Constant Pressure Research Articles

Effects of Clay Contamination on the Stability of Aqueous Foams at High Pressure

Summary Because of its low density, high viscosity, and good hole-cleaning performance, foam is used in the industry as a drilling and completion fluid. Due to these unique properties, foam can be applied in underbalanced drilling. After an extended period, however, the degradation of its thermodynamically unstable structure leads to the gradual loss of these valuable properties. While a number of research studies have been performed to investigate foam flow behavior, more is needed to know about their drainage characteristics and stability at high pressure. The primary goal of this investigation is to examine the effects of clay contaminants on the drainage of foam at high pressure. Moreover, the results and findings of this study not only show the effect of clay contaminants on foam stability but also help develop clay-based stable foam formulations without using chemicals that have the potential to contaminate groundwater or seawater. This paper shows the findings of an investigation on the aqueous foam stability in the presence of clay (bentonite and kaolinite) contaminants. Experiments were conducted at ambient temperature while varying foam quality and clay concentration at a constant pressure of 6.8 MPa. During the study, the foam was created in a flow loop. After generation, its rheology and stability were measured using a pipe viscometer and a vertical test tube (column). The hydrostatic pressure profile in the column was measured with time to assess foam drainage. The results show that clay type and concentration affect aqueous foam drainage and flow behavior. The impact of clay on these foam properties is controlled by foam quality. Adding more than 2.5% bentonite considerably enhanced foam stability and viscosity. In contrast, the impacts of kaolinite on these foam properties were minimal at the same concentration. The drainage became negligible when 5% bentonite was added to the foam. However, at a reduced concentration (2.5%), bentonite addition was only an effective stabilizer for low-quality foam (40%). Microscopic examination of the foams prepared under ambient conditions demonstrated the accumulation of colloidal particles at the plateau borders and nodes that block the drained liquid flow and reduce drainage.

Studying the air ventilation effect on the hydromechanical behaviour of cracked rock media around large-scale gallery using a double-scale FE2 model

The interaction between rock and the atmosphere occurs through air circulation within underground galleries, thereby affecting the hydromechanical long-term behaviour of the rock in the vicinity of galleries and its drainage. To study this air-rock interaction, a coupled hydromechanical model within a double-scale finite element framework is improved to simulate partial saturated cases at small scale in the crack network. The capillary water distribution at the microscale is not modelled. The introduction of the capillary pressure is therefore realised from a macroscopic phenomenon consideration, but it depends on the evolution of the mesoscopic structure and geometry (as the normal opening of mineral contacts) inside 2D Representative Elementary Areas. The gas flow is also neglected by assuming a constant gas pressure. Then, the developed model is applied to model an underground gallery ventilation process, which is reproduced with constant air relative humidity inside the gallery and classical imposition at the gallery wall. The numerical simulation results show that long-term gallery air ventilation induces a drainage of the liquid water present in the rock towards the gallery that leads to an obvious desaturation process close to the gallery wall. Furthermore, the gallery air ventilation inhibits the development of shear strain localisation around the gallery.

Abstract 384: SLC7A11 modulates sensitivity to the first-in-class mitochondrial peroxiredoxin 3 inhibitor thiostrepton (RSO-021) via a ferroptosis independent pathway

Abstract Mitochondrial peroxiredoxin 3 (PRX3) has been identified as an actionable cancer vulnerability that is currently being investigated in the first-in-human phase 1 clinical trial, MITOPE (NCT05278975). RSO-021 (thiostrepton or TS) is a redox-active drug that inhibits PRX3’s peroxidase activity via covalent adduction of its active site peroxidatic and resolving cysteine residues, forming an irreversible crosslink across the protein dimer. Covalent inhibition of PRX3 results in tumor cell death due to a diminished ability to remove high levels of mitochondrial reactive oxygen species (ROS) in cancer cells. To better understand the mechanism underpinning sensitivity and resistance, TS-tolerant human mesothelioma cell lines were generated under constant TS pressure and subjected to a drug-screen comprising chemotherapeutic agents, metabolic inhibitors, ROS modulating agents and ferroptosis-inducing compounds, to identify synergistic interactions compared with TS- sensitive cell lines. Erastin, an SLC7A11 inhibitor exhibited the greatest synergy when combined with TS, potentiated PRX3 covalent crosslinking and cellular ROS levels. Synergy with TS was enhanced by cystine depletion and could be phenocopied by siRNA knockdown of SLC7A11. SLC7A11 was up-regulated in TS-tolerant cells and resistance could be overcome with erastin. TS-tolerant cell lines have significantly reduced glutathione levels and slowed proliferation. Ferroptosis inhibitors ferrostatin-1 and liproxstatin-1 did not inhibit TS or TS in combination with erastin. In summary, SLC7A11 up-regulation confers tolerance to TS through a mechanism involving a cysteine-dependent modulation of the redox state independent of canonical ferroptosis, that can be overcome by the addition of an SLC7A11 inhibitor. The correlation between SLC7A11 with response to TS in a 33-patient primary mesothelioma explant co-clinical trial, and patients enrolled into the MITOPE phase 1/2 trial will be presented. Citation Format: Terri Messier, Victoria Gibson, Aleksandra Bzura, Joanna Dzialo, Charlotte Poile, Stephanie Stead, Alexis Saaman, George N. Naumov, Dean A. Fennell, Brian Cunniff. SLC7A11 modulates sensitivity to the first-in-class mitochondrial peroxiredoxin 3 inhibitor thiostrepton (RSO-021) via a ferroptosis independent pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 384.

In Vitro Evaluation of the Antioxidant Capacity of 3,3-Disubstituted-3H-benzofuran-2-one Derivatives in a Cellular Model of Neurodegeneration.

Oxidative stress represents a hallmark for many degenerative pathologies of the Central Nervous System. Throughout life, the constant pressure of noxious stimuli and/or episodes of traumatic events may expose the brain to a microenvironment where the non-balanced reactive oxygen species inevitably lead to neuronal loss and cognitive decline. HO-1, a 32 kDa heat-shock protein catalyzing the degradation of heme into carbon monoxide (CO), iron and biliverdin/bilirubin is considered one of the main antioxidant defense mechanisms playing pivotal roles in neuroprotection. Restoring the redox homeostasis is the goal of many natural or synthetic antioxidant molecules pursuing beneficial effects on brain functions. Here, we investigated the antioxidant capacity of four selected benzofuran-2-one derivatives in a cellular model of neurodegeneration represented by differentiated SH-SY5Y cells exposed to catechol-induced oxidative stress. Our main results highlight how all the molecules have antioxidant properties, especially compound 9, showing great abilities in reducing intracellular ROS levels and protecting differentiated SH-SY5Y cells from catechol-induced death. This compound above all seems to boost HO-1 mRNA and perinuclear HO-1 protein isoform expression when cells are exposed to the oxidative insult. Our findings open the way to consider benzofuran-2-ones as a novel and promising adjuvant antioxidant strategy for many neurodegenerative disorders.

Study on the characteristics of a novel wrap-around cooled diaphragm compressor for hydrogen refueling station

This study introduces a novel wrap-around cooled diaphragm compressor, designed for employment in hydrogen refilling station. The performance of this innovative compressor is evaluated using a specially developed experimental platform. The analysis focused on the impact of pressure ratio and suction gas temperature on the compressor's performance, and the cooling effect is assessed under varying temperatures of the cooling medium. The findings indicate that both the isentropic and volumetric efficiencies of the diaphragm compressor decrease with an increase in pressure ratio, with maximum values reaching 70% and 65% respectively. Under constant pressure ratio conditions, the exhaust temperature is found to increase with the rise in suction temperature. For a given suction temperature, a higher-pressure ratio resulted in a higher exhaust temperature. Furthermore, the cooling effect of the wrap-around cooling pipeline is found to be more pronounced under high pressure ratio conditions, with a maximum temperature reduction of 189.5 °C.

Thermodynamics analysis of acetaminophen and its metabolites using density functional theory

AbstractThe thermodynamics factors of acetaminophen and its metabolites were considered using density functional theory (DFT) at 298.15 K temperature and 1 atm. pressure. The resultant Thermodynamics factors were at that time analyzed and compared to determine the influence of temperature and pressure on the stability of the metabolite and its potential behavior in changed environments. The results display that the internal energy, enthalpy, Gibbs free energy, entropy, heat capacity at constant volume (Cv), and Cp at constant pressure (Cp) all affected by the temperature increases. The internal energy (U) of the most stable molecule increases with the increase in temperature, while the heat capacity (H) decreases with the decrease in pressure. The heat capacity and heat capacity of sulfate (APS) are stable at changed temperatures and pressures. These results will make available valued information on the Thermodynamics behavior of Acetaminophen (AP), Acetaminophen cysteine (APCys), Acetaminophen glucuronide (APGlc), and Acetaminophen sulfate (APS) metabolites which can be used to recognize their behavior in the body and how they are metabolized. Furthermore, the results of this study will be responsible for a better understanding of the thermal stability of these molecules under different conditions and guide the development of new drugs and therapies.

Study on the efficiency characteristics of a stacked cone two-dimensional piston pump

This paper proposes a two-dimensional piston pump with a stacked cone-roll structure. The pump rotates continuously while also moving back and forth in the axial direction. It utilizes the suction and discharge ports to alternate the flow of oil, ensuring proper distribution and completing the suction and discharge process. The operating mechanism of the piston pump was analyzed, and subsequently, a mathematical model was developed to determine its mechanical efficiency and volumetric efficiency was established. Furthermore, the AMESim simulation model was built to obtain the variation curves of the input torque and leakage flow of the drive unit under different load pressures and rotational speeds. Ultimately, a prototype was fabricated and a test apparatus was assembled to evaluate the volumetric efficiency and mechanical efficiency under varying speeds and load pressures. The empirical findings were largely congruent with the modeling findings, indicating that the volumetric efficiency rose from 86.3% to 92.2% as the speed increased, whereas the mechanical efficiency declined from 93.8% to 89.1% under a constant load pressure. Under constant speed conditions, the volumetric efficiency of the stacked tapered roller-type two-dimensional piston pump fell from 94.1% to 91.3% as the load pressure increased. However, the mechanical efficiency grew from 87% to 90.2%. These findings confirm the practicality of the pump design.

Vancomycin heteroresistance caused by unstable tandem amplifications of the vanM gene cluster on linear conjugative plasmids in a clinical Enterococcus faecium.

Vancomycin heteroresistance is prone to missed detection and poses a risk of clinical treatment failure. We encountered one clinical Enterococcus faecium strain, SRR12, that carried a complete vanM gene cluster but was determined as susceptible to vancomycin using the broth microdilution method. However, distinct subcolonies appeared within the clear zone of inhibition in the E-test assay, one of which, named SRR12-v1, showed high-level resistance to vancomycin. SRR12 was confirmed as heteroresistant to vancomycin using population analysis profiling and displayed "revive" growth curves with a lengthy lag phase of over 13 hours when exposed to 2-32 mg/L vancomycin. The resistant subcolony SRR12-v1 was found to carry an identical vanM gene cluster to that of SRR12 but a significantly increased vanM copy number in the genome. Long-read whole genome sequencing revealed that a one-copy vanM gene cluster was located on a pELF1-like linear plasmid in SRR12. In comparison, tandem amplification of the vanM gene cluster jointed with IS1216E was seated on a linear plasmid in the genome of SRR12-v1. These amplifications of the vanM gene cluster were demonstrated as unstable and would decrease accompanied by fitness reversion after serial passaging for 50 generations under increasing vancomycin pressure or without antibiotic pressure but were relatively stable under constant vancomycin pressure. Further, vanM resistance in resistant variants was verified to be carried by conjugative plasmids with variable sizes using conjugation assays and S1-pulsed field gel electrophoresis blotting, suggesting the instability/flexibility of vanM cluster amplification in the genome and an increased risk of vanM resistance dissemination.

A realist evaluation of devices used for the prevention of heel pressure ulcers: An ethnographic study of clinical practice

BackgroundIt is known that heel offloading devices are widely used in clinical practice for the prevention of heel pressure ulcers, even though there is a lack of robust, good quality evidence to inform their use. ObjectiveTo explore how and why heel offloading devices are used (or not used) and reasoning behind their use in population at high risk of developing heel pressure ulcers. MethodsAn ethnographic study was conducted as part of a realist evaluation in three orthopaedic wards in a large English hospital. Twelve observations took place, with 49 h and 35 min of patient care observed. A total of 32 patients were observed and 19 members of the nursing team were interviewed and in-depth interviews with the three ward managers were conducted. ResultsAlthough the focus of the study was on offloading devices, constant low pressure heel specific devices were also observed in use for pressure ulcer prevention, whilst offloading devices were perceived to be for higher risk patients or those already with a heel pressure ulcer. Nursing staff viewed leadership from the ward manager and the influence of the Tissue Viability Nurse Specialists as key mechanisms for the proactive use of devices. ConclusionsThis study informs trial design as it has identified that a controlled clinical trial of both types of heel specific devices is required to inform evidence-based practice. Involving the ward managers and Tissue Viability Nurse Specialists during set up phase for clinical equipoise could improve recruitment.Tweetable abstractHow, for whom, and in what circumstances do devices work to prevent heel pressure ulcers? Observations of clinical practice.

Performance analysis of a novel ejector-assisted condenser outlet split dual-evaporator refrigeration system

The performance of an ejector-assisted condenser outlet split dual-evaporator cycle is compared with a conventional dual-evaporator cycle albeit consisting a pressure reducing valve. The cycles do not employ any separator due to its inability to efficiently separate the liquid and the vapor phases. The comparison of both the cycles has been made for the same cooling capacity in low-temperature evaporator and unit flow rate of R134a and R1234yf as refrigerants. The impacts of changing the operating temperatures of evaporator and condenser have been examined in the current investigation. The study reveals that with the increase in temperature of the high-temperature evaporator, the cooling capacity of the high-temperature evaporator yields, while that of the low-temperature evaporator plummets in both the cycles. Further, the compressor work is allayed in the ejector-assisted cycle; thus, the COP is enhanced considerably. The percentage COP improvement over the basic cycle is obtained from 14.7 to 17.53% for the refrigerant R1234yf and from 14.45 to 17.32% for R134a; however, the COP of both the cycles with R12134yf is slightly lower than with R134a. The ejector has been modeled assuming a constant pressure theory. The observed trend indicates that the entrainment ratio is improved with the rise in the temperature of low-temperature evaporator, whereas it is decreased with the rise in the temperature of high-temperature evaporator.

A resonant high-pressure microsensor based on a composite pressure-sensitive mechanism of diaphragm bending and volume compression

In this paper, a composite pressure-sensitive mechanism combining diaphragm bending and volume compression was developed for resonant pressure microsensors to achieve high-pressure measurements with excellent accuracy. The composite mechanism was explained, and the sensor structure was designed based on theoretical analysis and finite element simulation. An all-silicon resonant high-pressure microsensor with multiple miniaturized cavities and dual resonators was developed, where dual resonators positioned in two resonant cavities with suitably different widths are used to perform opposite characteristics in pressure and the same characteristics at different temperatures, which can improve pressure sensitivities and realize temperature self-compensation by differential frequency output. The microsensor was fabricated by microfabrication, and the experimental results showed that the sensor had an accuracy of ±0.015% full scale (FS) in a pressure range of 0.1~100 MPa and a temperature range of −10~50 °C. The pressure sensitivity of the differential frequency was 261.10 Hz/MPa (~2523 ppm/MPa) at a temperature of 20 °C, and the temperature sensitivities of the dual resonators were −1.54 Hz/°C (~−14.5 ppm/°C) and −1.57 Hz/°C (~−15.6 ppm/°C) at a pressure of 2 MPa. The differential output had an outstanding stability within ±0.02 Hz under constant temperature and pressure. Thus, this research provides a convenient solution for high-pressure measurements because of its advantages, namely, large range, excellent accuracy and stability.

Evaluation of Recovery of Tight Sandstone Gas Reservoirs Based on a Seepage Steady-State Model

As an important indicator for measuring the effectiveness and level of oil and gas field development, recovery rate has always been a focus in the research of oil and gas fields. Reservoirs of tight sandstone gas formations have significant characteristics of low porosity, high permeability, and high water content, which leads to greater difficulty in their development and makes it challenging to evaluate the recovery rate. Newtonian mechanics, as an important component of the mechanical system, is an innovative application of classical mechanics in the field of seepage mechanics when applied to the two-phase flow of gas and water. Firstly, starting from the perspective of mechanics analysis, we derive a steady-state model for gas–water two-phase infiltration and obtain the productivity equation based on this model. Then, according to the steady-state model, we establish a method to calculate the effective control radius of gas reservoirs under different production conditions and reservoir physical properties. Finally, using Matlab 2018a programming based on the productivity equation, we calculate the gas recovery under different conditions during constant pressure drop production and constant production rate production. The results indicate that the effective control radius of the reservoir decreases with an increase in the economic ultimate daily gas production, increases with an increase in production pressure difference, slightly decreases with an increase in startup pressure gradient, and correspondingly increases with an increase in microtube radius and quantity. Regardless of whether it is production with a fixed pressure drop or production with a fixed production rate, the gas recovery decreases as the production pressure drop and bottomhole abandonment pressure increase, but it increases as the proportion of the single-well control radius increases. In production with a fixed pressure drop, the gas recovery remains consistent across different reservoir quality indices. However, in production with a fixed production rate, the gas recovery initially increases rapidly and then gradually slows down as the reservoir quality index increases, and there is an obvious critical permeability (0.1 mD). The research findings are based on the mechanical analysis of porous media, delving into the laws governing fluid flow during infiltration. The derived infiltration model can be used to calculate the effective control radius and evaluate recovery rates, providing practical guidance for reservoir development.

Experimental study on charging and discharging characteristics of copper finned metal hydride reactor for stationary hydrogen storage applications

With the shift in power generation methods from conventional to renewable, the need for energy storage has increased, and hydrogen as a carrier has great potential. The storage of hydrogen is one of the main obstacles to the effective deployment of the hydrogen economy. Since metal hydride offers a higher energy density than conventional methods, it can potentially be used to store and deliver hydrogen. Also, the metal hydride hydrogen storage system is the primary element of the energy storage system that connects hydrogen production and consumption. Therefore, the present study is focused on the development and testing of a metal hydride reactor. In the present experimental study, 9 kg of La0.7Ce0.1Ca0.3Ni5 is loaded in a single tube copper finned reactor attached to an external jacket, and the charging and discharging characteristics related to hydrogen storage are analysed along with variations in its thermal performance under various operating conditions. Also, the effect of HTF temperature on the hydrogen release performance of the copper finned reactor is studied under constant discharge pressure and constant discharge flow rate. Further, a comparison has been made between the copper and aluminium finned reactors. This fabricated copper finned reactor attained volumetric and gravimetric storage densities of 21.78 kg per m3 of H2 and 0.77%, respectively. The results indicated that La0.7Ce0.1Ca0.3Ni5 filled within the copper finned reactor stores 1.45 wt.% (130.7 g) of hydrogen in 680 s, corresponding to 25 bar feed gas pressure. At the HTF temperature of 60 °C, the copper-finned reactor discharged 1.42 wt.% (127.3 g) of hydrogen in 1450 s, showing the release of 98% of the stored mass of hydrogen. Further, the developed copper finned MH reactor could supply hydrogen at a constant rate of 13 lpm with a capability of 90% discharge even at a discharge temperature of 30 °C. Beside this, the comparative results showed that adding copper fins showed a considerable improvement over aluminium fins during discharging compared to the charging process. The copper-finned reactor consumed 20.9% and 23.6% less time to release 1 wt.% of hydrogen than the aluminium-finned reactor at discharge temperatures of 40 °C and 50 °C, respectively.

Experimental Study on the Performance of Frictional Drag Reducer with Low Gravity Solids

Reducing energy consumption during drilling operations is beneficial to both the environment and economy. Frictional drag reducers (FDR) are widely used to reduce the energy loss caused by turbulent flow. FDR plays an important role in flow lines as they can reduce the frictional pressure drop effectively, and benefit the selection of circulating fluid and pump. However, several factors can influence the performance of FDR, including fluid additives and incorporated solids, such as drill solids. Thus, the main objective of this paper is to study the influence of low gravity solids (LGS) on the performance of the FDR. This paper is mainly based on experimental study. The experimental work contains two parts: rheology characterization and flow loop tests. Rheology characterization tests were performed to calculate the flow consistency index (K) and flow behavior index (n). Flow loop experiments were conducted for two geometry (0.457 inch and 0.797 inch diameter). Xanthan gum was used as a fractional drag reducer. Bentonite and quartz sand were added as low gravity solids. Three designed water-based mud systems are tested for drag reduction efficiency of Xanthan gum. Flow rate of the mud varied from 3 gpm to 16 gpm. Concentration of Xanthan ranged from 0.1 lbm/bbl to 0.6 lbm/bbl. Low weight solids were added with weight percentage of 0.5%, 1%, 2% and 2.5%. The result shows that xanthan gum is an efficient drag reducer for adequate reasons. Firstly, even at al low concentration, xanthan gum shows high resistance to degradation. Secondly, the maximum drag reduction with xanthan gum is up to 70.54% with a concentration of 0.6 lbm/bbl. However, the existence of different low gravity solids influence the efficiency of xanthan gum in different styles. Experiment results indicate that the higher the weight percentage of bentonite, the lower the drag reduction effectiveness. While with the increasing concentration of quartz sand, the drag reduction does not show an intense change. This study intents to give an instructive guidance on usage of frictional drag reducers in drilling mud system design. Removal of low gravity solids from the mud is difficult, which pose a danger to the drilling fluid. By understanding the effectiveness of FDR, we can reduce energy consumption when irremovable low gravity solids exist. FDR can be used for modifying the mud contents to develop a lower pressure gradient under turbulent flow condition. In the same scenario, adding FDR can suppress turbulent at a constant pressure gradient but with a higher flow rate.

Investigation of thermal properties of gadolinium doped carbon nanotubes

Thermal properties characterizations for 10% and 15% Gd doped multi wall carbon nanotubes (MWCNTs) were investigated. TGA/DSC and TEM techniques were used for characterization. The features of mass loss characteristics for synthesized nanocomposite carbon nanomaterials were investigated. The specific heat capacities of the samples at a constant pressure increased as the temperature increased.

A creep/recovery model of dry fiber fabric during compaction considering temperature and in‐plane tension

AbstractIn the manufacturing of fiber‐reinforced composite materials, the preforming stage of dry fiber fabric entails compaction operations carried out under constant pressure, a specific preforming temperature, and in‐plane tension. Throughout this process, permanent deformation and creep/recovery behavior are observed in the fabric, correlating with factors such as time, sustained pressure, temperature, and in‐plane tension. Effective control of fiber volume fraction and material composition necessitates a thorough comprehension of these phenomena as well as the capacity to predict them with accuracy. To solve this, a viscoelastic‐plastic model was put forth, which provides an account of the viscous effects on the fabric during its stages of compression and recovery. The proposed model incorporates changed Burgers units to manage time‐dependent deformations and plastic units to address permanent deformations. Through the application of a single set of parameters, the model precisely and comprehensively characterizes through‐thickness creep/recovery behavior of preformed dry fiber fabrics under varying conditions, including creep stress, temperature, and in‐plane tension. To enhance the practical utility of the model, an application has been developed and validated against experimental data conducted under diverse test conditions. The results demonstrate consistency between experimental curves and model‐predicted curves across various compression scenarios.Highlights A viscoelastic‐plastic model was proposed with a single parameter set. Stress, temperature, and in‐plane tension all exacerbated creep/recovery. Model captures temp. and time‐related creep/recovery with in‐plane tension. The model has been transformed into a practical application tool.

Measurement of laminar burning speed at high pressures using plasma affected flame

Measurements of a propagating flame are crucial to the understanding and verification of important flame phenomena. Specifically, laminar, unstretched flame speed is desired to verify complex flame behavior such as turbulence or chemical kinetic models. This data is also necessary as advanced and more efficient combustion devices operate at these high pressures where this data is less reliable from the onset of flame instabilities. This research provides laminar burning speed (Suo) and Markstein length (Lb) measurements utilizing a novel technique which incorporates flame propagation during and just after the ignition phase. The analysis utilizes a constant pressure technique where the expansion of a spherical flame is visually measured. Flame propagation of stoichiometric flame from 1 to 50 atm are examined up to a radius of 20 mm. The inclusion of early flame propagation improves the measurement of Suo through the addition of a larger data set than usually possible in the conventional method. The measurement method utilizes electrical data of the spark formation with a thermodynamic model to predict the kernel velocity and temperature which result from plasma formation. In addition, morphology of the early kernel at high pressure is reported as well as comparisons to the conventional Suo measurement.

On thermodynamics and heat and mass transfer aspects of CH4 adsorption onto coconut shell-based carbonaceous material

The current study investigates the equilibrium methane (CH4) adsorption capacity and the adsorption kinetics of a locally produced coconut shell-derived activated carbon (AC CARB 6X12 60) for pressure and temperatures ranging from 0 to 55 bar and -20 to 70 °C, respectively. The adsorption isotherms and kinetics are determined using an in-house developed adsorption test rig. A maximum methane adsorption uptake of 0.140 kg/kg is obtained at -20 °C and 40 bar pressure. The adsorption equilibrium isotherm data are fitted using Toth, Dubinin-Astakhov (DA), and Modified-DA isotherm models. Afterwards, the kinetics study is done considering pseudo first order, second order, Elovich, and intra-particle diffusion models. In continuation, based on the DA isotherm model, Clausius Clapeyron relation, and Maxwell's relations, the expressions for the crucial thermodynamic parameter of adsorbed phase, i.e., isosteric heat of adsorption, specific heat capacity, enthalpy, and entropy is derived, and same is estimated using DA isotherm parameters. Additionally, the activated carbon's thermophysical properties (i.e., thermal conductivity, thermal diffusivity, and specific heat) are determined using the TPS 2500 S analyzer, which works on the hot-disk principle. Using the most suitable isotherm (DA) and kinetic model (pseudo second order), heat and mass transfer analysis is carried out on novel reactor configuration with an external cooling jacket, double row of cooling pipes with external longitudinal fins for methane storage using a 3D transient model in Comsol Multiphysics. The charge characteristics are studied for gas charging pressure varying from 1 to 50 bar and cooling fluid temperature of -20 to 70 °C. Iso-concentration contours are plotted to identify the pressure-temperature combination resulting in identical storage capacity (i.e., including both gaseous and adsorbed phases). Further simulations are carried out for constant pressure charging and constant flow discharge conditions to expound upon the effects of the dormancy period, gas charging pressure, and cooling/heating fluid temperature. 14% improvement in total discharge amount is obtained with a dormancy period between charging and discharging compared to no dormancy case.

An investigation of vibrational analysis, thermodynamics properties and electronic properties of Formaldehyde and its stretch by substituent acetone, acetyl chloride and methyl acetate using first principles analysis

This study finds the equilibrium configuration, vibrational analysis, thermodynamic properties, and electronic properties of formaldehyde and its derivatives, namely acetone, acetyl chloride, and methyl acetate, using First Principles Analysis. It emphasizes the impact of substituents on the carbonyl group and the need for this comprehensive analysis. The computational methods employed in this work are Gaussian DFT), GaussSum and Moltran calculations. For formaldehyde, the optimization step starts from the energy of -114.51282 Hartree and gets optimized in the energy -114.5129634 Hartree. Similarly for Acetone, Acetyl chloride and Methyl acetate, optimization step start from -193.74375 Hartree, -613.26 Hartree, -266.805 Hartree and gets optimized in the energy -193.1744033 Hartree, -613.2941798 Hartree, -266.8358066 Hartree. Infrared (IR) spectroscopy is used to analyze vibrational frequencies. The C-H and C=O vibrations are highlighted, showing characteristic peaks for each compound. Heat capacity at constant volume (Cv), heat capacity at constant pressure (Cp), internal energy (U), enthalpy (H), entropy (S) and Gibb’s free energy (G) with change in temperature sharply increase from 10 K to 50 K and decreases the increase in rate from 50 K to 500 K. In the derivative of Formaldehyde, Methyl Acetate has the highest energy gap (i.e. -7.4222 eV) and Acetyl Chloride has the small energy gap (i.e. 5.6137 eV). The Chemical parameters like ionization potential, electron affinity, chemical hardness, chemical potential, electronegativity, electrophilicity index, and chemical softness have been also calculated. Electrostatic Potential (ESP) Surfaces, Molecular Electrostatic Potential (MEP), and Electron Density (ED) are visualized to understand charge distribution and reactivity regions. DOS spectra illustrate the density of electron states per unit energy.

Correlation between Voltage, Strain, and Impedance as a Function of Pressure of a Nickel‐Rich NMC Lithium‐Ion Pouch Cell

AbstractFulfilling the service life of a Lithium‐Ion battery in each intended application requires further understanding of the cells' lifetime and reliability. Derived from literature, controlling the external pressure constant on Lithium‐Ion battery cells is an inevitable factor to extend the cycle lifetime. Thus, active knowledge of the cells' strain and understanding the impact of an external pressure on the impedance is mandatory to evaluate an optimum pressure to improve the cell performance. This work presents correlations between voltage, strain, and impedance as a function of the applied constant external pressure on a nickel‐rich nickel‐mangan‐cobalt (NMC) lithium‐ion pouch cell. Utilizing a high precision universal testing machine reveals a negligible change of the cells' maximum stroke within the pressure range from 0 to 1000 kPa. Additionally, an optimum pressure between 100 and 300 kPa is revealed by analyzing a series of electrochemical impedance spectroscopy data measured at different constant external pressures. Within this pressure range the charge transfer resistance as well as the diffusive processes exhibit its optimum.