Critical Pressure Value Research Articles

Wpływ niejednorodności skał na stabilność ściany odwiertu

"One of the complications that arise while drilling wells is hydraulic fracturing. Hydraulic fracturing pressure is the pressure at which the integrity of the rock in the walls of the well is compromised, leading to the formation of artificial cracks. Various authors have proposed formulas to determine the hydraulic fracturing pressure Phf in the absence of actual data. Рhf = 0.87 Рrock Рhf = 0.85 (Рrock – Рres) + Рres Phf = [μ/(1 – μ)] (Рrock – Рres) + Рres Рhf = [2μ/(1 – μ)] Рrock where: μ – Poisson's ratio, which takes values of 0.25–0.4 for dense clay, 0.33–0.4 for clay with sandstone interlayers, 0.1–0.2 for shales, 0.3–0.35 for sandstone, 0.28–0.33 for limestone; Рrock, Рres – rock and reservoir pressure, respectively. This study examines the problem of determining hydraulic fracturing pressure taking into account the heterogeneity of rocks. The work can be roughly divided into two parts. In the first part, the physical properties of porous bodies in contact with fluids are studied, treating them as a two-phase medium. When a porous body comes into contact with fluids, the fluids penetrate into them, transforming them into a two-phase medium. The term “fluids” refers to both liquids and gases, with real liquids considered incompressible and gases highly compressible. The remaining part of the porous body, excluding the pores, is called the skeleton. Pores in porous bodies are connected through capillary tubes. In the second part, the influence of the magnetic field and rock heterogeneity on the stability of the well wall is studied. Formulas are derived to determine hydraulic fracturing pressure, depending on the mechanical properties of the rocks and the reservoir pressure. Based on the theory of destruction, the critical value of excess pressure (or hydraulic fracturing pressure) is determined, which is necessary to ensure the safety of drilling oil and gas wells. The machines used in drilling operations in the oil and gas industry must be easy to operate, reliable, and capable of long-time use. When designing such machines, considerations such as being lightweight, economical, and quick and inexpensive to prepare should be taken into account from the outset.

Устойчивость треугольника Рёло под действием нормальной нагрузки

A figure of constant width is such a figure that the distance between any parallel reference lines is the same. It is clear that a circle has this property, but not only it. The simplest figure of constant width (except for a circle) is the Reuleaux triangle. This work solves the problem of stability of the Reuleaux triangle under normal load. The critical pressure value has been obtained.

Oversized diameter helium pulsating heat pipe

A cryogenic pulsating heat pipe (PHP) whose capillary tube diameter does not satisfy the classical Bond number (Bo) criterion has been experimentally tested and showcased in this work. Helium is the working fluid employed and the PHP diameter is ∼ 1.75 times its recommended critical diameter of 0.57mm. All the investigations reported till date on helium PHP have adhered to tube diameter of 0.5mm evidently meeting the Bo < 4 criterion. However, this helium PHP corresponds to Bo = 12 at 4.2K and, in fact, is the first cryogenic PHP demonstrating its functionality at such a high Bond number for helium. The motivation for such an investigation is initially presented with a deliberation on different PHP critical diameter criteria. A hypothesis emphasizing on the need to re-evaluate the upper limit of tube diameter for cryogenic PHPs is proposed. In support of this, a closed-loop PHP constructed from a 1mm inner diameter stainless steel tube is utilized. It is composed of 20 parallel channels and has a projected length of 0.4m. The functionality of this large diameter helium PHP is validated by experimentally characterizing its thermal performance and pressure as a function of heat load up to 1.5 W within an exhaustive range of filling ratios (10 to 90 %). This is conducted both in vertical and horizontal orientation. Zones where the PHP quickly surpasses the helium critical temperature and pressure values and still functioning are identified. Finally, its reliability is exhibited by 65 h stability test conducted at constant operational conditions.

Evaporation rate and kinetic mechanism of noble antimony under vacuum

Herein, a novel mathematical and statistical method is applied to the kinetic study of vacuum gasification of noble-antimony alloys. The evaporation rates of pure and noble antimony in a unit time at 823–1023 K and 5–600 Pa are determined using a vacuum differential gravimetric furnace, and their respective evaporation mechanisms under vacuum are analyzed in detail in conjunction with their triple point. Results show that the actual evaporation rates of pure and noble antimony are consistent with those obtained using a nonlinear logistic model (ω=A2+(A1-A2)/[1+P/P0a); the goodness of fit (R2) is > 0.9965 at all temperatures. The critical pressure values of pure and noble antimony at 823–1023 K are obtained, which are linearly dependent on the temperature. According to the theoretical and actual maximum evaporation rates of pure and noble antimony, the evaporation coefficient is corrected and the relation between the actual evaporation rate and temperature (lgω=AT+B) is further obtained, which can be used to calculate and predict the evaporation rates of noble antimony at different temperatures. By studying the evaporation rate of pure and noble antimony, this study provides the kinetic parameters for vacuum gasification of noble antimony and simultaneously enriches the kinetic database, which develops and improves the theory and practice of vacuum gasification of noble-metal alloys.

Determination of the critical value of bottomhole pressure during flow well operation

The main process in oil and gas production is the extraction of hydrocarbons to the surface. In all methods of oil production, hydrocarbons are transported through tubing from the bottom of the well to the wellhead. The methods of oil production are classified based on factors such as reservoir pressure, physical properties of oil, and reservoir properties of the productive formation. These methods include: – Flowing method: In this method, oil naturally rises to the surface under the pressure of reservoir energy. – Gas lift method: Oil is lifted to the surface by injecting gas into the well. – Pumping method: Also known as mechanized method, oil is brought to the surface with the aid of pumps. In the present study, the stress state in the formation zone at the bottom hole was examined, and the critical values of the bottom hole pressure and formation flow rate were determined.

Prediction of wellbore sand production potential from analysis of petrophysical data coupled with field stress: a case study from the Shah-Deniz gas field (Caspian Sea Basin)

Identifying the optimal azimuth and inclination for wellbore drilling in sandy formations can be considered a valuable aid in reducing sand production risks, lost time, and decreasing drilling costs in the petroleum industry. Therefore, a numerical systematic approach was provided to predict sand production in wellbore SDX-5, drilled in a deep-water sandstone reservoir in the Shah-Deniz gas field (South Caspian Basin), which has never been done previously. Additionally, this systematic approach uses geomechanical and geodynamical criteria, along with petrophysical information (density and sonic log) and tectonic characteristics of the study area, which are influenced by the active tectonic stresses of the Apsheron-Balkhan zone. The subsurface data sources employed are more eco-friendly, available, and continuous than experimental tests. The computations conducted achieved azimuth, inclination, polar, and depth profile plots for the Lower Balakhany Formation. The calculations reveal that the optimum azimuth for the wellbore drilling trajectories is parallel to SHmax and oblique drilling to near horizontal is the result of optimum inclination. Polar plots showed optimum azimuth, inclination, and effect of wellbore trajectory on critical collapse pressure and collapse drawdown pressure with pressure values simultaneously, which identify safer alternatives for achieving higher petroleum production rates without sanding. Depth profile plots provide a simultaneous overview of the values of critical collapse pressure, critical sanding pressure for instantaneous drawdown, and optimum wellbore production pressure during drilling and production operations. Moreover, optimum reservoir fluid production (maximum discharge) rates can be identified and imposed as upper limits to prevent sand production.

Force Field for Calculation of the Vapor-Liquid Phase Equilibrium of trans-Decalin

Based on the TraPPE force field, previously unknown values of the parameters of the intermolecular interaction potential of trans-decalin were determined. Parametrization was carried out using experimental data on saturated vapor pressure and density at atmospheric pressure. The found parameters make it possible to adequately describe the boiling and condensation lines of trans-decalin and also predict the critical values of pressure, density, and temperature with satisfactory accuracy. Calculations of vapor-liquid phase equilibrium conditions for a binary CO2—trans-decalin mixture in supercritical conditions for CO2 were carried out. When quantitatively comparing the calculated values with experimental data, an underestimation of pressure at a temperature of 345.4 K by 30% is observed, which decreases to 5% for temperatures up to 525 K.

Computer modelling of thin-walled shell structures with geometric imperfections

The study presented in the article focuses on modelling of thin-walled cylindrical shell structures with initial geometrical imperfections under external radial pressure. The critical pressure of the perfect shell obtained using linear analysis significantly exceeded that calculated by the Papkovich formula. This discrepancy can be attributed to the shell displacement constraints and the fact that linear analysis provides non-conservative estimates. Initially, the geometric imperfections were assumed to follow an eigenmode-affine pattern with varying amplitudes. Critical pressure values iteratively determined using the modified Ricks method were found to be lower than the critical pressure of the first buckling mode. Importantly, all these values remained notably higher than the normative value. Subsequently, the initial imperfections were modelled as combinations of sinusoidal deviations with different amplitudes and varying numbers of waves along the perimeter. Short-wavelength eigenmode-affine imperfections were superimposed on longer-wavelength deviations. The research indicated that while the long-wavelength imperfections had a marginal impact on the critical pressure values, they notably altered the post-buckling behaviour of the shell, as depicted in load-deflection figures in the form of loops. These processes occurred at pressure levels considerably higher than the normative value. The simulation results are in good agreement with established theories regarding the pre- and post-buckling behaviour of thin-walled shells. Nonlinear analysis revealed that the actual critical pressure values exceeded the normative value by 30-45%, and the post-buckling pressure values exhibited a gradual decrease without posing a threat to abrupt changes in the geometry of the shells. This outcome provides a basis for a more accurate estimation of the load-carrying capacity of the shell structures.

Insight into effect of high pressure on the structural, electronic, and optical properties of KH2PO4

The Potassium dihydrogen phosphate (KH2PO4: KDP) of ferroelectric phase is a polarized structure that can be used for nonlinear optical transformation. Using the generalized gradient approximate (GGA), we study and predict the crystal structural trends, electronic structures, charge densities, and optical properties of KDP crystals with paraelectric (PE) and ferroelectric (FE) phases under pressures ranging from 0 to 20 GPa. We have studied how pressure affects the structural and electronic properties of KDP. It is found that under high pressure, KDP undergoes a transition from Fdd2 structure to I-42d structure. The calculations indicate that when the hydrostatic structural pressure of the ferroelectric KDP is applied to 11.36 GPa, the KDP has a paraelectric phase structure. The 11.36 GPa is the critical pressure value at which the structure undergoes phase transition. We further showed that as the pressure increases, the lattice size and ion displacement undergo a strong distortion. Surprisingly, the band gap of KDP greatly increases with the increase of pressure. The results show that high pressure enhances the compactness of the KDP system and enhance the laser damage threshold, which can open a new way for high pressure manipulation of frequency doubling materials in optoelectronic applications.

Experimental investigation of saturated vapor pressure and critical parameter for R1234ze(Z) (cis-1,3,3,3-tetrafluoropropene) and R1336mzz(Z) (cis-1,1,1,4,4,4-hexafluoro-2-butene)

In this study, metal-bellows variable volumetry was used to measure the saturated vapor pressures and critical parameters of R1234ze(Z) and R1336mzz(Z). The critical temperature, critical pressure, and critical density values were evaluated, and new vapor pressure correlations were formulated based on the obtained data. The low uncertainties of the measured values indicate the reliability and reproducibility of the data. The combined expanded uncertainties of critical temperature, critical pressure, and critical density were less than 50 mK, 21 kPa, and 0.6 % (k = 2, 0.95 level of confidence), respectively. 17 vapor pressure data points of R1234ze(Z) and 20 vapor pressure data points of R1336mzz(Z) were obtained at temperatures ranging from 260 K to 441 K. The combined expanded uncertainties of the temperature and saturated vapor pressure measurements were less than 20 mK and 2.2 kPa (k = 2, 0.95 level of confidence), respectively. The results provide important thermophysical data for the use of R1234ze(Z) and R1336mzz(Z) in HTHP, and can aid in the design and optimization of HTHP systems.

Detailed pathway for a fast low-temperature synthesis of strongly thermochromic W-doped VO2 films with a low transition temperature

We report the discharge characteristics, and population of chosen atomic neutral (V, O and Ar) and ionic (V+, V2+, O+ and Ar+) species in the discharge during low-temperature (350 °C) depositions of W-doped VO x films onto a 170 nm thick Y-stabilized ZrO2 layer on a 1 mm thick conventional soda-lime glass. The depositions were performed using reactive deep oscillation magnetron sputtering with a pulsed O2 flow control and to-substrate O2 injection into a high-density plasma in front of the sputter V-W target. The pre-selected critical values of the oxygen partial pressure were in the range from 82 mPa to 92 mPa. Optical emission spectroscopy proved a relatively high density of O atoms in front of the substrate, which is important for production of the W-doped VO2 films. It was found that setting of the amount of O2 in the gas mixture determines not only the elemental and phase composition of the films and their deposition rate but also the crystallinity of the thermochromic VO2 phase in them. The crystalline W-doped VO2 films with a low transition temperature of 28 °C exhibited a high modulation of the solar energy transmittance of 8.9%. The results are important for further improvement of this new scalable sputter deposition technique for a fast (53 nm min−1 at a target-substrate distance of 100 mm in this work) low-temperature synthesis of high-performance durable thermochromic VO2-based multilayer coatings designed for smart-window applications.

Automation of the air conditioning system for aseptic rooms of pharmaceutical production

&lt;span lang="EN-US"&gt;As modern control systems are becoming more complex, and the implemented technology more sophisticated, the importance of the different characteristics of those systems, such as reliability, availability, security, and protection, is increasing. In this article, an automation design for the air conditioning system of classified areas of the Parenteral solutions plant of the eastern pharmaceutical laboratory company of Santiago de Cuba province, Cuba, is proposed because there is a lack of optimal environmental conditions for development and production of pharmaceuticals at a large scale. The proposal is focused on the design of a supervision system and automatic control of the environmental variables that influence the drug production process. The entire algorithm for the design was developed to monitor critical and non-critical variables and control values of temperature, relative humidity, differential pressure, and air velocity according to standards established by pharmaceutical companies. The design of the automation system includes, apart from the control and supervision algorithm for operation efficiency, the necessary instrumentation.&lt;/span&gt;

Numerical Modeling of Physical Cell Trapping in Microfluidic Chips.

Microfluidic methods have proven to be effective in separation and isolation of cells for a wide range of biomedical applications. Among these methods, physical trapping is a label-free isolation approach that relies on cell size as the selective phenotype to retain target cells on-chip for follow-up analysis and imaging. In silico models have been used to optimize the design of such hydrodynamic traps and to investigate cancer cell transmigration through narrow constrictions. While most studies focus on computational fluid dynamics (CFD) analysis of flow over cells and/or pillar traps, a quantitative analysis of mechanical interaction between cells and trapping units is missing. The existing literature centers on longitudinally extended geometries (e.g., micro-vessels) to understand the biological phenomenon rather than designing an effective cell trap. In this work, we aim to make an experimentally informed prediction of the critical pressure for a cell to pass through a trapping unit as a function of cell morphology and trapping unit geometry. Our findings show that a hyperelastic material model accurately captures the stress-related softening behavior observed in cancer cells passing through micro-constrictions. These findings are used to develop a model capable of predicting and extrapolating critical pressure values. The validity of the model is assessed with experimental data. Regression analysis is used to derive a mathematical framework for critical pressure. Coupled with CFD analysis, one can use this formulation to design efficient microfluidic devices for cell trapping and potentially perform downstream analysis of trapped cells.

Revealing the microstructures and seepage characteristics in the uncured rubber-cord composites using micro-computed tomography and lattice Boltzmann approach

The internal microstructure distribution of cord-rubber-air during the processing of uncured rubber-cord composites (URCs) determines the finished product's performance. For the first time, we used computed tomography (CT) and the lattice Boltzmann method (LBM) to establish a geometrical representation model of the real microscopic pore-fracture structures of URCs and investigate the seepage law of fluid in porous URCs, where the reinforced rubber formula was originally designed to reduce CT artifacts of cord. The results showed that the average porosity and pore radius of the original cord (0.2711 and 15.53 μm, respectively) were considerably larger than those of the URCs (0.0509 and 4.46 μm, respectively); the pore number of the cord was the largest when the pore radius was 5–10 μm, accounting for 29.36% of the total number; however, the pore number accounted for 31.36% of the total number of the URCs when the pore radius was 2–3 μm. Moreover, the characteristics of the pore/throat surface area and pore volume/throat length exhibited perfect consistent patterns with those of the pore radius. Furthermore, the fluid flow velocity increased in both cord and URCs as the displacement differential pressure increased, but decreased dramatically as the fluid kinematic viscosity increased. The critical values of displacement differential pressure and kinematic viscosity were different in the cord and URCs samples, presenting 11.1209 Pa/1.3696 × 10−3 m2/s and 14.2984 Pa/2.8869 × 10−4 m2/s, respectively. This phenomenon should be attributed that when the uncured rubber was injected into the original cord sample, its porosity decreased, its pore radius decreased, the number of micro-scale pores increased, and flow resistance became larger, resulting in a higher critical value of displacement differential pressure and a lower critical value of kinematic viscosity.

Research on stability of laminated composite plate under nonlinear aerodynamic load

In this paper, we propose an finite element approach based on classical plate theory to investigate the dynamic stability of a layered composite plate subject to nonlinear aerodynamic load. This study considers the influence of temperature, nonlinear geometry, and nonlinear aerodynamic load on composite plate structures simultaneously. Specifically, the present work conduct comparison the results of the critical pressure value between the nonlinear aerodynamic load and the linear aerodynamic load, thereby pointing out some necessary cases which must consider the nonlinearity of aerodynamic load for calculating the aerospace structures. We determine the critical pressure value and vibrational amplitude response of the plate by means of calculation. The outcomes of our calculations can be useful in designing and repairing body shells and wings of aircraft equipment.

Solving the Lamé problem in the quasi-brittle setting to substantiate the solution scheme for rock breaking by the blast-hole method

Introduction. The blast-hole method of mining and preparing rocks for excavation has been used by mankind since ancient times. However, there are no generally accepted and generally recognized design and calculation methods for this process, which was established in the review part of this work. Research objective is to develop a basic analytical model for hard rock quasi-brittle materials breaking by a blast-hole method using static thrusts. Methods of research. A detailed analysis of the breaking mechanism through the transition state from the rock material continuity to its separation is the methodological basis of the developed quasi-static model for calculating the energy-power indicators of the process of separating volumes (pieces) of rock into separate parts. It makes it possible to justify and determine: the irreversible energy of rupture through the energy constant rock material in relation to the process energy efficiency, critical load resulting in local breaking, the size and number of the primordial tension cracks, as well as the number of through cracks. Result. The obtained indicators and parameters formed the body of the energy balance equation of the irreversible energy of rupture of rock pieces. The developed methodology for setting and solving the problem of the limiting state of quasi-brittle materials rupture in the form of a thickwalled cylinder (the Lamé problem) that simulates a certain solid volume deformed by a uniformly distributed blast-hole pressure of thrusts, is universal and can serve as a base for assessing a set of issues related to mining. The resulting interrelation of indicators made it possible to derive an equation for the energy balance of the rock volumes rupture. Due to the solution for this equation, the critical value of the blast-hole pressure that results in local breaking, the size of primordial cracks, and the corresponding limiting burst pressure were obtained for the first time. Theoretical novelty. Within the framework of the general approach of the quasi-brittle materials breaking linear theory, based on the developed methodology, the problem of the limiting state of the rock in the form of natural joint loaded with a static thrust through a single blast-hole, was correctly stated and solved by the energy method for the first time. As a result of the research, an analytical dependence of the rock static breaking energy intensity was obtained, which includes both the volumetric specific energy of potential deformation and the specific surface energy

Heat transfer mechanism of electrostatic chuck surface and wafer backside to improve wafer temperature uniformity

Semiconductor manufacturing technology keeps toward scaling down to a few nanometers. To protect the process yield and achieve the success of chip manufacturing, the center-to-edge uniformity of the wafer's temperature has become a crucial parameter. The thermal characteristics of the wafer are dominantly affected by the electrostatic chuck, which is generally used to support the wafer in the manufacturing process. In particular, the backside gas, which passes through the interface between the wafer and electrostatic chuck, is important for cooling the wafer below a critical temperature. The heat transfer via a backside gas can be explained by the layer-bulk model, and its pressure is a key factor to determine the cooling effectiveness. In this paper, a one-dimensional thermal circuit model is established for a system including the wafer, electrostatic chuck, and backside gas to calculate the convective heat transfer coefficient caused by the backside gas. The numerical results showed that the uniformity of the wafer's temperature became worse as the backside gas pressure increased in a low-pressure range but significantly improved above a critical value of the gas pressure. Based on our findings, we concluded that the backside gas pressure should be optimized to improve the uniformity of the wafer temperature.

Thermodynamics, phase structure of Bardeen massive black hole in Gauss-Bonnet gravity

This work provides the exact solution of the Bardeen black hole in association with [Formula: see text] Gauss–Bonnet massive gravity in Anti-de-Sitter [Formula: see text] space–time. It is a modification of the Gauss–Bonnet when gravity couples with nonlinear matter fields which is the function of the electromagnetic field. The obtained solution gives rise to [Formula: see text] EGB Bardeen black holes when the massive gravity parameter is set to zero and it yields a [Formula: see text] Gauss–Bonnet black hole in the absence of magnetic monopole charge. Further, we analyze and adopt the thermodynamic quantities like mass ([Formula: see text]), temperature [Formula: see text] and heat capacity [Formula: see text] in the presence of massive gravity and nonlinear electrodynamics. In addition, we extend our results by considering the cosmological constant [Formula: see text] as a thermodynamical variable [Formula: see text] and obtain the critical values of pressure, temperature, horizon radius and analyze the behavior of the global parameter [Formula: see text]. The effect of a massive parameter ([Formula: see text]) of the critical exponent is opposite to the magnetic monopole charge ([Formula: see text]) and Gauss–Bonnet parameter ([Formula: see text]). According to our analysis the phase transition between a small and large black hole and van der Waals phase transition are analogous to each other.

Wear resistance of structural steels nitrided in a cyclically switched discharge with dry friction

The paper examines the method of conducting tribological studies in the dry mode of friction of nitrided and unhardened structural steels 20 and 45 in order to achieve comparable results of laboratory tests with operational characteristics. Preliminary studies of anodized steels of the same steels indicate that under conditions of extreme friction it is extremely difficult, and in some cases impossible, to use such values of specific pressure on the friction surface, at which it would be realistic to compare the results obtained for different samples made of different brands materials and processed using various technological processes. Since during the tests, constant lubrication of the friction zone was ensured, a layer of lubricant was present on the friction surface up to a certain pressure value, which led to extremely small indicators of linear wear. However, depending on the characteristics of the modified surface, there was a critical value of pressure at which the layer of lubricant was squeezed out of the friction zone, which led to instant adhesion of the surfaces. Thus, the study of wear resistance in the dry mode of friction ensures a significantly higher productivity of experiments.&#x0D; Unlike experiments with limit friction, dry friction can be used for different steels at the same pressure value, which eliminates the problem of comparability of results and contributes to the objectivity of conclusions regarding the effectiveness of various modification processes.&#x0D; According to the results of previous experiments, such a compromise pressure value can be 16 MPa.&#x0D; Another important phenomenon for the analysis of the influence of the modification results on the wear resistance characteristics of the surface is established - the effect of relaxation processes in the near-surface layers, which have already acquired structural transformations under the influence of pressure in the friction zone.&#x0D; For all steels, there is some slowing down of the intensity of wear after a break with a gradual return to the intensity characteristic of a certain brand of steel. The reason for such a phenomenon can only be the relaxation of stresses and the equalization of the characteristics of the structure in the near-surface layers. At the same time, the result is the strengthening of the surface, which explains the decrease in the intensity of the wear process. over time, as the strengthened layer breaks down, the indicators of the surface condition become equal to those before the break and the intensity of wear is restored.

Supersonic flutter of variable stiffness circular cylindrical shells

Curvilinear reinforcement fibres allow to tailor the elastic properties of composite laminates in space, leading to Variable Stiffness Composite Laminates (VSCL). In this work, the aeroelastic stability of VSCL cylindrical shells under a supersonic airflow along the axial direction is analysed in order to verify if curvilinear fibres can be used to increase the flutter speed. A linear mathematical model for thin circular cylindrical VSCL shells is developed for that purpose. The aerodynamic pressure caused by the supersonic airflow is modelled recurring to the linearised piston theory. The p-version of the finite element method is used to transform the differential equations of motion from partial to ordinary. Using the latter, eigenvalue problems are defined to obtain the natural frequencies and mode shapes of vibration, and the critical flutter conditions. Various types of curvilinear fibre paths are explored, to find paths that result in higher values of critical flutter free stream pressure. The values are compared with the ones of conventional, constant stiffness, composite laminated shells.