Effect Of Pressure Variation Research Articles

Enlightening the hydrostatic pressure variation effect on physical properties of mechanically stable La2Ge2O7 pyrochlore oxide: Insights from first principles for solar cell advancement

Enlightening the hydrostatic pressure variation effect on physical properties of mechanically stable La2Ge2O7 pyrochlore oxide: Insights from first principles for solar cell advancement

The Effect of Pressure Variations on the Electronic Structure, Phonon, and Superconducting Properties of Yttrium Hydrogen Selenide Compound

The Effect of Pressure Variations on the Electronic Structure, Phonon, and Superconducting Properties of Yttrium Hydrogen Selenide Compound

Assessing the effects of pressure variations on combustion dynamics in vortex-tube flows

In our investigation, we scrutinize combustion stability in vortex-tube combustion at high operating pressures by examining stability limits, flame configurations, and pressure oscillations. Our examination deeply probes the intricacies of flow and flame behaviors in terms of aerodynamic, thermodynamic, and flamedynamic aspects to identify the fundamental reasons behind stability variances at different pressure levels. The findings indicate that combustion instability escalates with rising operating pressures, marked by increased variability in flame patterns and a monotonic upsurge in pressure oscillation amplitudes. Although aerodynamic and thermodynamic stabilities remain unaffected, the thermoacoustic stability is compromised at elevated pressures. This is evidenced by the strong link between the Rayleigh criterion and the amplitude of pressure fluctuations, with an increased “gain” in the flame transfer function as pressure mounts. The core of the observed thermoacoustic instability is traced back to heightened density variations and mean flow velocities at high pressures, leading to amplified momentum flux oscillations.

Doping and Pressure Effects on Yttrium Hydrogen Selenide

In this paper, the structural, electronic, phonon, and optical properties of lanthanum (La)‐doped yttrium hydrogen selenide (YHSe), along with the effects of pressure variations on its optical properties, are investigated using the density functional theory method. Both the La‐doped and YHSe systems are dynamically stable, as indicated by phonon calculations showing no imaginary frequencies in the Brillouin zone (BZ). The influence of pressure on optical properties is examined, revealing that increased pressure enhances these properties, particularly by improving the absorption coefficient in the ultraviolet (UV) range. Moreover, the bandgap energy of both La‐doped YHSe and YHSe compounds is explored. Increasing La concentration reduces the bandgap and enhances the density of states (DOS) at Fermi energy, inducing metallic characteristics in YHSe. Furthermore, the optical properties are examined at various La concentrations, most of which exhibit a nonlinear relationship as the La concentration increases. Doping under extreme conditions significantly enhances the optical properties of La‐doped YHSe, particularly in the UV‐light wavelength range. Specifically, the absorption coefficient reaches its maximum value in the energy range of 6.678 −13.023 eV within the UV region for all concentrations, indicating strong absorption in this range. This suggests the material’s effectiveness in absorbing electromagnetic radiation, particularly in the UV range, making it a promising candidate for photochromic applications. A thorough exploration of the optical properties under doping reveals prominent peaks, particularly in response to the UV spectrum, with a slight shift toward higher energies beyond the UV range. This suggests that the material under study holds promise as a candidate for sustained photochromic performance over time.

Fabrication and characterization of a rapid-response, ultrasensitive dual-head interferometric pressure sensor.

A novel, to the best of our knowledge, dual-head Michelson interferometer-based pressure sensor with ultrahigh sensitivity and rapid response has been fabricated and optimized. The sensor consists of two diaphragm-based sensing heads, which operate on the principle of path-length variations of the interferometers due to the effect of pressure variation within the pressure channel. Pressure has been measured independently by the heads in terms of the fringe counts across two photodetectors with different sensitivities and working ranges. Head 1 had a linear working range of 0-6psi and a sensitivity, resolution, and response time of 1295.04 fringe counts/psi, 25.74µpsi, and 0.86ms, respectively, which were 2.46, 2.46, and 0.86 times better than those of head 2. However, head 2 had a larger working range of 0-15psi. Heads 1 and 2 yielded repeatable responses with negligible hysteresis and an average absolute error of 0.55% and 0.58%, respectively, compared to the predicted results. The proposed sensor has great potential for use in laboratory and industrial nonintrusive precise and fast-response pressure sensing applications.

Autogenerative high-pressure anaerobic digestion modelling of volatile fatty acids: Effect of pressure variation and substrate composition on volumetric mass transfer coefficients, kinetic parameters, and process performance

Pressurised anaerobic digestion is a valuable process that allows the production of biogas with a high methane content, reducing the energy costs for the biogas upgrading and injection into the distribution grid. This technology has attracted scientific research attention in the last decade, and kinetic models have been formulated. In this work, a modified Anaerobic Model Digestion n.1 of an autogenerative high‑pressure anaerobic digestion of volatile fatty acids in batch configuration is proposed by evaluating the effect of increasing the autogenerative pressure in the reactor on the prediction of the dynamic performances and kinetic parameters. Experimental results from the literature were used for developing, calibrating, and validating the model. Results highlighted the dependence of the mass transfer coefficient of the main component of biogas on the increasing autogenerative pressure: the higher the pressure, the higher the volumetric mass transfer coefficient. At atmospheric pressure, the volumetric mass transfer coefficient is almost equal (about 0.065–0.067 1/s). By increasing the pressure, H2 showed the highest value (0.098 1/s at 20 bar), while for CH4 and CO2, comparable values were assessed (0.085 1/s at 20 bar). Results also highlighted the effect of the pressure variation on acetate, butyrate, and propionate Monod maximum specific uptake rate, half saturation value, the first order decay rate, and the Upper and Lower pH levels for acetate degraders. Moreover, hydrogen produced during the process was considered an additional substrate, for which the kinetic parameters were assessed. Finally, simulation findings are consistent with the literature data in terms of volatile fatty acid consumption.

Effect of pressure variations on film boiling characteristics of liquid nitrogen

Liquid nitrogen is a widely used cryogenic fluid in various industrial and scientific applications. Film boiling is inevitable when a hot surface is exposed to a cryogenic fluid like liquid nitrogen. This mode of boiling can affect the heat transfer rate and cooling efficiency of the process. The present study investigated the effect of operating pressure on film boiling characteristics of liquid nitrogen using continuum-based numerical simulations. Simulations were performed at atmospheric, intermediate, and near-critical pressures using a coupled level-set and volume of fluid method of interface tracking. Bubble dynamics and heat flux variations were examined at different degrees of wall superheat. The results show that the pressure condition significantly affects the bubble dynamics and boiling of liquid nitrogen. At higher pressure, the specific heat of the vapor phase increases, resulting in a higher heat transfer rate. It was also noted that at high levels of superheat, the bubbles detach from the heating surface faster, resulting in a higher transfer of heat. The effect of pressure on the number of bubble formation sites was also investigated. The simulations also reveal that the local thermodynamic conditions, such as pressure, temperature, and vapor concentration, significantly influence the bubble size.

Reduction of TSS, COD, Oil and Fat in Palm Oil Mill Waste Using Dissolved Air Flotation Method

This study aims to determine the effect of variations in pressure and contact time of wastewater with air to decrease the parameters of TSS, COD, and oils and fats contained in palm oil wastewater. This study uses a series of Dissolved Air Flotation (DAF) process units with the addition of Poly Aluminum Chloride (PAC) coagulant. This research begins with the manufacture of a series of DAF tanks and flotation tanks. Waste flow is carried out in batches and the air is flowed upflow through the bottom hole of the DAF tank. The pressure variables used in decreasing the parameters of TSS, COD, and oil and fat are absolute 2; absolute 2.5; and absolute 3 atm. The contact time variables for decreasing TSS, COD, and oil and fat parameters were 15, 30, 45, 60, and 75 minutes. The results showed a decrease in each of the tested parameters. The effective pressure to reduce the value of the TSS parameter is the absolute pressure of 3 atm and the absolute pressure of oil and grease is 2.5 atm. While the effective pressure to reduce the value of the COD parameter is an absolute pressure of 3 atm. The best contact time between air and wastewater to set aside the values of the TSS, COD, and oil-fat parameters was 75 minutes.

The effect of pressure changes during simulated diving on the shear bond strength of orthodontic brackets.

This study investigated the effect of pressure variations to which divers are subjected on shear bond strength of orthodontic brackets bonded to teeth with resin modified glass ionomer cement (RMGIC) or composite resin. Eighty extracted premolars were randomly divided into two groups. Group 1: orthodontic brackets were bonded with RMGIC. Group 2: orthodontic brackets were bonded with composite resin. Each group was further divided into two subgroups. Subgroup A: The samples were kept at sea level pressure (101 kPa). Subgroup B: The samples were pressurised once from 101 kPa to 405 kPa for five minutes, then depressurised to 101 kPa. Shear bond strength was then measured. Shear bond strength of brackets bonded with RMGIC in the simulated diving group was significantly less than that of ambient pressure group (P = 0.019), while no significant difference was found between the simulated diving group and ambient pressure group for brackets bonded with resin cement (P = 0.935). At ambient pressure, there was no significant difference between shear bond strength of brackets bonded with RMGIC and composite resin (P = 0.83). In simulated diving conditions, there was a statistically significant difference between shear bond strength of brackets bonded with the RMGIC and composite (P = 0.009). Pressure changes during scuba diving may have an adverse effect on the retention of brackets bonded with RMGIC. Using composite resin for bonding brackets appears to be good strategy for patients such as divers who will be exposed to pressurised environments.

THE EFFECT OF VARIATION OF ZEOLITE AS ADSORBENT MEDIUM AND ADSOPTION PRESSURE TOWARD THE QUALITY OF OXYGEN PRODUCED FROM PRESSURE SWING ADSORPTION (PSA)

One of the most important element in human life is oxygen. To produce good quality of oxygen, a purification process is needed. Pressure Swing Adsorption with the adsobent of zeolite is the most comon method used for oxygen purification. This study aimed to find out media variation of of zeolite as adsorbent medium and adsoption pressure toward oxygen quality produced from PSA. Variation of adsrobent medium used were 13X zeolite and combination of 13X zeolite and Bayah zeolite (zeolite 13X+ZAB). The study result shows that the use of 13X zeolite and 13X+ZAB zeolite can significanly increase the quality of oxygen in PSA compare to without using zeolite. The use of 13X zeolite produce higher quality of oxygen, this is because 13X zeolit is a zeolite which has high ability to adsorb nitrogen and 13X zeolite has high surface area. The higher the adsorbent surface area the more adsorbat was adsrobed so that 13X zeolite will adsorb niotrogen. Meanwhile the addition of Bayah natural zeolite into 13x zeolite (13X zeolite +ZAB) is to overcome the problem of the vapor releasing which can hinder the performance of PSA in certain period of time, so that it is needed one media of adsorbent of natural zeolite which can adsorb liquid produced from this PSA. The effect of pressure variation toward oxigen quality produced from PSA is that the higher the pressure applied the faster the process of lowering the quality of oxygen would be, this is because the adsorben was more saturated. The pressure highly affect the adsorbability occur in PSA colomn.

ANALISA VARIASI TEKANAN, TEMPERATURE, UKURAN RUNNER TERHADAP FILLING TIME OPTIMAL PADA INJEKSI MOLDING

AbstractPlastic based packaging systems for food box lid products receive special attention from manufacturers and the most common process is injection molding. This study aims to analyze the effect of variations in pressure, temperature, and runner size on filling time in the injection molding process for food box products using Autodesk Inventor 2015 software in order to obtain the optimal filling time. Experiments in the form of simulations were carried out by entering data on variations in pressure, temperature, and runner size. The results of this study obtained the optimal filling time at the melting temperature setting of 220℃, injection pressure of 90 Mpa, mold temperature of 40℃, and runner diameter of 6 mm. The optimal type of gate tunnel and runner circle type has a filling time analysis result of 0.34 seconds. Defects that occur during the injection molding simulation process are weld lines, air traps and short-shots. Based on these problems, a mold unit was designed with a two plate mold system type. Keywords: Plastic, Injection Molding, Experiment, Lid Food Box, Inventor, Mold.

Insights from molecular dynamics on CO2 diffusion coefficient in saline water over a wide range of temperatures, pressures, and salinity: CO2 geological storage implications

Successful design and execution of CO2 sequestration in saline aquifers requires a comprehensive understanding of CO2 transport properties. CO2 diffusion coefficient affects CO2 dissolution behavior in water/brine and controls phenomena such as shape of viscous fingers and onset of instabilities. Experimental determination of CO2 diffusion coefficient is a technically and economically challenging task. In this research work, we used Molecular Dynamics (MD) simulation to compute CO2 diffusion coefficient in various NaCl saline water concentrations (1–6 mol NaCl/kg water) under a broad range of temperatures (294–423 K) and pressures (10–30 MPa) to acquire a data set for CO2 diffusion coefficient in different conditions. According to the results, NaCl concentration increase gives rise to a decrease in CO2 diffusion coefficient by 15%, 29%, 49%, and 64% at 1 M, 2 M, 4 M, and 6 M solutions, respectively, compared to pure water. Presence of more cations due to salinity increase forms further hydration shells act as a barrier for CO2 diffusion. In addition, the rise in CO2 diffusion at elevated temperatures can be explained by the cation's hydration shell size reduction with temperature increment due to intensifying repulsive forces among water molecules. We proposed a new precise correlation for estimation of CO2 diffusion coefficients over temperatures and salinity ranges of this study. Regarding the pressure variation effects, no tangible changes were observed with pressure increase, validating a negligible influence on diffusion coefficient. Furthermore, the CO2 diffusion coefficient variability in presence of other salts, namely MgCl2, CaCl2, KCl, and Na2SO4, were computed separately. Comparing the influence of various salts, CaCl2 and KCl have the highest and lowest effect on the CO2 diffusion coefficient, respectively. Finally, a set of direct numerical simulations were conducted to study the impact of CO2 diffusion coefficient on CO2 dissolution process. The results obtained from this research work shed light on the importance of CO2 diffusion coefficient changes in saline water for prediction of dissolution process behavior.

Deformation of pores in response to uniaxial and hydrostatic stress cycling in Marcellus Shale: Implications for gas recovery

One of the main challenges during gas production from shale reservoirs is low recovery rate. One contributing factor to this outcome is an insufficient understanding of pore systems, especially pore behavior following changes in reservoir conditions or resulting from gas production practices. Because the pressure in the producing well can be controlled, understanding the effects of pressure variation on the pore size distribution and methane trapping is necessary to help design optimal conditions to improve the gas recovery rate. This work is the first systematic study of sub-millimeter pore deformation in shale caused by uniaxial and hydrostatic stress up to 100 MPa. Overmature samples from the Middle Devonian Marcellus Shale were analyzed using neutron scattering (SANS and USANS) techniques to interpret the response of nanopores to stress cycling of magnitude and duration compatible with the hydraulic fracturing treatments. Experiments reported here are performed at a series of uniaxial pressures up to 100 MPa and at hydrostatic pressures of deuterated methane 0 and 50 MPa. Since at the original depth of the shale samples' burial of 2184 m the hydrostatic pressure is approximately 27 MPa and the lithostatic pressure is about 55 MPa, the experimental conditions reasonably well simulate the reservoir pressure regime.Our SANS and USANS results show that different pore sizes are affected by uniaxial stress in different ways. Specifically, in the pore size range from 1 nm to 800 nm, a decrease of pore density with pressure is observed, with the most depleted being mesopores of about 100 nm in diameter. The observed decrease is likely related to deformation of kerogen, followed by a loss of pore nano-volume, as well as methane trapped in the micropores. For pores larger than 5 μm, USANS data suggest that the negative trend is reversed at above 74 MPa, and the number density of large macropores may increase with increased stress even above the original value. The increased number of macropores at high pressure may create new interconnected conduits for gas migration, resulting in a better recovery rate. Another important finding of this study is an irreversible rearrangement of pore size distribution taking place after pressure cycling. This irreversible reorganization of pore size distribution should be taken into account during management of well production to maximize recovery rate.

Effect of Hydrostatic pressure on structural, electronic, optical and mechanical properties of Lanthanum Oxide (La2O3)

Effect of pressure variation on structural, electronic, optical, and mechanical properties of lanthanum oxide (La2O3) have been investigated by using Cambridge Serial Total Energy Package (CASTEP) under reference of density functional theory (DFT) for ab initio calculations with plane wave basis set and pseudopotentials. The complete investigation of material demands calculations of many nuclei system on quantum scale and many nuclei system needs large simulations to predict accurate answers. DFT offers feasible solution of this complexity and allows investigation of materials on quantum scale accurately and precisely by considering electron density and finite k-points in Brillouin Zone (BZ).La2O3 is compressible under the effect of applied high pressure but not offer any phase or structural transformation state 0 GPa to 50 GPa. The properties of lanthanide materials can be controlled to a large extent and relative energy by considering behavior of 4f and 5d electrons behavior. The application of pressure from 0 to 50 GPa reveals a predominant characteristic associated with narrowing of bandgap. All the calculated optical properties such as the complex dielectric function ε(ω), optical conductivity σ(ω), energy loss function L(ω), absorption coefficient α(w), refractive index n (ω), reflectivity R (ω), and effective number of electrons neff, via sum rules shift towards the lower energies under the application of pressure. The influence of pressure on elastic constants and their related mechanical parameters have been discussed in detail.

Ab initio study of structural, opto-electronic, elastic, and thermal properties of KZnF3

In the present study, a theoretical model of potassium-based zinc perovskite (KZnF3) is investigated via structural, electronic, elastic, mechanical, optical, and thermal properties. In addition, lattice dynamics and effect of pressure variation on structural and electronic properties have also been observed. All said calculations are done within the framework of density functional theory (DFT). To authenticate our work we use several exchange correlation functionals. The calculated structural parameters, including cohesive energy, are in accordance with previous experimental and available theoretical studies. The decrease in lattice constant as well as bond lengths is noted with increase in pressure from 0 to 50 GPa. Electronic properties reveal that this material possess an indirect (R–Γ) bandgap while increase in pressure reveals widening of the bandgap. The elastic and mechanical properties show that (KZnF3) is mechanically stable in the cubic phase with predominantly ionic character. The evaluated optical responses of the KZnF3 compound are studied in terms of imaginary and the real parts of the dielectric function ε(ω), refractive index n(ω), reflectivity R(ω), and absorption coefficient α(ω). All of the optical parameters are in good accordance with electronic aspects. Finally, several thermal parameters are calculated, such as unit cell volume, entropy, and heat capacity (Cv) using the quasi-harmonic Debye model.

Simultaneous measurement of effective thermal conductivity and effective thermal diffusivity of Li2TiO3 pebble bed using transient hot-wire technique

Lithium-based ceramics in the form of pebble beds have been considered for tritium breeder material in the fusion reactor's breeder blanket. It is essential to study the thermal characteristics of these ceramic pebble beds subjected to fusion relevant conditions. Effective thermal conductivity (k), effective thermal diffusivity (α) and effective specific heat (cp) of a packed bed are some of the crucial parameters for the design of breeder blanket module. In the present study, the transient hot-wire technique was used to measurek, α and cp of lithium metatitanate (Li2TiO3) pebble bed fabricated at Institute for Plasma Research, India. Thermal properties of Li2TiO3 pebble bed (1 ± 0.15 mm pebble diameter and ∼63% packing fraction) are measured within the temperature range of 45 °C to 800 °C in stagnant helium gas environment. The filling gas pressure variation effect on the Li2TiO3 pebble bed's thermal properties for the pressure range of 0.105 MPa to 0.4 MPa has also been studied. Equations are suggested for k and α of Li2TiO3 pebble bed as a function of temperature at different pressure in the helium gas environment.

Pengaruh Variasi Tekanan Terhadap Kerapatan, Kadar Air Dan Laju Pembakaran Pada Biobriket Limbah Kayu Mahoni

Abstract— The use of biomass from mahogany wood waste briquettes as a substitute fuel for oil and gas requires briquette technology. Mahogany wood briquette is able to convert into fuel with a fairly good conversion efficiency, high density and ease of storage and distribution. The purpose of this study was to determine the effect of pressure variations on the density, moisture content and rate of burning of mahogany wood waste briquettes. The process of making charcoal biobriquettes begins with the carbonization process with a temperature of 400 ̊C, then smoothed and sieved with a size of 80 mesh - 100 to get the same size, and using tapioca adhesive 30% of the weight of the mixture. The mixture is put into a molding machine and then printed with a pressure of 80 kg/cm2, 115 kg/cm2, 150 kg/cm2, and 185 kg/cm2. Charcoal biobriquettes are dried in an oven at 105 ̊C for 1 hour. In this research, the mass density and moisture content of the mahogany wood waste met the Indonesian biobriquette standards, the results of this study obtained the higher density of 0,55 g/cm3at a pressure of 150 kg/cm2. The results lowest water content of 47,2% at a pressure of 185 kg/cm2. The lowest combustion rate is 0,257 g/min at a pressure of 185 kg/cm2. Keywords—: mahoni wood waste; pressure; moisture content; combustion rate.

The effect of pressure variation on droplet size distribution of dispersed oil under simulated deep-water conditions

Droplet size distribution of dispersed oil in deep-water is critical to the transport and biodegradation of spilled oil in deep-sea. Few studies have focused on the effects of pressure on chemically dispersed oil through experiments. This study thus simulated how the crude oil homogenously pre-dispersed by Corexit 9500A using baffled flasks would behave after being exposed to deep-water conditions. Key factors included dispersant-to-oil ratio (DOR), mixing energy (energy dissipation rate and Kolmogorov microscale), and pressure (up to 150 bar). The variations of pressure were demonstrated to have insignificant effects on the size distribution of pre-dispersed oil. Both the average and medium droplet sizes were correlated negatively with DOR and mixing energy in an established model with a p-value ≤ 0.0011. The log-normal and log-logistic distributions provided a reasonable fit to simulate the droplet size distribution. The two parameters of log-logistic distribution were dependent on DOR and mixing energy with a p-value < 0.005. The results would be valuable to advance the understanding of the behaviours and trajectories of chemically dispersed oil under deep-water conditions. The research helped provide more scientific evidence to improve the understanding of dispersed oil behaviours under high pressure and support deep-sea oil spill research and potential extension of the existing results from shallow water to deep water conditions.

Stabilization of Supramolecular Polymer Phase at High Pressures.

We utilize dynamic light scattering (DLS) and passive microrheology to examine the phase behavior of a supramolecular polymer at very high pressures. The monomer, 2,4-bis(2-ethylhexylureido)toluene (EHUT), self-assembles into supramolecular polymeric structures in the nonpolar solvent cyclohexane by means of hydrogen bonding. By varying the concentration and temperature at atmospheric pressure, the formation of the viscoelastic network (at lower temperatures) and predominantly viscous phases, based on self-assembled tube and filament structures, respectively, has been established. The associated changes in the rheological properties have been attributed to a structural thickness transition. Here, we investigate the effects of pressure variation from atmospheric up to 1 kbar at a given concentration. We construct a temperature-pressure diagram that reveals the predominance of the viscoelastic network phase at high pressures. The transition from the viscoelastic network organization of the tubes to a weaker viscous-dominated structure of the filaments is rationalized by using the Clapeyron equation, which yields an associated volume change of about 8 Å3 per EHUT molecule. This change is further explained by means of Molecular Dynamics simulations of the two phases, which show a decrease in the molecular volume at the filament-tube transition, originating from increased intermolecular contacts in the tube with respect to the filament. These findings offer insights into the role of pressure in stabilizing self-assemblies.

Effects of Temperature and Pressure on Purge Gas Chemical Compositions in Tritium Breeding Blanket

The effects of temperature and pressure conditions on the equilibrium chemical compositions of purge gas at the outlet of the test blanket module (TBM) in the helium-cooled ceramic reflector (HCCR) are studied. As the chemical species in the equilibrium states, nine chemical species are considered: H, T, O, H2, HT, T2, H2O, HTO, and T2O. The mole fractions of these chemical species are calculated using a Gibbs free energy minimization method starting from the initial state of a H2-HTO mixture. The standard Gibbs free energies for the tritium species used in the study are calculated from the molecular constants obtained by a coupled-cluster calculation. The effects of pressure variations on the equilibrium compositions are shown to be negligible. The effects of temperature variations are also insignificant when the temperature exceeds 800 K. When the initial H2/HTO ratio is more than 10, more than 90% of tritium is expected to be recovered in the form of HT.