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The power-law fluid flow in tree-like self-similar branching networks is prevalent throughout the natural world and also finds numerous applications in technology such as oil recovery and microfluidic devices. We investigate analysis of optimal power-law fluid flow conditions and the optimal structures within tree-like branching networks, focusing on maximizing flow conductance under the constraint of the network tube's volume and the surface area. The study considered fully developed laminar power-law fluid flow regimes without considering any losses in the network system. A key observation was the sensitivity of the dimensionless effective flow conductance to the network's geometrical parameters. We found that the maximum flow conductance occurs when a dimensionless radius ratio β ∗ satisfies the equation β ∗ = N − 1 / 3 and β ∗ = N − (n + 1) / (3 n + 2) under constrained tube-volume and surface-area, respectively. Here, N represents the bifurcation number of branches splitting at each junction, and n is the fluid power-law index. We further find that this optimal condition occurs when pressure drops are equipartition across each branching level. We validated our results with various experimental results and theories under limiting conditions. Further, Hess–Murray's law is justified and extended for the shear-thinning and shear-thickening fluid flows for an arbitrary number of branches N. Further, in this study, we also derive the relationships between the geometrical and flow characteristics of the parent and daughter tubes as well as the generalized scaling laws at the optimal conditions for the other essential parameters such as tube-wall stresses, length ratios, mean velocities, tube-volume, and surface-area of the tube distributing within the networks. We find that the fluid power-law index n does not influence the constrained tube-volume scaling at the optimal conditions; however, the scaling laws vary with n under the constrained tube's surface area. These findings offer valuable design principles for developing efficient transport and flow systems. [ABSTRACT FROM AUTHOR]

Lithium foils were demonstrated to absorb surrogate protium for tritium-powered betavoltaics. 20 μ m thick lithium foils were hole-punched from a ribbon of electrodeposited lithium on copper foil. The lithium foils were loaded with hydrogen in a custom Sievert apparatus where the pressure drop showed full hydriding at a hydrogen pressure of 2 bar and at all loading temperatures above the lithium melting point at 190, 200, 225, 250, and 300. Lithium hydride formation was confirmed with Raman spectroscopy after hydrogen loading. The kinetics of experimental hydride formation was compared to the diffusion-limited Mintz–Bloch model. While the Mintz–Bloch model showed good fit with the experimental loadings, the model overpredicted the loading kinetics starting at 250 °C and at higher temperatures. The overprediction was either caused by lithium hydride outgassing due to some reduction with some residual lithium hydroxide created from brief air exposure when sealing the lithium in the reactor or a transition from diffusion-limited hydride growth to surface or metal–hydride interface-limited hydride growth. [ABSTRACT FROM AUTHOR]

Gas–liquid two-phase stratified flow exists in many industrial processes. Although the flow pattern is simple, the interfacial shear prediction of stratified flow is still the focus of the study. The calculation of the shear stress at the gas–liquid interface is closely related to the measurement of the void fraction and pressure drop of the stratified flow. In this study, a new method for the calculation of interfacial shear stress of gas–liquid two-phase stratified flow is proposed. Differential pressure measurement and planar laser-induced fluorescence technology are combined to obtain important parameters for stratified flow under low-speed flow conditions (Ql = 0.10–0.25 m3/h, Qg = 0.35–1.00 m3/h). The interfacial shear stress is successfully calculated using macroparameters. The uncertainty associated with the calculated parameters using the proposed method is 2.67%, and this study verifies the accuracy of the linear relationship. The method provides a new way to obtain the interfacial shear stress of gas–liquid stratified flow. [ABSTRACT FROM AUTHOR]

We report on viscous adhesion measurements conducted in sphere-plane geometry between a rigid sphere and soft surfaces submerged in silicone oils. Increasing the surface compliance leads to a decrease in the adhesive strength due to elastohydrodynamic deformation of the soft surface during debonding. The force-displacement and fluid film thickness-time data are compared to an elastohydrodynamic model that incorporates the force measuring spring and finds good agreement between the model and data. We calculate the pressure distribution in the fluid and find that, in contrast to debonding from rigid surfaces, the pressure drop is non-monotonic and includes the presence of stagnation points within the fluid film when a soft surface is present. In addition, viscous adhesion in the presence of a soft surface leads to a debonding process that occurs via a peeling front (located at a stagnation point), even in the absence of solid–solid contact. As a result of mass conservation, the elastohydrodynamic deformation of the soft surface during detachment leads to surfaces that come closer as the surfaces are separated. During detachment, there is a region with fluid drainage between the centerpoint and the stagnation point, while there is fluid infusion further out. Understanding and harnessing the coupling between lubrication pressure, elasticity, and surface interactions provides material design strategies for applications such as adhesives, coatings, microsensors, and biomaterials. [ABSTRACT FROM AUTHOR]

Currently, the problem of air pollution is getting more and more serious, especially the pollution of tiny solid particles (PM, particulate matter) in the air, which poses a great challenge to the environment and human health. Therefore, it is particularly important to develop air filtration materials with high filtration efficiency and low resistance to meet this challenge. In this study, we propose to prepare air filtration membranes by centrifugal jet electrospinning technology, design multifactorial orthogonal coupling experiments, and investigate the effects of key process parameters of centrifugal jet electrostatic spinning, including solution concentration, airflow rate, rotational speed, and voltage, on the fiber diameter and uniformity by applying the polar analysis of variance and analysis of variance. PAN‐BaTiO3 electret nanofiber filtration membranes with high efficiency and low resistance were prepared by combining the optimized process of centrifugal blowing electrospinning. Various characterization methods (tensile test, water contact angle test, surface charge test, filtration test) were used to evaluate the effect of different BaTiO3 electret contents (0%, 0.1%, 0.5%, 1%) on the comprehensive performance of the filtration membranes, and the electret filtration efficiency of the electret filtration membranes prepared by the present process reached as high as 96.56% with a pressure drop of 29 Pa. [ABSTRACT FROM AUTHOR]

Corner tangential and bias combustion technology have significant advantages in optimizing combustion and pollutant emissions. This paper combined the corner tangential, bias combustion and jet technology for the first time to control thermoacoustic oscillations and pollutant NOx emissions synchronously. The control feasibility was examined by three variables: widths of corner tangential slots, bias jets ratios, and jet flow rates. Results indicate that the widths of corner tangential slots and bias jets ratios significantly affect the suppression effectiveness of thermoacoustic oscillations and NOx emissions. The synchronous control effectiveness with larger widths of corner tangential slots and smaller bias jets ratios is better than that with smaller widths of corner tangential slots and larger bias jets ratios. The maximum damping ratio of dynamic pressure and CH* can achieve 90.1% and 82%, respectively. The dynamic pressure drops from 39.2 Pa to 3.9 Pa and CH* reduces from 0.006 arb.units to 0.001 arb.units. A lower oscillations frequency will form by the bias jets, which avoids the occurrence of high-frequency and high-amplitude thermoacoustic self-excited oscillations. Besides, the NOx emissions drop from 26.2 ppm to 13.9 ppm reaching a maximum reduction of 12.3 ppm. Meanwhile, a slimmer flame root and flatter flame front are triggered. Two flame modes are summarized as Model A and Model B. This research realized an efficient simultaneous control of thermoacoustic oscillations and pollutant NOx emissions, which could be a helpful guideline for designing lean premixed flames. [ABSTRACT FROM AUTHOR]

Owing to the significant increase in air pollutants and the spread of infectious diseases, it seems that the use of face masks will become an essential item in human societies. Therefore, there is a need to conduct more research to develop novel types of respirators utilizing up-to-date science such as nanotechnology. In this study, we fabricated a nanocomposite fibrous filter containing modified graphene oxide (GO) and zinc oxide (ZnO) nanoparticles. This layer was used as an active filter for absorbing and removing air pollutants, such as suspended submicron particles (below 2.5 microns) and CO2, NO2, and SO2 gases. The synthesized nanostructures and fibrous filters were characterized by different analysis (FTIR, XRD, TGA, and FESEM), and the performance of the filters was surveyed by tests such as pressure drop, CO2, NO2, SO2 gas rejection, and particulate removal. The results showed that the stabilization of the modified GO and ZnO nanostructures on the fibrous filter improved the effectiveness of this filter as a mask for removing toxic particles and gases, and the filter containing nanoparticles had the best performance. [ABSTRACT FROM AUTHOR]

Pressurised sand filters used in drip irrigation need periodic backwashing to flush the contaminant particles out of the porous media. This process consumes high amounts of energy and water. The selection of more efficient backwashing operational conditions requires accurate information of the pressure drop and the bed expansion, the latter being not measured in commercial filters. An experimental study with a scaled filter that used a window to observe the bed expansion was conducted with three porous media types (glass microspheres and two silica sands), two packed media bed heights (200 mm and 300 mm) and four nozzles (one commercial and three prototypes). The 24 combinations of the filter experimental configuration were investigated for different superficial velocities. Both data and video recordings for all the 705 tests conducted were carefully analysed to obtain mean values and standard deviations of the height of the expanded bed. The behaviour of the fluidised bed dynamics was characterised. Results indicated that the nozzle design had a strong influence on the pressure drop, and, in consequence, on the power required for backwashing. It also had an observable impact on the fluidised bed dynamics although its effect on determining the overall height of the expanded bed was limited, this being more dependent on the type of the porous media. The most effective combination in terms of energy efficiency and porosity of the expanded bed was obtained with microspheres, though its retention efficiency might be questionable from the literature review, and the frustoconical nozzle geometry. • Video and data recordings of 705 backwashing tests were analysed. • The nozzle design plays a main role on the total pressure drop. • The nozzle design influences the fluidised bed dynamics. • The height of the expanded bed is mostly dependent on the media type. [ABSTRACT FROM AUTHOR]

CO2 injection in shale reservoirs is more suitable than the conventional recovering methods due to its easier injectivity and higher sweep efficiency. In this work, Grand Canonical Monte Carlo (GCMC) simulation is employed to investigate the adsorption/desorption behavior of CH4-C4H10 and CH4-C4H10-CO2 mixtures in organic and inorganic nanopores during pressure drawdown and CO2 huff and puff processes. The huff and puff process involves injecting CO2 into the micro- and mesopores, where the system pressure is increased during the huffing process and decreased during the puffing process. The fundamental mechanism of shale gas recovery using the CO2 injection method is thereby revealed from the nanopore-scale perspective. During primary gas production, CH4 is more likely to be produced as the reservoir pressure drops. On the contrary, C4H10 tends to be trapped in these organic nanopores and is hard to extract, especially from micropores and inorganic pores. During the CO2 huffing period, the adsorbed CH4 and C4H10 are recovered efficiently from the inorganic mesopores. On the contrary, the adsorbed C4H10 is slightly extracted from the inorganic micropores during the CO2 puffing period. During the CO2 puff process, the adsorbed CH4 desorbs from the pore surface and is thus heavily recovered, while the adsorbed C4H10 cannot be readily produced. During CO2 huff and puff, the recovery efficiency of CH4 is higher in the organic pores than that in the inorganic pores. More importantly, the recovery efficiency of C4H10 reaches the highest levels in both the inorganic and organic pores during the CO2 huff and puff process, suggesting that the CO2 huff and puff method is more advanced for heavier hydrocarbon recovery compared to the pressure drawdown method. In addition to CO2 storage, CO2 sequestration in the adsorbed state is safer than that in the free state. In our work, it was found that the high content of organic matter, high pressure, and small pores are beneficial factors for CO2 sequestration transforming into adsorbed state storage. [ABSTRACT FROM AUTHOR]

An open type of microchannel with diamond pin fins (OM-DPFs) is introduced for the cooling of high-performance electronic chips. For a Reynolds number (Re) of 247~1173, a three-dimensional model is established to explore the hydrothermal properties of the OM-DPF and compare it to traditional heat sinks with closed rectangular microchannels (RMs), heat sinks with open microchannels (OMs), and the results in the existing research. Firstly, the synergy between tip clearance and pin fins on the hydrothermal properties is discussed. Secondly, the entropy production principle is adopted to analyze the irreversible losses for different heat sinks. Lastly, the total efficiencies of different heat sinks are assessed. The RMs present the worst heat transfer with the lowest friction loss. For the OMs, the temperature and pressure drop are decreased slightly compared to those of the RMs, and the irreversible loss is reduced by 4% at Re = 1173 because of the small tip clearance. But the total efficiency is lower than that of the RMs because the pressure drop advantage is offset by the weak heat transfer. For the OM-DPF, the combined structure has a noticeable impact on the multiple physical fields and hydrothermal characteristics, which present the best thermal performance at the cost of the highest friction loss. The irreversible loss of heat transfer in the OM-DPF is reduced obviously, but the friction irreversible loss significantly increases at high Re values. At Re = 429, the total entropy production of the OM-DPF is reduced by 47.57% compared with the RM. Compared to the OM and the single-pin fin structure in the literature, the total efficiency of the OM-DPF is increased by 14.56% and 40.32% at Re = 614. For a pump power of 0.1 W, the total thermal resistance (Rth) of the OM-DPF is dropped by 23.77% and 21.19% compared to the RM and OM. For a similar Rth, the pump power of the combined structure is 63.64% and 42.86% lower than that of the RM and OM. Thus, the novel combined heat sink can achieve efficient heat removal while controlling the energy consumption of liquid cooling systems, which has bright application prospects. [ABSTRACT FROM AUTHOR]

This study reports an investigation into both isotropic and anisotropic permeability effects on gas production behavior during depressurization-induced natural gas hydrate dissociation at site NGHP-01-10D in the Krishna-Godavari basin. Numerical simulations were performed on a reservoir-scale model incorporating a single vertical well, examining different scenarios of permeability ratios (rrz). The investigation assessed gas and water production rates, cumulative production volumes, the gas-to-water ratio, and the spatial distribution of reservoir parameters throughout a production duration of 3 years. The findings indicate that permeability anisotropy has a substantial impact on hydrate dissociation and gas recovery. For rrz > 1, horizontal pressure propagation was promoted and gas production increased. For example, at t = 1100 days, the total gas production improved from 7.88 × 105 ST m3 for rrz = 1 to 55.9 × 105 ST m3 for rrz = 10. For rrz < 1, vertical pressure propagation resulted in higher water production with concomitantly lower rates of gas production rates. Spatial distribution analysis revealed that higher rrz values led to more extensive radial propagation of pressure drop, temperature decrease, gas saturation increase, and hydrate dissociation. The study concludes that higher horizontal permeability enhances depressurization effects, resulting in higher gas production rates and more favorable gas-to-water ratios. [ABSTRACT FROM AUTHOR]

Microchannel heat sink is widely applied in high-density heat flux devices for its high efficiency in heat dissipation. However, the most effective geometrical configuration of microchannels for best heat transfer augmentation with least pump power penalty is still unknown. In this research, the heat transfer augmentation in a microchannel heat sink with different shaped periodic reentrant cavities on channel sidewalls are numerically studied. Three different kinds of channel structures are introduced, including convex quarter-circular, concave quarter-circular, and inclined shaped reentrant cavities. The comprehensive performances of the proposed microchannels are compared with that of the smooth straight channel, with respect to the pressure drop, friction coefficient, Nusselt number, and performance factor. The results indicate that the comprehensive performance of the microchannel heat sink with periodic reentrant cavities is superior to the smooth straight channel, because its reentrant cavities can strengthen the mixing of fluids and lower the pressure loss. The proposed microchannels can enhance the heat transfer by 1.7 times, reduce the pressure drop by 3.7%–22.4% at Re 648.2, with the heat transfer entropy production decreased by 15.9%–48.2%. The inclined shaped microchannel has the best overall performance factor among the three proposed channels, which achieves up to 1.59 at Re 648.2. [ABSTRACT FROM AUTHOR]

Purpose: We tested the hypothesis that heat stress influences the closed-loop cardio-postural control by an increased blood pressure (BP) drop and postural sway. Methods: Fourteen healthy individuals (eight women) performed two orthostatic tests under thermal reference (TC; ~ 24 ºC) and HOT (~ 38 ºC) conditions. The center-of-pressure (COP) displacements and the electromyography (EMG) activity of the calf muscles (medial gastrocnemius and tibialis anterior) were recorded during the initial orthostasis (ORT onset) after the supine-to-stand challenge. At the same period, BP (beat-to-beat) was continuously monitored, and supine-to-stand variations (∆%) were calculated. Sublingual temperature (Tsl) was measured as a surrogate of internal temperature. Results: Tsl increased in HOT compared to TC (TC 36.5 ± 0.3 vs. HOT 36.7 ± 0.3 ºC; p < 0.01). COP distance was greater in HOT compared to TC condition (TC 596.6 ± 242.4 vs. HOT 680.2 ± 249.1 mm; p < 0.01). EMG activity of the gastrocnemius decreased in HOT compared to TC condition (TC 95.5 ± 19.8 vs. HOT 78.4 ± 22.8%mV; p = 0.02). EMG of tibialis did not change between TC and HOT (TC 83.5 ± 42.9 vs. HOT 66.1 ± 31.9% mV; p = 0.29). BP showed a greater fall in HOT compared to TC condition (∆%TC − 24.5 ± 13.2 vs. ∆%HOT − 33.2 ± 20.2%; p = 0.01). Conclusion: Heat stress causes a greater fall in blood pressure and a reduction in musculoskeletal pump activity during orthostatic onset. These effects could be potential mechanisms that underlie augmented postural instability under a heated environment. [ABSTRACT FROM AUTHOR]

Effective length of swirl flow is important for its application in the industry, however, the length of the swirl flow in a horizontal pipe is largely unexplored. In this article, effects of swirl on a horizontal bubbly flow and its development in a 25 mm horizontal pipe with a length of 4 m were studied by an experimental and theoretical method. In the experiments, the superficial gas velocities ranged from 0.068 to 0.566 m/s and the liquid velocities ranged from 0.283 to 1.132 m/s. The results show that: instead of dispersed bubbles in the non-swirl bubbly flow, a gas column flow is transformed downstream of the swirler; then, it breaks up into separated gas slugs, and finally, transforms to a non-swirl bubble flow. The pressure drop in the swirl flow gradually decreases and approximates to that in the non-swirl flow along the streamwise direction. The transition mechanism for the gas column flow was proposed here, and the transition criteria of the gas column flow were developed based on Kelvin–Helmholtz instability, then, the effective length of swirl on the gas column flow can be predicted. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing is a widely utilized technique for rock stimulation in geothermal and oil and gas operations. To fracture the rock, the pumped fluid pressure required should exceed the sum of the stresses at the injection point and the rock's mechanical strength. In scenarios where the rock is isotropic, hydraulic fractures typically propagate in directions perpendicular to the minimum principal stress. Contrary to this conventional understanding, our research, involving a series of true-triaxial hydraulic fracturing tests on the finely laminated Montney shale formation, demonstrates that this principle does not hold for transversally isotropic materials. Our experimental findings indicate that fractures in such materials occur along the bedding planes, aligning against the intermediate principal stress rather than the minimum principal stress. Based on these observations, we propose a conceptual model that integrates the in situ stresses with the tensile anisotropy of the rock. Additionally, in our experimental work, we saw that change in viscosity of the injected fluid greatly influences the fracture geometry, which can be used to engineer the fracture initiation and propagation as it seems to inhibit the parting of the beddings and to reorient the fracture along with the principal stresses. Highlights: Laboratory true-triaxial tests for transversally isotropic rocks exhibit hydraulic fractures against intermediate principal stress. Characteristics of the pressure curve during hydraulic fracturing can be used to differentiate tensile and shear/slip fractures. Tensile fracture during hydraulic fracturing indicates sharp pressure drop with faster pressure recovery. Rock fabric and fluid viscosity have great impacts on the fracture initiation, propagation and interactions during hydraulic fracturing. [ABSTRACT FROM AUTHOR]

The selective catalytic reduction (SCR) system plays a crucial role in reducing diesel exhaust emissions. To further enhance the performance of the SCR system, a three-dimensional numerical simulation model was established and experimentally validated for its reliability. Subsequently, the length (L1) and porosity (ε1) of carrier 1, as well as the length (L2) and porosity (ε2) of carrier 2, were varied to achieve an axial non-uniform distribution of the catalysts. The impact of this axial non-uniform distribution on the SCR system's performance was investigated. Finally, a fuzzy grey relational analysis method was employed to evaluate and optimize the influence of the aforementioned four individual parameters on the SCR system's denitrification (de-NOx) efficiency and pressure drop. The results indicate that variations of L1 have the greatest impact on de-NOx efficiency, while changes of ε2 have the most significant effect on pressure drop. The fuzzy grey relational degrees of L1, L2, ε1, and ε2 on de-NOx efficiency are 0.8267, 0.6288, 0.7457, and 0.8233, respectively. Similarly, the fuzzy grey relational degrees of L1, L2, ε1, and ε2 on pressure drop are 0.3552, 0.4894, 0.1045, and 0.7931, respectively. Compared with uniformly distributed catalysts, axially non-uniform distributed catalysts can improve de-NOx efficiency by 2.22% and reduce pressure drop by 46 Pa. This study provides theoretical and engineering references for improving the SCR catalyst coating process. [ABSTRACT FROM AUTHOR]

The study aims to examine how duct length affects the performance of a solar air heater (SAH) with a D‐shaped ribbed absorber plate, compared to a smooth absorber plate. The optimized D‐shaped ribs from previous research investigations are utilized in the present work to explore the absorber plate's length influence on the Nusselt number. The study reveals a slight decrease in the Nusselt number as the length of the absorber plate with D‐shaped ribs is increased. The observed behavior is attributed to the diminishing capacity of air to extract heat from the heated surface within the elongated duct. Moreover, the study calculates the pressure drop and thermo–hydraulic performance parameter (THPP) associated with the D‐shaped ribs and formulates correlations to establish a quantitative understanding of the relationship between duct length and D‐shaped rib performance. The maximum value of THPP was found to be 1.17 within the considered range of duct height. Furthermore, correlations have been derived for the Nusselt number and friction factor in terms of duct length to hydraulic diameter ratio and Reynolds number with maximum deviations of +1.7 and +2.13, respectively. These correlations serve as valuable tool for engineers and researchers seeking to optimize the design of SAHs, enabling them to balance the benefits of D‐shaped ribs with the considerations of duct length. This research contributes to the growing body of knowledge of SAH design, offering insights into the trade‐offs and intricacies of utilizing D‐shaped ribs and adjusting duct length for improved THPP. [ABSTRACT FROM AUTHOR]

This study investigated the effects of magnetic field on pressure drop and heat transfer enhancement of nanofluid in a pipe containing porous medium by a 2D simulation. The study involves modeling the flow of nanofluid as a single-phase flow and simulating fluid flow through the porous medium using the Darcy–Brinkman–Forchheimer equation. A constant uniform heat flux around the pipe is used as the thermal boundary condition. The simulations evaluate the effect of several parameters, such as Reynolds number, porosity, thermal conductivity of the porous medium, and nanofluid material. The findings show that utilizing a magnetic field increases heat transfer in nanofluid. Based on the simulations, both pressure drop and heat transfer rates increase with increasing Reynolds number. The rate of heat transfer increases as the thermal conductivity of porous medium increases, and among the selected materials, Ag has the greatest impact on heat transfer, followed by copper, gold, aluminum, and steel. By comparison of metallic ( Al , Cu ) and metallic oxide ( Si O 2 , Ti O 2 , CuO ) nanoparticles it is observed that using Al provides the highest heat transfer. Moreover, increasing porosity (0.8–0.98) decreases heat transfer coefficient. The performance evaluation criteria (PEC) are also examined as a determinant term to select the desirable condition. (The aluminum water nanofluid that is subjected to a magnetic field and moves through a silver-porous medium with a porosity of 0.9 has the highest PEC.) [ABSTRACT FROM AUTHOR]

Gas dehydration plays a critical role in gas refining processes due to the potential problems caused by the presence of water vapor. The inclusion of water vapor can lead to issues such as hydrate formation, pressure drop, and pipeline corrosion. In this research, a deep eutectic solvent (DES) absorbent was employed to absorb water vapor and subsequently, its absorption performance was compared with the absorption of tri-ethylene glycol (TEG) and lithium chloride, the most commonly used absorbents in water vapor separation processes. To do so, the influence of several effective parameters, including the inlet air flow rate, different ratios of choline chloride to urea (ChCl:Urea), the weight percentage of liquid water in the absorbent, and the viscosity of DES were investigated. The results demonstrated that DES is highly efficient for water vapor separation, outperforming both TEG and aqueous lithium chloride solutions. Moreover, increasing the inlet air flow rate was found to decrease absorption recovery due to reduced residence time. Additionally, a ChCl ratio of 1:2 yielded the highest absorption efficiency. [ABSTRACT FROM AUTHOR]

In this work, the effect of gas jets used in the deep vertical vibratory compaction technique are studied. Gas jets play a vital role in treating structured loess foundations by the pneumatic-vibratory probe compaction method. Utilizing the geotechnical particle finite-element method numerically, we estimate the limit gas injection pressure and delineate the injection-induced damage and plastic zones. The behavior of structured soil is described using an elastoplastic constitutive model considering its structure evolution. The analysis of structured loess under gas injection is based on the cavity expansion approach. Experimentally, we performed a scale model test of gas injection to investigate the mechanism of the gas jets on the surrounding soil and compared relevant results with numerical results. Numerical results show that the limit gas injection pressure for structured loess beyond a depth of 8.0 m ranges from 1,409.7 to 1,467.2 kPa, increasing with the increase of overburden depth while the current cavity expansion radius decreases. The radius of the plastic zone induced by cavity expansion is 2.0 to 3.0 times the current cavity radius within this depth range; for the damage zone, however, it ranges from 0.1 to 0.4 times. The horizontal pressure recorded during the model test is observed to be lower compared with the numerical simulation results. This discrepancy can be attributed to factors such as the neglect of gas leakage within the soil and the utilization of a uniform parameter. The gas jets expand soil in cyclic shear form. It goes through a process from destruction of soil structure to compression in the horizontal direction; then, its pressure gradually drops to zero in the expansion direction of the dominant channel in soil. [ABSTRACT FROM AUTHOR]

In the design of high-performance heat and mass transfer devices such as liquid-cooled heat sinks, catalytic reactors, and catalytic convertors, parallel mini/microchannels are favored owing to their special potentials. Offering low pressure drop, providing high transfer surface area to volume ratio, and being easy to manufacture and optimize have been drawing thermal and chemical engineers attention to parallel channels for past decades. When working with parallel channels, the challenge of flow maldistribution is commonly faced which decreases their efficiency significantly. System total pressure drop and flow uniformity are two parameters that determine the system performance. In the present study, a variety of practical ideas, aiming to enhance parallel channels performance, are studied numerically. Inventive manifold designs with high hydraulic performance are created through the course of this study. The results of these designs are compared with basic conventional designs which show substantial enhancement. Analyzing less successful designs lead us to deep understanding of fluid dynamics in parallel channel heat and mass transfer devices. [Display omitted] [ABSTRACT FROM AUTHOR]

In order to have a heat transfer per volume, heat exchangers have to have high overall heat coefficient. The effects of a transverse wedge on the heat transfer, the pressure drop, and the thermal efficiency factor (TEF) of air flow through a tube bundle heat exchanger was investigated. TEF increases continuously with the wedge aspect ratio (α). Form α = 0.275, 0.550, 0.758 to 1, TEF increases continuously from 1.157 to 1.84, 1.11 to 1.72, 1.05 to 1.42, and 1.02 to 1.39 for x/L = 1/3, 2/3, 1, and 0, respectively. [ABSTRACT FROM AUTHOR]

Fluidic oscillators utilize internal flow dynamics to produce oscillatory fluid jets. The Coanda surface in the mixing chamber of a fluidic oscillator plays a critical role by facilitating controlled fluid manipulation through flow attachment and redirection. The mixing chamber pressure drop, jet oscillating frequency, and deflection angles are hence dependent on the geometry of the Coanda surface. In this study, the Coanda surface is modified by using rectangular ribs of different aspect ratios. The effects of ribbed Coanda surface on oscillating jet characteristics are computed numerically through two-dimensional unsteady Favre-averaged Navier–Stokes equations. The aspect ratio (ARribs ), the ratio of rib height to rib base, is varied from 0.64 to 1.56 and air is used as a working fluid. An increase in the ARribs increases the jet oscillation frequency. The highest aspect ratio achieves an oscillation frequency of 820 Hz, contrasting with 355 Hz for the smooth case. On the other hand, the jet deflection angles are decreased as the aspect ratio increases. Interestingly the introduction of the ribs on the Coanda surface decreased the pressure drop in the oscillator. A decrease in pressure drop of 22% for an aspect ratio of 1.56 was achieved as compared to the smooth case. These results are attributed to the influence of the ribs on the formation of a separation bubble formed in the mixing chamber. The jet performance parameter, frequency-deflection-pressure ratio, was found to be 43% higher for ARribs of 1.56 as compared to the smooth case. [ABSTRACT FROM AUTHOR]

In the present investigation, a detailed numerical investigation of the flow and heat transfer characteristics of a channel with an elastic fin (vortex generator) and an elastic wall has been carried out using finite element method. The Fluid- Structure Interaction (FSI) model is used to capture the interaction between the fluid and the solid structure. A sinusoidal time dependent velocity profile has been imposed at the inlet of the channel and the right half of the upper wall of the channel is heated and exposed to constant temperature boundary condition. Due to the sinusoidal velocity profile at the inlet, the elastic fin oscillates periodically and act as a vortex generator, which causes more turbulence in the flow. The obtained results showed that the Nusselt number over the heated wall is affected by the position of the flexible fin, height of flexible fin and elasticity modulus of elastic fin. Moreover, due to the elasticity of the elastic wall and sinusoidal behavior of the inlet velocity, the elastic wall oscillates periodically upward and downward. The Nusselt number values over the heated wall are increased with decrease of the elastic modulus value of the elastic wall. However, the decrease in elastic modulus value of the elastic wall contributes to an increase in the pressure drop inside the channel. It should be added that the interplay between the fluid motion and the deformable structures leads to enhanced turbulence, as the flexible fin and elastic wall introduce additional disturbances and fluctuations into the flow regime. Consequently, this heightened turbulence level has profound implications for heat transfer processes within the system. [ABSTRACT FROM AUTHOR]

In a multi‐cavity mold, parts from each cavity have consistent properties if the runner system ensures balanced melt‐front advancement. An unbalanced mold, however, narrows the processing window, complicating quality control and making it harder to maintain standards. Molds with an inherently balanced filling, such as the H‐type runner system, are preferred. However, as the number of cavities increases, improvements are needed to address the issues caused by shear heating. Additionally, the material waste in the H‐type runner system is significantly greater than in the fishbone runner system. Based on the rheological concept, a two‐stage analytical approach is established to optimize the fishbone runner system. The diameter of each runner in the fishbone runner system is optimized by controlling pressure drop and remaining time to achieve balanced filling. The impact of these factors is thoroughly examined, as well as why they must be controlled during optimization. The proposed work links the physical situation to its mathematical model, proving highly beneficial for new runner system designs, especially without commercial software assistance. Highlights: A new approach to solving unbalanced filling in multi‐cavity molds.Pressure drop and remaining time are key factors for optimization.Two‐stage analytical approach ensures optimization accuracy.The optimal runner system reduces injection pressure for molding.An alternative method for designing fishbone runners without CAE assistance. [ABSTRACT FROM AUTHOR]

The hydrodynamic coefficients on a deeply submerged solid/porous disk subjected to forced heave oscillation have been investigated in analytical and experimental approaches. The analytical model is developed by means of a matched eigenfunction expansion method (MEEM) using a quadratic relationship between the pressure drop and traversing fluid velocity across the porous disk. For the improvement and validation of the analytical model, a series of experiments with the solid/porous disks is conducted for various porosities, Keulegan-Carpenter (KC) numbers, and oscillation periods. In addition to the small-scale hole vortices across the porous disk, the effect of edge vortices on the hydrodynamic coefficients is empirically implemented by curve-fitting with experimental data. The inclusion of edge vortices in the analytical model results in good agreement with experimental data of the damping coefficient for a deeply submerged disk. However, there are some discrepancies in the added mass, with noticeable differences occurring in the disk with low porosity. [ABSTRACT FROM AUTHOR]

Purpose: This research focuses on the development and characterization of oil-wetted spun-bonded polypropylene (PP) non-woven filters for improved air intake systems in automobiles. The study aims to enhance engine performance, durability, fuel economy and emission reduction by addressing key aspects such as contaminants filtration efficiency, loading capacity, pressure drop, temperature performance and longevity. Design/methodology/approach: The research methodology involves the utilization of textile fabrics, particularly oil-wetted spun-bonded PP non-woven filters, renowned for their effective particle collection capability from intake air. Experiments were conducted using a Box–Behnken design with three variables – oil concentration, areal density and dust quantity – each at three different levels to establish correlations with the filter's dust holding capacity (DHC) and pressure drop. Findings: The findings indicate that immersing particles in oil-coated medium significantly enhances the filter's DHC. Notably, castor oil as a coating demonstrates remarkable results, with a 97.53% increase in DHC and a high particulate matter filtration efficiency of 94.12%. Originality/value: This study contributes to the originality of research by emphasizing the importance of oil density in determining the filter's DHC and filtration efficiency. Furthermore, it highlights the superiority of castor oil over coconut oil-coated filter media, advancing air intake and/or filter systems for automotive engines. [ABSTRACT FROM AUTHOR]

Cryogenic liquids such as liquid oxygen and liquid hydrogen are extensively used in many processes and manufacturing industries. In these industries, transferring cryogens via pipelines is a routine phenomenon. As the boiling points and latent heat of cryogens are low, excessive vaporization of these cryogens is innate. Therefore, ensuring that the cryogen reaches the utility in its liquid form is challenging. In the case of liquid hydrogen and liquid helium, the pipelines are jacketed with a high boiling cryogen like nitrogen. The idea is to dump most of the heat into cheap nitrogen to limit the loss of precious hydrogen or helium. From a heat inleak point, maximizing the amount of nitrogen in the jacket is advantageous by choosing large cross‐sectional areas. Also, larger flow cross sections would lower pressure drops and, therefore, lower pumping costs. However, such a choice would add to the mass of the pipeline. An increase in the mass of the pipeline increases the need for better structural support of the pipeline assembly. Therefore, the design of cryogen jackets for limiting heat inleak is a multi‐objective optimization problem. In this work, we model the heat leak into the hydrogen via the nitrogen jacket and the pressure drop of liquid nitrogen, and we find the mass of the pipeline assembly. Then, we optimize the design of nitrogen jackets fitted over hydrogen pipelines. We employ the evolutionary optimization technique, genetic algorithm (GA), to perform this optimization.cryogen; genetic algorithm; heat inleak; liquid hydrogen; optimization. [ABSTRACT FROM AUTHOR]

We report measurements performed to understand the effects of gas (QG) and liquid (QL) flow rates, surface tension (σGL), liquid viscosity (μL), and particle diameter (dp) on dynamics of local liquid spreading, pressure drop, and overall liquid holdup in a pseudo‐2D trickle bed. We show that an increase in the gas‐phase inertia leads to a decrease in the lateral liquid spreading, whereas an increase in the liquid‐phase inertia leads to an increase in the lateral liquid spreading. We also show that an increase in dp causes a reduction in the lateral liquid spreading. Using dimensionless numbers (AB and We), we propose a regime map showing contributions of different forces to the local liquid spreading. We show that the interplay between the inertia and capillary forces governs the liquid distribution near the inlet, whereas the relative contribution of gravitational force increases toward the outlet. Finally, we propose a relation between AB and We for "bed‐scale" liquid spreading. [ABSTRACT FROM AUTHOR]

AbstractIn this study, an experimental investigation of the hydrodynamics of a novel 3-dimensional centrifugal tray was carried out. Using a high-capacity cylindrical centrifugal tray (HCC centrifugal tray), the centrifugal force and, inertial separation technologies were applied to remove the capacity limitations caused by the gravitational constraints. An air-water system was used in a rectangular cross-section plexiglass tower (30 cm × 50 cm). The pressure drop (dry and total), weeping, entrainment and clear liquid height of the tray were measured, and finally, a comparison to ConCap, sieve and, valve trays was provided. The results revealed a positive hydrodynamic behavior of the tray, particularly when a high gas velocity was used. Also, the capacity and operating window of the tray were found to be markedly larger than those of the conventional trays. This novel HCC centrifugal tray offers a promising approach to retrofit and debottleneck the tray columns in industrial applications, since it is both practical and inexpensive. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusion This study evaluated the hemodynamic performance of arterial and venous cannulae in a compliant pediatric extracorporeal membrane oxygenation (ECMO) mock circuit in pulsatile and non‐pulsatile flow conditions.The ECMO setup consisted of an oxygenator, diagonal pump, and standardized‐length arterial/venous tubing with pressure transducers. A validated left‐heart mock loop was adapted to simulate pediatric conditions. The pulsatile flow was driven by a computer‐controlled piston pump set at 120 bpm. A roller pump was used for non‐pulsatile conditions. The circuit was primed with 40% glycerol‐based solution. The cardiac output was set to 1 L/min and the aortic pressure to 40–50 mmHg. Four arterial cannulae (8Fr, 10Fr, 12Fr, 14Fr) and five venous cannulae (12Fr, 14Fr, 16Fr, 18Fr, 20Fr) (Medtronic, Inc., Minneapolis, MN, USA) were tested at increasing flow rate in 12 combinations.The pulsatile condition required lower ECMO pump speeds for all cannulae combinations at a given flow rate, inducing a significantly smaller increase of flow in the mock loop. Under non‐pulsatile conditions, the aortic and arterial pressures in the cannulae were higher (p < 0.01) while no significant differences in pressure drop and pressure‐flow characteristics (M‐number) were observed. The total hemodynamic energy was higher in case of non‐pulsatile flow (p < 0.01).Under non‐pulsatile conditions, the system was characterized by overall higher pressures, resulting in higher support to the patient. The consequent increase of potential energy compensates for increases of kinetic energy, leading to a higher total hemodynamic energy. Pressure gradients and M number are independent of the testing conditions. Pulsatile testing conditions led to more physiological testing conditions, and it is recommended for ECMO testing. [ABSTRACT FROM AUTHOR]

Hydrocyclones utilize centrifugal sedimentation to separate dispersed phases from a continuous liquid phase, offering advantages such as the absence of moving parts, ease of operation, and low maintenance costs. They are widely used in the mineral, petrochemical, and biotechnological industries, with their performance being significantly influenced by geometric and operational variables. This review examines the impact of key geometric (e.g. inlet, cone, vortex finder, overflow, outflow, and cylinder) and operational (e.g. particle size, solid concentration, feed flow rate, and pressure drop) parameters on hydrocyclone performance. Recent innovations, new developments, and perspectives to address specific industrial demands are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, an analytical model of an Unmanned Aerial Vehicle (UAV) propulsion system using liquid hydrogen to supply a fuel cell is presented. The article also describes experimental tests of the performance of a liquid hydrogen (LH 2) tank at different ambient temperatures and ground tests of the UAV propulsion system using LH 2. These tests were used to validate and calibrate the analytical model. The model is of reduced order and is based on the literature. Despite the simplicity of the model, the tank Boil-Off Gas (BOG) rate and pressure drop, the time for complete evaporation of LH 2 , the fuel cell performance, and the coolest temperature that the hydrogen can reach, were predicted with deviations not exceeding 0.3%, 0.5%, 2.2%, 0.6%, and 0.5% respectively. The final proposed model allows the incorporation of different conditions, materials, and geometries to suit each mission, all at low operational cost. • Analytical modeling of a UAV liquid hydrogen propulsion set. • Experimental data on liquid hydrogen tank and propulsion chain are presented. • Customization of conditions, materials, and geometries at a low operational cost. • Boil-off gas and pressure drop predicted with deviations below 0.3% and 0.55%. [ABSTRACT FROM AUTHOR]

Solar propane steam reforming offers a promising solution for hydrogen production, effectively addressing the challenges associated with hydrogen transportation and facilitating solar energy storage. In this context, the present study employs a combination of computational fluid dynamics and response surface methodology to optimize a multi-layer porous propane steam reformer. The research specifically emphasizes the influence of non-uniform catalytic porous structures on hydrogen production efficiency. The developed multi-objective optimization aims to identify the optimal combination of pore sizes to enhance propane conversion and hydrogen production rate while minimizing pressure drop. The optimized configuration achieved an 11.22% reduction in pressure drop, as well as 6.83% in hydrogen production and 8.04% in propane conversion, compared to the optimized uniform configuration of the solar porous reformer presented in our previous study (Jahangir et al., 2022) [1]. Furthermore, it was found that utilizing a multi-layer porous structure results in a more uniform temperature gradient, allowing a greater portion of the reformer to engage in the catalytic reaction. This is beneficial for reducing the potential risks of catalyst sintering and coke formation. • A multi-layer porous solar propane reformer has been numerically studied. • Optimal structure boosts C 3 H 8 conversion, H 2 production, and reduces pressure drop. • Best performance is achieved at d 1 = 2.62 mm, d 2 = 3.50 mm, d 3 = 1.29 mm. • Optimized design rises H 2 production by 6.83%, reducing pressure drop by 11.22%. [ABSTRACT FROM AUTHOR]

The results on zirconia-amine bifunctional modification of hierarchically porous silica monoliths for continuous-flow processes ar presented. The study reports the synthesis and properties of the modified porous monoliths and their performance in the tandem process of deacetalization-Knoevenagel condensation reaction. The properties of the materials were studied by thermal analysis, FTIR spectroscopy, XRF and nitrogen adsorption. It was found that both active centres were uniformly distributed along the monolithic cores, and the antagonistic interaction of the acid and base centres was not observed. It was shown that hydrophobicity of the monolith surface has opposite effects on the efficiency of the studied reactions. The overall rate of the tandem process depends on the rate of the condensation reaction. The performance of the bifunctional microreactors was checked and compared with those of cascade-connected monofunctional microreactors and batch reactor. The yield of cyanocinnamate product obtained in both flow systems was ca. 78%; however, pressure drop in the bimodified reactor was only half of that in the cascade. An effective way of water supply to the reaction system has been proposed. The research demonstrates the benefits of using flow-through structured micro-/mesoreactors in tandem reaction processes. [ABSTRACT FROM AUTHOR]

China possesses abundant coal resources and has extensive potential for exploitation. Nevertheless, the coal rock exhibits low strength, and the coal seam fractures due to mining activities, leading to an increased rate of gas emission from the coal seam. This poses significant obstacles to the exploration and development of the coal seam. This paper focuses on studying the failure mechanism of fractured coal rock by conducting uniaxial and triaxial compression experiments on the coal rock found at the Wangpo coal mine site. Simultaneously, in conjunction with the findings from the field experiment, a gas migration model of the mining fracture field is constructed to elucidate the pattern of coal seam gas distribution during mining-induced disturbances. The study structure reveals that coal rock exhibits three distinct failure modes: tensile failure, shear failure, and tension-shear failure. The intricate fissure in the rock layer will intensify the unpredictability of rock collapse patterns. The compressive strength of coal rock diminishes as the confining pressure drops. The coal rock in the working face area will collapse as a result of the lack of confining pressure. In the rock strata above the mining fracture zone, the gas pressure is first higher and then significantly falls with time. After 100 days of ventilation, the low gas pressure area changes little, so to ensure the safety of the project, the ventilation time of the fully mechanized mining surface is at least 100 days. The research results will help to establish the core technology system of coal seam development and improve the competitiveness of coal seam resources in China. [ABSTRACT FROM AUTHOR]

Where precision is paramount in managing temperature and fluid dynamics, micro heat exchangers (MHXs) emerge as indispensable tools. This review investigates the significance of MHX technology, offering readers a comprehensive roapmap from conceptualization to market application. We dissect the nuances of material selection, shedding light on cutting‐edge advancements poised to revolutionize MHX efficiency. Furthermore, we explore how the geometry of MHX influences heat transfer dynamics and pressure drop, providing insights into enhancing the overall effectiveness. We delve into the various types of control instrumentation, offering a detailed analysis of their applicability. Beyond the technical prowess, the economic landscape plays a pivotal role in the adoption of MHX technology. [ABSTRACT FROM AUTHOR]

The exhaust gas burner, a critical component of a solid oxide fuel cell (SOFC) thermal management system, is essential for the stable and reliable operation of the entire system. This study establishes a test bench that simulates the gas composition and temperature of the fuel cell stack anode and cathode gases and conducts comprehensive experimental research on an exhaust gas burner used in a 15-kW SOFC power generation system. The experimental results show that the burner has the operational characteristic of reliable combustion over a wide range of excess air ratios. The burner can achieve stable and reliable combustion under low-flow ignition, steam injection, reforming, and power-generation conditions with excess air ratios of 29–45, 21–28, 23–37, and 11–27, respectively. Rapid changes in the excess air ratio did not lead to combustion instability; for example, during power generation, an increase of 47.6% in the excess air ratio resulted in a 3.5% decrease in the burner outlet temperature. However, under the steam injection condition, with an excess air ratio of 28 and a steam-to-carbon ratio of 3, the temperature decreased significantly. The burner also exhibited low-pressure loss, with a maximum anode exhaust pressure drop of only 233 Pa. Furthermore, the burner exhibited excellent performance during condition transitions, although a certain time delay occurred in the temperature response to the flow rate changes. • Established a test platform to explore burner characteristics comprehensively. • Proven reliable combustion across various conditions. • Maintained stable combustion despite rapid air ratio changes. • Significant temperature drop during steam injection. • Low pressure loss and excellent performance in condition transitions. [ABSTRACT FROM AUTHOR]

With advancements in additive manufacturing (AM) techniques, high-quality triply periodic minimal surface (TPMS) structures can now be produced. TPMS walled heat exchangers (HX) hold significant potential for industrial applications and are receiving increasing attention. This paper explores the impact of various TPMS design variables on flow and thermal performance to optimize TPMS heat exchangers for compactness, high efficiency, and low pressure drop. The design variables examined include the type of TPMS lattice, unit cell size, wall thickness, aspect ratio, TPMS orientation, and equivalent thickness. The study reveals that the flow and heat transfer performance of TPMS structures are significantly affected by these design variables. For the Gyroid, Diamond, and SplitP lattices, performance is nearly identical when the surface-to-volume ratio is kept constant. The average velocity of the fluid in the TPMS HX should be 0.3 m/s. The corresponding Re is between 300~800. Thin wall thickness, small equivalent thickness, and flat lattice configurations can significantly reduce pressure drop while maintaining the overall heat transfer coefficient. Additionally, the angle between the flow direction and TPMS orientation can increase pressure drop. Three aluminum heat exchangers were successfully printed using an AM machine, and testing results are comparable with theoretical prediction. [ABSTRACT FROM AUTHOR]

In this study, the flow condensation of R-410A within 18 square microchannels arranged horizontally in parallel was experimentally investigated. All components of pressure drop, including expansion, contraction, deceleration, and friction, were quantified specifically for microchannels. The test conditions included saturation temperature, vapor quality, and mass flux, ranging from 18.86 to 24.22 bar, 0.09 to 0.92, and 200 to 445 kg/m2·s, respectively. The frictional pressure loss made up approximately 92.89% of the overall pressure reduction. The findings demonstrate that the pressure drop rises with higher mass flux and a lower saturation temperature. By comparing with correlations and semi-empirical models outlined in the literature across various scales, specimen types, and refrigerant media, correlations developed for two-phase adiabatic flows in multi-channel configurations can effectively predict the pressure drop in microchannel condensation processes. The model introduced by Sakamatapan and Wongwises demonstrated the highest predictive accuracy, with a mean absolute deviation of 8.4%. [ABSTRACT FROM AUTHOR]

The automotive industry is increasingly focused on developing more energy-efficient and eco-friendly air-conditioning systems. In this context, CO2 microchannel gas coolers (MCGCs) have emerged as promising alternatives due to their low global warming potential (GWP) and environmental benefits. This paper explores the application of machine learning (ML) algorithms to predict the thermohydraulic performance of MCGCs in automotive air-conditioning systems. Using data generated from an experimentally validated numerical model, this study compares various ML techniques, including both linear and nonlinear regression models, to forecast key performance metrics such as refrigerant outlet temperature, pressure drop, and heat transfer rate. Spearman's correlation was employed to develop performance maps, whereas the R2 and MSE metrics were used to evaluate the models' predictive accuracy. The linear models gave around 70% forecasting accuracy for pressure drop across the gas cooler and 97% accuracy for refrigerant outlet temperature, whereas the nonlinear models achieved more accurate predictions, with an accuracy ranging from 71% to 99%. This implies that nonlinear regression generally performs better than linear regression models in assessing the overall thermohydraulic performance of microchannel gas coolers. This research brings forth new ideas on how ML methods can be applied to enhance efficiency and effectiveness in gas coolers, contributing to the development of more eco-friendly automotive air-conditioning systems. [ABSTRACT FROM AUTHOR]

This study introduces a novel predictive model for atomization droplet size, developed using comprehensive data collected under elevated temperature and pressure conditions using a twin swirl airblast nozzle. The model, grounded in flow instability theory, has been meticulously parameterized using the Particle Swarm Optimization (PSO) algorithm. Through rigorous analysis, including analysis of variance (ANOVA), the model has demonstrated robust reliability and precision, with a maximum relative error of 19.3% and an average relative error of 6.8%. Compared to the classical atomization model by Rizkalla and Lefebvre, this model leverages theoretical insights and incorporates a range of interacting variables, enhancing its applicability and accuracy. Spearman correlation analysis reveals that air pressure and the air pressure drop ratio significantly negatively impact droplet size, whereas the fuel–air ratio (FAR) shows a positive correlation. Experimental validation at ambient conditions shows that the model is applicable with a reliability threshold of We1/Re1 ≥ 0.13 and highlights the predominance of the pressure swirl mechanism over aerodynamic atomization at higher fuel flow rates (q > 1.25 kg/h). This research effectively bridges theoretical and practical perspectives, offering critical insights for the optimization of airblast nozzle design. [ABSTRACT FROM AUTHOR]

Organic-rich hot Qusaiba shale is the primary source rock of most of the Paleozoic hydrocarbon reservoirs of eastern and central Arabia. Representative near-surface Qusaiba shale samples were collected and characterized from one of its outcrop sections at the Tayma quadrangle in northwest Saudi Arabia. The petrophysical and geochemical characterization indicated porosity and permeability of 8.2% and 2.05 nD, respectively, with good total organic carbon (TOC) of 2.2 mg/g and mature kerogen of gas-prone type III. The tight characteristics of the formation can lead to high capillary pressure and extensive post-fracking water retention, leading to flow blockage and a reduction in gas productivity. Three different surfactants and one ionic liquid, namely, Triton X-100, Triton X-405 and Zonyle FSO surfactants and Ammoeng 102 ionic liquid, were tested as additives to fracking fluid to investigate their effectiveness in optimizing its performance. The chemical solutions exhibited no sign of instability when exposed to solution salinity and temperatures up to 70 °C. The investigated chemicals' performance was examined by measuring methane/chemical solutions' surface tension and their ability to alter shale's wettability. The results indicate that Zonyl FSO is the most effective chemical, as it is able to significantly reduce surface tension and, hence, capillary pressure by 66% when added at critical micelle concentration (CMC). Using Zonyl FSO surfactant at a maximum tested concentration of 0.2% induced a relatively smaller capillary pressure drop (54%) due to the drastic drop in the contact angle rendering shale very strongly water-wet. Such a drop in capillary pressure can lower the fracking fluid invasion depth and therefore ease the liquid blockage removal during the flowback stage, enhancing gas recovery during the extended production stage. Triton X-100 at CMC was the second most effective surfactant and was able to induce a quite significant 47% drop in capillary pressure when added at the maximum tested concentration of 0.05%. This was sufficient to remove any liquid blockage but was less likely to alter the wettability of the shale. Based on the findings obtained, it is suggested to reduce the blockage tendency during the fracking process and elevate any existing blockage during the flowback stage by using Zonyl FSO at CMC where IFT is at its minimum with a higher contact angle. [ABSTRACT FROM AUTHOR]

Accurate wind speed measurement in low-pressure conditions is crucial for the thermal performance validation and attitude control of stratospheric aircraft. As air density decreases, traditional wind speed measurement systems based on principles such as dynamic pressure, heat transfer, ultrasound, and particle velocimetry face significant challenges when applied in low-pressure environments, often failing to achieve the required measurement accuracy. This paper presents the development of a wind speed simulation system based on a rotation method designed to operate in low-pressure conditions, utilizing a space environment simulation chamber in conjunction with a high-precision turntable. The system was employed to conduct response tests on a constant heat flow thermal sphere anemometer within a stratospheric pressure range of 1 kPa to 30 kPa. The experimental results revealed that at extremely low Reynolds numbers, the probe signal exhibited increasing nonlinearity, significantly affecting the response curve at pressures below 15 kPa. While the sensitivity of the hot-sphere probe remained relatively stable at wind speeds above 5 m/s, it decreased nonlinearly as the pressure dropped when wind speeds fell below 5 m/s. Furthermore, this paper analyzes the impact of various interpolation methods on wind speed conversion errors, providing valuable data to support the future development and validation of stratospheric aircraft. [ABSTRACT FROM AUTHOR]

The paraventricular nucleus of the hypothalamus (PVN) regulates physiological and behavioural responses evoked by stressful stimuli, but the local neurochemical and signalling mechanisms involved are not completely understood. The soluble guanylate cyclase (sGC) within the PVN is implicated in autonomic and cardiovascular control in rodents under resting conditions. However, the involvement of PVN sGC‐mediated signalling in stress responses is unknown. Therefore, we investigated the role of sGC within the PVN in cardiovascular, autonomic, neuroendocrine, and local neuronal responses to acute restraint stress in rats. Bilateral microinjection of the selective sGC inhibitor ODQ (1 nmol/100 nl) into the PVN reduced both the increased arterial pressure and the drop in cutaneous tail temperature evoked by restraint stress, while the tachycardia was enhanced. Intra‐PVN injection of ODQ did not alter the number of Fos‐immunoreactive neurons in either the dorsal cap parvocellular (PaDC), ventromedial (PaV), medial parvocellular (PaMP), or lateral magnocelllular (PaLM) portions of the PVN following acute restraint stress. Local microinjection of ODQ into the PVN did not affect the restraint‐induced increases in plasma corticosterone concentration. Taken together, these findings suggest that sGC‐mediated signalling in the PVN plays a key role in acute stress‐induced pressor responses and sympathetically mediated cutaneous vasoconstriction, whereas the tachycardiac response is inhibited. Absence of an effect of ODQ on corticosterone and PVN neuronal activation in and the PaV and PaMP suggests that PVN sGC is not involved in restraint‐evoked hypothalamus‐pituitary‐adrenal (HPA) axis activation and further indicates that autonomic and neuroendocrine responses are dissociable at the level of the PVN. [ABSTRACT FROM AUTHOR]

Instead of the expected 3.8–5.4% increase in the heat transfer coefficient due to the better thermal conductivity of silicon carbide tubes compared to glass tubes, the observed increase was 18–22% for 150–275 kg·h−1 airflow and 6 kg·s−1 propane-1,2-diol coolant in tubes. This additional 15–17% increase is probably due to local flow turbulisation due to the roughness of the sintered carbide of 4–10 µm, which unfortunately also causes a 17–24% higher air pressure drop. The hand calculation model used underestimates the heat transfer coefficient by −2% to 10%, which is better than CHEMCAD 8 modeling results. [ABSTRACT FROM AUTHOR]

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Generally, 100% vacuum residue is not processed in fixed-bed residue hydrogenation units, and the proportion of vacuum residue in feedstock is not higher than 65% . The A fixed bed residue hydrogenation unit has six cycles, and the operating results show that the higher the proportion of vacuum residue in feedstock, the shorter the operating cycle of the unit. The volume space velocity of the B fixed bed residue hydrogenation unit is 0.20 h-1. If the volume space velocity decreases to 0.15 h-1 and 0.10 h-1, the reactor pressure drop is expected to increase to 2.3 MPa and 3.4 MPa, respectively. The yield of hydrogenated heavy oil in the A fixed bed residue hydrogenation unit is as high as 93.25%, and the conversion rate of fractions above 520 °C is only 25.38%. Ebullated bed residue hydrocracking technology and slurry bed residue hydrocracking technology can process vacuum residue. The pressure drop in the reactors of the ebullated bed unit C and the slurry bed unit D is stable, with a pressure drop of only 0.42 MPa in reactor of unit D. The conversion rates of typical ebullated bed residue hydrocracking technology and slurry bed residue hydrocracking technology can reach 85.87% and 91.49%, respectively. [ABSTRACT FROM AUTHOR]

The FCC unit is closely related to its upstream and downstream units, especially for single series refineries, the change of the working condition of the upstream unit will have a significant impact on the production and operation of the downstream unit. During the catalyst replacement period of the residue hydrogenation unit, the FCC unit blended vacuum residue, resulting in severe deterioration of the properties of the FCC feedstock. The increase in vanadium content in the feedstock led to a decrease in the activity of the equilibrium catalyst and an increase in the olefin content of the FCC gasoline, causing rapid coking of heat exchanger group E101 in the S Zorb unit and affecting its operation. Therefore, during the catalyst replacement period of the residue hydrogenation unit, it is recommended to purchase light paraffin-base crude oil with low sulfur and metal content in advance, in order to alleviate the vanadium poisoning of the FCC unit catalyst; try to increase the catalyst consumption of the FCC unit to over 2.0 kg/t to prevent excessive vanadium content of the equilibrium catalyst; if E101 is rapidly coking and has caused excessive pressure drop, chemical cleaning can be used to clean the coking in the E101 tube pass. [ABSTRACT FROM AUTHOR]

AbstractAccurate estimation of frictional pressure loss in an annulus is crucial for selecting appropriate pump systems, determining horsepower requirements, and controlling hole cleaning. Generally, when calculating the friction factor, the temperature of the fluid and the rotation of the inner pipe are not considered, which can lead to errors in estimating the pressure difference in the annulus. In this study, to ensure accurate pressure drop calculations, the effects of temperature and inner pipe rotation, along with other parameters, were included. An extensive experimental study was conducted at Izmir Katip Celebi University’s Flow Loop using two Carboxymethyl cellulose (CMC) solutions, across various fluid velocities, fluid temperatures, diameter ratios, and inner pipe rotation speeds. A dimensional analysis was performed to identify the parameters that affect friction factors in the annulus. Finally, friction factor equations were developed based on the experimental data using optimization algorithms such as interior point (fmincon), genetic, minimax, and simulated annealing. The findings showed that the predictions from all the algorithms tested in the study closely matched the experimental results; however, the interior point algorithm (fmincon) provided the best performance, with an average absolute percentage error of 9.4%. [ABSTRACT FROM AUTHOR]