Flow System Research Articles

Controlled two-step synthesis of n-type conjugated ladder polymers using a flow reactor

The coplanar backbone of conjugated ladder polymers (cLPs) enhances electron transfer and π-π interactions, making cLPs promising materials for various applications in organic electronics and optoelectronics. Nevertheless, the limited solubility and intricate synthetic processes for cLPs make it challenging to control their molecular weight and corresponding properties, and pose as significant obstacles to their widespread application. Here, an n-type cLP, PNDI-2BocL, was synthesized using a flow reactor for the first time, with controlled molecular weights. The polymerization reaction conditions to synthesize a precursor polymer, PNDI-2Boc, were first optimized in flow, followed by sequential ladderization in batch through the injection of an acid solution. The reaction time of polymerization was varied from 7.5 to 15 min, yielding soluble PNDI-2BocL with a number-averaged molecular weight (Mn) ranging from 9.8 to 54.0 kg/mol with a deviation of 11 %. Additionally, 15 min of polymerization and ladderization were successfully conducted in a single flow system sequentially for the first time. In the molecular weight-dependent studies, higher optical absorption at longer wavelengths, increased degrees of crystallinity, and higher electron mobilities in organic field-effect transistors (OFETs) were observed for higher molecular weight PNDI-2BocL. Our results highlight the importance of controlling the molecular weights of cLPs and demonstrate that the flow synthesis technique provides a viable solution for synthesizing soluble cLPs in a controlled, reproducible, and rapid manner.

Spectrophotometric determination of bisphenol A in beverages using multi-dispersion calibration

Bisphenol A (BPA) is an endocrine disruptor that may be present in plastics and coatings of food and beverage packages. In this regard, the World Health Organization recommends the maximum migration of BPA to foodstuffs as < 0.6 mg kg−1. Analytical BPA determination procedures have been based on chromatographic techniques, which generate waste with organic solvents. Alternatively, proposed spectrophotometric procedures have often shown high detection limits for foodstuffs analysis, requiring pre-concentration prior to determination. The analysis of beverages is susceptible to interferences because of their complex formulation comprising dyes and sugars, for example, that hinder spectrophotometric determinations. Multi-signal calibrations are powerful tools used to minimize matrix effects, and recently, they have proven efficient when performed in flow analysis systems, denominated as multi-dispersion calibration (MDC). This work proposes a multi-pumping flow system for the spectrophotometric determination of BPA based on the reaction with sulfanilamide (used for the first time) after diazotization to yield a compound with an absorption maximum at 446 nm. After the optimization of the main parameters, a linear response was observed between 0.25 and 10 mg L−1. The detection limit (by external calibration), coefficient of variation (n = 20), and determination rate were estimated at 0.11 mg L−1, 4.0 %, and 33 h−1, respectively. The MDC was exploited to analyze beverage samples to minimize interferences, especially due to dyes and sucrose. The detection limit estimated for this method was 0.057 mg L−1. Recoveries from 84 to 114 % and the agreement of comparative analysis of the samples with the reference procedure (at the 95% confidence level) demonstrated the accuracy of the proposed procedure. Therefore, the developed alternative is reliable with proper sensitivity and minimum sample preparation for the spectrophotometric determination of BPA in beverages.

Phosphorus removal in surface flow treatment wetlands for domestic wastewater treatment: Global experiences, opportunities, and challenges

Treatment Wetlands (TWs) are widely used for the treatment of domestic wastewater, with an increasing emphasis on provision of multiple co-benefits. However, concerns remain regarding achieving stringent phosphorus (P) discharge limits, system robustness and resilience, and associated guidance on system design and operation. Typically, where P removal is intended with a passive TW, surface flow (SF) systems are the chosen design type. This study analysed long-term monitoring datasets (2–30 years) from 85 full-scale SF TWs (25 m2 to 487 ha) treating domestic sewage with the influent load ranging from 2.17 to 54,779 m3/d, including secondary treatment, tertiary treatment, and combined sewer overflows treatment. The results showed median percentage removals of total P (TP) and orthophosphate (Ortho P) of 28% and 31%, respectively. Additionally, median areal mass removal rates were 5.13 and 2.87 gP/m2/yr, respectively. For tertiary SF TWs without targeted upstream P removal, 80% of the 44 systems achieved ≤3 mg/L annual average effluent total P. Tertiary SF TWs with targeted upstream P removal demonstrated high robustness, delivering stable effluent TP < 0.35 mg/L. Seasonality in removal achieved was absent from 85% of sites, with 95% of all systems demonstrating stable annual average effluent TP concentrations for up to a 30-year period. Only two out of 32 systems showed a significant increase in effluent TP concentration after the initial year and remained stable thereafter. The impact of different liner types on water infiltration, cost, and carbon footprint were analysed to quantify the impact of these commonly cited barriers to implementation of SF TW for P removal. The use of PVC enclosed between geotextile gave the lowest additional cost and carbon footprint associated with lining SF TWs. Whilst the P-k-C* model is considered the best practice for sizing SF TWs to achieve design pollutant reductions, it should be used with caution with further studies needed to more comprehensively understand the key design parameters and relationships that determine P removal performance in order to reliably predict effluent quality.

Dental Color-Matching Ability: Comparison between Visual Determination and Technology.

The choice of the correct color is of paramount importance in esthetic dentistry; however, there is still no consensus on the best technique to determine it. The aim of the present study is to compare the accuracy of a recently introduced colorimeter in shade matching with human vision. In addition, possible variables affecting color-matching by human eye have been analysed. 18 disc-shaped composite samples with identical size and shape were produced from a composite flow system (Enamel plus HriHF, Micerium): Nine were considered control samples (UD 0-UD 6), and nine were test samples with identical flow composite shade to the control ones. Parallelly, 70 individuals (dental students and dental field professionals) were individually instructed to sit in a dark room illuminated with D55 light and to perform visual shade matching between control and test discs. An error matrix containing ΔE94 between control and test discs was generated, containing four match-clusters depending on perceptibility and acceptability thresholds. The frequency and severity of errors were examined. The colorimeter achieved a 100% perfect matching, while individuals only achieved a 78%. A higher occurrence of mismatches was noted for intermediate composite shades without a statistically significant difference. No statistically significant differences were reported for age, sex, and experience. A statistically significant difference was present among the Optishade match and the visual determination. The instrumental shade-matching evaluation proved to be significantly more reliable than the human visual system. Further research is needed to determine whether the same outcomes are achieved in a clinical setting directly on patients.

Koopman analysis of the singularly perturbed van der Pol oscillator.

The Koopman operator framework holds promise for spectral analysis of nonlinear dynamical systems based on linear operators. Eigenvalues and eigenfunctions of the Koopman operator, the so-called Koopman eigenvalues and Koopman eigenfunctions, respectively, mirror global properties of the system's flow. In this paper, we perform the Koopman analysis of the singularly perturbed van der Pol system. First, we show the spectral signature depending on singular perturbation: how two Koopman principal eigenvalues are ordered and what distinct shapes emerge in their associated Koopman eigenfunctions. Second, we discuss the singular limit of the Koopman operator, which is derived through the concatenation of Koopman operators for the fast and slow subsystems. From the spectral properties of the Koopman operator for the singularly perturbed system and the singular limit, we suggest that the Koopman eigenfunctions inherit geometric properties of the singularly perturbed system. These results are applicable to general planar singularly perturbed systems with stable limit cycles.

Analysing fluid flow and heat transfer comparatively in flow passage systems: Evaluating thermal impacts and geometric configurations

This research thoroughly examines heat transfer and fluid flow in a passage flow system, highlighting the difficulties posed by different geometric arrangements and temperature conditions that may affect the system's performance. The main aim is to evaluate the impacts of different geometric characteristics on the velocity, pressure, and temperature profiles inside the flow route. These factors encompass cavity dimensions, tube diameter, and input conditions. An inclusive comparison of three different geometric designs at controlled temperatures is conducted using computational fluid dynamics (CFD) simulations. The findings indicate that the optimal geometric parameters improve thermal performance, with certain arrangements displaying improvements in heat transfer rates up to 30 %. In this regard, the higher cavity dimensions and suitable input velocities are exposed as advantages. The first sample exhibited a higher velocity of 0.024 m s-1 due to its simpler geometry and favorable heating conditions, while the third sample demonstrated a higher temperature of 465 K due to its complex cavity shape and multiple heating sources. This study suggests that enhancing efficiency in heat management applications necessitates a strategic design approach for passage flow systems, which must account for flow characteristics and geometric specifications. This research would provide insightful information for designers and engineers looking at enhancing fluid flow systems across a range of industrial applications.

Zibotentan in Microvascular Angina: A Randomized, Placebo-Controlled, Crossover Trial.

Background: Microvascular angina is associated with dysregulation of the endothelin system and impairments in myocardial blood flow, exercise capacity, and health-related quality of life. The G allele of the noncoding single nucleotide polymorphism RS9349379 enhances expression of the endothelin-1 gene (EDN1) in human vascular cells, potentially increasing circulating concentrations of Endothelin-1 (ET-1). Whether zibotentan, an oral ET-A receptor selective antagonist, is efficacious and safe for the treatment of microvascular angina is unknown. Methods: Patients with microvascular angina were enrolled in this double-blind, placebo-controlled, sequential crossover trial of zibotentan (10 mg daily for 12 weeks). The trial population was enriched to ensure a G allele frequency of 50% for the RS9349379 single nucleotide polymorphism. Participants and investigators were blinded to genotype. The primary outcome was treadmill exercise duration (seconds) using the Bruce protocol. The primary analysis estimated the mean within-participant difference in exercise duration after treatment with zibotentan versus placebo. Results: A total of 118 participants (mean ±SD; years of age 63.5 [9.2 ]; 71 [60.2% ] females; 25 [21.2% ] with diabetes) were randomized. Among 103 participants with complete data, the mean exercise duration with zibotentan treatment compared with placebo was not different (between-treatment difference, -4.26 seconds [95 ] CI, -19.60 to 11.06] P=0.5871). Secondary outcomes showed no improvement with zibotentan. Zibotentan reduced blood pressure and increased plasma concentrations of ET-1. Adverse events were more common with zibotentan (60.2%) compared with placebo (14.4%; P<0.001). Conclusions: Among patients with microvascular angina, short-term treatment with a relatively high dose (10 mg daily) of zibotentan was not beneficial. Target-related adverse effects were common.

Experimental measurement of the size distribution of microbubbles prepared by reciprocating syringe technique

Microbubbles have captured the attention of scholars due to their exceptional physical and chemical properties that exhibit practical applications. Transcranial Doppler ultrasound is a diagnostic tool used in clinical medicine to identify patent foramen ovale (PFO) heart disease caused by incomplete fusion of primary and secondary septum after birth, using microbubbles. The volume of gas and size of the bubbles determine the consequences of air entering the bloodstream. Therefore, it is imperative to investigate stable and efficient microbubble generation technology. The team designed and developed a new type of bubble generator and performed basic research on the flow and mixing rules in the gas-liquid two-phase system in the syringe. The shadow imaging method was used to explore the influence of the equipment operation parameters on the experimental system's microbubble flow process. After analyzing multiple sets of experimental data, it was found that the diameter of bubbles decreases as the frequency increases. After ten times of high-frequency reciprocating movement of the equipment, the microbubble size distribution is mainly between 10–100 μm, the mean diameter is between 23–26 μm, and the relative standard deviation is less than 4.5 %. Compared to manual methods, the device exhibits good accuracy and repeatability.

Coupling photocatalytic trifluoromethylation with biocatalytic stereoselective ketone reduction in continuous flow

Photocatalysis and biocatalysis represent powerful efficient tools in synthetic chemistry. While, both have individually shown promising results, their integration remains challenging, particularly in continuous flow processes. This work presents a semicontinuous setup, combining photo- and biocatalysis in a multistep synthesis for the production of optically pure (S)-3,3,3-trifluoro-1-phenylpropan-1-ol. Initially, a photocatalytic trifluoromethylation of a methyl ketone in α-position in a self-made photoreactor was tested in flow, followed by enzymatic ketone reduction catalyzed by an alcohol dehydrogenase (variant of an ADH from Lactobacillus kefir). The study addresses the challenge of enzyme stability in aggressive solvents, developing a robust immobilization approach for the selected ADH with a PVA/PEG cryogel matrix. This strategy has been investigated in this work to ensure enzyme stability in THF, marking a notable advance in compatibility for continuous cascades. The separate process steps were finally combined in a semicontinuous flow system, achieving a space–time yield for the photocatalytic step of 39.8 g L−1 h−1 and of 1.12 g L−1 h−1 for the enzymatic step. The study signifies one of the first instances of combining photo- and biocatalysis in continuous cascades, offering an innovative approach to synthesizing chiral 3,3,3-trifluoro-1-phenylpropan-1-ol.Graphical abstract

Density-driven free convection in heterogeneous aquifers with connectivity features

Free convection usually happens in variable-density groundwater flow systems, and it favors contaminant transport by enlarging length scales and shortening timescales compared to advection and diffusion/dispersion alone. Previous studies have demonstrated that heterogeneity with multi-variate Gaussian distribution for logarithmic permeabilities (log10k) plays an important role in the onset, growth, and/or decay of instability during the density-driven convective process. Nevertheless, the connectivity features (i.e., connected structures of extremely high/low-k values), which are common in natural aquifers, have received little attention. In this study, the classical problem of transient free convection has been modified and numerically simulated by Monte Carlo approach to investigate the effects of connectivity features in heterogeneity on the unstable convective processes. Results show that free convection is promoted by the connected high-k structures and retarded by the connected low-k structures during mainly the early-stage mass loading. The impacts of connectivity features tend to be amplified by higher variation in log10k distributions, and can be secondarily influenced by correlation lengths and anisotropy. Under the multi-variate Gaussian assumption, the existence of connected high-k structures leads to underestimation of density-driven instability, in which the risk differs based on the statistics of permeability fields, metrics of interest and timeframe. This study highlights the importance of understanding connectivity features in heterogeneous geological media when assessing density-dependent solute transport in groundwater systems.

Non-modal analysis of transient growth in a liquid annular jet surrounded by gas flow

Transient energy growth is a common mathematical concept in many fluid flow systems, and it has been widely investigated in recent years using non-modal analysis. Non-modal analysis can characterize the short-term energy amplification of perturbations, which is influenced by the Reynolds number, the Weber number, and the initial conditions such as the wavenumber. In gas–liquid coaxial nozzles, annular jets are often produced, and their breakup process is influenced by transient energy growth. However, research in this area has been limited so far. This paper for the first time investigates the transient energy growth of an annular liquid jet in static gas and validates it using a modified annular jet model. In the derivation process, the gas–liquid interfaces inside and outside the annular liquid film are taken into account. It has been found that there exists an optimal initial condition for a certain Reynolds number and a Weber number. The increase in the Reynolds number and ratio of inner and outer radius of the annular jet can maximize the transient growth under a specific initial wavenumber, while the increase in gas/liquid density ratio and the Weber number will minimize the transient growth. It is also found that transient energy growth is caused by the displacement of the free boundary.

Sewage Treatment by Kolkata’s Natural Wetland System

The metropolis of Kolkata stands uniquely positioned to implement a natural sewage treatment paradigm through the utilization of waste stabilization ponds, specifically within the East Kolkata Wetlands (EKW). These shallow oxidation ponds harness solar irradiation and algae bacteria symbiotic processes to effectively treat incoming sewage. Concurrently, nutrient-rich effluents are assimilated through fish production, converting available nutrients into protein—a hallmark of nature-based treatment. A portion of raw sewage is used to cultivate a chunk of vegetables before treatment in fish ponds, and the reclaimed water after treatment is used for vegetable and paddy cultivation downstream. This investigation explains the delineation of a sewage flow system to EKW, a Ramsar-designated site. Substantively, it offers quantitative insights into the sewage volumes and quality undergoing treatment. The sewage flow is higher in the winter months (909.07 MLD) compared to the summer months (709.34 MLD). In general, the sewage from the Kolkata city flowing to the EKW is moderately polluted. Extensive scrutiny of sewage from pond inlets and outlets serves as a quantitative metric for evaluating treatment efficacy. EKW efficiently treats the sewage, demonstrating 59.1% Biological Oxygen Demand (BOD) removal and a 99.28% reduction in fecal coliform. The natural treatment system excels in removing ammoniacal nitrogen (80.38%) and phosphate (90%). The treated water’s quality along the EKW boundary, culminating at the Kulti Gong River discharge point, was systematically assessed. Analytical findings indicate that all measured concentrations in the treated water adhere to prescribed inland surface water discharge standards prescribed by the Central Pollution Control Board, India, barring a marginal elevation in BOD during winter. Evidently, the EKW system adeptly manages substantial sewage volumes, fostering efficient treatment while concurrently facilitating resource recovery through fish production, yielding economic dividends. Despite its substantial land footprint, preserving this inherently sustainable wastewater management paradigm is imperative.

Genetic adaptation despite high gene flow in a range-expanding population.

Signals of natural selection can be quickly eroded in high gene flow systems, curtailing efforts to understand how and when genetic adaptation occurs in the ocean. This long-standing, unresolved topic in ecology and evolution has renewed importance because changing environmental conditions are driving range expansions that may necessitate rapid evolutionary responses. One example occurs in Kellet's whelk (Kelletia kelletii), a common subtidal gastropod with an ~40- to 60-day pelagic larval duration that expanded their biogeographic range northwards in the 1970s by over 300 km. To test for genetic adaptation, we performed a series of experimental crosses with Kellet's whelk adults collected from their historical (HxH) and recently expanded range (ExE), and conducted RNA-Seq on offspring that we reared in a common garden environment. We identified 2770 differentially expressed genes (DEGs) between 54 offspring samples with either only historical range (HxH offspring) or expanded range (ExE offspring) ancestry. Using SNPs called directly from the DEGs, we assigned samples of known origin back to their range of origin with unprecedented accuracy for a marine species (92.6% and 94.5% for HxH and ExE offspring, respectively). The SNP with the highest predictive importance occurred on triosephosphate isomerase (TPI), an essential metabolic enzyme involved in cold stress response. TPI was significantly upregulated and contained a non-synonymous mutation in the expanded range. Our findings pave the way for accurately identifying patterns of dispersal, gene flow and population connectivity in the ocean by demonstrating that experimental transcriptomics can reveal mechanisms for how marine organisms respond to changing environmental conditions.

Comparative analysis of varied thermal conductivity and viscosity models in a hybrid nanofluid flow - a non-similar solution

ABSTRACT We aim to investigate the flow of an ethylene glycol-based hybrid nanofluid over a horizontal surface with a free stream velocity. To assess the viscosity and thermal conductivity of nanoparticles with various shapes, we employed the Brinkman, Timofeeva, and Yamada Ota unit cell models. The study explores heat transfer in the flow system considering the effects of viscous and ohmic dissipations, linear radiative heat flux, and heat generation under convective boundary conditions. A non-similar system is developed using appropriate non-similarity transformations up to the third-level truncation and numerically solved using the bvp4c algorithm. The novelty of the proposed model lies in obtaining the non-similar solution and incorporating the Brinkman, Timofeeva, and Yamada Ota unit cell models. The results indicated that the Brinkman viscosity model resulted in an increase in the wall heat transfer rate with a rise in particle volume fraction. It is also inferred that platelet-shaped nanoparticles exhibit a significantly higher heat transfer rate compared to spherical-shaped nanoparticles.

Cadmium sequestration with MgCuAl-layered double hydroxide@montmorillonite nanocomposite in batch and circulated fluidized bed column experiments

In this study, montmorillonite cationic clay coated with MgCuAl-Layered double hydroxide nanoparticles was investigated for its capacity to adsorb cadmium ion (Cd2+) from aqueous solutions. Montmorillonite, MgCuAl−LDH, and a novel MgCuAl-Layered double hydroxide@montmorillonite nanocomposite (MCA−LDH@MMt) were characterized using various mechanisms including BET surface areas, XRD, TEM, FTIR, and SEM/EDS analysis. The adsorption behaviour of MCA−LDH@MMt towards Cd2+ ion was studied using batch and continuous flow systems. pH, contact time, initial Cd2+concentration, MCA−LDH@MMt dose and particle size, agitation speed, and temperature were examined in the batch system. The higher removal efficiency of Cd2+was reported at pH 5 at 70 mg/l initial concentration and 0.2 g/100 ml best adsorbent dose with 150 rpm. The adsorption of Cd2+ on MCA−LDH@MMt followed Langmuir model and yielded a maximum adsorption capacity of 129.82 mg/g. While the pseudo-second-order model better simulates the cadmium kinetics data, and adsorption rate parameters values showing that the adsorption process was chemisorption and the rate-determining step of controlling cadmium adsorption onto MCA−LDH@MMt not intra-particle diffusion. A three-phase, commonly known as gas-liquid-solid circulated fluidized bed column was used to continuously eliminate Cd2+. Four influencing parameters were studied: liquid and air flow rate, bed height, and initial Cd2+concentration. The adsorption efficiency of Cd2+in a continuous system increased when the liquid flow rate decreased and the bed height increased. The time required for MCA−LDH@MMt to reach saturation increases as the bed height and the air flow rate increase. Column data were described using Bohart-Adams, Thomas, and Yoon and Nelson models of adsorption for given experimental conditions. The Bohart-Adams could represent the initial regime of the breakthrough curves, while the Thomas model was better at describing the whole curve of metal ion adsorption for a given experimental condition.

On the analysis of static thermal instabilities occurring in two-phase flow systems

In this study, we investigate a novel type of static thermal instability that occurs in two-phase flow systems. The instability is theoretically and experimentally confirmed to occur for flow boiling micro-channel scenarios and flow condensing scenarios. The theory presented is independent of the evaporator geometry as well as flow boiling/condensing situations. A stability criteria is derived using a Reynolds Transport approach applied to the evaporator of a two-phase pumped loop (TPPL) system. The theory is then validated experimentally using a TPPL containing a parallel micro-channel evaporator. The instability is confirmed with pressure, temperature, and void fraction measurements acquired at the exit of the evaporator. The findings reveal that static thermal instabilities can arise when simultaneous heat addition and reduction in system saturation temperature occurs (or vice versa). The implications of the thermal instability result in dramatic changes in evaporator heat flux, as well as a flow transition from stratified laminar flow to vigorous turbulent flow with high void fractions. By identifying the additional instability mechanisms, this work contributes to enhancing system reliability and predictability of TPPL systems.

Aqueous benzene, toluene, ethylbenzene and xylene (BTEX) removal using core-shell structure activated carbon ball as a permeable reactive barrier material

Permeable reactive barriers (PRBs) are passive and sustainable treatment systems for remediating the diffusion of contaminant plumes in groundwater. Several conventional reactive materials such as activated carbon (AC) have long been used as reactive media for PRBs. AC, which is known for its high adsorption capability and cost-effectiveness, is commonly used to remove multiple pollutants from groundwater. Unfortunately, among the reactive materials, AC can fill in the barrier and pose practical problems, such as a pressure drop, solid losses during handling, and safe disposal of filled sorbents, because of its low particle strength. In this study, AC balls were prepared using zeolite as the core and powdered AC, quartz, and calcite as the shell. AC ball with excellent mechanical strength and high permeability properties in the form of a core–shell layer is a good alternative to conventional reactive materials. The adsorption characteristics of benzene, toluene, ethylbenzene, and p-xylene (BTEX) from solutions using AC balls were investigated. The adsorption equilibrium is in the order of X > E > T > B. The adsorption capacity for B (4.90 mg/g), T (3.37 mg/g), E (1.16 mg/g) and X (0.46 mg/g) were observed at solution pH = 7. To validate the proposed models, batch experiments indicated that the pseudo-2nd-order (11.61 and 10.54 mg/g) and Langmuir models (8.81 and 5.27 mg/g) were the most suitable for describing the kinetics and equilibrium of benzene and toluene, respectively. Regeneration experiments were performed using chemical extraction (methanol) and microwave (MW) heating. When the AC ball was reused six times, the removal efficiency for benzene was maintained above 81 % using methanol, whereas that for benzene was increased to 91 % using MW. A series of experiments revealed that AC balls have considerable reusability. The AC ball can be effectively used as a medium for the removal of benzene in a continuous flow system such as column and sandbox. Based on these results, AC balls are a potential reactive medium for field-scale PRB practical remediation applications.

Removal of livestock odor gas ammonia, hydrogen sulfide, methanethiol by electron beam in a continuous flow system

Odor is becoming one of the serious environmental issues as the industry develops. Electron beam technology has recently attracted attention as an AOP (Advanced Oxidation Process) for air purification, water treatment, and soil remediation. This work studied the removal of major livestock odor such as ammonia (NH3), hydrogen sulfide (H2S), and methanethiol (CH3SH) using a continuous gas flow electron beam treatment process. The effects of initial odor gas concentration, type of background gas, absorbed dose of the electron beam, voltage of the electron accelerator, and odor gas flow rate on the removal of odor gas were all studied in this continuous gas flow treatment system. As the absorbed dose of electron beam was increased, the removal efficiencies of odor gases NH3, H2S, and CH3SH all increased gradually. As the initial concentration of odor gas was decreased and as the flow rate of odor gas was increased, the removal efficiencies also increased. Regarding background gas, the odor gas removal efficiency was found to be in descending order of O2 > air > N2. The lower the voltage (MeV) of the electron beam, the higher the odor gas removal efficiency. This was attributed to the fact that, to set the same absorbed dose (kGy), as the voltage decreases, the current value (mA) increases. For the byproducts, as the absorbed dose of electron beam was increased, the concentration of byproducts increased. Regarding the gas-phase continuous electron beam treatment reactions, the optimal operating conditions must be derived by considering various operational variables, including the initial concentration, electron beam dose, background gas type, gas flow rate, and electron beam voltage. The results of this study show that, among several possibly relevant variables in removing odor gases in the continuous flow electron beam irradiation process, the current value can be considered one of the most important variables, along with the initial concentration and background gas.

Hybrid nanocomposites impact on heat transfer efficiency and pressure drop in turbulent flow systems: application of numerical and machine learning insights

This research explores the feasibility of using a nanocomposite from multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) for thermal engineering applications. The hybrid nanocomposites were suspended in water at various volumetric concentrations. Their heat transfer and pressure drop characteristics were analyzed using computational fluid dynamics and artificial neural network models. The study examined flow regimes with Reynolds numbers between 5000 and 17,000, inlet fluid temperatures ranging from 293.15 to 333.15 K, and concentrations from 0.01 to 0.2% by volume. The numerical results were validated against empirical correlations for heat transfer coefficient and pressure drop, showing an acceptable average error. The findings revealed that the heat transfer coefficient and pressure drop increased significantly with higher inlet temperatures and concentrations, achieving approximately 45.22% and 452.90%, respectively. These results suggested that MWCNTs-GNPs nanocomposites hold promise for enhancing the performance of thermal systems, offering a potential pathway for developing and optimizing advanced thermal engineering solutions.

Accurate machine-learning-based prediction of aerodynamic and heat transfer coefficients for cylindrical biomass particles

Cylindrical biomass (straw) particles play a crucial role in the numerical simulations of biomass co-firing in coal-fired boilers, wherein the aerodynamic and heat transfer coefficients of these particles are particularly important. Despite the existence of models proposed thus far for various specific conditions, developing a universal model for cylindrical particles remains challenging in multiphase flow systems. In this paper, a total of 1092 validated computational fluid dynamics (CFD) datasets of cylindrical drag, lift, torque coefficients and average Nusselt number are acquired based on direct numerical simulations of OpenFOAM body-fitted meshes, and a hybrid algorithmic framework of N+1 convolutional neural network (CNN) machine learning optimality is established. where multiple single-tree models (referred to as N models) are combined with an additional CNN layer (referred to as +1 model).The framework inherits the advantages of a single-tree models while significantly improving the overall algorithmic generalisation performance, with the aim of allowing efficient use of time and minimal expertise in the fluid modelling process. The mean relative absolute errors for drag, lift, torque coefficient, and the average Nusselt number was evaluated, and the results demonstrated a reduction of 75.19 %, 89.48 %, 89.53 %, and 85.70 %, respectively, in the mean relative absolute errors compared to the extremely randomised tree single-tree model. We extended the model scope to different aspect ratios (1 ≤ Ar ≤ 30), angles of incidence (0° ≤ θ ≤ 90°), and Reynolds numbers (1 ≤ Re ≤ 4000), and conducted random predictions. Compared with traditional mathematical relationships, the proposed framework reduced the average relative error to 0.99 %. The simultaneous application of models for the prediction of unknown parameters was validated against relevant early literature, which demonstrated that the average relative error of drag coefficients for the predicted values remained within 2.07 %. The N+1 (CNN) hybrid algorithm framework exhibited high accuracy and excellent adaptability, furnishing a substantial quantity of data to support the Euler–Lagrange model of non-spherical biomass particle multiphase flow in industrial applications.