Capillary Pressure Difference Research Articles

Clinical, echocardiographic and haemodynamic predictors of morbidity and mortality in pulmonary hypertension: a nation-wide registry

Abstract Background and aims In this retrospective analysis of a nation-wide registry on pulmonary arterial hypertension (PAH), group IV and V, we aimed to evaluate the clinical, echocardiographic,haemodynamic and neurohumoral predictors of morbidity and mortality. Methods This study included 903 patients enrolled from 24 cardiology centers participating in the RegiStry on clInical outcoMe and sUrvival in pulmonaRy hypertension Groups (SIMURG II). ESC/ERS 2022 risk scoring model was used for risk predictions at baseline assessment. Composite endpoint (CEP) definitions were adopted from the SERAPHIN and GRIPHON trials. Results Age was 51.27 + 21.37 years, and 72 % of patients were female. Incident cases were noted in 65.9 % of overall group. Idiopathic PAH (IPAH), PAH-associated with congenital heart diseases (CHD-PAH), PAH-associated with connective tissue diseases (CTD-PAH), porto-PAH, Group IV and V pulmonary hypertension (PH) were documented in 33 %, 33.5 %, 12 %, 1.6 %, 20 % and 1.7 % of overall patients, respectively. Background mono and dual targeted combinations, and sequential dual or triple combinations were noted in 17 %, 57 % and 26 % of patients, respectively. Baseline low-, intermediate- and high-risk were noted in 1.2 %, 14.1 %, and 84.7 %, respectively. Median follow-up time was 867 (412-1667) days. Overall rates of mortality and CEP were 26 % and 39%, respectively. Prevalent versus incident cases were associated signifinatly lower mortality and CEP rates (p=0.028 and p=0.024, respectively). Mortality and CEP rates were 31 % and 44 % in IPAH, 20 % and 39 % in CHD-PAH, 31 % and 43 % in CTD-PAH, and 25 % and 30 % in group IV patients, respectively. CHD-PAH compared with other groups was associated with a higher Kaplan-Meier (K-M) survival and CEP-free survival (p< 0.0001 and p=0.00023, respectively). Survival was associated with prevalent versus incident status, baseline functional class (FC) and six-minute walk distance (6MWD) in all subgroups (p<0.0001 for all), NT-brain natriuretic peptide and right atrial area in IPAH,CHD-PAH and CTD-PAH, and mixed venous O2 saturation % in IPAH and CHD-PAH (p varying from <0.0001 to 0.027). But, TAPSE / systolic pulmonary artery pressure ratio, right atrial-pulmonary capillary wedge pressure difference, pulmonary vascular resistance and its ratio to systemic vascular resistance, cardiac index were not related with survival. Baseline high versus intermediate /low risk was associated with a lower overall survival and CEP-free survival ( p=0.03 and p=0.003, respectively). Male sex [hazard ratio(HR):1.73;1.2-2,51,p = 0.004], 6MWD (p<0.001), FC III/IV (HR: 2.52;1.47-4.32, p<0.001) and baseline low-risk (HR:0.37;0.21-0.65, p<0.001) were independent predictors of mortality. Conclusions Our nation-wide data revealed current insights regarding the clinical, echocardiographic,haemodynamic and neurohumoral predictors of morbidity and mortality in PAH and group IV PH.

Self-Driven Gas Spreading on Mesh Surfaces for Regeneration of Underwater Superhydrophobicity.

Underwater superhydrophobic surfaces stand as a promising frontier in technological applications such as drag reduction, antifouling, and anticorrosion. Unfortunately, the air film, known as the plastron, on these surfaces tends to be unstable. To address this problem, active approaches have been designed to preserve or restore plastrons. In this work, a self-driven gas spreading superhydrophobic mesh (SHM) surface is designed to facilitate recovery of the plastron. The immersed SHM can be "wetted" by gas, even when the plastron is removed. We demonstrate that the injected gas can spread spontaneously along the SHM over a large area, which greatly simplifies the plastron replenishment process. By incorporating a locally coated gas-producing layer, we achieve rapid in situ plastron recovery and long-term immersion stability, extending the plastron lifespan by at least 48 times. We also provide a framework for designing an SHM with suitable structural dimensions for gas spreading. Furthermore, an SHM with asymmetric structural dimensions enables unidirectional gas transport by the capillary pressure difference. This SHM surface shows excellent drag reduction properties (37.2%) and has a high slip recovery coefficient (73.4%) after plastron loss. This facile and scalable method is expected to broaden the range of potential applications involving nonwetting-related fields.

Engulfing behavior of vapor bubbles in downward facing heated surface boiling

Boiling of the coolant at the hot surface provides relatively better cooling by absorbing latent heat along with convection heat transfer as compared to heat transfer under single-phase conditions. In boiling, the orientation of heated surface also plays a crucial role. Downward facing boiling is complex than upward facing boiling, as the detachment of the bubble inhibited due to the heater surface orientation. Consequently, the bubble residence time and interaction with other bubbles are different in such boiling conditions. Our experiments on a large downward facing flat surface (100 × 400 mm2) revealed unexplored boiling phenomena. The boiling process is dominated by a complex engulfing phenomenon, which is rarely reported in the past. The engulfing phenomena have been captured using high-speed photography, wherein, at low heat fluxes, it is observed that larger bubbles engulf small bubbles by opening their mouth and swallowing the small bubbles. However, at higher heat fluxes, this phenomenon disappears. A larger vapor blanket is formed due to engulfing of bubbles, which may lead to departure from nucleate boiling. This engulfing behavior depends on the heat flux and subcooling. With the increase in heat flux, it is found that the rate of vapor engulfing increases. We have attempted to explain the science behind such engulfing phenomenon based on the capillary pressure difference. These results are consistent at various subcooling. This research provides new insights into nucleate boiling and may help in developing advanced mathematical models for accurate heat transfer prediction on downward facing nucleate boiling.

A dual-layer flow field design capable of enhancing bubble self-pumping and its application in water electrolyzer

The conventional flow-field configurations such as parallel and serpentine flow fields in proton exchange membrane water electrolyzer have encountered serious bubble accumulation phenomena in channels, blocking the water delivery to the electrode and creating a large mass-transfer resistance. Therefore, we propose a dual-layer flow field design. Specifically, the degassing layer is tightly installed on the base layer, forming a dual-layer configuration, capable of enhancing the self-pumping effect (bubbles automatically detach from the outer surface of the electrode) due to the formation of capillary pressure difference between the upper and lower surfaces of bubbles. Firstly, we theoretically analyze the feasibility of this dual-layer design through numerical simulation. The results show that the bubbles in the channel will be sucked into the degassing layer from the base layer, thus creating more space for water supply to the electrodes, which is further verified by in-situ visualization. Finally, it is found that an introduction of the degassing layer significantly upgrades the cell performance (approximately 0.15 V at 5.0 A cm−2) compared with conventional single-layer design. Therefore, this study provides insights for future flow-field design in high-performance water electrolyzers.

Utilizing Differences in Mercury Injection Capillary Pressure and Nuclear Magnetic Resonance Pore Size Distributions for Enhanced Rock Quality Evaluation: A Winland-Style Approach with Physical Meaning

Pore structure is a fundamental parameter in determining the hydrocarbon storage capacity and flow characteristics of a reservoir. Mercury injection capillary pressure (MICP) and nuclear magnetic resonance (NMR) are two commonly utilized techniques for characterizing rock pore structures. However, current studies indicate that disparities in testing methodologies due to distinct physical characteristics lead to a partial misalignment in pore size distributions. We conducted MICP (dynamic) and NMR (static) experiments on eight tight sandstone and eight shale samples and proposed a method to utilize information from the differences in MICP and NMR pore size distributions, aiming to enhance the accuracy of rock quality analysis. We observed that in rock cores where large pores are interconnected with smaller pore throats, MICP tends to overestimate the proportion of these smaller pores and underestimate the larger ones. Furthermore, we integrated information from both dynamic and static experimental processes based on physical significance and found that the fitting accuracy of the newly proposed method is superior to the Winland r35 equation. Compared to the Winland r35 equation, our new method significantly improves fitting accuracy, increasing the R-squared value from 0.46 to 0.93 in sandstones and from 0.80 to 0.87 in shales. This represents a potential high-precision, comprehensive tool for rock quality analysis, offering a new perspective for an in-depth understanding of rock properties.

Effects of cathode gas diffusion layer porosity and contact angle distributions along through-plane direction on the performance of polymer electrolyte membrane fuel cell

In the present work, a numerical model for polymer electrolyte membrane fuel cell (PEMFC) has been employed to investigate the effects of porosity and contact angle distributions of the porous layer on the performance of PEMFC. The three-dimensional, two-phase, and non-isothermal flow solver considers heat transfer, electrochemical reaction, and liquid water saturation. Various cases with different cathode gas diffusion layer (GDL) porosities are performed. The results showed that a better performance is achieved when the GDL porosity is increased because of the reduced mass transport resistance of oxygen. The effects of the porosity distributions on the PEMFC performance were examined by comparing the predictions from the cases with non-uniform porosity and uniform porosity in the cathode GDL. It was shown that the current density of the cases with non-uniform porosity is higher than that of the uniform porosity case when the operation voltage is low. This is due to the fact that non-uniform porosity distributions in the cathode GDL enhance the reactant transport. When the operation voltage is high, the current densities of the cases with non-uniform porosity and uniform porosity are almost the same. Moreover, the influence of contact angle distributions in cathode GDL was explored. Various cases with gradient-decreasing, gradient-increasing, and uniform constant contact angles from GDL/channel interface to GDL/catalyst layer interface were studied. It was found that the case with gradient-increasing contact angle has a better performance due to the larger capillary pressure difference to remove more water. The poor performance of the case with gradient-decreasing contact angle is related to the phenomenon of flooding in the catalyst layer.

Critical Condition of the Depth Limit of Oil Accumulation of Carbonate Reservoirs and Its Exploration Significance in the Lower Ordovician of the Tazhong Area in the Tarim Basin

Critical Condition of the Depth Limit of Oil Accumulation of Carbonate Reservoirs and Its Exploration Significance in the Lower Ordovician of the Tazhong Area in the Tarim Basin

A novel method for quantifying hydrocarbon micromigration in heterogeneous shale and the controlling mechanism

Almost 70 years after shale oil was first studied, “self-souring” was widely regarded as an essential feature of shale oil. Recently, micromigration, which is a bridge connecting hydrocarbon generation, expulsion and enrichment in shale, has been discovered and confirmed as shale oil exploration deepens. However, due to strong heterogeneity, quantitative evaluation of hydrocarbon micromigration in shale remains unclear, making scientific understanding of shale oil enrichment mechanisms highly challenging. Based on the mass balance principle, we provide a quick and novel method to quantify hydrocarbon micromigration with the most commonly available geochemical data from Rock-Eval/total organic carbon (TOC) analysis by subtracting the real hydrocarbon generation potential (HGPR) from the original hydrocarbon generation potential (HGPO). The HGPR is calculated from pyrolysis parameters after light hydrocarbon calibration. Based on a kerogen kinetic theory, the HGPO is restored by utilizing a data-driven model with IBM-SPSS statistics. The results show that the Fengcheng Formation (P1f) shale features medium TOC contents, mixed kerogen types, mature to overmature levels, and high oil contents. Sixty-five percent of the P1f shale samples exhibit hydrocarbon intramicromigration, while the rest exhibit hydrocarbon extramicromigration. Shale oil contents and composition are closely related to hydrocarbon micromigration. The greater the hydrocarbon intramicromigration is, the higher the shale oil content. Micromigration occurs due to differences in hydrocarbon expulsion, pore space, and capillary pressure among shales. This method has a worldwide application for shale oil evaluation, and the findings will help to uncover shale oil differential enrichment mechanisms.

Experimental Investigation of Two-Phase Flow Properties of Heterogeneous Rocks Based on X-Ray Microfocus Radiography

Summary An uncommon facet of formation evaluation is the assessment of flow-related in-situ properties of rocks. Most of the models used to describe two-phase flow properties of porous rocks assume homogeneous and/or isotropic media, which is hardly the case with actual reservoir rocks, regardless of scale; carbonates and grain-laminated sandstones are but two common examples of this situation. The degree of spatial complexity of rocks and its effect on the mobility of hydrocarbons are of paramount importance for the description of multiphase fluid flow in most contemporary reservoirs. There is thus a need for experimental and numerical methods that integrate all salient details about fluid-fluid and rock-fluid interactions. Such hybrid, laboratory-simulation projects are necessary to develop realistic models of fractional flow in complex rocks, i.e., saturation-dependent capillary pressure and relative permeability. Furthermore, these two crucial properties are usually measured independently. Capillary pressure is typically assessed using static measurements and unrealistic pressure conditions, whereas relative permeability is evaluated dynamically. Consequently, the disparity between the nature of the two experimental procedures often results in a potentially significant loss of information. We document a new high-resolution visualization technique that provides experimental insight to quantify fluid saturation patterns in heterogeneous rocks which allow for the simultaneous and dynamic evaluation of two-phase flow properties. The experimental apparatus consists of an X-ray microfocus scanner and an automated syringe pump. Rather than using traditional cylindrical cores, thin rectangular rock samples are examined, their thickness being one order of magnitude smaller than the remaining two dimensions. During the experiment, the core is scanned quasicontinuously while the fluids are being injected, allowing for time-lapse visualization of the flood front. Numerical simulations are then conducted to match the experimental data and quantify effective saturation-dependent relative permeability and capillary pressure. The experimental results indicate that flow patterns and in-situ saturations are highly dependent on the nature of the heterogeneity and bedding-plane orientation during both imbibition and drainage cycles. In homogeneous rocks, fluid displacement approaches piston-like behavior. The assessment of capillary pressure and relative permeability is performed by examining the time-lapse water saturation profiles resulting from fluid displacement. In spatially complex rocks, high-resolution time-lapse images reveal preferential flow paths along high-permeability sections and a lowered sweep efficiency. Our experimental procedure emphasizes that capillary pressure and transmissibility differences play an important role in fluid-saturation distribution and sweep efficiency at late times. The method is fast and reliable to assess mixing laws for fluid-transport properties of rocks in spatially complex formations.

Study on pre-concentration of trace heavy metal ions in water quality detection using FO-electroosmotic integrated chip

The focus of this study is on the enhanced concentration effect of the pump effect in forward osmosis (FO) and electroosmotic integrated chip. The study investigates the strengthening effect of the FO process, driven by the pump effect, on the electroosmotic flow process under the same energy consumption, using low-concentration heavy metal ions (Cr3+) as the target enrichment. In the chip system, the pump effect, caused by capillary pressure difference, successfully replaces the osmotic pressure of the draw solution as a new driving force for the FO process. By adjusting the size and number of channels and avoiding errors, the study achieves the highest efficiency of the FO process in the chip, concentrating Cr3+ from 1.26 × 10−4 mol/L to 8.01 × 10−4 mol/L (6.4 times) within 32 min. Excluding the influence of the electrokinetic (EK) limit of low-concentration samples, the concentration efficiency of an individual electroosmotic chip in this study is positively correlated with cross-nanochannel voltage (Vcn). The integrated FO and electroosmosis chip reduce the duration required to concentrate 50 mL Cr3+ sample to the limit from 90 min to 16 min (5.6 times) compared to the single electroosmotic process. Furthermore, a series of Cr3+ samples with concentrations below the detection limit of the UV–vis spectrophotometer were concentrated and detected by the integrated chip. The results indicate that the concentration limit of the FO-electroosmotic integrated chip for samples can increase the detection limit of Cr3+ from 1.37 × 10−4 mol/L to 3.67 × 10−6 mol/L.

Two-Stage Microporous Layers with Gradient Pore Size Structure for Improving the Performance of Proton Exchange Membrane Fuel Cells.

In this paper, we report the preparation of a gas diffusion layer (GDL) with different gradient pore size structures. The pore structure of microporous layers (MPL) was controlled by the amount of pore-making agent sodium bicarbonate (NaHCO3). We investigated the effects of the two-stage MPL and the different pore size structures in the two-stage MPL on the performance of proton exchange membrane fuel cells (PEMFC). The conductivity and water contact angle tests showed that the GDL had outstanding conductivity and good hydrophobicity. The results of the pore size distribution test indicated that introducing a pore-making agent altered the pore size distribution of the GDL and increased the capillary pressure difference within the GDL. Specifically, there was an increase in pore size within the 7-20 μm and 20-50 μm ranges, which improved the stability of water and gas transmission within the fuel cell. The maximum power density of the GDL03 was increased by 37.1% at 40% humidity, 38.9% at 60% humidity, and 36.5% at 100% humidity when compared to the commercial GDL29BC in a hydrogen-air environment. The design of gradient MPL ensured that the pore size between carbon paper and MPL changed from an initially abrupt state to a smooth transition state, which significantly improved the water and gas management capabilities of PEMFC.

Driving forces and their relative contributions to hydrocarbon expulsion from deep source rocks: A case of the Cambrian source rocks in the Tarim Basin

To thoroughly understand the dynamic mechanism of hydrocarbon expulsion from deep source rocks, in this study, five types of hydrocarbon expulsion dynamics (thermal expansion, hydrocarbon diffusion, compaction, product volume expansion, and capillary pressure difference (CPD)) are studied. A model is proposed herein to evaluate the relative contribution of different dynamics for hydrocarbon expulsion using the principle of mass balance, and the model has been applied to the Cambrian source rocks in the Tarim Basin. The evaluation results show that during hydrocarbon expulsion from the source rocks, the relative contribution of CPD is the largest (>50%), followed by compaction (10%–40%), product volume expansion (5%–30%), and thermal expansion (2%–20%). The relative contribution of diffusion to hydrocarbon expulsion is minimal (<10%). These results demonstrate that CPD plays an important role in the hydrocarbon expulsion process of deep source rocks. The hydrocarbon expulsion process of source rocks can be categorized into three stages based on the contribution of different dynamics to the process: the first stage is dominated by compaction and diffusion to expel hydrocarbons, the second stage is dominated by product volume expansion and CPD, and the third stage is dominated by product volume expansion and CPD. This research offers new insights into hydrocarbon exploration in tight oil and gas reservoirs.

Experimental study on fracture effect on the multiphase flow in ultra-low permeability sandstone based on LF-NMR

Multiphase flow affected by fractures is essential for enhanced oil recovery in ultralow-permeability reservoirs. In this study, CO2/water flooding of intact and fractured cores was performed under in-situ stress, and low-field nuclear magnetic resonance was employed to monitor the pore structure evolution and multiphase flow. The adsorption pore (AP), percolation pore (PP), and migration pore (MP) were determined in the ultralow permeability sandstone, and the PPs and MPs contributed to oil recovery during CO2 flooding. Three-scale pores contributed to oil production during water flooding. Compared with water flooding, CO2 flooding had a considerably higher average recovery efficiency, which was associated with pronounced gas channeling and lower ultimate oil recovery. In CO2 flooding, the oil production in PPs and MPs depended on the pressure difference, whereas that in APs was determined by oil swelling. But for water flooding, oil migration in the AP and MP was dominated by capillary imbibition and pressure difference, respectively. The fracture enhanced the oil recovery during CO2 flooding by increasing the CO2 sweep area in the PPs and MPs. It also improved oil recovery during water flooding based on the increment of the oil-water flow area in the APs and MPs. The mass transfer in CO2 flooding between the fracture and the matrix occurred through the PP and MP connected to the fracture, controlled by the pressure difference, number of PP and MP connected to the fracture, and oil swelling capacity. For water flooding, the oil-water exchange in the fracture-matrix system was dominated by number of pores connected to the fracture, hydrophilic ability of the rock, and pressure difference. These results can be used for enhancing oil recovery in fractured ultralow-permeability reservoirs.

Thermal performance of a single loop pulsating heat pipe with asymmetric adiabatic channel

The thermal performance of an asymmetric single-turn closed-loop pulsating heat pipe (aCLPHP) has been investigated experimentally. In an asymmetric closed-loop, the working fluids may exhibit a consistent two-phase oscillatory-circulatory flow as a direct consequence of the capillary pressure difference. The adiabatic channels of different cross-sections will cause a pressure difference, boosting the flow of heated vapor and liquid. So, a novel aCLPHP of 208 mm with an evaporator of 35 mm length was fabricated from 2.4 and 3.4 mm inner diameter copper capillary tubes. The setup was subjected to gradual and abrupt heat loads (in vertical bottom heating mode) to find out the effects of inclination angles (0°, 30°, 60°, and 90°), working fluids, and filling ratios (FR) on the thermal performance. A constant supply of coolant in the condenser chamber through a bath assisted in dissipating the heat from the heat pipe. The simultaneous temperature and pressure signals at 10 Hz were recorded through a data acquisition system to analyze the thermal performance and flow characteristics. The average thermal resistance is mapped to different operating conditions to compare the conventional (uniform cross-section) and asymmetric adiabatic channel configurations. The pseudo-steady state operation was obtained up to 100 W power supply at 60% FR of pure water in the vertical orientation. Due to asymmetry, the heat carrying capacity was increased by 75% and 50% for working fluid water and acetone, respectively. The heat pipe was operating at lower inclination angles, except horizontal orientation only with pure water. Hence, introducing an asymmetric adiabatic section is a simple, reliable, and cost-effective approach to improve the capability of a single-turn CLPHP for the thermal management of various electronic components.

Experimental and modeling study of foam coarsening kinetics in porous media

The geometric confinement significantly affects the foam coarsening dynamics in porous media. We present the experimental and modeling studies of coarsening-induced foam structural evolution in a porous microfluidic chip. The findings are expected to shed light on predicting the foam structure in many applications, such as foam-assisted enhanced oil recovery process and CO2 geological sequestration. It is shown that, in porous media, small bubbles are constantly consumed by large bubbles due to inter-bubble gas diffusion until most bubbles grow to the pore or throat size. The coarsening of edge bubbles (bubbles contacting the boundary) dominates the foam coarsening process, showing a linear increase in the average area of edge bubbles with time in a steady-state growth state. A mass transfer model is proposed to fit the foam coarsening rate of edge bubbles, including critical parameters such as liquid film permeability, gas-liquid interfacial tension, the molar volume of the dispersed phase, and the polydispersity of bubble size distribution. We emphasize that, under the same experimental conditions, foams with a broader size distribution exhibits a faster coarsening rate due to higher capillary pressure differences among the bubbles as the mass transfer driving force.

Discrepancy of simulating snap-off processes in 2D and 3D pore-throats

3D pore-throats with uniform thickness were commonly used to explore snap-off processes in experimental studies, and always simplified as 2D areal models in simulation of snap-off processes. However, 3D effects of capillary force, viscous force and wall cannot be neglected. We assume that snap-off processes in 2D and 3D pore-throats may exist discrepancy. Snap-off processes in both 2D and 3D pore-throats were simulated with various capillary numbers Ca, viscosity ratios μr and size ratios M of throat and pore. The results showed: (1) snap-off was more prone to occur with the same M in 3D pore-throats due to the larger capillary pressure difference; (2) the increase of M inhibited occurrence of snap-off, and the inhibition effect of M was more obvious in 2D pore-throats; (3) snap-off only occurred with M < 7/35 in 2D pore-throats, which was significant different from the Roof theory (M < 1/2). These findings indicate that 2D areal models are not suitable to simplify the 3D pore-throat in simulating snap-off processes.

Three-dimensional pore-scale observation of drying process of porous media

X-ray micro-tomography was used to comprehensively study the pore-scale drying process and characterize the liquid film region and the invasion front. Our finding reveals that the decrease in saturation is not uniform across the pore size. The capillary rearrangement, which refers to the restructuring of the liquid phase due to the capillary pressure difference, drives the liquid to flow from large pores to small pores. As a result, the decrease in liquid saturation occurs preferentially within the larger pores. A sharp decrease in liquid saturation occurred at the invasion front, where saturation ranged from 1 to around 0.15(0.15<S<1). The obtained invasion width σp that characterized the extent of roughness and disorder of the invasion front obeyed the scaling law of the percolation model. Therefore, this region is significantly limited by the interaction between capillary and gravity. However, with more multi-pore connected clusters observed within the porous medium, the critical exponent τ of the cumulative cluster size distribution CDF(s) obtained from the cluster region (0<S<0.15) deviates from the universal power-law behavior. This result indicates the presence of liquid film within the cluster region, where the viscous force becomes comparable to the capillary force. We also found that the total gas-liquid-specific interfacial area has no effect on the drying rate. This result provides new evidence that the liquid film region is vapor saturated.

The "Balloon-Like" Sign: Differential Diagnosis between Postoperative Air Leak and Residual Pleural Space: Radiological Findings and Clinical Implications of the Young-Laplace Equation.

Simple SummaryPostoperative residual pleural space and postoperative air leaks after lung resection are two different clinical entities requiring completely different approaches. Residual postoperative pleural space is a part of the pleural cavity that is not fully reoccupied by the remaining lung after pulmonary resection. No treatment is needed in the asymptomatic residual pleural space without any persistent air leak, and chest drain removal can be safely planned. On the contrary, an active and prolonged air leak after lung resection is an absolute contraindication to chest drain removal that may culminate in hypertensive pneumothorax, subcutaneous emphysema, and severe respiratory symptoms. In order to further contribute to an appropriate differential diagnosis between these two settings, we propose a radiological sign that is observed only in the case of residual plural space. In this case, in fact, the lung takes the form of a round balloon due to the hyperinflation condition, which is governed by the Young–Laplace equation describing the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of wall tension.In this paper, we propose a radiological sign for an appropriate differential diagnosis between postoperative pleural space and active air leak after lung resection. In the case of residual pleural space without any active air leak, the lung takes the form of a round balloon due to the hyperinflation condition, which is governed by the Young–Laplace equation describing the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of wall tension. The two principal mechanisms by which a lung forms a spherical image are shear-controlled detachment induced by shear stress on the membrane surface, and spontaneous detachment induced by a gradient in Young–Laplace pressure. On the contrary, the lung maintains its tapered shape in the case of an active air leak because the continuous air refill does not allow a complete parenchyma re-expansion.

A Dynamic Pore Network Model for Imbibition Simulation Considering Corner Film Flow

AbstractWetting films can develop in the corners of angular pores under strong wetting conditions. Modeling the dynamics of corner film remains elusive using direct numerical simulations because of the significant scale difference between main meniscus and corner film flow. In this paper, the modified interacting capillary bundle model (ICB), developed in our previous work to describe accurately corner film dynamics in a single square tube, is incorporated into a single‐pressure dynamic pore network model (DPNM) to simulate imbibition in strongly wetting porous media with corner film flow. The traditional pore network is decomposed into several layers of interacting subpore networks where the 0th layer of subpore network simulates the main meniscus flow and higher layers the corner film flow. The fluid flow between different layers is captured by interlayer throats. In addition, the snap‐off mechanism caused by the thickening of wetting corner film is considered. The accuracy of the developed model is validated for four cases: spontaneous imbibition in a single square tube, wetting fluid redistribution through corner films under a capillary pressure difference, snap off in a narrow throat connecting two large pores, and imbibition dynamics in a real microfluidic porous geometry. The validated model is then used to simulate both spontaneous and controlled imbibition in a pore network with random pore size distribution. The interaction between corner film and main meniscus flow in porous media is analyzed from a pore‐scale perspective.

Monolithic Al2O3 Xerogels with Hierarchical Meso‐/Macropore System as Catalyst Supports for Methanation of CO2

AbstractCylindrical, cm‐sized monolithic Al2O3 xerogels with hierarchical meso‐/macropore system were prepared by sol‐gel synthesis. The influence of both solvent exchange and drying on monolith stability and the resulting pore system was studied following mass and volume of the monolith as well as by porosimetry and electron microscopy. Crack‐free drying of the monoliths requires a proper management of drying stress. This is achieved by adjusting the drying rate and solvent exchange procedure applied to the intermediate lyogels. Moreover, mainly through differences in capillary pressure, changing the pore fluid allows an adjustment of the mesopore width from 7.6 nm to 10.5 nm. Neither solvent exchange nor drying affect the macropores, the width of which stays at 1.5 μm. Finally, CO2 methanation over Ni‐impregnated Al2O3 monoliths reveals CO2 conversion and CH4 selectivity comparable to an industrial Ni/Al2O3 benchmark catalyst.