Water Flow Research Articles

Development of a Negatively Charged Polyether Sulfone Membrane Enriched with MIL-101(Cr)-Modified Magnetic Activated Pyrolytic Coke for Enhanced Dye Removal, Permeability, and Antifouling Properties

Developing high-performance nanofiltration membranes for effectively treating wastewater contaminated with organic pollutants has become increasingly important. Given the hazardous nature of these contaminants, proper treatment of wastewater is crucial before it is released into natural water bodies. This study synthesized a novel composite membrane by incorporating Fe3O4@APC@MIL-101(Cr) nanocomposites into a polyether sulfone (PES) matrix using a phase inversion technique. The inclusion of 0.5wt.% Fe3O4@APC@MIL-101(Cr) significantly enhanced the membrane's hydrophilicity, porosity, and surface characteristics. The optimized membrane achieved an impressive pure water flux (PWF) of 90.24L/m²h, reflecting a 400% improvement over pristine PES membranes. Moreover, it exhibited excellent rejection rates of 97.21% for crystal violet (CV) and 99.43% for methylene blue (MB), alongside a rejection efficiency of 57.73% for the anionic dye methyl orange (MO). The antifouling performance was notably improved, as evidenced by an increase in the flux recovery ratio (FRR) from 46% for bare PES membranes to 81.11% for hybrid membranes. Additionally, the effects of various salt types on the membrane's separation performance were investigated. The Fe3O4@APC@MIL-101(Cr) modified PES membranes demonstrate significant potential as effective candidates for treating wastewater contaminated with dye pollutants.

Protein digestion and amino acid absorption mechanisms along the midgut of Musca domestica larvae

A model of protein digestion and peptide and amino acid absorption along the midgut of Musca domestica larvae was proposed and supported by RNA-Seq analyses, protein bioinformatics, microvillar-membrane-enriched midgut proteomics, and enzymatic activities. Peptidase genes are highly expressed in the posterior midgut (PM), whereas those for cathepsins have expression limited to the middle midgut (MM). MM has the lowest levels of gene expression of almost all peptidases but has high expression of genes for membrane-bound serine endopeptidases. The anterior midgut (AM) has intermediate expression values of serine endopeptidase and aminopeptidase (AP) genes and low expression of carboxypeptidases (CPs). Gene expression and peptidase activities were usually consistent for putative intracellular and membrane-bound enzymes. However, secreted peptidase gene expression and activities have divergent values, especially in the PM, which may be due to the countercurrent water flux causing enzyme recycling, thus decreasing their excretion. Data suggest that Trys and APs act in the AM. In the acidic MM, lysozymes kill microorganisms found in the diet, releasing proteins digested by cathepsins D, which may also digest Trys coming from the AM. Finally, highly active serine endopeptidases, CPs, dipeptidases, and APs complete protein digestion in PM. Absorption of peptides and amino acids coupled to protons may occur along the midgut, especially in PM, as occurs for facilitated amino acid transport. Absorption with sodium ions is probably restricted to AM and PM. Our findings provide valuable insights into the protein digestion and amino acid absorption mechanism in M. domestica larvae.

Vegetation greening mitigates the positive impacts of climate change on water availability in Northwest China

Climate change alters water availability (precipitation minus evapotranspiration, i.e., water yield, WY), especially in arid regions like Northwest China (NWC) where water resources are limited. Despite large-scale implementation of ecological restoration projects has contributed to greener vegetation, this may exacerbate dryland water stress, which in turn interferes with climate change impacts on WY. To better understand this issue we used the random forest model to differentiate the effects of climate change and human activities on WY. We also employed the structural equation model to explore how vegetation greening influenced climate-induced WY trends. The results showed that the multi-year average WY in NWC was 2162.21 t and demonstrated a rising trend from 1982 to 2018, primarily driven by climate change. In contrast, anthropogenic activities had minimal effects on WY but were effective in amplifying the warming and wetting effects of climate (6.64 %-7.98 %) and counteracting unfavorable climate stress effects. Vegetation greening exacerbated soil water depletion, leading to increased evapotranspiration and mitigating the positive effects of climate change on WY. Our results are crucial for an effective comprehension of the role of vegetation in regulating terrestrial water fluxes in arid regions, providing a theoretical basis for ecological restoration.

Amino acid-based nanoparticles-incorporated thin-film nanocomposite forward osmosis membranes for efficient desalination and heavy metal ions rejection

The current study explores potential applications of state-of-the-art thin-film nanocomposite forward osmosis (TFN-FO) membranes, modified with histidine-functionalized graphene quantum dots (His-GQDs) and MIP-202(Zr) nanoparticles (NPs), for sustainable desalination and heavy metal ions rejection. The porous and layered structure of the applied NPs, along with various hydrophilic functional groups on their surface, contribute to improving the fabricated membranes' ion/water separation performance. The successful preparation and incorporation of desired NPs into the polyamide layer was investigated using typical analytical methods. Under the common FO test conditions, the best-performing TFN-MQ2 membrane displayed a water flux of 21.8 LMH, which was over 1.5 times greater than the water flux of blank TFC. Simultaneously, the selectivity was found to be approximately 1.7 times greater than that of the unmodified TFC membrane. Moreover, the optimal TFN-MQ2 membrane exhibited superior rejection rates for Cu2+ ions (98.5 %) and Pb2+ ions (98.1 %), surpassing all other samples in heavy metal ion rejection. The findings of this study suggest that carefully choosing cost-efficient and eco-friendly nanofillers (such as amino acid-based NPs) can enhance the desalination performance of TFN-FO membranes and bolster their resistance to fouling and rejection of heavy metal ions. Not to mention, the overall costs of membrane production will be reduced.

Adjusting Oxidation Pathways via Fine-tuning Atomic Ratios in Window-opening MO0F Membranes for Efficient Self-cleaning

Peroxymonosulfate (PMS) can be used as a green oxidant to mitigate catalytic membranes fouling and restore filtration performance through advanced oxidation processes (AOP). However, the adjustment of oxidation pathways and the understanding of underlying mechanisms for efficient cleaning without sacrificing the filtration performance need to be studied systematically. We optimized the membranes microenvironment via thermal modification from 25 °C to 400 °C below the catalyst ZIF-8 framework's decomposition temperature. The modified membranes have a doubled pure water flux (158.3 LMH bar−1) and remain rejection rates due to intact ZIF-8 framework structure with “window-opening” effect. The methyl dissociation and self-catalyzed graphitization were regulated by changing temperature, resulting in adjustable nonradical pathway proportion (correlated with the C/Zn atomic ratio at 0.96). The enhanced nonradical pathway targeted attacks on electron-rich regions of organic compounds, resulting in efficient cleaning and almost complete flux recovery (99.3%). The theoretical simulations revealed that methyl groups dissociation and graphitization significantly influence the electron density and adsorption energy at active sites for tunable oxidation pathways and enhanced catalytic performance. Our work offers a rational strategy to improve both filtration and catalytic performance in catalytic membranes. The enhanced understanding of oxidation mechanisms guides the design of designing efficient AOP membrane cleaning systems.

Quantification of the Effect of Soil and Biophysical Parameters on Water Balance Modelling Using SWAT+ in Forested Catchments

ABSTRACTAccurate simulation of water balance components is crucial for effective water and land management practices. The performance of process‐based hydrological models relies on the accurate determination of input variables. The objective of this study is to quantify the magnitude of the effect of soil properties (depth and texture) and biophysical parameters on water balance simulation for a forested catchment using the Soil and Water Assessment Tool (SWAT+). Simulations were carried out for a baseline scenario using the default soil inputs, followed by extending the soil profile depth up to 15 m under three different rainfall scenarios. Sensitivity analysis of model outputs was performed using the SENSitivity ANalysis (SENSAN) programme of the Parameter ESTimation (PEST) suite, coupled with SWAT+. The results showed that increasing soil profile depth to 15 m led to around 50% increase in water yield, and around 20% reduction in percolation with slight variations across the three rainfall scenarios. Evapotranspiration rates were slightly increased in deeper soil profiles. The sensitivity of evapotranspiration, surface runoff, and percolation to LAI‐related biophysical parameters was pronounced, highlighting the need to include such parameters in SWAT+ model calibration. The water uptake from deeper soil layers by deep roots, even in rocky substrates, as documented in the literature, is not adequately captured by the SWAT+ model. Our work showed that in general, developing local soil databases with detailed information on deeper layers is needed, to improve the accuracy and reliability of hydrological models in predicting water fluxes, thereby supporting informed water resources management decisions.

The Effect of Sharklet Patterns on Thermal Efficiency and Salt-Scaling Resistance of Poly (vinylidene fluoride) Membranes During Direct Contact Membrane Distillation

Membrane distillation (MD) can treat high-salinity brine. However, the system's efficiency is hindered by obstacles, including salt scaling and temperature polarization. When properly implemented, surface patterns can improve the mass and heat transfer in the boundary layer, which leads to higher MD efficiency. In this work, the performance of direct contact membrane distillation (DCMD) using Sharklet-patterned poly (vinylidene fluoride) (PVDF) membranes is investigated. Both non-patterned and patterned PVDF membranes are prepared by lithographically templated thermally induced phase separation (lt-TIPS) process with optimized conditions. Sharklet patterns on the membranes improve the DCMD performance: up to 17 % higher water flux and 35 % increased brine-side heat transfer coefficient. The scaling resistance of the membranes during DCMD is tested by both saturated CaSO4 solution and hypersaline NaCl solutions. Patterned PVDF membranes show an average of 30 % higher water flux and up to 45 % lessened flux decline over time compared with non-patterned membranes when treating high-concentration brines. Post-mortem analysis reveals that Sharklet-patterned membranes display less salt-scaling on surfaces with smaller-sized CaSO4 and NaCl crystals, maintain a relatively cleaner surface, and exhibit better retention of hydrophobicity.

Bidirectional solar water production enabled by a breathable Janus photothermal material

Solar-driven interfacial water evaporation offers a promising solution to the global scarcity of freshwater. Despite advances in increasing evaporation rates, current condensate productivity is limited to 0.3 − 0.5 kg m−2 h−1 due to unidirectional vapor diffusion, which is insufficient to satisfy water demands. This paper introduces a bidirectional solar water production (BSWP) device that utilizes a breathable Janus photothermal material made from recycled cotton fabric. The BSWP device allows vapor to diffuse in both upward and downward directions of the evaporation interface. This design features dual condensers, addressing the limitations of traditional solar stills by reducing vapor concentration and minimizing light loss due to condensation on the top cover receiving light. Under 1 sun illumination, the BSWP device achieves a water yield of 1.06 kg m−2 h−1 with a solar-to-water efficiency of 71%. An 10-hour outdoor experiment demonstrates that the BSWP device can yield a water flux of 9.65 kg m−2, showcasing its potential for efficient water generation in practical environmental conditions. The present work provides a new perspective on the structural design of direct solar desalination configurations, potentially offering a more effective solution to cope with global water scarcity.

Promoting algae separation of forward osmosis by peracetic acid and chitosan quaternary ammonium salt: Purification efficiency, membrane fouling alleviation, and lipid production

Forward osmosis (FO) is a prospective technology for microalgae biomass recovery, whereas severe membrane fouling still limits its application. To improve the separation efficiency of FO, peracetic acid (PAA) oxidation followed by chitosan quaternary ammonium salt (HTCC) coagulation was proposed. The synergistic effect of PAA-HTCC on the characteristics of Chlorella vulgaris and the separation performance of FO were systematically studied, and the mechanism was revealed. With PAA-HTCC treatment, the harvesting efficiency of algal cells was increased to 88.5 %, and algal aggregates with sizes of 100-300 μm were formed while maintaining excellent cell viability. Membrane fouling caused by microalgae was mitigated, with the water flux increased from 15.0 to 19.2 L/(m2·h), and the recovery flux increased to 90.0 %. The lipid production capacity of microalgae was significantly promoted, with the lipid productivity increased from 10.5 to 27.9 mg·L−1·d−1. During PAA oxidation, •OH and •CH3 were the major reactive species, which could remove electronegative organics coated on algal cells, contributing to the aggregation of microalgae in the coagulation by HTCC. Moreover, PAA-HTCC could also provide carbon sources for microalgae growth, thus the water purification efficiency of FO and the lipid production of concentrated microalgae were simultaneously promoted. The proposed strategy has certain significance for water purification and resource utilization of algae.

Mixed Matrix PVDF Microfiltration Membranes with In-situ Synthesized Polyethyleneimine Particles as a Platform for Flow Through, High Capacity, Weak Base and Salt Tolerant Anion Exchange Membrane Adsorbers for Downstream Bioprocessing

The rapid growth of the monoclonal antibody (mAb) therapeutic market has led to a need for improved downstream bioprocessing, including mAb capture and release from bioreactor harvests followed by product purification and polishing. Membrane chromatography (MC) is poised to displace resin-based column chromatography in mAb product polishing. To remove negatively charged product impurities (e.g., host cell proteins, DNA, viruses, and endotoxins), anion exchange (AEX) membrane adsorbers offer higher process rates and eliminate the risks of cross contamination as they can be deployed as single use separation devices, which are increasingly being utilized in downstream bioprocessing to increase manufacturing speed and decrease production cost. Here, we describe a one-pot and single step phase inversion casting process for the preparation of a family of mixed matrix polyvinylidene fluoride (PVDF) microfiltration (MF) membranes with in-situ synthesized polyethyleneimine (PEI) microparticles that can serve as flow through, high capacity, and salt tolerant weak base AEX membrane adsorbers. These new membranes have a high content of weak base (WB) groups (primary and secondary amines) by virtue of the utilization of bis(2-chloroethyl)amine hydrochloride (BCAH) as crosslinker in the in-situ synthesis of PEI microparticles in the dope dispersions prior to membrane casting. By varying the concentration of PEI and BCAH in the casting dispersions, we successfully utilized nonsolvent induced phase separation (NIPS) with isopropyl alcohol as the nonsolvent in the membrane coagulation bath to prepare a mixed matrix PVDF-PEI MF membrane with (i) a relatively uniform and open microstructure in which the PEI particles completely cover the PVDF spherulites present at the membrane surface and cross section, (ii) high water flux (>1000 liters/m2/hr. at 2 bar) and (iii) a high loading of BCAH crosslinked PEI microparticles (51.0 wt.%) containing weak base primary, secondary, and tertiary amine groups. The protein binding measurements show that this new mixed matrix PVDF-PEI MF membrane can serve as a flow through, high capacity, and salt tolerant WB AEX membrane adsorber with a bovine serum albumin (BSA) dynamic binding capacity of ∼60 mg BSA per mL of membrane in a 50 mM TRIS buffer containing 100 mM of NaCl (15 mS/cm) at 10% breakthrough and flow rate of 10 MV/min. The overall results of this study indicate that our mixed matrix PVDF-PEI MF membranes with in-situ synthesized and BCAH crosslinked PEI microparticles have a promising potential to serve as a platform for the design, preparation, and scale up of a new generation of flow through, high capacity, salt tolerant, WB AEX membrane adsorber materials for downstream bioprocessing.

Structure-performance relationship in tailored poly(amide-sulfone) membranes for desalination

Poly(amide-sulfone)s were considered the missing link for water desalination membranes, owing to their exceptional properties resulting from the synergism effects of two amide and sulfone structures. To achieve this, a sulfone-based diamine was first synthesized by reacting 4,4′-dichlorodiphenyl sulfone with 3-aminophenol. Subsequently, alternative copolymers of poly(amide-sulfone) were prepared via polycondensation reactions of the synthesized diamine monomer and various diacid chlorides including adipoyl dichloride, isophthaloyl dichloride, and terephthaloyl dichloride. The chemical structures were approved using Fourier transform infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy. Porous membranes of the polymers as substrates were prepared by solution casting and phase-inversion method. To form thin film composite membranes, a thin polyamide layer was created through interfacial polymerization on the top surface of prepared substrates using m-phenylenediamine and trimesoyl chloride. After characterization, the performance of all membranes was assessed by evaluating pure water flux, NaCl rejection, and flux recovery ratio using a cross-flow filtration system. The impact of the amide group within the poly(amide-sulfone) substrate structure on thin-film efficiency was explored. Results, revealed that the structure significantly influenced membrane performance. Specifically, the highest pure water flux was 549.50 L.m−2.h−1. Also, NaCl rejection of 98.27 % and flux recovery ratio of 94.21 % were observed among them at pressure of 10 bar. This study provided valuable insights for developing novel poly(amide-sulfone) membranes tailored for desalination applications.

Novel polymeric membranes based on green reduced graphene oxide for the Nanofiltration of emerging contaminants from water in a ternary system

Polymeric membranes containing reduced graphene oxide (rGO) have demonstrated efficacy in the remediation of contaminated water. The objective of this study was to examine the impact of the morphological and physicochemical properties of polyacrylonitrile membranes (hPAN) containing rGO on their filtration and adsorption performance. The rGO was prepared via a green route (g-rGO), and the filtration experiments applied the removal of emerging contaminants in a ternary system that simulates real conditions. The incorporation of g-rGO into the membrane resulted in the formation of a thinner finger-like sublayer, an increased in the membrane’s roughness, and an enhancement in the pure water flux. The batch experiments revealed adsorption rates of 72%, 55%, 75%, 96%, and 80% for ciprofloxacin (CIP), moxifloxacin (MOX), and levofloxacin (LEV), Cu(II) and Zn(II), respectively. The adsorption rate for CIP and MOX increased by 151% and 87.5%, respectively, in comparison to the pristine hPAN membrane. In the filtration experiments conducted in a ternary system, the membrane hPAN@g-rGO5 exhibited a rejection rate of 62%, 59%, and 68% for acetaminophen, atrazine, and sulfamethoxazole, respectively. The density functional theory (DFT) study indicated that sulfamethoxazole was the most removed emerging contaminant of the ternary system, primarily due to its higher size and the presence of π-π interactions and hydrogen bonding.

Xylem and Phloem in Petioles Are Coordinated With Leaf Gas Exchange in Oaks With Contrasting Anatomical Strategies Depending on Leaf Habit.

As the single link between leaves and the rest of the plant, petioles must develop conductive tissues according to the water influx and sugar outflow of the leaf lamina. A scaling relationship between leaf area and anatomical traits of xylem and phloem is expected to improve the efficiency of these tissues. However, the different constraints compromising the functionality of both tissues (e.g., risk of cavitation) must not be disregarded. Additionally, deciduous and evergreen plants may have different strategies to produce and package their petiole conduits to cope with environmental restrictions. We explored in 33 oak species the relationships between petiole anatomical traits, leaf area, stomatal conductance, and photosynthesis rate. Results showed allometric scaling between anatomical structure of xylem and phloem with leaf area. We also found correlations between photosynthesis rate, stomatal conductance, and anatomical traits in the petiole. The main novelty is how oaks present a different strategy depending on the leaf habit. Deciduous species tend to increase their diameters to achieve greater leaf-specific conductivity. By contrast, evergreen oaks develop larger xylem conductive areas for a given leaf area than deciduous ones. This trade-off between safety-efficiency in petioles has never been attributed to the leaf habit of the species.

Can Developments in Air–Water Flow Instrumentation Advance Hydraulic Design?

Can Developments in Air–Water Flow Instrumentation Advance Hydraulic Design?

Feasibility of coaxial deep borehole heat exchangers in southern California

This paper investigates the feasibility of coaxial deep borehole heat exchanger (CDBHE) applications to the University of California San Diego (UCSD) campus. By collecting different geophysical source data for various formations and well logs around the UCSD campus, a multilayered thermophysical model for the ground on the site is established. Water circulation within a closed coaxial loop system considers the geothermal energy extraction under uncertainty consideration of the unknown deeper layers heat flow gradient as coupled with the variation of pipe insulation properties, flow rates, outer pipe diameter, grout, and depths between 1 and 4 km. A finite-element framework models the Navier–Stokes fluid flow and heat transfer in the CDBHE system, validated with a field test on CDBHE from the literature. Results show that a 4-km CDBHE could produce a thermal power of 600 kW under the optimum geological conditions at the UCSD site: the water flow rate of 2.78 L/s and a ground thermal gradient of 60 ℃/km. Thermal power shares from different layers indicate that deeper formation layers contribute more to the thermal power than the shallower layers because increasing the CDBHE length from 1 to 4 km can lead to a maximum of 900% increase in thermal power and a 50% expansion in thermal plume for a CDBHE with an insulated inner pipe between the upper and lower bound heat flow bounds. An inner pipe with an insulated depth of 2 km produces only 1–6% less power than a fully insulated inner pipe for the 4-km CDBHE, and thus, a partially insulated vacuum-insulated tube (VIT)-plastic inner pipe is suggested as the best practice. Furthermore, the CDBHE thermal power increases by 5% when the grout thermal conductivity increases from 1 to 3.65 W/(K∙m), close to the formation thermal conductivity, and then maintains almost the same, and the 4-km CDBHE with flow rates of 2.78–6.94 L/s at the UCSD site can directly supply a low-temperature heating radiator system for room heating. This study suggests practical ranges for geothermal energy extraction for southern California. A CDBHE with a well-insulated inner pipe of 0.05 W/(m∙K), the thermal power of lower and upper-bound heat flow cases can vary by 60% from the mean. Finally, water as the working fluid is more efficient than CO2, doubling CDBHE's thermal power. The effects of the investigated factors provide guidelines for future geothermal resource exploitation in southern California.

Modelling of high-velocity free-surface flows: a revised interfacial area approach

The specific interface area transport equation is derived from first principles, and a closure model for turbulent flow is proposed. The flow is modelled by a two-phase method providing velocities of both phases at the bubbly, spray and the intermediate large scale interface (LSI) regimes. The interface area is transported by the interface velocity – a linear combination of corresponding phase velocities and a turbulent drift velocity. The resulting equation includes the source terms due to the bubble (droplet) breakup and coalescence, and turbulent splashes at the interface. A model is proposed for the source term in the LSI regime. The model is implemented in the developer's version of the Simcenter STAR-CCM+ ® CFD code. The new model is applied to self-aerating water flows down stepped chutes; the results are in reasonable agreement with the experimental data.

Impact of Three Gorges Dam construction on spatiotemporal variations in the hydrodynamic regime of Poyang Lake (China)

As an important large-scale river-connected lake in the middle–lower reaches of the Yangtze River, Poyang Lake has complex interactions with the main stream of the river. The full operation of the Three Gorges Dam (TGD) on the main stream of the Yangtze River has caused substantial changes in the relationship between the river and the lake, and the hydrological and hydrodynamic regime of Poyang Lake have also shown obvious variations in response. This study constructed a 2D hydrodynamic model of Poyang Lake based on GPU acceleration to realize a long-term simulation of the water flow evolution of Poyang Lake. By comparing the differences in water level at Hukou station between 20-year periods before and after TGD construction, the impact of TGD construction on Poyang Lake was characterized. Results showed that in comparison with the values for the pre-dam period, the water level of Poyang Lake decreased by 0.4–2.0 m and the flow velocity increased by 0.01–0.04 m/s in the post-dam period, and both showed a trend of reduction spatially from the north toward the south. Additionally, the inundation area of the lake decreased by 9 %, the 10-m characteristic water level at Xingzi station advanced by 27 days, the duration of low water extended by 37 days, and in typical dry, normal, and wet years, the time of occurrence of low water advanced. Moreover, TGD construction has aggravated the conditions of Poyang Lake in the dry season. The findings of this study are of great importance in relation to refining the spatiotemporal distribution characteristics of habitats, and supporting further investigation of the changes in the aquatic ecosystem of Poyang Lake under TGD regulation.

Double helix rotating TENGs driven by ultra-low loading for harvesting high-entropy water flow energy

Double helix rotating TENGs driven by ultra-low loading for harvesting high-entropy water flow energy

An experimental investigation on the role of the operating time of the mist device on the thermal performances of a water-sprayed air-cooled condenser and on the energy consumption of the cooling system

Water spraying upstream of an air-cooled condenser enables high heat dissipation. Meanwhile, a good control on the spray-heater parameters is crucial to avoid excesses of water and heat transfer destruction. This paper aims to experimentally illustrate the impact of the operating time of the mist device on the condenser thermal performances and the refrigerator energy consumption. To better visualize water stagnation phenomena, experiments are performed using a low pressure spraying device with 0.0065 L/min in water flow rate and 2-4 bar in pressure range. Several series of measurements have been performed on the refrigerant temperatures and pressures and on power consumption for different operating times of the mist device. Measured results showed that with 2 min of misting, the condenser inlet airflow and the refrigerant condensing pressure drop respectively from 32 to 27.4°C and 10 to 7.2 bar, while for 1 min of misting they decrease from 32 to 28°C and 10 to 7.6 bar, respectively. In this work, compared to the system without misting, maintaining the mist system in operation for 2 min allowed 54.9% enhancement in the Coefficient of Performance and 17.2% reduction in energy consumption. Consequently, the operating time of the mist device highly affects the condenser cooling performances and the refrigerator power consumption. Meanwhile, it is found that, above 2 min of misting, the condenser inlet airflow is saturated and the condensing pressure hardly changes while water stagnation is occurring. Hence, misting should be applied momentarily to avoid heat transfer destruction and water losses.

Liquid and gas permeabilities of nanostructured layers: Three-dimensional lattice Boltzmann simulation

Liquid water and gas permeabilities in nanostructured catalyst layers (CLs) (pore size ∼10–150 nm) and microporous layers (MPLs) (pore size ∼50 nm-5 μm) are crucial to reduce the mass transport loss in proton exchange membrane fuel cells (PEMFCs). Experimental measurement of their permeabilities poses great challenges due to their brittle and thin characteristics. Presently, considerable discrepancy exists in the reported permeability values for CLs and MPLs in the literature with variation spanning several orders of magnitude. This study digitally reconstructed various nanostructures of similar pore size as CLs and MPLs to calculate their permeabilities using the Lattice Boltzmann Method (LBM) based on no-slip (e.g. for liquid water flow in MPL and CL's secondary pores) or slip condition (e.g. for gas flow in MPL). Analysis was performed to evaluate the range of pore size in nanostructures for the two boundary conditions. A comprehensive investigation was conducted under various parameters such as the Reynolds number (Re), sphere diameter, porosity, and pore structure. The results revealed that permeability exhibits an increasing trend with the diameter and porosity. The predicted permeability of randomly arranged spheres agrees well with established correlations. The random sphere structure demonstrates higher permeability than their body-centered cubic (BCC) and face-centered cubic (FCC) counterparts. Under slip boundary condition, the permeability was enhanced, compared to the no-slip condition. This study's novelty lies in using distinct boundary conditions to assess the permeabilities of liquid and air, based on flow pattern analysis in the CL and MPL pore structures. A new empirical correlation describing the influence of the Knudsen number (Kn) on the slip permeability was developed, exhibiting consistency with simulation across the entire porosity spectrum.