Increase In Pressure Gradient Research Articles

Early and mid-term outcomes of double-chambered right ventricle repair: An 8-year experience.

Double-chambered right ventricle is a rare and progressive condition that is characterised by obstruction of the right ventricular tract. Double-chambered right ventricle is usually associated with ventricular septal defect. Early surgical intervention is recommended in patients with these defects. Based on this background, the present study aimed to review early and midterm outcomes of primary repair after double-chambered right ventricle. Between January 2014 and June 2021, 64 patients with a mean age of 13.42 ± 12.31 years underwent surgical repair for double-chambered right ventricle. The clinical outcomes of these patients were reviewed and assessed retrospectively. An associated ventricular septal defect was present in all the recruited patients; 48 (75%) patients of sub-arterial type, 15 (23.4%) of perimembranous, and 1 (1.6%) patient of muscular type. The patients were followed up for a mean period of 46.73 ± 27.37 months. During their follow-up, a significant decrease in the mean pressure gradient from 62.33 ± 5.52 mmHg preoperatively to 15.73 ± 2.94 mmHg postoperatively was observed (p < 0.001). Notably, there were no hospital deaths. The development of double-chambered right ventricle in association with ventricular septal defect results in an increased pressure gradient within the right ventricle. The defect needs correction in a timely manner. In our experience, the surgical correction of double-chambered right ventricle is safe and shows excellent early and mid-term results.

Capillary rheometry as a model methodology for obtaining insight in feed mash behaviour at conditions approximating pellet manufacturing

Pellet manufacturing is a useful tool for improving the handling of livestock feed. Pellet manufacturing consists, among others, of a compaction step, which is strongly affected by feed formulation. The role of feed formulation is thought to result from the fact that feed mash physicochemical properties change depending on ingredient composition. This variation in physicochemical properties subsequently affects mash behaviour during compaction, leading to variation in both physical pellet quality and energy costs during pellet manufacturing. Methodologies that allow for the study of material behaviour at pellet manufacturing conditions are needed to investigate the effect of feed formulation on mash flow behaviour. Such methodologies, however, are currently not generally available in the field of feed manufacturing. In this short communication we aim to discuss the application of capillary rheometry as a potential method for studying feed behaviour in the die, at conditions comparable to those during pellet manufacturing. The similarity between the design of the capillary rheometer and the geometry of a ring-die compactor allows for the simulation of some of the conditions experienced by feed mash during compaction, using smaller quantities of sample materials. The observed relation between flux and pressure gradient, for feed mashes evaluated in this short communication, resembles a Herschel-Bulkley relation, indicating that the increase in pressure gradient depends non-linearly on flow rate. While individual pressure gradients provide insight in the relative energy costs of compaction, a modelling approach is recommended to simulate the behaviour of feed mash at conditions more closely approximating those during pellet manufacturing. In summary, capillary rheometry provides an option for studying feed mash behaviour at conditions approximating those in the pellet press during pellet manufacturing.

P81: Development Of A Pre-Operative Planning Tool For Patients With Mitral Regurgitation

Mitral regurgitation is the most frequent valve disease in patients over the age of 65 years. In patients with high surgical risk, transcatheter mitral valve intervention (TMVI) is the preferred therapy. However, patient selection for this therapy remains a challenge. This study aims at developing a simulation tool to assist surgeons pre-operatively to choose the treatment based on the patient’s characteristics. In this study, a clinical data (echocardiography and CT scans) of a TMV recipient with a history of severe mitral calcification was considered. Left ventricular (LV) and mitral valve (MV) models were obtained from pre-TMVI CT scans. Pre- and post-TMVI hemodynamics were generated by a lumped-parameter model which were then applied as boundary conditions for two fluid–structure interaction (FSI) simulations with contractile LV and dynamic MV; first, a pre-TMVI simulation with the anatomical MV model and second, a post-TMVI simulation with a Tendyne transcatheter mitral valve model. Mitral pressure gradients (MPG) and effective orifice area (EOA) were calculated. The predictions of the pre-TMVI simulations closely resembled Echo data. Calcified mitral leaflets led to a narrowing of the diastolic opening area resulting in an increased pressure gradient over the MV; EOA (FSI: 2.1 cm2, ECHO: 1.9 cm2), MPG (FSI: 3.8 mmHg, ECHO: 3.4mmHg). These values improved significantly for the post-TMVI simulation (EOA: 4.5 cm2, MPG: 1.1 mmHg), Figure 1. By combining medical imaging and computer modeling, we established a validated tool that can be used pre-TMVI to assist clinicians to select the optimal therapy based on patients’ characteristics.Figure 1. Pre-, and post-TMVI simulation of a patient with severely calcified mitral valve; TMVI: transcatheter mitral valve intervention

Portal Hypertension in Nonalcoholic Fatty Liver Disease: Challenges and Paradigms.

Portal hypertension in cirrhosis is defined as an increase in the portal pressure gradient (PPG) between the portal and hepatic veins and is traditionally estimated by the hepatic venous pressure gradient (HVPG), which is the difference in pressure between the free-floating and wedged positions of a balloon catheter in the hepatic vein. By convention, HVPG≥10 mmHg indicates clinically significant portal hypertension, which is associated with adverse clinical outcomes. Nonalcoholic fatty liver disease (NAFLD) is a common disorder with a heterogeneous clinical course, which includes the development of portal hypertension. There is increasing evidence that portal hypertension in NAFLD deserves special considerations. First, elevated PPG often precedes fibrosis in NAFLD, suggesting a bidirectional relationship between these pathological processes. Second, HVPG underestimates PPG in NAFLD, suggesting that portal hypertension is more prevalent in this condition than currently believed. Third, cellular mechanoresponses generated early in the pathogenesis of NAFLD provide a mechanistic explanation for the pressure-fibrosis paradigm. Finally, a better understanding of liver mechanobiology in NAFLD may aid in the development of novel pharmaceutical targets for prevention and management of this disease.

Experimental study of swirling flow pneumatic liquid-carrying characteristics in the vortex tool inserted tube under liquid loading conditions

Liquid unloading by vortex tool is one of the most important applications of swirling flow pneumatic conveying. However, due to swirl decay, the evolution of gas–liquid flow patterns and the dynamic characteristics of pressure drop downstream of the vortex tool are much more complex than those in non-swirling flow. In this study, the gas–liquid flow patterns and pressure drop inside the vortex tool inserted tube (ID = 60 mm) under liquid loading conditions were experimentally studied and compared with those of the plain tube. With the superficial gas velocities ranging from 0.5 to 6.0 m/s and superficial liquid velocities of 0.01, 0.02, and 0.04 m/s, the effects of the structural parameters and stages of vortex tools on the pressure drop were discussed. The experimental results reveal that three distinct swirling flow patterns can be identified downstream of the vortex tool, namely swirling gas column flow, swirling churn flow and swirling annular flow. The insertion of vortex tool facilitates an earlier transition of the churn flow to the annular flow, and the induced swirling flow can restrain the liquid from falling back. The helix angle of the corkscrew deflector has a more significant effect on the pressure drop than its length. By reducing the helix angle from 54° to 45°, the total pressure drop and downstream pressure gradient are significantly decreased, even lower than those of the plain tube. But the series combination of 54° and 45° vortex tools results in a significant increase in the downstream pressure gradient. Additionally, at low gas flow rate, negative frictional pressure drop occurs in both plain tube and vortex tool inserted tube. Hence, the new friction factor correlations were established respectively for the positive and negative friction regions in the cases of the tube with and without vortex tool, and most of the frictional pressure gradient predictions are within an error band less than 20%.

Electrokinetic and Electroconvective Effects in Ternary Electrolyte Near Ion-Selective Microsphere.

The paper presents theoretical and experimental investigations of the behavior of an electrolyte solution with three types of ions near an ion-selective microparticle with electrokinetically and pressure-driven flow. A special experimental cell has been developed for the investigations. An anion-selective spherical particle composed of ion-exchange resin is fixed in the center of the cell. An enriched region with a high salt concentration appears at the anode side of the particle when an electric field is turned on, according to the nonequilibrium electrosmosis behavior. A similar region exists near a flat anion-selective membrane. However, the enriched region near the particle produces a concentration jet that spreads downstream akin to a wake behind an axisymmetrical body. The fluorescent cations of Rhodamine-6G dye are chosen as the third species in the experiments. The ions of Rhodamine-6G have a 10-fold lower diffusion coefficient than the ions of potassium while bearing the same valency. This paper shows that the concentration jet behavior is described accurately enough with the mathematical model of a far axisymmetric wake behind a body in a fluid flow. The third species also forms an enriched jet, but its distribution turns out to be more complex. The concentration of the third species increases in the jet with an increase in pressure gradient. The pressure-driven flow stabilizes the jet, yet electroconvection has been observed near the microparticle for sufficiently strong electric fields. The electrokinetic instability and the electroconvection partially destroy the concentration jet of salt and the third species. The conducted experiments show good qualitative agreement with the numerical simulations. The presented results could be used in future for implementing microdevices based on membrane technology for solving problems of detection and preconcentration, and thus simplifying chemical and medical analyses utilizing the superconcentration phenomenon. Such devices are called membrane sensors, and are actively being studied.

Inhibiting the phosphatase activity of soluble epoxide hydrolase attenuates chronic kidney disease-induced calcific aortic valve disease in rats

Calcific aortic valve disease (CAVD) is the most frequent valvulopathy ultimaltely leading to aortic stenosis, one of the driving causes of an increased morbidity and mortality in aging and in patients with chronic kidney disease (CKD). Up to date, there is no available pharmacological treatment to prevent the development and progression of CAVD. Previous studies suggested that the bifunctional enzyme, soluble epoxide hydrolase (sEH), is involved in the regulation of cardiovascular calcification development. Our study aimed to investigate whether the phosphatase activity of sEH is involved in CAVD. Sprague Dawley sEH-P knocking rats (sEH-P KI) were generated using CRISPR/Cas9 method. Eighteen-week-old WT and sEH-P KI rats underwent subtotal nephrectomy (5/6Nx) to mimic CKD. These animals were afterword fed with a high-phosphate chow diet (1.8% phosphorus). In parallel, sham-operated animals on a standard diet (0.9% total phosphorus) served as controls. Twelve weeks after surgery, renal and cardiac parameters were determined and histological analysis of aortic valves was performed. Twelve weeks after surgery, the development of renal dysfunction in 5/6Nx + phosphate WT rats was shown by the augmentation in plasma creatinine and urea nitrogen concentrations and the decline in estimated glomerular filtration rate compared to sham-operated WT rats. These animals also displayed anemia, polyuria and polydipsia. The genetic inhibition of sEH-P did not allow to prevent these alterations. However, inhibiting sEH-P limited hydroxyapatite crystals deposition in the aortic valve of 5/6Nx + phosphate rats compared to 5/6Nx + phosphate WT rats (Fig. 1B, C), associated with a prevention of the decrease in intercusp distance and of the increase in aortic valve mean pressure gradient and in peak aortic valve velocity (Fig. 1A). In addition, left-ventricular diastolic (E/e′) and systolic dysfunction (fractional shortening) as well as cardiac fibrosis were prevented by sEH-P inhibition. Additional experiments on recombinant human and rat sEH allowed to demonstrate that sEH-P metabolizes pyrophosphate anions (PPi), a potent inhibitor of cardiovascular calcification, and that PPi degradation is efficiently prevented by sEH-P inhibition. Taking altogether, these results demonstrate that inhibition of sEH-P prevents aortic valve calcification and its hemodynamical consequences in the 5/6Nx + phosphate rat model, and may serve as a potential therapeutic strategy for the treatment of CAVD.

Long-term valve performance of St Jude Medical Epic porcine bioprosthesis in aortic position.

The aim of this study was to review long-term clinical outcomes and valve performance after Epic Supra valve implantation in aortic position. From 2011 to 2022, 44 patients (mean age 75 ± 8years) underwent surgical aortic valve replacement (SAVR) with an Epic Supra valve at our hospital. Survival, incidence of late complications, and echocardiographic date were retrospectively analyzed. During a mean follow-up period of 6.2 ± 3.5years, the overall survival rate was 91 ± 4% at 2 and 88 ± 5% at 5years, while rates of freedom from major adverse cardiovascular and cerebrovascular events (MACCE) were 86 ± 5% and 83 ± 6%, respectively. There was one case of reoperation for prosthetic valve endocarditis at 6years after the initial surgery. Echocardiographic examinations showed 5-year rates of freedom from severe structural valve deterioration (SVD) and moderate SVD of 100 and 92%, respectively. There was no significant increase in mean pressure gradient or decrease in left ventricular ejection fraction from 1week after surgery to the late follow-up period. Long-term clinical results and durability of the Epic Supra valve in aortic position were satisfactory.

Advantages of Multiposition Scanning in Echocardiographic Assessment of the Severity of Discordant Aortic Stenosis.

The aim of this study was to perform a comparative analysis of severity of discordant aortic stenosis (AS) assessment using multiposition scanning and the standard apical window. All patients (n = 104) underwent preoperative transthoracic echocardiography (TTE) and were ranked according to the degree of AS severity. The reproducibility feasibility of the right parasternal window (RPW) was 75.0% (n = 78). The mean age of the patients was 64 years, and 40 (51.3%) were female. In 25 cases, low gradients were identified from the apical window not corresponding to the visual structural changes in the aortic valve, or disagreement between the velocity and calculated parameters was detected. Patients were divided into two groups: concordant AS (n = 56; 71.8%) and discordant AS (n = 22; 28.2%). Three individuals were excluded from the discordant AS group due to the presence of moderate stenosis. Based on the comparative analysis of transvalvular flow velocities obtained from multiposition scanning, the concordance group showed agreement between the velocity and calculated parameters. We observed an increase in the mean transvalvular pressure gradient (ΔPmean) and peak aortic jet velocity (Vmax), ΔPmean in 95.5% of patients, velocity time integral of transvalvular flow (VTI AV) in 90.9% of patients, and a decrease in aortic valve area (AVA) and indexed AVA in 90.9% of patients after applying RPW in all patients with discordant AS. The use of RPW allowed the reclassification of AS severity from discordant to concordant high-gradient AS in 88% of low-gradient AS cases. Underestimation of flow velocity and overestimation of AVA using the apical window may lead to misclassification of AS. The use of RPW helps to match the degree of AS severity with the velocity characteristics and reduce the number of low-gradient AS cases.

Flow in Microchannels between Sealing Surfaces of Casing Connections: LBM Simulation

Great difficulties have been encountered in the study of the seal failure of casing connection. The in situ microscopic seal surfaces under complex loads are hard to be obtained due to the engagement characteristics of thread. In this study, a method to construct the microscopic seal surfaces of a specified 7 ″ casing PTC under complex loads was proposed. Then, the lattice Boltzmann method (LBM) was applied to simulate the fluid flow inside the microchannel between the seal surfaces. The effect of pressure gradient and wettability on the flow behavior of a multicomponent fluid system at the microscopic scale was analyzed. Pressure gradient has a huge influence on the volume fraction of sealing compound and the average velocity of displacing fluid. The volume fraction of sealing compound decreases with the increase of pressure gradient. Break-through can be observed for fluid systems with relatively larger pressure gradient. For the systems with Δ p = 0.658 , Δ p = 0.439 , and Δ p = 0.219 , the break-through time steps are around 61000, 99000, and 295000, respectively. Wettability has huge impact on the distribution of sealing compound, and break-through was not observed for the fixed pressure difference Δ p = 0.110 with various wettability. It is expected to provide some new insights for understanding the seal failure of casing connections at the microscopic level.

Production and transport of turbulent kinetic energy from premixed flames subjected to mean pressure gradients

The influence of mean favorable pressure gradients on the production and transport of turbulent kinetic energy is experimentally investigated in a premixed bluff-body combustor. The combustor wall geometry is modified into converging, straight, or diverging configurations to experimentally alter the mean pressure gradient in the reacting flow field. For each configuration, turbulent kinetic energy production and transport dynamics are characterized with high-speed particle image velocimetry and simultaneous CH* chemiluminescence imaging. For all cases, the premixed reaction increases the turbulent kinetic energy and integral length scales in the flow. However, increasing the magnitude of the mean favorable pressure gradient increases the turbulent kinetic energy produced by the flame. The source of increased turbulent fluctuations from reactants to products is first investigated with a steady flow energy analysis, and is accompanied with a Reynolds decomposed investigation of the kinetic energy in the flow. As the mean pressure gradient increases, the turbulent kinetic energy in the flow increases due to stronger magnitudes of flame-generated turbulence in the form of baroclinic torque. The evolution of the flame-generated turbulence is examined by decomposing the transport equation of turbulent kinetic energy. Increasing the mean favorable pressure gradient augments the largest magnitude transport terms, and the budget of turbulent kinetic energy is primarily driven by pressure gradient work and viscous dissipation. The results here differ from previous direct numerical simulation (DNS) studies, and should ultimately motivate additional research to aid the development of computational models which can better predict turbulent flame-flow dynamics in confined environments with mean pressure gradients.

Multi-scale simulation of the fracture behavior of non-stoichiometric gadolinia-doped ceria solid electrolytes under the coupled mechanical and electrochemical field

Solid oxide fuel cell (SOFC) works in a complex working environment, which is affected by many factors such as temperature, load and electrochemical reaction. When there are cracks in the material, the multi-field coupling effect will cause the electrolyte performance degradation, even failure and damage. In this paper, the coupling effects of mechanical and electrochemical field on mechanical behavior of gadolinia-doped ceria (GDC) electrolyte are investigated by using the Atom-to-Continuum (AtC) multi-scale method combining molecular dynamics (MD) and finite element method (FEM). Based on the electrochemomechanical coupling theory, we derive the defect diffusion equation of the finite element form. The non-stoichiometry of the cracked GDC electrolyte is calculated, and it is found that the stress concentration at the crack tip will induce non-stoichiometric effects, causing further concentration of oxygen vacancy defects at the crack tip. Subsequently, the effect of electrochemomechanical coupling effect on the fracture toughness of GDC electrolyte is studied by using the AtC multi-scale method. At 800°C under oxygen partial pressure logPO2=−22, this multi-field coupling effect reduces the fracture toughness of 10GDC and 20GDC by 16.13% and 23.33%, and this effect is more apparent with the increase of oxygen partial pressure gradient and external load.

Piezovoltaics from PdHx

Metal hydrides have wide applications in energy science. A large pressure gradient propels the hydrogen atoms out. A piezovoltaic device, a pressure gradient-driven battery, can therefore be realized when the migrations of protons and electrons are separated by different conductors. Here we investigate the piezovoltaic performance of PdHx with various proton conductors as electrolytes and experimentally detect an output current of ≲40 nA and a voltage of ∼0.8 V for a 3 μg sample. We also demonstrate the escape of hydrogen atoms from a palladium lattice under an increasing pressure gradient using X-ray diffraction. The relationship between piezovoltaics (chemical process) and piezoelectricity (physical process) is like that between a chemical battery and a capacitor. Our work demonstrates the piezovoltaic application of metal hydrides and provides a new way to convert mechanical energy into electrical energy.

Risk evaluation of CO2 leakage through fracture zone in geological storage reservoir

CO2 storage in saline aquifers is an effective way to reduce the emission of CO2 into the atmosphere. The potential leakage problems are the main challenge for CO2 storage projects. However, the quantitative evaluation and analysis of the driving forces for the potential CO2 leakage problems are still lacking. In this paper, a stratified model embedded with a highly-permeable fracture zone was constructed to simulate CO2 leakage in the post-injection period. The acting forces and dimensionless numbers were systematically analyzed, and four stages were defined based on the leakage characteristics. Ultimately, a novel regression model was developed to predict the percentage of secure storage for CO2 at any dimensionless numbers. Results showed four distinct CO2 leakage stages: fast CO2 leakage stage (T1); decreasing CO2 leakage stage (T2); fast water sink stage (T3); and stable countercurrent flow stage (T4). Viscous force, gravity force, and capillary force were the dominant driving forces in turn in the first three stages. A stable countercurrent flow and CO2 leakage were maintained in the last period. In addition, the turning point of the flow pattern was delayed, and Gravity number (Gr) and Bond number (Bo) decreased obviously with the increase of initial pressure gradient. More importantly, most of the leaked CO2 was trapped in riskier forms (i.e. structural and residual trapping), and heavy acidification occurred in the shallow aquifer. The novel regression model showed that the percentage of secure storage could be enhanced by increasing Gr and/or decreasing the Ca. It is suggested that the pressure gradient at the end of injection should be optimized to store more CO2 and decrease the leakage risk simultaneously.

Present-Day In Situ Stress Analysis in Shale Reservoir of Haiba Block, Southern Sichuan Basin, South China

Natural gas from shale gas reservoirs has been an important contributor for reserve growth, deliverability construction, and profits growth in natural gas industry in the world. Hydraulic fracturing is commonly required in the shale gas commercial development, and thus understanding the present-day in situ stress field is greatly significant for the hydraulic fracturing and efficient development in shale gas reservoirs. However, there are no systematic investigations on the present-day in situ stress field in the Haiba Block from the Sichuan Basin, South China. In this study, the present-day in situ stress orientations and magnitudes in shale reservoir of Haiba Block are investigated based on the well interpretations from borehole image log and geomechanical modeling. Then, the effects of stresses on hydraulic fracturing, horizontal wells, and natural fracture reactivation were discussed. The results indicate that the horizontal maximum principal stress (SHmax) orientation is mainly in the NE-SW-trending, NW-SE-trending, and WNW-ESE-trending in the Haiba Block. The magnitudes of horizontal maximum and minimum principal stresses are 13.5 MPa~85.5 MPa and 2.8 MPa~31.6 MPa, respectively. In the Haiba Block, the differential stress is generally low in the northern part, which indicates that complex hydraulic fracture networks may be produced. While the natural fractures are generally stable under the present-day in situ stress field. When the increase of pore pressure gradient is about 30 KPa/m, nearly all natural fractures in the Longmaxi Formation may be reactivated. The results can provide the insights into a better understanding of the present-day in situ stress distribution so as to optimize perforation orientation, hydraulic fracturing design, and enhance gas production in shale gas reservoirs.

Subtotal Nephrectomy Associated with a High-Phosphate Diet in Rats Mimics the Development of Calcified Aortic Valve Disease Associated with Chronic Renal Failure

Introduction. This study addressed the hypothesis that subtotal nephrectomy associated with a high-phosphorus diet (5/6Nx + P) in rats represents a suitable animal model to mimic the cardiovascular consequences of chronic kidney disease (CKD) including calcified aortic valve disease (CAVD). Indeed, the latter contributes to the high morbidity and mortality of CKD patients and sorely lacks preclinical models for pathophysiological and pharmacological studies. Methods. Renal and cardiovascular function and structure were compared between sham-operated and 5/6 Nx rats + P 10 to 12 weeks after surgery. Results. As expected, 11 weeks after surgery, 5/6Nx + P rats developed CKD as demonstrated by their increase in plasma creatinine and urea nitrogen and decrease in glomerular filtration rate, estimated by using fluorescein-isothiocyanate-labelled sinistrin, anemia, polyuria, and polydipsia compared to sham-operated animals on a normal-phosphorus diet. At the vascular level, 5/6Nx + P rats had an increase in the calcium content of the aorta; a decrease in mesenteric artery dilatation in response to a stepwise increase in flow, illustrating the vascular dysfunction; and an increase in blood pressure. Moreover, immunohistology showed a marked deposition of hydroxyapatite crystals in the aortic valve of 5/6Nx + P rats. Echocardiography demonstrated that this was associated with a decrease in aortic valve cusp separation and an increase in aortic valve mean pressure gradient and in peak aortic valve velocity. Left-ventricular diastolic and systolic dysfunction as well as fibrosis were also present in 5/6Nx + P rats. Conclusion. This study demonstrates that 5/6Nx + P recapitulates the cardiovascular consequences observed in humans with CKD. In particular, the initiation of CAVD was shown, highlighting the interest of this animal model to study the mechanisms involved in the development of aortic stenosis and test new therapeutic strategies at an early stage of the disease.

Degradation of 2,4-diclorophenol via coupling zero valent iron and hydrodynamic cavitation for sulfite activation: A turbulence modeling

The 2,4-dichlorophenol (2,4-DCP) is an important chemical precursor that can affect human endocrine system and induce pathological symptoms. This research reports the degradation of 2,4-DCP using lab-scale hydrodynamic cavitation (HC) approach, which is considered a green and effective method. To promote the degradation efficiency, the zero-valent iron (Fe0) as the catalyst for sulfate radical (SO4•−) generation via activation of sulfite (SO32−) salts was simultaneously used. Degradation efficiency was favorable in acidic pH than the alkaline pH due to higher production of active radicals and was dependent on the dose of Fe0 and SO32−. Under optimal condition, degradation efficiency by Fe0/HC/sulfite (96.67 ± 2.90%) was considerably enhanced compared to HC alone (45.37 ± 2.26%). Quenching experiments suggested that SO4•−, •OH, 1O2, and O2•− radicals were involved in the degradation of 2,4-DCP by Fe0/HC/sulfite process, but the dominant role was related to •OH (70.09% contribution) and SO4•− (29.91% contribution) radicals. From the turbulence model, turbulent pressure at venturi throat decreased from −0.42 MPa to −2.02 MPa by increasing the inlet pressure from 1.0 to 4.0 bar and increase in pressure gradient has intensified bubble collapse due to higher turbulence tension.

Further discussion of CO2 huff-n-puff mechanisms in tight oil reservoirs based on NMR monitored fluids spatial distributions

Due to the poor physical properties of tight reservoirs, CO2 huff-n-puff (HNP) is considered a potential enhanced oil recovery (EOR) method after primary depletion. Optimization plays a critical role in the effective implementation of CO2 huff-n-puff. But the optimization requires a good understanding of the EOR mechanisms. In this work, the spatial distribution of oil saturation under different experimental conditions was analyzed by the NMR method to further discuss the HNP mechanisms. According to the variation of 1D frequency signal amplitude, we divided the core into the hardly movable area and movable area, the region with the obvious signal decline was defined as the movable area, and the hardly movable area was the region with limited signal decline. Based on that the recovery characteristics of different scenarios were evaluated. Firstly, the necessity of the soaking stage was studied, where three scenarios with different soaking times were carried out. Secondly, the injection pressure was adjusted to investigate the effect of the pressure gradient. The T2 spectra show that soaking has significantly improved the production of crude oil in small pores, and higher oil recovery in a single cycle is observed, but it is lower when the elapsed time (total operation time) is the same. 31.03% of oil can be recovered after 3 cycles HNP, which increases to 33.8% and 37.06% for the 4 cycles and 6 cycles cases. As the pressure gradient increases, more oil is removed out of the matrix, and the oil in the deep part of the reservoir can be effectively recovered. During the CO2 huff-n-puff process, the oil distributions are similar to the solution gas drive, the residual oil is distributed at the close end of the core and the range that the oil can be efficiently recovered is limited.

Experimental study on nonlinear seepage characteristics of coal under true triaxial stress loading

The characteristics of coalbed methane flow are jointly determined by the fracture and stress environment. Previous studies conducted under conventional triaxial or uniaxial stress conditions cannot truly reflect the in situ stress environment and neglected the influence of intermediate principal stress on the nonlinear seepage characteristics of coal. For this study, coal seepage tests were performed under true triaxial stress, allowing the nonlinear seepage characteristics of coal to be analyzed under different principal stresses. This enables the applicability of nonlinear seepage characterization equations and the change laws of relevant parameters to be clarified. The results show that the nonlinear seepage characteristics of coal under true triaxial stress increase as the principal stresses and gas pressure gradient increase. Using the Forchheimer equation for characterization, the nonlinear effect factor, viscous permeability, and inertial permeability gradually decrease with increasing principal stress in all directions. Intermediate principal stress σ2 has the most significant effect on nonlinear effects and inertial permeability, whereas principal stress σ3 has the greatest effect on viscous permeability. Using the Izbash equation for characterization, the fitting coefficients λ, m increase with increasing principal stress. Principal stress σ2 has the most significant effect on m, whereas principal stress σ3 has the greatest influence on λ. Comparative analysis shows that both Forchheimer and Izbash equations accurately characterize the nonlinear seepage characteristics of coal under real triaxial stress. The Forchheimer equation requires more theoretical parameters to measure the degree of nonlinear seepage and thus better describes the evolution process of linear to nonlinear seepage.

Evaluation of the influence of hydrodynamic cavitation treatment of dark petroleum products on the yield of fractions with boiling points up to 400°C

Objectives. The reduction of the anthropogenic burden on the environment is generally associated with the transition to alternative energy sources. However, some of these have only regional significance, while the effectiveness of others remains doubtful. On this point, innovative processes aimed at increasing the depth of oil refining may be equally important for reducing the carbon footprint. Wave-based technologies such as cavitation may also be included in these processes. Among the various methods for inducing such cavitation phenomena in oil refining, hydrodynamic approaches are especially promising. It has been shown that the treatment effectiveness increases with greater pressure or when augmenting the number of cavitation processing cycles. The aim of this work is to identify the factor (i.e., pressure gradient or number of treatment cycles) having the greatest influence on the change of the characteristics of the oil product.Methods. Cavitation phenomena were created by pumping dark oil products through a diffuser. The pressure gradient ranged from 20 to 50 MPa, while the number of cavitation processing cycles varied from 1 to 10. The influence of cavitation conditions on the change of fractional composition of petroleum products was analyzed. Target fractions are those having a boiling point up to 400°C.Results. It is shown that increased pressure generated in the diffuser leads to a linear increase in the yield of desired cuts. The dependence of the yield of these fractions on the number of processing cycles is described by the growth model with saturation. A proposed equation describes the influence of pressure and number of cycles on the yield of the fractions from initial boiling point temperature (TIBP) to 400°C following cavitation processing of dark oil products. Some of the coefficients of this equation have been associated with the physicochemical characteristics of the feedstock.Conclusions. An equation for predicting the maximum possible yield of the TJBP-400°C fraction as a result of cavitation processing under different conditions of the process is proposed according to the physicochemical characteristics of the feedstock. The prediction error did not exceed 12%. The equation analysis and comparison of energy consumption between different process regimes shows that a higher yield of the target product is achieved by increasing pressure gradient rather than the number of processing cycles.