Pressure Gas Research Articles

Optimization and analysis of the inflow distribution influence on the middle discharge blow tank pneumatic conveying characteristics

The influence of different inflow gas distribution modes on the pneumatic conveying characteristics of the middle discharge blow tank was studied using an in-house pneumatic conveying experimental setup. The flow rates of pressurized gas, supplementary gas, and fluidized gas were varied in this study. The gas distribution mode was then optimized to improve the energy efficiency of the blow tank of a pneumatic conveying system. The results show that the particle mass flow rate, the solid-to-gas ratio, and the pressure drop increase first and then decrease with the pressurized gas and fluidized gas valves opening. In the case of supplementary gas, the particle mass flow rate and solid-to-gas ratio increase first and then decrease. However, an opposite trend is observed for the pressure drop, which decreases first and then increases. The results highlighted that the optimized gas distribution mode increases the mass flow rate of particles and the solid-to-gas ratio by 28.48% and 15.15%, respectively. The pressure drop of the blow tank has also increased slightly, by 0.88%. Therefore, the delivery capacity and efficiency of the middle discharge blow tank are greatly improved at the cost of a slight increase in energy consumption.

Numerical study of gas pocket distribution and pressurization deterioration mechanism in a centrifugal pump

In the event of a loss-of-coolant accident at a nuclear power plant, a large amount of steam enters the main pump, causing the pump's pressurization to deteriorate or even fail. To reveal the deterioration mechanism of the pump performance, the gas-liquid distribution characteristics in the centrifugal pump were studied by using structured grids and the Eulerian-Eulerian model. Based on the dimensional analysis method, a predictive correlation for bubble size was established, which included factors such as inlet gas volume fraction (IGVF), rotational speed, liquid flow rate, and impeller geometric parameters. When the predictive correlation is applied to the numerical simulation, the numerical two-phase pressurization agrees well with that obtained from the experiment. As the IGVF increases, the gas begins to accumulate at the impeller inlet under the effect of the pressure gradient force. Due to the large increase in liquid velocity, the gas begins to accumulate from the middle of the diffuser flow channel. The area occupied by the gas pocket in the impeller loses its pressurization capability. The pressure vortex formed at the inlet of the channel causes the diffuser to lose its pressurization capacity. An increase in rotational speed and a decrease in liquid flow rate can effectively prevent the formation and development of gas pockets in the impeller.

Evaluation and management of dyspnea as the dominant presenting feature in neuromuscular disorders.

Dyspnea is a common symptom in neuromuscular disorders and, although multifactorial, it is usually due to respiratory muscle involvement, associated musculoskeletal changes such as scoliosis or, in certain neuromuscular conditions, cardiomyopathy. Clinical history can elicit symptoms such as orthopnea, trepopnea, sleep disruption, dysphagia, weak cough, and difficulty with secretion clearance. The examination is essential to assist with the diagnosis of an underlying neurologic disorder and determine whether dyspnea is from a cardiac or pulmonary origin. Specific attention should be given to possible muscle loss, use of accessory muscles of breathing, difficulty with neck flexion/extension, presence of thoraco-abdominal paradox, conversational dyspnea, cardiac examination, and should include a detailed neurological examination directed at the suspected differential diagnosis. Pulmonary function testing including sitting and supine spirometry, measures of inspiratory and expiratory muscle strength, cough peak flow, sniff nasal inspiratory pressure, pulse oximetry, transcutaneous CO2, and arterial blood gases will help determine the extent of the respiratory muscle involvement, assess for hypercapnic or hypoxemic respiratory failure, and qualify the patient for noninvasive ventilation when appropriate. Additional testing includes dynamic imaging with sniff fluoroscopy or diaphragm ultrasound, and diaphragm electromyography. Polysomnography is indicated for sleep related symptoms that are not otherwise explained. Noninvasive ventilation alleviates dyspnea and nocturnal symptoms, improves quality of life, and prolongs survival. Therapy targeted at neuromuscular disorders may help control the disease or favorably modify its course. For patients who have difficulty with secretion clearance, support of expiratory function with mechanical insufflation-exsufflation, oscillatory devices can reduce the aspiration risk.

Dose titration of intravenously administered gamma-hydroxybutyric acid for sedation in Holstein-Friesian calves

Gamma-hydroxybutyric acid (GHB) is a short-chain fatty acid that can potentially provide safe, prolonged sedation with minimal cardiorespiratory effects. This preliminary trial, performed in 10 three-week-old male Holstein-Friesian calves, investigated the effects of GHB administered intravenously over 5 min at a dose of 100 (G100, n=2), 150 (G150, n=4) or 200 mg/kg (G200, n=4). Once lateral recumbency was achieved, scores for sedation depth (range: 0 = no sedation to 3 = marked) and response to noxious stimulation (range: 0 = strong to 3 = absent), heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP) and arterial blood gases were monitored every 15 min until sternal recumbency. Times from end of administration to lateral recumbency and return to sternal/standing positions were recorded. Dose G100 resulted in mild sedation and ataxia without decubitus. Doses G150 and G200 respectively resulted in time to lateral recumbency 8 ± 2 and 9 ± 3 min, lasting 189 ± 41 and 283 ± 29 min, while overall median (range) scores for sedation were 3 (1−3) and 3 (2−3) respectively and response to noxious stimulation 0 (0−3) and 0 (0−3) respectively. The mean ± SD for HR was 110 ± 10 and 106 ± 11 bpm respectively; for MAP 87±9 and 94±5 mmHg respectively; and for RR 28 ± 5 and 26 ± 5 bpm respectively. The mean ± SD for arterial partial pressure of oxygen (PaO2) at these two dose rates was 74 ± 6 and 74 ± 2 mmHg respectively, while the arterial partial pressure of carbon dioxide oxygen (PaCO2) was 53 ± 3 and 47 ± 0.8 mmHg respectively. Based on these preliminary results we conclude that GHB has the potential to be used as a long-acting sedative in calves. Further studies are needed to confirm this.

Pneumatic Piston Control Optimization

Abstract Piston control can be applied to regulate position, speed, acceleration, and force. The primary distinction between pneumatic and hydraulic cylinders lies in the working fluid: hydraulic systems utilize practically incompressible fluid, whereas pneumatic systems use compressible gas. Consequently, hydraulic cylinders offer more precise control over position and speed. In contrast, pneumatic cylinders are more influenced by external loads. However, pneumatic systems are simpler, more cost-effective than hydraulic systems, and more commonly used in laboratories, workshops, and production lines. They are typically employed for end-to-end motions [1] without requiring precise position control within the stroke. If a method to control pneumatic cylinders for intermediate positions within the stroke were developed, their application could be significantly expanded. In the paper titled “Pneumatic Piston Control Modelling and Optimization,” a method for controlling pneumatic pistons for industrial applications is presented [2]. Since then, the initial modelling has been further developed through practical experiments and fine-tuning. This paper summarizes the modelling efforts and introduces the experimental results.

A Lab-scale Investigation of the Mars Kieffer Model

The Kieffer model is a widely accepted explanation for seasonal modification of the Martian surface by CO2 ice sublimation and the formation of a “zoo” of intriguing surface features. However, the lack of in situ observations and empirical laboratory measurements of Martian winter conditions hampers model validation and refinement. We present the first experiments to investigate all three main stages of the Kieffer model within a single experiment: (i) CO2 condensation on a thick layer of Mars regolith simulant; (ii) sublimation of CO2 ice and plume, spot, and halo formation; and (iii) the resultant formation of surface features. We find that the full Kieffer model is supported on the laboratory scale as (i) CO2 diffuses into the regolith pore spaces and forms a thin overlying conformal layer of translucent ice. When a buried heater is activated, (ii) a plume and dark spot develop as dust is ejected with pressurized gas, and the falling dust creates a bright halo. During plume activity, (iii) thermal stress cracks form in a network similar in morphology to certain types of spiders, dendritic troughs, furrows, and patterned ground in the Martian high south polar latitudes. These cracks appear to form owing to sublimation of CO2 within the substrate, instead of surface scouring. We discuss the potential for this process to be an alternative formation mechanism for “cracked” spider-like morphologies on Mars. Leveraging our laboratory observations, we also provide guidance for future laboratory or in situ investigations of the three stages of the Kieffer model.

Non-thermal atmospheric pressure gas discharge plasma enhances tendon-to-bone junction repair in a rabbit model

Non-thermal atmospheric pressure gas discharge plasma enhances tendon-to-bone junction repair in a rabbit model

Numerical Modeling of the Interaction of a Monodisperse Gas Suspension with a Shock Wave Moving at an Angle to the Separation Boundary of a Homogeneous Gas and a Gas Suspension

The work is devoted to the study of the influence of the dispersed phase on the dynamics of gas suspensions during numerical modeling of the dynamics of gas suspensions. In this study, based on the continuum technique of dynamics of inhomogeneous media, the interaction of a shock wave propagating from a homogeneous gas with a gas suspension was numerically simulated. For each of the components of the mixture, a complete hydrodynamic system of equations of motion was solved, which included the equations of conservation of density, the equations of conservation of the spatial components of the momentum of the mixture components, and the equations of conservation of energy of the components. The carrier medium was described as a viscous, compressible heat-conducting gas. The mathematical model took into account interfacial heat transfer. The mathematical model also took into account the interphase exchange of momentum, which included the force of aerodynamic drag, the dynamic force of Archimedes and the force of added masses. The system of equations of the mathematical model was integrated using the finite difference method. To suppress numerical oscillations, a nonlinear correction scheme was used. Large volumetric contents of the dispersed phase were considered. The influence of interfacial interaction on the process of shock wave propagation has been studied.

Study on Nonlinear Parameter Inversion and Numerical Simulation in Condensate Reservoirs

The B6 metamorphic buried hill condensate gas reservoir exhibits a highly compact matrix, leading to a rapid decline in bottom-hole pressure during initial production. The minimal difference between formation and saturation pressures results in severe retrograde condensation, with multiphase flow further increasing resistance. Conventional numerical simulations often overestimate reservoir energy supply due to their failure to account for this additional resistance, leading to inaccuracies in bottom-hole pressure predictions and gas–oil ratio during history matching. To address these challenges, this study conducted research on nonlinear numerical simulation for buried hill condensate gas reservoirs and established a method for calculating a multiphase pressure sweep range based on the well testing theory. By correcting and fitting the pressure propagation boundaries with numerical simulation, the nonlinear flow parameters applicable to the B6 gas field were inversed. This study revealed that conventional Darcy flow is inadequate for predicting pressure propagation boundaries and that it is possible to reasonably characterize the pressure sweep range through nonlinear flow. This approach resulted in an improvement in the accuracy of historical matching for bottom-hole pressure and gas–oil ratio, which improve the historical fitting accuracy to 85%, providing valuable insights for the development of similar reservoirs.

High-velocity compressible gas flow modelling through porous media considering the quadratic pressure gradient: Part 2. experimental investigations and numerical analysis

This research investigates reliability of existing methods for analysis of transient Pressure Pulse Decay (PPD) test results. Analysis of experimental data reported by previous studies using existing conventional analysis methods revealed significant discrepancies, in some cases with more than 300% error between different experiments on the same sample. New experiments (Knudsen number ranged from 0.22 to 0.34) were designed and conducted in our laboratory, reducing the uncertainty by eliminating slip flow and net stress effects under low and high-pressure conditions. These experimental results aligned much better with the recently proposed analytical solution for improved interpretation of PPD experimental results. The differences are around 25% between different pulses, confirming the reliability of the conducted experiments and newly proposed methodology.Numerical simulations using a commercial software package were conducted to complement experimental and analytical findings. The simulator, which demonstrated good agreement with the proposed analytical solution, facilitated conducting sensitivity analyses on permeability variations and compressive storage capacity effects. These simulations validated the findings of the proposed analytical solution, which accounts for both pressure difference and absolute pressure values, and explains the discrepancies observed in lower pressure scenarios using conventional methods.Overall, this study presents a comprehensive framework integrating experimental, analytical, and numerical approaches to enhance our understanding and better analysis of transient PPD test results for compressible gas flows. The findings also offer a more robust approach for analysing gas flow behaviour in porous media.

A note on higher-order and nonlinear limiting approaches for continuously bounds-preserving discontinuous Galerkin methods

In Dzanic (2024) [12], a limiting approach for high-order discontinuous Galerkin schemes was introduced which allowed for imposing constraints on the solution continuously (i.e., everywhere within the element). While exact for linear constraint functionals, this approach only imposed a sufficient (but not the minimum necessary) amount of limiting for nonlinear constraint functionals. This short note shows how this limiting approach can be extended to allow exactness for general nonlinear quasiconcave constraint functionals through a nonlinear limiting procedure, reducing unnecessary numerical dissipation. Some examples are shown for nonlinear pressure and entropy constraints in the compressible gas dynamics equations, where both analytic and iterative approaches are used.

Exact cosmological solutions for a Chaplygin Gas in anisotropic petrov type D spacetimes in Eddington-inspired-Born-Infeld gravity: Dark Energy model

We consider a Petrov Type D physical metric g, an auxiliary metric q and a Chaplygin Gas of pressure P in Eddington-inspired-Born-Infeld theory. From the Eddington-inspired-Born-Infeld-Chaplygin Gas equations, we first derive a system of second order nonlinear ordinary differential equations. Then, by a suitable change of variables, we arrive at a system of first order linear ordinary differential equations for the non-vanishing components of the pressure P, the physical metric g and the auxiliary metric q. Thanks to the superposition method, we collect an analytical solution for the nonlinear system obtained, which allows to retrieve new exact cosmological solutions for the model considered. By studying the Kretschmann invariant, we see that a singularity exists at the origin of the cosmic time. By the Kruskal-like coordinates, we conclude that this solution is the counterpart of the Friedman-Lemaître-Robertson-Walker spacetime in the Eddington-inspired-Born-Infeld theory. The Hubble and deceleration parameters in both directions of the physical metric g and the auxiliary metric q, as well as their behaviours over time, are also studied. The thermodynamic behaviour of the Chaplygin Gas model is investigated and, as a result, we show that the third-law of thermodynamics is verified. This means that the value of the entropy of the Chaplygin Gas in the perfect crystal state is zero at a temperature of zero Kelvin, which yields a determined value of the entropy and not an additive constant. Finally, we show that the solutions change asymptotically to the isotropic regime of expansion of Dark Energy. With this, we infer that the Chaplygin Gas can show a unified picture of Dark Energy and Dark Matter cooling during the expansion of the Universe.

Direct coupling of pressurized gas receiver to a brayton supercritical CO2 power cycle in solar thermal power plants

Three layouts of Brayton supercritical CO2 power cycles directly coupled to the receiver are proposed for Generation 3 solar power plants: conventional recompression, recompression with partial cooling, and recompression with intercooling. To achieve direct coupling, the solar heat is introduced downstream of the turbine, where CO2 pressure is lower. A higher temperature rise diminishes the receiver's dimensions, thus increasing its energy efficiency. It also lowers the average working temperature since the maximum temperature is fixed at 700 °C, thereby reducing losses. However, optical efficiency decreases as the receiver size diminishes. Both intercooling and partial cooling layouts further increase the cycle's net efficiency, which reduces the receiver's size, following similar trends observed with an increase in temperature rise. Considering all these effects, various factors push in opposite directions, affecting overall efficiency and costs. This competitive interplay results in overall efficiencies ranging from 30.26 % to 31.58 % and Levelized Costs of Electricity (LCOEs) between 162.47 €/MWh and 166.81 €/MWh. In conclusion, similar outcomes in terms of energy and economics are achieved with the three layouts, suggesting the simplest layout (recompression) as the most advisable. If thermal storage is incorporated, partial cooling becomes preferable due to its significant increase in the receiver's temperature rise.

Degree of PEGylatation of Lumbricus terrestris Hemoglobin Improves Microcirculatory Blood Flow but Increases the Rate of Auto-Oxidation.

The demand for red blood cells (RBCs) is on the rise due to the increasing diagnosis of chronic diseases such as sickle cell anemia, malaria, and thalassemia. Despite many commercial attempts, there are no U.S. FDA-approved artificial RBCs for use in humans. Existing RBC substitutes have employed various strategies to transport oxygen, extend the circulation time, and reduce organ toxicity, but none have replicated the natural protective mechanisms of RBCs, which prevent hemoglobin (Hb) dimerization and heme iron oxidation. Lumbricus terrestris (earthworm) erythrocruorin (LtEc) is a naturally occurring extracellular hemoglobin (Hb) with promising attributes: large molecular diameter (30 nm), high molecular weight (3.6 MDa), low auto-oxidation rate, and limited nitric oxide-scavenging properties. These characteristics make LtEc an ideal candidate as an RBC substitute. However, LtEc has a significant drawback, its short circulatory half-life. To address this issue, we explored thiol-mediated surface PEGylation of LtEc (PEG-LtEc) at varying polyethylene glycol (PEG) surface coverages. Increasing PEG surface coverage beyond 40% destabilizes LtEc into smaller subunits that are 1/12th the size of LtEc. Therefore, we evaluated two PEG surface coverage options: PEG-LtEc-0.2 (20% PEGylation) and PEG-LtEc-1.0 (100% PEGylation). We conducted experiments using golden Syrian hamsters with dorsal window chambers and catheters to assess the efficacy of these solutions. We measured microvascular parameters, organ function, cerebral blood flow, circulation time, mean arterial pressure, heart rate, and blood gases and performed histology to screen for toxicity. Our findings indicate that both PEG-LtEc molecules offer significant benefits in restoring microvascular parameters, organ function, cerebral blood flow, and circulation time compared to LtEc alone. Notably, PEG-LtEc-1.0 showed superior microvascular perfusion, although it exhibited a higher rate of auto-oxidation compared to PEG-LtEc-0.2. These results underscore the advantages of PEGylation in terms of tissue perfusion and organ health while highlighting its limitations.

Pressure Characteristics and Secondary Ignition Effects of Gas Produced in RDE Using Lignite and Anthracite/CH4 Fuel.

This study aims to address the energy efficiency release and environmental impact of coal dust in rotating detonation engines (RDEs) by monitoring the detonation characteristics of lignite and anthracite in methane gas-solid mixtures using high-precision sensor technology. Experimental results indicate that the peak detonation pressure of anthracite is 1.4% higher than that of lignite, and its detonation wave propagation speed is at least 5.5% faster, suggesting that anthracite exhibits more stable and efficient fuel energy release characteristics during detonation. Additionally, the sensor technology enabled detailed recording of pressure fluctuations and gas composition changes during the detonation process, providing accurate data for assessing and controlling emissions of harmful gases such as carbon monoxide and carbon dioxide. These data are crucial for designing more efficient and environmentally friendly coal dust detonation systems, enhancing mine safety and environmental protection. The outcomes of this research not only advance technological progress in the field of energy science but also address efficiency and environmental issues in industrial applications, offering significant support for achieving safer and more sustainable energy production methods.

(Invited) Thermal and Plasmon-Mediated Catalytic Transfer Hydrogenation Reactions on Nanostructured Metal Surfaces

Catalytic hydrogenation reactions play crucial roles in fine chemical production and pharmaceutical synthesis. Compared to direct hydrogenation of organic compounds with pressurized hydrogen gas, catalytic transfer hydrogenation reactions using inexpensive and readily accessible small molecules as hydrogen-donors has been considered as a more versatile, scalable, and sustainable pathway toward enhanced chemoselectivity under mild reaction conditions. Noble metal nanoparticles, especially those within the sub-5 nm size regime, can efficiently catalyze the dehydrogenation of a series of hydrogen-storing molecules, such as ammonia borane, hydrazine, formaldehyde, formic acid, and isopropanol, to produce surface-adsorbed hydrogen species that actively hydrogenate a variety of organic substrate molecules. The transfer hydrogenation/hydrogenolysis reactions are mechanistically complex, and may occur selectively along multiple distinct pathways, exhibiting kinetic features signifying the Langmuir–Hinshelwood, Eley–Rideal, autocatalysis, and reversible reaction mechanisms, respectively, depending on the compositions of the metal catalysts and the chemical nature of the hydrogen donors. In this talk, I will share with the audience some new insights concerning the detailed mechanisms of transfer hydrogenation reactions over metal nanocatalyst surfaces. We employ surface-enhanced Raman scattering (SERS) as an in situ fingerprinting spectroscopic tool to precisely resolve the detailed structural evolution of molecular adsorbates during catalytic reactions, based upon which the key intermediates along different reaction pathways are unambiguously identified. The results of deliberately designed in situ SERS measurements show that the chemoselective transfer hydrogenation of nitrophenyl isocyanide by ammonia borane may proceed on noble metal nanocatalyst surfaces selectively through either a unimolecular or a bimolecular pathway, depending on how the nitrophenyl isocyanide adsorbates interact with the metal nanoparticle surfaces. The experimental observations are corroborated by density functional theory calculations, which shed light on the underlying relationships between catalyst-adsorbate interactions and reaction pathway selection. We have further demonstrated that the photoexcited plasmonic hot carriers in the metal nanoparticles can be effectively harnessed to fine-regulate the activation energy barriers associated with the rate-limiting steps for the transfer hydrogenation of nitrophenyl isocyanide on Pd nanocatalyst surfaces when ammonium formate serves as the hydrogen donor. Our results clearly demonstrate the feasibility of using plasmonic hot carriers to kinetically modulate catalytic molecule-transforming processes.

Corrosion Initiation on Reinforcing Steel with Mill Scale in Mortar

Corrosion of reinforcing steel rebar is the main cause of loss of the long-term reliability of concrete structures. When the rebar is corroded, the rust induces cracks and detachment of the cover concrete. The mill scale, a thick oxide film, is formed on the rebars when the rebar is hot rolled. The role of mill scale on the corrosion resistance of rebars in concrete has not been clarified, yet. This study studied the corrosion behavior of rebars with mill scale in mortar.The samples are commercial rebars with 19 mm diameter, which have a mill scale of several tens of micrometers in thickness. The rebars without mill scale prepared by the electrolytic polishing were used as the comparison samples. A Hyperbaric-oxygen accelerated corrosion test (HOACT) [1] was carried out using the rebars embedded in the mortar with a 5.5 mm cover thickness. To prompt the breakdown of passive film on the rebars, 2.1 M NaCl solution was mixed with the mortar. In the HOACT, pressurized oxygen gas is supplied to the sample, and the oxygen reduction reaction on the steel surface is enhanced, leading to the steel's corrosion acceleration. The oxygen pressure was 0.6 MPa and the test period was 14 days. The corrosion of the rebar with a mill scale was more significant than that without a mill scale. This result shows that the mill scale reduces the corrosion resistance of the steel rebar in concrete [2].To investigate the effect of the mill scale on the corrosion resistance of the rebar, anodic polarization measurements of the rebars with and without the mill scale were carried out in a saturated Ca(OH)2 solution containing Cl-. The pitting potential of the rebar with mill scale was more noble than that of the sample without mill scale. However, when the mill scale was scratched, the pitting potential was significantly shifted to the less noble direction, and it was below that of the rebar without the mill scale. These results show that the mill scale improves the corrosion resistance of the rebar in concrete, in contrast, the corrosion resistance of the rebar with a defective mill scale becomes even worse than that of the rebar without the mill scale [2].[1] K. Doi, S. Hiromoto, H. Katayama, E. Akiyama, J. Electrochem. Soc., 165(9), C582-C589 (2018).[2] K. Doi, S. Hiromoto, T. Shinohara, K. Tsuchiya, H. Katayama, E. Akiyama, Corrosion Science, 177, 108995 (2020).

Influence of slip effect on dynamic performance of miniature tilting-pad dynamic pressure gas bearing

Influence of slip effect on dynamic performance of miniature tilting-pad dynamic pressure gas bearing

Thermal Analysis of Parabolic and Fresnel Linear Solar Collectors Using Compressed Gases as Heat Transfer Fluid in CSP Plants

This study introduces the use of compressed air as a heat transfer fluid in small-scale, concentrated linear solar collector technology, evaluating its possible advantages over traditional fluids. This work assumes the adoption of readily available components for both linear parabolic trough and Fresnel collectors and the coupling of the solar field with Brayton cycles for power generation. The aim is to provide a theoretical analysis of the applicability of this novel solar plant configuration for small-scale electricity generation. Firstly, a lumped thermal model was developed in a MatLab® (v. 2023a) environment to assess the thermal performance of a PT collector with an evacuated receiver tube. This model was then modified to describe the performance of a Fresnel collector. The resulting optical–thermal model was validated through literature data and appears to provide realistic estimates of temperature distribution along the entire collector length, including both the receiver tube surface and the Fresnel collector’s secondary concentrator. The analysis shows a high thermal efficiency for both Fresnel and parabolic collectors, with average values above 0.9 (in different wind conditions). Th5s study also shows that the glass covering of the Fresnel evacuated receiver, under the conditions considered (solar field outlet temperature: 550 °C), reaches significant temperatures (above 300 °C). Furthermore, due to the presence of the secondary reflector, the temperature difference between the upper and the lower part of the glass envelope can be very high, well above 100 °C in the final part of the collector string. Differently, in the case of PTs, this temperature difference is quite limited (below 30 °C).

Effectiveness Spatiotemporal of Pressure Unloading and Gas Extraction in Remote Upper Protected Seam Mining.

Severe gas hazards are increasing in deep mining areas, and there exists an enormous traditional challenge for protected seam mining. In this work, we conducted a multifaceted investigation into the spatiotemporal effectiveness exerted by pressure unloading from a distant safeguarded stratum in concert with the application of gas extraction methodologies. The stress and displacement evolution in the protected coal seam (PCS) are analyzed by applying Flac3D, and then positives are verified by the measurement of coal seam deformation and investigation of the unloading boundary. The results show that diminution coefficient of 0.62, and record an expansive deformation rate of 5.83%. The opportune temporal window for effective gas drainage is discerned, with its time window spans from 58 to 67 days as the expanse between 350 and 400 m progresses at the working face. Continuous and effective gas extraction occurs when transverse cracks in the PCS reach an optimal state of pressure relief. The final cumulative gas extraction was 320,300 m3 with an extraction efficiency of 34.3%. A residual gas volume of 3.68 m3/t and a residual gas pressure of 0.5 MPa reflect the efficient gas extraction.