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The interface tends to behave as a circular shape under the effect of surface tension in the two-dimensional two-phase fluid flow. In this study, based on the coupled volume-of-fluid and level set (VOSET) method, an accurate circle-based interface reconstruction (CIR) algorithm for structured meshes is proposed, which features a straightforward implementation procedure. A portion of the standard circle is employed to approximate the curve interface, without the need for complex classification, coordinate transformation, and equation transformation. The radius of this circle is computed simply by the curvature and signed distance at the mixed cell center, and the center of this circle is determined using a straightforward dichotomy method under the mass conservation constraints. Results indicate that the coupled VOSET and CIR (VOSET-CIR) method maintains superior computational accuracy in the signed distance, interface curvature, and dynamic interface reconstruction compared to the coupled VOSET and piecewise linear interface calculation (VOSET-PLIC) method, with accuracy improvements ranging from 34% to 1490% across different test cases. Furthermore, the VOSET-CIR method outperforms the efficient least squares volume-of-fluid interface reconstruction (ELVIRA) and PLIC algorithms in reconstructing random circles and surpasses the quadratic spline based interface reconstruction (QUASI) algorithm in reconstructing random squares. In terms of computational efficiency, except for the initial PLIC algorithm, the time costs of the VOSET-CIR method are substantially lower than those of the ELVIRA and QUASI algorithms, as well as the VOSET-PLIC method. [ABSTRACT FROM AUTHOR]

Collision between particle and wall is common in granular two-phase flow. This study is helpful to optimise flow conveying system, reduce attrition between materials and devices, and improve development of economy. The collision between a single coarse particle (3 mm in diameter) and wall in a viscous media was investigated by Hertz–Mindlin no-slip contact model based on the coupled computational fluid dynamics and discrete element method (CFD-DEM). Effects of impact velocity and viscosity of media on contact processes and contact force are studied in this research. The calculated results from the collision model are consistent with experimental data, and contact velocity and viscosity of media show significant effects on the contact force of particles. With the reduction of the dimensionless number St , the ratio of unloading time to loading time increases significantly. [ABSTRACT FROM AUTHOR]

• Water desalination performances of COFs membranes were studied by molecular dynamics. • Water permeation of CTF-FUM and TPMA monolayer membranes are 3 orders of magnitude higher than TFC. • CTF-FUM and TPMA membranes could exhibit nearly 100% salt rejection. • Membrane thickness should be considered for designing 2D hydrophobic COF membranes. To explore energy-efficient two-dimensional porous materials for water desalination is an urgent demand for rational utilization of water and sustainable development. In addition, how the pore hydrophilicity influencing the desalination performance remains elusive. Basing on molecular dynamics (MD) simulations, we herein proposed ultrathin membranes of 2D covalent organic frameworks (COFs) with triazine units that are competent to reject ions efficiently while giving access to high water permeability. The ordered porous structure of these two COFs membranes (CTF-FUM and TPMA) enable nearly 100% salt rejection and show remarkable higher water permeation (∼57.2 and ∼ 48.1 L cm−2 day−1 MPa−1, respectively) over 3 magnitude compared to commercial TFC membranes (∼0.03 L cm−2 day−1 MPa−1). As a further step, the influence of layer number on membrane desalination performance was discussed to understand the underlying mechanisms. Compared to TPMA multilayer, it was found that CTF-FUM multilayer with hydrophobic pore shows less water permeability and higher transport resistance, and even has no obvious water transport through the 8-layer membrane. This MD simulation work gives a microscopic insight into 2D COF membranes on desalination and suggests that TPMA multilayer might be a promising membrane material for desalination applications. [ABSTRACT FROM AUTHOR]

Flow boiling stands out as an efficient mode of heat transfer with significant potential for reducing carbon footprint. Based on a coupled Volume-of-Fluid and Level Set (VOSET) method, this numerical study reveals the microlayer and its evaporative heat flux distributions, as well as the effects of microlayer evaporation and depletion on bubble dynamic behavior, flow pattern, wall superheat distribution, and boiling crisis for the flow boiling in a mini-channel. These aspects are firstly comprehensively reported by the numerical method. Results indicate that the rapid evaporation of a thin microlayer positioned beneath elongated bubbles significantly contributes to heat dissipation during flow boiling in a mini-channel. The heat flux through the microlayer surpasses 300 kW/m2, accounting for approximately 42% of heat dissipation at 200 kW/m2. Furthermore, this contribution increases to over 70% as the heat flux exceeds 500 kW/m2. As a result, in comparison to scenarios without microlayers, the presence of microlayers results in an average heat transfer coefficient (HTC) that is 3.97 times larger within the range of 200–500 kW/m2. Additionally, microlayer evaporation delays the happening of flow boiling crisis. Without microlayers, the wall superheat exceeds 180 K at 500 kW/m2, whereas under microlayer influence, the maximum local wall superheat is only 37.09 K at 1000 kW/m2. With further increases in heat flux, the emergence of large dry patches resulting from microlayer depletion induces the beginning of heat transfer deterioration. Finally, the ongoing coalescence of elongated bubbles necessitates a prolonged period for rewetting dry patches at the exit of the mini-channel, triggering the flow boiling crisis at 1300 kW/m2. The study results provide crucial guidance for the development and application of the flow boiling heat transfer technology for the thermal management of data centers. [ABSTRACT FROM AUTHOR]

• A comprehensive review on numerical simulations of boiling heat transfer from atomistic to mesoscopic and macroscopic scales is presented. • Critical issues related to nanoscale bubble nucleation mechanisms, pool boiling, and flow boiling are highlighted. • Potential solutions and future research in the field of boiling heat transfer using the MDS, LB and CFD methods are proposed. Boiling is an efficient heat transfer mode with significant potential for thermal management in high-power electronic equipment. However, a comprehensive understanding of the boiling process, which encompasses bubble nucleation, growth, coalescence, slipping, and detachment across various scales, remains challenging. Molecular dynamics simulation, lattice Boltzmann, and computational fluid dynamics methods are popular and powerful tools for investigating boiling heat transfer phenomena at microscopic, mesoscopic, and macroscopic scales. These methods enable researchers to uncover the underlying boiling mechanisms and propose heat transfer enhancement techniques. Therefore, this paper provides a comprehensive review of boiling heat transfer, spanning from atomistic to mesoscopic and macroscopic scales, utilizing these three numerical methods. It addresses critical issues related to nanoscale bubble nucleation mechanisms, pool boiling, and flow boiling, and proposes potential solutions and future researches, supplementing our previous review [Some advances in numerical simulations of multiscale heat transfer problems and particularly for boiling heat transfer, Annu. Rev. Heat Transf., 6 (2022) 217–269]. Besides, by shedding light on the characteristics of these numerical methods in studying boiling heat transfer, this paper aims to foster their development and advance enhanced heat transfer technologies. [ABSTRACT FROM AUTHOR]

The inner doubly iterative efficient algorithm (IDEAL), an advanced fully implicit algorithm for solving the pressure-velocity coupling problem, lacks a comprehensive implementation procedure on commonly used collocated unstructured grids. Therefore, this study provides a thorough demonstration of the fundamental principles, solving procedures, discretizations of momentum and pressure equations, Rhie-Chow interpolation implementation, mass continuity processing, and boundary condition treatment associated with the IDEAL algorithm on a collocated unstructured grid. Additionally, a comparative analysis between the semi-implicit method for pressure-linked equations (SIMPLE) and the IDEAL algorithm is conducted concerning computational efficiency under different grid types and flow conditions. The results indicate a significantly higher computational efficiency achieved by the IDEAL algorithm across all tested cases, attributed to its ability to overcome two fundamental assumptions inherent in the SIMPLE algorithm. The average acceleration ratio for these cases is approximately 3.13 (tSIMPLE/tIDEAL). This study serves as a valuable reference for the further development and application of the IDEAL algorithm in solving flow problems with complex irregular domains discretized by unstructured grids. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) porous flow fields have been utilized to achieve ultrahigh power density for proton exchange membrane fuel cells (PEMFCs). However, issues such as the severe corrosion and high interface contact resistance of 3D porous flow field limit the effective enhancement in power density. In this work, porous flow fields with various pore structures, i.e., Ni foam and Ti felt are employed and further decorated with carbon coating using the chemical vapor deposition (CVD) method to improve the anti-corrosion capacity. Meanwhile, the through-plane electrical conductivity and hydrophobicity are collectively improved for Ni foam and Ti felt by the carbon coating. Single fuel cell (FC) tests show that both the peak power density (PPD) and limiting current density (LCD) are improved for PEMFCs assembled with C@Ni foam and C@Ti felt flow fields in the cathode. The corresponding electrochemical impedance spectroscopy (EIS) confirms that the improved PPD (C@Ti felt) is attributed to the collective improvements in electrical conductivity and anti-corrosion capacity, and the improved LCD (C@Ni foam) is attributed to enhanced water removal capacity. The triple improvements in the intrinsic property of porous flow field materials obtained in this work are expected to offer novel approaches for developing PEMFCs with ultrahigh power density. [Display omitted] • Carbon coating is introduced in porous flow field by chemical vapor deposition (CVD). • Through-plane contact resistance is reduced for C@Ni and C@Ti porous flow field. • Anticorrosion capacity was enhanced for C@Ni and C@Ti porous flow field materials. • Water removal capacity is improved for C@Ni and C@Ti porous flow field materials. • Electrochemical performance is enhanced for fuel cell with C@Ni and C@Ti. [ABSTRACT FROM AUTHOR]

Global warming due to greenhouse gas emissions has continuously threatened the climate and environment. Zirconium-based metal-organic frameworks (Zr-MOFs) with Zr 6 inner cores represent a subfamily of nanoporous materials with good physicochemical stabilities, showing significant prospects for practical applications in gas separation. A molecular simulation study is reported here to investigate the membrane separation of CO 2 /N 2 and CO 2 /CH 4 mixtures in five Zr-MOFs (Zr-fum, UiO-66, DUT-52, Zr-cca, UiO-67) with similar ligand in their structures and different pore-limiting diameter (PLD) ranging from 0.36 nm to 0.59 nm. The gas permeation and separation performance are evaluated with the concentration gradient-driven molecular dynamics (CGD-MD) method. The results show that the separation of both gas mixtures is dominated by the preferential sorption of CO 2 over N 2 and CH 4 , respectively. Meanwhile, the PLD of MOFs is also a significant factor governing permeation. MOFs with a larger PLD have a higher permeability and a lower selectivity for CO 2 /N 2 and CO 2 /CH 4 separation. Free-energy profiles were calculated to describe the insights into CO 2 separation, that the larger PLD can cause a lower energy barrier when gases transport through the pore of MOFs. The results were compared with the grand canonical Monte Carlo and equilibrium molecular dynamics (GCMC + EMD) approach, a traditional method to predict gas adsorption and diffusion in MOFs. As the GCMC+EMD approach neglected the interaction between components and potential mass transfer resistance at the surface of the membranes, the results obtained from the CGD-MD method in this work are more reliable. This study provides microscopic insights into CO 2 separation in Zr-MOF membranes and suggests their potential use for gas separation. [ABSTRACT FROM AUTHOR]

Effectively addressing crude oil spills remains a global challenge due to its high viscosity and limited flow characteristics. In this study, we successfully prepared a modified sponge (PCP@MS) by embedding the photothermal material of Co-HHTP and coating the melamine sponge (MS) with low-surface-energy polydimethylsiloxane (PDMS). The PCP@MS exhibited outstanding hydrophobicity with WCA of 160.2° and high oil absorption capacity of 59–107 g/g. The PCP@MS showed high separation efficiency of 99.2% for various oil-water mixtures, along with notable self-cleaning properties and mechanical stability. The internal micro-nano hierarchical structure on the sponge surface significantly enhanced light absorption, synergizing with the photo-thermal conversion properties of Co-HHTP, enabled PCP@MS to achieve a surface temperature of 109.2 °C under 1.0 solar light within 300 s. With the aid of solar radiation, PCP@MS is able to heat up quickly and successfully lowering the viscosity of the surrounding crude oil, resulting in an oil recovery rate of 8.76 g/min. Density functional theory (DFT) calculation results revealed that Co-HHTP featured a zero-gap band structure, rendering advantageous electronic properties for full-wavelength light absorption. This in situ solar-heated absorbent design is poised to advance the practical application of viscous oil spill cleanup and recovery. [Display omitted] • PCP@MS possesses remarkable self-cleaning, chemical and mechanical stability. • PCP@MS exhibits efficient oil-water separation and high absorption capacities. • Zero-gap band structure of Co-HHTP enhances PCP@MS's photothermal performance. • The recovery rate of PCP@MS exceeds 92% over 10 cycles of crude oil absorption. • PCP@MS is capable of remediating high-viscosity crude oil at a rate of 8.76 g/min. [ABSTRACT FROM AUTHOR]

• A proposed surrogate model can well predict the cathode transport process of PEMFC. • Cathode gas channels with high performance are designed by topology optimization. • A continuity optimized strategy is proposed to increase the inlet velocity to 7 m s−1. • The topology optimized gas channels are superior to the traditional designs. • Topology optimized gas channels are compared with the bio-inspired gas channels. Optimizing the gas channels (GCs) plays an important role on improving the performance of proton exchange membrane fuel cells (PEMFCs). In this study, a topology optimization (TO) model is developed for optimizing the cathode GCs. A reduced two-dimensional (2D) reactive transport model is developed based on the 3D half-cell model, which considers the multiscale oxygen reactive transport processes inside GCs, the gas diffusion layer and the catalyst layer. The reduced 2D surrogate model can predict the polarization curve agreeing well with experimental results. The TO is employed to optimize the GCs with the objectives of reducing flow resistance and increasing the current density. A continuous scheme is developed to conduct the TO under high inlet velocity. GCs with five different inlet/outlet configurations are optimized. As validated by 3D simulations, the TO structures can obtain higher current density with reduced pressure drop compared with parallel GCs. Finally, the TO GCs are compared with existing bio-inspired GCs. The tree-like structure with wider inlet/outlet channels and narrower center channel is considered as a promising design for future investigation. The present study is helpful for the designing of next-generation of GCs for better cell performance. [ABSTRACT FROM AUTHOR]

Carbon capture, utilization, and storage have been an effective way to deal with global climate issues. Injecting CO2 into depleted oil reservoirs can reach the dual goal of carbon storage and enhanced oil recovery. To optimize the gas injection strategy, it is necessary to understand the underlying mechanisms of three-phase fluid flow of oil, water, and gas. In this study, a lattice Boltzmann color gradient model is used to investigate the pore-scale three-phase displacement process in porous media. Gas is injected into the porous domain initially occupied by water and oil. Typical microscopic behaviors, including coalescence and split-up, pinch-off, double and multiple displacement, as well as parallel flow, are identified and discussed. Effects of water content (ϕ), capillary number (Ca), wettability and viscosity ratio (M) on the flow pattern, and oil recovery rate are explored. The oil ganglia inhibit the development of gas fingers, causing stronger viscous fingering characteristics with increasing ϕ. The fingering pattern is located in the crossover zone for the Ca from 5 × 10−5 to 5 × 10−4. As ϕ increases, the oil recovery rate reduces. The oil ganglia tend to occupy small pores as oil wettability enhanced, making it more difficult to be drained out. The reduction of oil viscosity is beneficial to improve connectivity, thereby effectively enhancing the oil recovery. Finally, the CO2 storage rate is also evaluated. It is found that the storage rate is very sensitive to the initial oil–water distributions. In general, the storage rate increases as ϕ decreases, Ca increases, and oil wettability enhances. [ABSTRACT FROM AUTHOR]

A full-knowledge of the temperature distribution in a data center is crucial for the design and operation to avoid thermal failure. However, it is a great challenge to conduct full-field simulations using the computational fluid dynamics/heat transfer (CFD/HT) method due to the unacceptable computational cost caused by the multi-scale structure of data centers. In this paper, a novel multi-scale model based on POD and CFD coupling is proposed to predict the thermal and fluid characteristics in data centers from room scale to chip scale. The temperature and flow fields in an air-cooled data center are predicted and analyzed under the scales of room, server, IGBT and chip. Based on the CFD results of Room-Server level, 16 sets of design cases' temperature fields for Server-IGBT level are compared using the POD and CFD methods, which shows that the maximum average absolute deviation and average relative deviation are 0.004 °C and 0.59%, respectively. Subsequently, three sets of off-design cases for Server-IGBT level and IGBT-Chip level are predicted using the aforementioned methods, yielding the maximum relative deviation 7.21% and 0.98%, respectively. The salient outcome is the remarkable 175-fold reduction in CPU processing time achieved with the POD model compared to traditional CFD simulations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Double transition metal atoms on GDY break the scaling relationship. • Machine learning speeds up the screening catalysts and reveals the descriptors. • Relations of intermediate adsorption energies aid catalyst selection in deep CO 2 RR. • GDY-based catalysts with strong CO binding exhibit high selectivity towards CH 4. Electrochemical CO 2 reduction reaction (CO 2 RR) has become a promising application in addressing energy challenges and environmental crises. However, the scaling relationship between the reaction intermediates constrains the successful deep reduction of CO 2. Dual-metal-site catalysts (DMSCs) have emerged as potential electrocatalysts for CO 2 RR by breaking the scaling relationship due to their more adaptable active sites. Herein, this study aims to investigate the correlation between the adsorption energies of essential intermediates in CO 2 RR catalysis with double transition metal atoms anchored on graphdiyne monolayer (TM 1 -TM 2 @GDY) through machine-learning (ML) assisted density functional theory (DFT) calculations. The results reveal the important descriptors of CO 2 RR catalyzed by TM 1 -TM 2 @GDY, and demonstrate that the heteronuclear TM 1 -TM 2 @GDY have great potential for deep CO 2 reduction. Especially, Co-Mo@GDY and Co-W@GDY show low limiting potential (-0.60 V and −0.39 V, respectively) and high selectivity on the reaction from CO 2 to CH 4 based on the free energy diagrams. This study indicates that the two TM atoms on GDY act cooperatively for the catalysis of CO 2 RR. Notably, utilizing ML eliminates the need to calculate all transition metal combinations by DFT, which is a great boost in quickly investigating catalytic performance and high screening for excellent catalysts. [ABSTRACT FROM AUTHOR]

To develop high-performance non-precious metal-based electrocatalysts for oxygen reduction reaction (ORR) is an urgent demand. We herein report an ingenious strategy to develop highly selective and competitive precious metal-free ORR electrocatalyst Co/CoO/SnO encapsulated in N-rich mesoporous carbon (CCS@NPC) nanocubes, via a simple one-step introduction of all functional components. Atomically mixed composites with significantly enhanced catalytic activity were obtained by adopting amorphous mesoporous ternary metal oxides CoSnO 3 nanocubes as precursor and template. The synergistic effect of the triphase nanohybrids (Co, CoO & SnO) anchored in nitrogen-doped mesoporous carbon nanocubes promoted the catalytic reactions, owning to the anisotropic morphology, great heterojunction interfaces, and structural stability. The large-scale prepared CCS@NPC exhibited excellent electrocatalytic activity toward ORR with an admirable onset potential (1.01 V) and diffusion-limited current density (5.88 mA cm−2). The CCS@NPC showed stronger stability (20 h) and higher methanol tolerance with the concentration up to 8.0 M, compared to that of commercial Pt/C. • Oxygen vacancies-rich CCS@NPC catalyst was synthesized without any solvent. • Introducing porous CoSnO 3 and ZIF-67 increased the specific surface area obviously. • Synergies among Co/Co/SnO and N-doped carbon nanocubes enhanced the ORR kinetics. • CCS@NPC showed super methanol tolerance with high concentration (8.0 M). [ABSTRACT FROM AUTHOR]

Membrane separation technology has been widely used in the separation and capture of CO 2 to reduce carbon emissions. The performances of facilitated hybrid membranes (FHMs) can be improved by properly adding metal-organic framework (MOF)-based nanoparticles (NPs) and modifying polymers to the polymer matrix. Grafting and blending methods are widely used to introduce modifying polymers to improve the compatibility between NPs and the polymer matrix, and the performance of FHMs for CO 2 separation. However, the separation performance of FHMs decreases significantly when the long chains of the polymer infiltrate into the pores of the MOF at the interface between the modifying polymer and MOF. To in-depth understand the nano-scale polymer-NPs interfacial interaction mechanism of the grafting and blending methods, we herein employed molecular dynamic (MD) simulation method combined with experiments to investigate the interface between NPs of Cu-MOF (Cu-BDC) and four commonly used modifying polymers (PEG, polyethylene glycol; PEI, polyethylenimine; PVA, polyvinyl alcohol; PPy, polypyrrole) with PVDF (polyvinylidene difluoride) as the polymer matrix. The results showed that the blending method for modification can effectively avoid the polymer blockage in Cu-BDC pores by using four modifying polymers, while the grafting method caused polymer infiltration for PEG and PEI. The relationship between the polymer diameter and the pore limiting diameter (PLD) of the Cu-BDC was evaluated to analyze the polymer infiltration effect. FHMs of Cu-BDC/PEG@PVDF were synthesized based on the MD simulation results, which showed excellent CO 2 separation performance due to the good compatibility between the Cu-BDC and the modified matrix polymer. This work offers an insight in nano-scale into the interface design between the MOF and the polymer for FHMs separating CO 2. [Display omitted] • The interface interaction between MOF and modifying polymers was studied by molecular dynamics. • Using blending method to avoid the modifying polymer (PEG and PEI) infiltrating into MOF(Cu-BDC) pores. • The compatibility between modified matrix polymer and MOF was improved. • Cu-BDC/PEG@PVDF was synthesized and exhibited good performance for CO 2 separation. [ABSTRACT FROM AUTHOR]

Complex multi-component pollutant-oil-water emulsions have caused serious environmental problems and increased the difficulty of purification treatment in the last few decades. The membrane based on two-dimensional (2D) materials can rationally control the interlayer distance, thus improved the separation performance of the membrane for complex wastewater. We herein reported a composite membrane, in which 2D metal-organic frameworks (MOFs) Co -CAT-1 with super-hydrophilicity cross-linked by polyethylene imine (PEI) was integrated into graphene oxide (GO) and then coated on polyvinylidene fluoride (PVDF) membrane (CPG membrane). The CPG membrane exhibited highly efficient in separating oil-water (including crude oil) emulsions, achieving a flux of 219 L∙m−2∙h−1∙bar−1 and a separation efficiency of 99.2 %. Moreover, the separation efficiency for complex emulsions after several cycles was maintained >99 % for dyes and 76 % for heavy metal ions (Ni2+, Pb2+, Zn2+). The remarkable fouling resistance and reusability of CPG membrane in purifying complex oil-in-water emulsions can be attributed to their internal cross-linking, electrostatic interactions, hydrogen bonding attraction, and π-π stacking. Molecular dynamics simulations were employed for in-depth studies on the separation processes of dye- and heavy metal ions-emulsions, revealing the mechanisms of mass transfer within the membrane. This work aims to construct stable and multifunctional membranes for separating pollutant-oil-water emulsions with multi-component. [Display omitted] • CPG composite membrane was fabricated via a facile self-assembly process. • The membrane showed promising synergistic separation performance and excellent reusability for multi-component emulsions. • CPG composite membrane exhibits excellent underwater oil repellency, anti-fouling, and superior resistance to extreme conditions. • The molecular dynamics simulations were employed to reveal the separation mechanism. [ABSTRACT FROM AUTHOR]

• The construction of the enhanced plate used in the AHU is proposed. • The highest enhanced effects are obtained for "H12-R10-h4" (PEC=1.45 at Re=5000). • All nine enhanced channels can enhance heat transfer at the same pressure drop. • The DMTD is proposed for the cross-flow AHU heat exchanger design. • The heat exchanger picked up is "H7.5-R10-h3" which has the maximum ratio of the heat exchange rate (40.5 kW) over the flow loss power (3.25 kW). In this paper, the construction process of the enhanced plate, the heat transfer and fluid flow characteristics, and the domain decomposition method for AHU performance estimation are presented. The AHU heat exchanger 3D model is built from plate modeling to heat exchanger assembling. The heat transfer plate modeling starts from a basic flat plate, elliptic cylindrical dimples (ECDs) are firstly added to the fixed location, and then spherical crown dimples (SCDs) are applied to the flat surface among the ECDs. For the enhanced channels, the effect of channel height is weaker than SCD depth on the Nusselt number and friction factors. For all enhanced channels, the PECs are larger than 1.1 within Re from 5000 to 35,355. The performance of a deeper depth of SCD is superior to that of a shallow one when the channel height is the same. Among the nine channels studied, the highest enhanced effects are obtained for "H12-R10-h4" (PEC=1.45 at Re=5000). And all nine enhanced channels can enhance heat transfer at the same pressure drop among the Reynolds number of 5000 to 35,355. The energy saving performance decreases with Re, and the channels with smaller SCD depth can save more energy when channel height is identical at the higher Reynolds number region. A decomposition thermal design method is proposed for the cross-flow AHU heat exchanger design, and the typical AHU design result is picked based on the heat exchange rate and flow loss power. The recommended heat exchanger is "H7.5-R10-h3" whose heat exchange rate is 40.5 kW when flow loss power is 3.25 kW. [ABSTRACT FROM AUTHOR]

A molecularly imprinted polymers (MIPs)-isolated AuNP-enhanced fluorescence sensor, AuNP@MIPs-CdTe QDs, was developed for highly sensitive and selective detection of oxytetracycline (OTC) in aqueous medium. The developed sensor combined the advantages of strong fluorescence signal of metal-enhanced fluorescence (MEF), high selectivity of MIPs, and stability of CdTe QDs. The MIPs shell with specific recognition served as an isolation layer to adjust the distance between AuNP and CdTe QDs to optimize the MEF system. The sensor demonstrated the detection limit as low as 5.22 nM (2.40 μg/L) for a concentration range of 0.1–3.0 μM OTC and good recovery rates of 96.0–103.0% in real water samples. In addition, high specificity recognition for OTC over its analogs was achieved with an imprinting factor of 6.10. Molecular dynamics (MD) simulation was utilized to simulate the polymerization process of MIPs and revealed H-bond formation as the mainly binding sites of APTES and OTC, and finite-difference time-domain (FDTD) analysis was employed to obtain the distribution of electromagnetic field (EM) for AuNP@MIPs-CdTe QDs. The experimental results combined with theoretical analyses not only provided a novel MIP-isolated MEF sensor with excellent detection performance for OTC but also established a theoretical basis for the development of a new generation of sensors. [Display omitted] • The imprinted polymers-isolated AuNP-enhanced fluorescence sensor was synthesized. • Metal-enhanced fluorescence combined with imprinted polymers to improve performance. • Molecular dynamics simulation revealed imprinted sites were identified by H-bonds. • The sensor showed great potential for oxytetracycline detection in water samples. [ABSTRACT FROM AUTHOR]

Facilitated transport mixed matrix membranes (FTMMMs) separation technology has shown advantages in improving CO 2 recycling efficiency and reducing the environmental impacts associated with carbon emission. The design of FTMMMs is highly dependent on the selection of a compatible combination of polymer and filler. Herein, a novel grafted nanoparticles (GNPs) filler UiO-66-NM@PEG with multiple groups prone to hydrogen bond was designed to alleviate the phase separation and performance degradation caused by filler/polymer poor compatibility. In the GNPs configuration, by employing the coexistence strategy of coupling reaction and covalent bonds, maleic anhydride (MAH) was coupled with the amino group on UiO-66-NH 2 without clogging or cracking, and the generated carboxyl groups can be cross-linked with the hydroxyl groups on the poly (ethylene glycol) (PEG) by covalent bonds. The UiO-66-NM@PEG demonstrated excellent interface compatibility between the filler and matrix phase of UiO-66-NM@PEG/PVDF, which was further convinced by molecular modelling. The resultant UiO-66-NM@PEG/PVDF achieved a simultaneous enhancement of gas permeability (537.6 Barrer) and ideal CO 2 /N 2 selectivity (47.8), which surpassed Robenson upper bound. Moreover, the UiO-66-NM@PEG/PVDF has a lasting sustainability over 960 h (40 days), and a valid anti-acid/alkali corrosion resistance in harsh environments. More importantly, UiO-66-NM@PEG can also be well mixed with other mixture matrices such as hydroxy-terminated polydimethylsiloxane (PDMS) and polyether-block-polyamide copolymer (PEBAX) to promote permeability/ideal selectivity up to (724.1 Barrer/21.1) and (307.4 Barrer/31.4). We thus concluded that this rational-design GNPs approach provides a general toolbox for controllable engineering in GNPs whereby enhanced favorable filler/matrix compatibility in FTMMMs with optimized CO 2 /N 2 separation properties. By the means of covalent "bridge-crosslinking", the UiO-66-NM@PEG/PVDF FTMMM with favorable phase compatibility between filler/matrix displayed excellent gas separation performance. [Display omitted] • A novel grafted filler UiO-66-NM@PEG was synthesized via Covalent "Bridge-crosslinking" strategy. • The membrane showed excellent sustainability over 40 days and corrosion resistance. • UiO-66-NM@PEG exhibited favorable filler/matrix compatibility in other two matrices. • The performance of UiO-66-NM@PEG/PVDF surpassed Robenson upper bound. [ABSTRACT FROM AUTHOR]

• A method for studying microlayer effects on flow boiling is proposed. • The availability of combining radius-based and taylor models in describing microlayer formation is verified. • The implementation procedure of the microlayer model is fully demonstrated. • The effects of different microlayer models on flow boiling are illustrated. • The contribution of microlayer evaporation to heat transfer is 75%−83%. The microlayer evaporation below the vapor bubble contributes much to heat dissipation and bubble growth, but it is hard to explore this microcosmic phenomenon. This study proposes a method for investigating the subcooled flow boiling heat transfer in a rectangular channel by considering the microlayer, conjugated heat transfer, a reasonable nucleation site density, and an accurate liquid-vapor interface. The implementation procedure of the microlayer model in the numerical simulation is fully demonstrated. Based on that, the bubble growth, flow pattern, heat transfer, microlayer depletion, evolutions of evaporative heat flux and dry patch during the subcooled flow boiling under different initial microlayer thicknesses are presented. Results indicate that microlayer evaporation contributes much to bubble volume and heat dissipation. The vapor volume generated by the microlayer evaporation exceeds that flows out of the channel because of the condensation effect at the liquid-vapor interface induced by the subcooled liquid, indicating bubble growth and expansion are completely attributed to microlayer evaporation. Simultaneously, much heat dissipates from the heat source due to microlayer evaporation, which contributes over 70% to both local and whole heat transfer. Because of microlayer depletion, some dry patches may appear at the elongated bubble tail. Therefore, liquid slug, elongated bubble, and dry patch circulate in the studied mini-channel, corresponding to heat transfer modes of liquid convection, microlayer evaporation, and vapor convection, supporting the three-zone heat transfer model. In addition, the initial microlayer thickness is related to the thermal resistance and affects the microlayer evaporation rate, leading to different flow patterns and heat transfer characteristics. The initial microlayer thickness is related to the slipping velocity of bubbles based on the Taylor model, which is recommended for the flow boiling study in a mini-channel. [ABSTRACT FROM AUTHOR]

Self-cleaning porous membrane can serve as condensing surface for its capacity of transporting condensate to the back through the pores thus keeping the surface clean during the whole condensing period. However, the three-dimensional (3D) condensate behaviors including the initial nucleation, growth and permeation in the porous structures have seldom been clarified comprehensively. In this work, the 3D pseudopotential LB model with a phase change model are employed, and the condensation process inside the porous membrane with various porosity, wettability, additional external force and section geometric configurations are investigated. It's found that with the increase of porosity, surface hydrophobicity and additional external force, more rapid penetration of condensate in the porous media and correspondingly faster removal rate of liquid can be obtained, and the subsequent vapor condensation is enhanced. But the nucleation time gets longer with high porosity and surface hydrophobicity. The additional external force has little effect on the nucleation time. Larger porosity and lower flow resistance inside the straight channel lead to higher condensation rate at the initial stage of condensation, while the porous structure with distorted pores with the same porosity contributes to improve the total condensation amount. This work helps to select the porous membranes with different porosity, wettability or pore scale geometric characteristic and external field for different condensation conditions in specific applications. [ABSTRACT FROM AUTHOR]

• Density based topology optimization method is used to design microchannel heat sinks. • Five inlet and outlet structures are considered by bi-objective optimization. • Straight line inlet and outlet with extension area presents best overall performance. • Reynolds number, thermal conductivity ratio and fluid heat generation are studied. • 2D optimized results are stretched to 3D geometry and validated by 3D CFD simulation. Topology optimization can generate better structures of microchannel with improved cooling performance. In this paper, microchannel heat sinks with five different inlet and outlet structure combinations are optimized using bi-objective topology optimization based on the density method. The layouts of channels are optimized to minimize the power dissipation and total heat generation at the same time. The results show that the straight line inlet and outlet with extension areas (SE) can reduce 20%-50% power dissipation when realizing the same heat transfer performance compared with traditional one channel inlet and one channel outlet (OC). Effects of Reynolds number, the ratio of solid and fluid thermal conductivity and the dimensionless heat generation coefficient in fluid domains are also investigated. The simple channels can be obtained with higher ratio of solid and fluid thermal conductivity and/or higher dimensionless heat generation coefficient in fluid domains. With optimization further considered in the inlet and outlet regions, better overall performance can be obtained. Finally, the 2D optimized structures are further validated by three-dimensional numerical simulation. It is found that the optimized design can realize 53.28% increment of Nusselt number with 40.89% reduction in pressure drop compared with traditional microchannel heat sinks. [ABSTRACT FROM AUTHOR]

Fundamental understanding of coupled physicochemical processes is crucial for improving the heat storage/release performance of thermochemical heat storage systems. In this study, for the first time a coupled lattice Boltzmann model is developed to simulate the particle-scale physicochemical processes during Ca(OH) 2 dehydration, including fluid flow, heat transfer, vapor mass transport and chemical reaction. The dehydration processes of a single Ca(OH) 2 particle, a single particle with coated ceramic shell and packed particles are studied, and thorough parametric studies are performed. The results show that the dehydration reaction rate of a single particle is mainly determined by the temperature and Ca(OH) 2 concentration. Introducing more micro-pores or meso-pores into the particle is favorable to achieve quicker heat storage, but at the cost of lower energy density. Increasing the Reynolds number from 0.3 to 3 or increasing the inlet temperature by 50 K can shorten the reaction time t c by at least 33.8%. Dedicate design of the shell coated on the particle can enhance the dehydration process with t c decreased by 3.5%. The underlying heterogenous structures greatly affect the reaction rate of packed particles, and local cracks should be prevented to achieve fast and stable heat storage response. • Reactive transport process of Ca(OH) 2 dehydration at particle scale is simulated. • Temperature and solid concentration determine the dehydration of single particle. • Coating ceramic shell would increase the dehydration reaction rate of particle. • Structural heterogeneity strongly affects the dehydration of packed particles. • Effects of structural and operational parameters on the dehydration are studied. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ca(ClO) 2 promoted sludge disintegration and VFAs production in acidogenic phase. • The functional microbes in methanogenic phase were enriched by Ca(ClO) 2. • Ca(ClO) 2 enhanced methane yield from two-phase anaerobic digestion system. • Ca(ClO) 2 -based method realized the balance between economy and efficacy. This study investigated the effects of calcium hypochlorite (Ca(ClO) 2) on biomethane generation from sludge two-phase anaerobic digestion system. In first (acidogenic) phase, volatile fatty acids (VFAs) were largely generated when pretreated by Ca(ClO) 2 , while the methane yield was severely inhibited. In second (methanogenic) phase, the methane yield was observably enhanced by Ca(ClO) 2. Further calculation showed that the total methane yield from the two phases was firstly promoted from 156.0 ± 4.5 to 269.9 ± 5.2 mL when Ca(ClO) 2 dosage enhanced from 0 to 1.6 g/L, which then reduced to 235.4 ± 5.5 mL when Ca(ClO) 2 content reached 2.0 g/L. Mechanism analysis showed that the suppression of Ca(ClO) 2 on coenzyme F 420 activity was relieved in methanogenic phase, and the abundances of functional microbes in methanogenic phase were enriched when added with Ca(ClO) 2. The Ca(ClO) 2 -based method well realized the balance between efficacy and economy, possessing outstanding potential for large-scale applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • PF coupled with freezing enhanced methane yield from sludge anaerobic digestion. • Freezing assists PF facilitated methane production potential and hydrolysis rate. • Sludge disintegration was accelerated by combined PF and freezing pretreatment. • PF coupled with freezing enriched the microbes participated in anaerobic digestion. This study proposed a novel sludge pretreatment technology by combining freezing with potassium ferrate (PF) for synergistically enhancing the methane yield from sludge anaerobic digestion. Experimental results showed that the methane production was promoted from 170.1 ± 5.6 to 223.8 ± 7.0 mL/g VSS (volatile suspended solids) when pretreated by freezing coupled with 0.05 g/g TSS (total suspended solids) PF, with 31.6% increase. Kinetic model analysis indicated that the methane production potential and hydrolysis rate of sludge after combined pretreatment were enhanced by 32.0% and 15.0%, respectively. Mechanism studies revealed that freezing coupled with PF pretreatment effectively disrupted both extracellular polymeric substances (EPS) and microbial cells in sludge, consequently resulted in violent sludge disintegration. All the microbes responsible for hydrolysis, acidification and methanogenesis were found to be enriched by co-treatment of freezing and PF. Moreover, the fecal coliform in pretreated sludge was largely inactivated after anaerobic digestion. [ABSTRACT FROM AUTHOR]

Three immiscible fluids systems are often encountered in energy and environmental disciplines, especially in the oil exploration field. It is essential to enhance oil recovery (EOR) by identifying the three-phase fluid flow mechanism of oil-gas-water system in complex geological structures. In the present study, a lattice Boltzmann (LB) color gradient model for three immiscible fluid flow in three-dimensional porous media is employed and validated using five benchmarks (i.e., the multiphase spinodal decomposition; the multiphase Young-Laplace test; the liquid lens; contact angles and 3D channel layered three-phase fluid flow). The effects of wettability, viscosity ratio (M) and capillary number (Ca) on the relative permeability curves are analyzed in detail. When the wetting condition is enhanced, the results indicate that the relative permeability of non-wetting phase raises while that for the wetting phase exhibits a decline. When M is not equal 1, the relative permeability of high viscosity phase is significantly increased, while the other two phases are less affected. Meanwhile, the maximal value of relative permeability does not exceed unity because of the low porosity in the porous medium. For the influence of Ca , simulation results indicate the relative permeability shows weak sensitivity to Ca. • A lattice Boltzmann color gradient model for three-phase fluid flow is proposed. • Pore-scale three-phase fluid flow in porous media is studied. • Three-phase relative permeability is predicted. • Effects of wettability, viscosity ratio and capillary number are explored. [ABSTRACT FROM AUTHOR]