however, at a higher pressure, the contribution from viscous flow increases as the pore widens while the influence of Knudsen and surface diffusion diminishes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

A Transient-Response methodology based on experiments and modeling for Cu-Redox Half-Cycle kinetic analysis on a Cu-SSZ-13 SCR catalyst

In this report the Standard SCR reaction catalyzed by Cu-SSZ-13 is a redox process consisting of a reduction half cycle (RHC) and an oxidation half cycle (OHC) that cycle the active Cu sites between the Cu(II) and Cu(I) states. In the current work, a transient-response methodology consisting of experimental transient response Cu-redox (TRCR) measurements and kinetic modeling was developed for detailed study of individual SCR Cu-redox half cycles. The TRCR protocol allows quantification of the reducible Cu density, Cu(II)-Cu(I) partitioning, relative native RHC and OHC rates, and limiting half cycle during SCR. The half-cycle kinetics are studied over a wide (170–450 °C) temperature, and in differential segments along the catalyst length using spatially resolved capillary inlet mass-spectrometry (SpaciMS). The protocol alone provides two independent measures indicating that OHC increases faster than RHC with temperature, and that at all but the lowest temperature SCR is RHC limited. Introducing the transient kinetic models allows half-cycle reaction pathways, orders and activation energies to be studied and determined; e.g., RHC involves surface and gas-phase NH 3 routes, and OHC with O 2 involves dimer formation. Application of the full methodology provides further confirmation and quantification of the protocol conclusions, and specifically the first measurements of RHC and OHC activation energies; specifically for parallel RHC surface and gas-phase routes, and experimentally obtained OHC activation energy vs. first-principle calculations in the literature. Beyond insights related to the degreened catalyst studied here, the methodology provides a broadly available approach for quantifying how aging processes selectively impact RHC and OHC.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Impact of an SRA (hexylene glycol) on irreversible drying shrinkage and pore solution properties of cement pastes

Cementitious materials shrink when exposed to decreasing relative humidities, which may result in cracking. Shrinkage reducing admixtures (SRAs) can be used to reduce this drying shrinkage. Although many studies have shown that SRAs reduce the surface tension of the pore solution, the effects of SRAs on other pore solution properties and their relationship to drying shrinkage have been poorly characterized. In this work, we investigate the impact of an SRA (hexylene glycol) on the drying and re-humidification of a cement paste over an extended relative humidity range. The reduction in the first drying shrinkage by the SRA depends on relative humidity. The SRA also significantly reduces the irreversible drying shrinkage. We concluded that the SRA impacts drying shrinkage by acting on the capillary forces, by acting on the specific range of relative humidity over which those forces occur, and potentially by acting on the surface stresses through pore wall adsorption.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A time-dependent chloride diffusion model for predicting initial corrosion time of reinforced concrete with slag addition

The effect of granulated blast furnace slag (GBFS) addition on the threshold chloride concentration (TCC) for rebar corrosion was investigated. A modified diffusion model, coupled with a time-dependent effective diffusion coefficient and surface chloride concentration, was proposed to predict the chloride profile. The corrosion initiation time was estimated based on the model predictions and the measured TCC. The results indicate that adding GBFS decreases the TCC by lowering the pH value of the pore solution. The evolution of corrosion potential and current density is found to obey a 3-parameter Weibull distribution. MIP tests show that adding GBFS contributes to refinement of pore structure by decreasing the fraction of large capillary pores. The time-dependent model exhibits good predictive strength and helps understand how GBFS addition delays the corrosion initiation by retarding the chloride diffusion, though a lower TCC is obtained.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Understanding of the factors slowing down metakaolin reaction in limestone calcined clay cement (LC3) at late ages

Factors which could explain the slowing down of the metakaolin reaction in LC{sup 3} blends are investigated. Portlandite availability and the presence of aluminium ions in the pore solution are shown not to be limiting factors. Hydrates can only precipitate in solution filled pores. Internal relative humidity measurements indicate that at 28 days solution is present only in pores with radii below 13 nm. An enhancement of metakaolin reaction was obtained at late ages when the larger capillaries are filled with solution. The lower limit of the water filled pores was more difficult to analyse since there is a lack of precision in determining interfacial energies of hydrates and pore solution of the system. However, this study gives an indication of order of magnitude where the growth of hydrates could be slowed down.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Selective transport of light vs. heavy rare earth elements by sulfate/bisulfate complexes in hydrothermal fluids

Here, this study explores the transport of rare earth elements (REE) in acidic sulfate-bearing hydrothermal fluids and the implications for the fractionation of light/heavy REE in critical mineral deposits. The speciation of Nd (light REE) and Yb (heavy REE) sulfate complexes were determined via in situ Raman spectroscopy using fused SiO 2 capillary cells up to 300 ºC at saturated water vapor pressure and in a hydrothermal diamond anvil cell up to 500 ºC and 540 MPa. The REE monosulfate (REESO 4 + ) and REE disulfate (REE(SO 4 ) 2 - ) species are stable below 150 to 250 ºC but become less stable at higher temperatures, particularly the light REE, due to the decreased solubility of REE sulfate solids. At higher pressure, these REE sulfate complexes display an increased stability field up to 400 ℃. The REE bisulfate complex (REEHSO 4 2+ ) was identified with a wide stability field below 400 ºC for the HREE in acidic Yb 2 (SO 4 ) 3 -bearing solutions, whereas in Nd 2 (SO 4 ) 3 -bearing solutions, the LREE bisulfate complex is restricted to below 100 ℃. These results suggest that bisulfate is a previously unrecognized selective ligand for heavy REE transport at low temperature in acidic oxidized hydrothermal fluids. Such fluids are responsible for hydrothermal alteration in many REE deposits. Prediction of phase stabilities across pressure, temperature, and composition space (P-T- x ) is crucial for predicting the role of aqueous REE sulfate complexes in the mobilization of REE in crustal fluids.

58 GEOSCIENCES↗
DOE OSTI2023

Influence of ion-pairing reagents on the separation of intact glycoproteins using hydrophilic-interaction liquid chromatography - high-resolution mass spectrometry

Hydrophilic-interaction liquid chromatography (HILIC) of intact proteins offers high-resolution separations of glycoforms of glycoproteins differing in the number of (neutral) glycans. However, to obtain efficient separations it is essential that the positively charged sites of the proteins are shielded by acidic (negative) ion-pair reagents (IPRs), so as to enhance the contribution of the hydroxyl groups of the (neutral) sugars in the glycoprotein. Here, we studied the influence of various IPRs that differ in physico-chemical properties, such as hydrophobicity and acidity, on the capillary-scale HILIC separation of intact (glyco)proteins. We evaluated the use of fluoroacetic acid (MFA), difluoroacetic acid (DFA), trifluoroacetic acid (TFA), and heptafluorobutyric acid (HFBA) as diluents for sample preparation, as solvents for sample loading on a reversed-phase trap prior to the HILIC separation, and as mobile-phase components for HILIC and HILIC-MS. To reduce the contribution of ion-exchange interaction with the (silica-based) stationary phase, we used an acrylamide-based monolithic column. We studied the influence of the different IPRs on each step of the separation of a mixture of proteins of different size and hydrophilicity and on the separation of the five glycoforms of ribonuclease B. The content of IPR in the sample was shown not to affect the separation and the MS detection. However, a low content of TFA and DFA in the mobile phase is favourable, as it reduces adduct formation and leads to higher signal intensity. The optimized HILIC conditions successfully resolved nine major glycoforms groups of a ~40 kDa glycoprotein horseradish peroxidase (HRP), as an example of a complex glycoprotein.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Effect of silver($\mathrm{I}$) ion reduction on the selectivity of olefins, paraffins, and aromatic compounds by gas chromatographic stationary phases consisting of silver($\mathrm{I}$) salts in ionic liquids

We report the olefin/paraffin selectivity offered by ionic liquid (IL) stationary phases can be enhanced through the addition of silver(I) ion, which is well-known to undergo selective complexation with unsaturated compounds. However, such stationary phases often suffer from the loss of chromatographic selectivity as silver(I) ion can be reduced to elemental silver. To maintain the separation performance of silver(I) ion/IL stationary phases, an understanding of factors and conditions that promote the reduction of silver(I) ion is needed. In this study, capillary gas chromatography columns featuring a stationary phase consisting of the 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C 10 MIM + ][NTf 2 - ]) IL impregnated with [Ag + ][NTf 2 - ] were examined to investigate the effects of temperature, hydrogen content in exposure gas stream, and time of heating/exposure events on olefin selectivity. Retention factors of representative analytes, such as C 6 olefins and paraffins as well as aromatic compounds, were measured after subjecting the columns to the aforementioned conditions, followed by an evaluation of selectivity factors over time. Selectivity factors of olefins and aromatic compounds were observed to decrease significantly when the stationary phases were heated to temperatures higher than 110°C as well as being subjected to mixed gas streams containing greater than 50 mol% of hydrogen. As constant column heating temperatures were applied under exposure gas mixtures containing hydrogen and nitrogen, a gradual decrease in analyte selectivity factors was observed under prolonged periods of time. However, application of a ternary gas mixture comprised of 25/50/25 mol% hydrogen/nitrogen/methane resulted in an increase in the 3-hexyne/cis-2-hexene selectivity when measured at 120°C for 60 h, due to a smaller decrease in the retention factor of 3-hexyne compared to cis-2-hexene.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Temperature-dependent changes in gas chromatographic separation metrics for trihexyl(tetradecyl)phosphonium-based ionic liquid stationary phases and comparison to conventional polysiloxane stationary phases

Here, to assess whether the trihexyl(tetradecyl)phosphonium chloride ([P 66614 + ][Cl - ]) ionic liquid (IL), employed as a gas chromatographic stationary phase, exhibits temperature-dependent phase transitions or structural heterogeneity, retention thermodynamics for probe molecules of varied chemical structure were investigated by gas chromatography (GC) over the temperature range of 25 to 64 °C using van’t Hoff analysis. All van’t Hoff plots for n-alkanes (C8–C12) and other probe analytes were linear, indicating the absence of detectable phase-transition behavior. The [P 66614 + ][Cl - ] IL was further compared with the [P 66614 + ] bis[(trifluoromethyl)sulfonyl]imide ([P 66614 + ][NTf 2 - ]) IL and commercial polysiloxane stationary phases in terms of temperature-dependent resolution behavior and chromatographic selectivity over the temperature range of 28–52 °C. The resolution factors of analytes in mixtures obtained using gas chromatography–mass spectrometry (GC–MS) and the summation of resolution values decreased smoothly with temperature on both IL stationary phases and on the dimethylphenylcyano-substituted polymeric stationary phase (OV-1701), whereas the poly(50% diphenyl/50% dimethyl siloxane) stationary phase (SPB-50) exhibited irregularities in its temperature-dependent summation of resolution profile, showing a distinct maximum in the temperature range of 34–40 °C. Selectivity values for the IL stationary phases were largely determined by the anion, with the [P 66614 + ][Cl - ] IL providing enhanced separation between polar and aromatic analytes, while the [P 66614 + ][NTf 2 - ] IL favored dispersive and π-π interactions that resulted in a reversal of elution order for some aliphatic–aromatic and alkyne-containing analyte pairs. Capillary columns prepared using different surface activation methods and coated with identical [P 66614 + ][Cl - ] IL stationary phase showed indistinguishable temperature-dependent trends in summation of resolution value and selectivity. An evaluation of analyte-specific selectivity provides insight into the characteristic separation behavior of the stationary phases and enables identification of analyte classes that are more efficiently separated on the [P 66614 + ]-based IL stationary phases compared to conventional stationary phase materials.

Chromatographic selectivity↗
DOE OSTI2021

Pore accessibility and trapping of methane in Marcellus shale

Accessibility of pore space in unconventional reservoirs is an important factor influencing both methane storage capacity and the kinetics of methane desorption. The determination of open (accessible) versus closed (inaccessible) porosity is therefore vital for the prediction of gas production potential. This study investigates accessibility of pores to methane in overmature middle Devonian Marcellus shale samples (cut parallel and perpendicular to bedding) using small and ultra-small neutron scattering (SANS and USANS) with contrast matching (CM), supplemented by other complementary techniques, such as mercury injection capillary pressure (MICP) and low pressure gas (N2 and CO2) adsorption. Our results demonstrate that for the samples studied, only about 6 % of pores with diameter 25-500 nm are accessible to methane. The accessibility fraction for pores larger than 500 nm is 35%. For nanopores smaller than 25 nm, pore accessibility could not be quantitatively determined due to increased methane density and condensation effects in confinement. Our observations indicate that methane penetrates the accessible small mesopores and micropores down to at least 1 nm in diameter, and the density of confined deuterated methane (CD4) is 0.68 g/cm3 for pores of diameter 25 nm and gradually increases with the decreased pore size. Moreover, elevated gas pressure causes formation of additional high-density methane nano-clusters. These clusters have a form of slightly anisotropic polydisperse discs oriented along bedding plane, about 1-12 nm in diameter and with average thickness of 3.6 nm. Utilizing samples cut parallel and perpendicular to the bedding, this study also briefly addresses anisotropy of pores. Based on the iso-size intensity ratio R, our SANS and USANS results demonstrate anisotropy in the out-of-bedding direction and suggest that the degree of anisotropy depends on the pore size. Specifically, for pore diameters ~2.5 to 250 nm, the extent of anisotropy is smaller than for pores ~500 nm to 6 µm in diameter. Finally, comparison of pore size distribution results calculated from SANS/USANS to those obtained using MICP shows good agreement at low pressures, but large difference at pressures above 1000 bar. Here, this discrepancy requires further testing; it is possible that the high mercury pressure used in MICP alters the mesopore and micropore structure of shales.

03 NATURAL GAS↗
DOE OSTI2021

Effect of topology changes on the breakup of a periodic liquid jet

Here, the breakup of a periodic jet is examined computationally, using a front-tracking/finite-volume method, where the interface is represented by connected marker points moving with the fluid, while the governing equations are solved on a fixed grid. Tracking the interface allows control of whether topology changes take place or not. The Reynolds and Capillary numbers are kept relatively low ($Re = 150$ and $Ca = 2$) so most of the flow is well resolved. The effect of topology changes is examined by following the jet until it has mostly disintegrated, for different “coalescence criterion,” based on the thickness of thin films and threads. The evolution of both two-dimensional and fully three-dimensional flows is examined. It is found that although there is a significant difference between the evolution when no breakup takes place and when it does, once breakup takes place the evolution is relatively insensitive to exactly how it is triggered for a range of coalescence criterion, and any differences are mostly confined to the smallest scales.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

Enabling high rate capability, low internal resistance, and excellent cyclability for vanadium redox flow batteries utilizing ultrafast laser-structured graphite felt

The electrochemical performance of vanadium redox flow batteries (VRFBs) was enhanced via laser-patterned graphite felt (GF) electrodes. The laser-structured GF electrodes engineered via preparing a series of well-ordered microscopic channel structures with an average width of 200 μm, creating a three-dimensional carbon framework. The ultrafast laser patterning increased the porosity by 10%, as compared to pristine electrode. The analysis of the overpotential distribution using electrochemical impedance spectroscopy revealed that the electrode polarization involving charge transfer and diffusion resistance is strongly alleviated with the aid of carbon micro-perforation. The advanced design of laser-structured GF electrode also exhibits high rate capability, low internal resistance, and excellent cyclability. The improved performance was attributed to the synergistic effect involving (i) high electrochemically active surface area for rapid electrochemical reactions (i.e., V(II)/V(III) and V(IV)/V(V) redox couples) and (ii) excellent transport properties for facile electron/ion/species transport. The micro-scale channels created with the laser-ablation technique act as capillary structures and enabled homogeneous and rapid wetting of GF electrodes as formulated with the classical Washburn equation. The VRFB equipped with the laser-structured GF electrodes delivered a high discharge capacity with exceptional capacity retention upon extended cycling (>84.9%). In conclusion, accordingly, the design of laser-structured electrode paves the pathway towards finely tuning the electrode internal microstructure for improved cyclability, durability, and capacity retention in various electrochemical energy storage/conversion devices (e.g. all-vanadium redox flow batteries).

25 ENERGY STORAGE↗
DOE OSTI2024

Integrated experimental studies of pore structure and fluid uptake in the Bossier Shale in eastern Texas, USA

Within the Haynesville-Bossier Shale complex, the Bossier Shale has not been extensively studied by either industry and academia, despite it being an unconventional gas reservoir and a potential caprock for carbon storage in the underlaying Haynesville Shale. The lack of knowledge of the complex pore structures and fluid-rock interactions hinders the effective extraction of gas and the characterization of fluid reservoirs and sealing capacity. Integrated experimental studies of pore structure and fluid-rock interactions were conducted in seven Bossier Shale core samples collected in eastern Texas. Petrographic, geochemical, and petrophysical properties such as mineral composition, organic richness, thermal maturity, porosity, pore/pore throat diameter distribution, water-accessible pores, liquid water imbibition, and water vapor adsorption were characterized using complementary approaches of thin-section petrography, scanning electron microscopy, X-ray diffraction, total organic matter, pyrolysis, mercury intrusion porosimetry, nuclear magnetic resonance, (Ultra-) small angle X-rays scattering as well as small angle neutron scattering with deuterated liquids and contrast variation. Further, the results show that the thermally mature Bossier Shales are composed of mixed argillaceous mudstone, mixed mudstone, and mixed carbonate mudstone. The shale contains both organic and inorganic pores, with porosities of 3.24-9.37 %, pore-to-throat ratios of 1.65 to 19.4, and water-accessible pores accounting for 28.7-72.6 % of total pores. Approaches of liquid water imbibition and water vapor adsorption, with and without direct contact of water with shale samples, indicate that liquid water first enters the nano-sized pores under high capillary pressures, and water vapor adsorption is mainly controlled by both clay minerals and pores with diameters less than 10 nm. These findings contribute to a better understanding of pore structures and water-shale interactions and their controlling factors in the Bossier Shale.

58 GEOSCIENCES↗
DOE OSTI2026

Integrated geological, economic, and risk assessment of underground hydrogen storage

Underground hydrogen storage (UHS) is a promising option to buffer variable renewable power and support the hydrogen economy. Yet this technology is early-stage, and key uncertainties remain about how coupled processes such as geochemical and geomechanical impacts affect long-term storage security. In this paper, we seek to integrate the results from a large, multi-scale research program to quantify core feasibility metrics and situate these studies within ongoing efforts. Through this work, we evaluate hydrogen recoverability during storage by assessing diffusive losses, losses to geochemical interactions and their subsequent impact on geomechanical properties, and losses to residual saturation during injection and withdrawal. Molecular and laboratory studies show that lithologic heterogeneity, pore geometry, and mineral surface chemistry govern hydrogen–rock interactions, controlling loss pathways. High-pressure coreflooding is used to estimate relative permeabilities and measure parameters needed for reservoir-scale sensitivity analyses. These core-scale experiments found early hydrogen breakthrough at low saturations driven by capillary and viscous fingering, which limits pore-space utilization at early times, while repeated injection and withdrawal cycles improve deliverability over time. Technoeconomic factors and purity requirements for end uses are also considered as part of our comprehensive feasibility analysis. Finally, we underscore the importance of geophysical monitoring and tailored injection strategies to maintain integrity and efficiency. Together, these results provide a quantitative foundation for safe, scalable deployment of UHS and highlight priorities for future integrated studies.

08 HYDROGEN↗
DOE OSTI2021

Novel in-capsule synthesis of metal–organic framework for innovative carbon dioxide capture system

Metal-Organic Frameworks (MOFs) have been developed as solid sorbents for CO2 capture applications and their properties can be controlled by tuning the chemical blocks of their crystalline units. A number of MOFs (e.g., HKUST-1) have been developed but the question remains how to deploy them for gas–solid contact. Unfortunately, the direct use of MOFs as nanocrystals would lead to serious problems and risks. Here, for the first time, we report a novel MOF-based hybrid sorbent that is produced via an innovative in-situ microencapsulated synthesis. Using a custom-made double capillary microfluidic assembly, double emulsions of the MOF precursor solutions and UV-curable silicone shell fluid are produced. Subsequently, HKUST-1 MOF is successfully synthesized within the droplets enclosed in the gas permeable microcapsules. The developed MOF-bearing microcapsules uniquely allow the deployment of functional nanocrystals without the challenge of handling ultrafine particles, and further, can selectively reject undesired compounds to protect encapsulated MOFs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Relative permeabilities for two-phase flow through wellbore cement fractures

Multiple fluids are likely to exist in fractures and flow paths associated with leaky wellbores, including liquids (e.g., crude oil) and gases (e.g., gas exsolved from liquid). These fluids occupy and move through different portions of the pore spaces within the fractures depending on many factors, including fluid properties, fracture size, and the amount of the different fluids. Upward leakage of any phase, through the fracture, can contaminate water-bearing formations, create hazardous surface conditions, and compromise the functionality of the wellbore. Early signs of wellbore leaks may be expressed by anomalous pressure behavior at surface monitoring points on cavern storage wells. These pressure anomalies are difficult to interpret, necessitating knowledge of the factors that affect the multiphase flow in fractures and porous media. These parameters are critical to modeling multiphase flow in fractures. This insight can guide further diagnosis and maximize leak remediation. Here, our study focuses on the relationship of the liquid–gas relative permeabilities for representative variable-aperture wellbore cement fracture. To obtain the relative permeability of each phase, two-phase flow tests were conducted where both fluids were flowing simultaneously through a fractured wellbore cement specimen under a range of factors, namely (1) aperture size, (2) capillary numbers, and (3) viscosity ratio. The flow experiments were conducted under a range of confining stresses and flow velocities, using nitrogen gas and silicone oils (of different viscosities) in a specially designed pressure vessel. The sum of gas and oil relative permeabilities were found to be less than one under all conditions, which indicates that the presence of one phase affects the permeability of the other phase, and vice versa. Since the gas phase flow conditions include a significant inertial flow component in addition to viscous flow, the inertial flow coefficients at different saturation states are presented. The factors affecting the relationship between the relative permeabilities are discussed in detail. A new mathematical model for estimating the relative permeability of wellbore cement fracture is presented and experimentally validated.

58 GEOSCIENCES↗
DOE OSTI2020

An energy model of droplet impingement on an inclined wall under isothermal and non-isothermal environments

The observation of spray-wall interaction is of great importance to understand the dynamics that occur during fuel impingement onto the chamber wall or piston surfaces in internal combustion engines. It is found that the maximum spreading length of an impinged droplet can provide a quantitative estimation of heat transfer and energy transformation for spray-wall interaction. Furthermore, it influences the air-fuel mixing and hydrocarbon and particle emissions at combusting conditions. In this paper, an analytical model of different droplet-wall impingement conditions is developed in terms of βm (dimensionless maximum spreading length, the ratio of maximum spreading length to initial droplet diameter) to understand the detailed impinging dynamic process. These conditions are grouped as: a single diesel droplet impinging on the wall with different inclined angles (α); cold wall - heated droplet and heated wall - cold droplet impingement when inclined angle of the wall is 0°, respectively. The analytical model is built up based on the energy conservation that considers kinetic energy, gravitation energy, and surface energy before impingement, as well as viscous dissipation, gravitation energy, adhesion energy, deformation energy, and heat energy after impingement. The experimental work of diesel droplet impinging on an inclined wall is performed at a certain range of the Weber number (We of 33 to 420) with various inclined angles (α of 0° to 45°), while for inclined angle is 0°, droplet and wall temperature are varied from 25°C to 150°C to study the effects of the inclined angle and temperature on the temporal evolution of the post-impingement characteristics (i.e. droplet spreading length, dynamic contact angle). The analytical model is validated and evaluated at the aforementioned experimental operating points. The validated model can be employed to predict maximum spreading length of the droplet impinged on the wall. It is further utilized to determine the transition from capillary regime to kinetic regime, then to viscous regime at different inclined angle of the wall.

42 ENGINEERING↗