In this paper, the hydrodynamics and the pressure drop of liquid–liquid slug flow in round microcapillaries are presented. Two liquid–liquid flow systems are considered, viz. water-toluene and ...ethylene glycol/water-toluene. The slug lengths of the alternating continuous and dispersed phases were measured as a function of the slug velocity (0.03–0.5
m/s), the organic-to-aqueous flow ratio (0.1–4.0), and the microcapillary internal diameter (248 and 498
μm). The pressure drop is modeled as the sum of two contributions: the frictional and the interface pressure drop. Two models are presented, viz. the stagnant film model and the moving film model. Both models account for the presence of a thin liquid film between the dispersed phase slug and the capillary wall. It is found that the film velocity is of negligible influence on the pressure drop. Therefore, the stagnant film model is adequate to accurately predict the liquid–liquid slug flow pressure drop. The influence of inertia and the consequent change of the slug cap curvature are accounted for by modifying Bretherton’s curvature parameter in the interface pressure drop equation. The stagnant film model is in good agreement with experimental data with a mean relative error of less than 7%.
The slug characteristics of dense phase pneumatic conveying of coarse particles were numerically studied on the basis of experimental verification. A light medium mixed flow pneumatic conveying was ...introduced to improve the slug formation. The slug conveying process, the slug and particles motion during slug formation, and the slug shape characteristics were evaluated. Three points are worth highlighting: (1) Slugs are continuously updated and rolled forward accompanied by exchange of particles exchanging. (2) Slug velocity increases with the slug conveying process, and the gap between particle velocity and slug velocity gradually declines. (3) The rear angle shows obvious segregated distribution for formed slug and collapsed slug, with the mean values of 37.0°degree and 74.6°, respectively.
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•Coarse particles slug flow pneumatic conveying process were simulated.•A light medium mixed flow pneumatic conveying for coarse particles was introduced.•Slugs continuously update and roll forward accompanying particles exchanging.•Rear angle could be used as an indicator to identify whether slug formation.
► We investigate the microchannel with physical and chemical methods together. ► We use the Danckwerts’ model to evaluate the mass transfer behavior. ► Increasing reactant's concentration will ...increase mass transfer coefficient. ► Volumetric mass transfer coefficient decreases along the channel. ► Volumetric mass transfer coefficient is correlated with slug velocity.
An alkaline hydrolysis reaction was used as the model reaction to investigate the performance of liquid–liquid slug flow microchannel. The specific interfacial area was determined through the photographic snapshot method physically by means of measuring the lengths of relevant slugs. The overall volumetric mass transfer coefficients were calculated through the Danckwerts’ model chemically. The influences of various operating conditions on the slug length, the overall volumetric extraction rate and the mass transfer coefficient were investigated quantitatively. A decreasing trend of volumetric mass transfer coefficients along the channel length was found. The linear dependence of the volumetric extraction rate on the volumetric mass transfer coefficient indicates that the overall rate of the process is determined by the mass transfer process. In addition, the volumetric mass transfer coefficients were correlated for different channel lengths.
Slugs and snails are widely distributed in natural humid habitats, and they are a worldwide problem in agriculture. The grey garden slug, a common terrestrial species, is considered the most severe ...pest of vegetables and field crops. Currently, the most common slug control methods rely on chemical pesticides, which can be damaging to the environment and human health. Nematodes are important natural enemies of slugs, and one species has been used as a commercial product for three decades. This study investigated and analyzed the differential gene expression profiles between nematode-infected slugs and uninfected slugs and identified the genes associated with immunity in the grey garden slug. The results provide a starting point for understanding the molecular mechanism of immune genes and physiological pathways, facilitating the identification of biological targets for slug management strategies in the field. The grey garden slug (Deroceras reticulatum ), a common terrestrial slug native to Europe with a global distribution including North America, is commonly considered the most severe slug pest in agriculture. The nematode Phasmarhabditis hermaphrodita , which has been used in the U.K. and Europe as a commercial biocontrol agent since 1994, has also recently been collected in Oregon and California and has long been considered a candidate biocontrol agent for slug management in the U.S. In this study, we report differential gene expressions in nematode-infected slugs using RNA-seq to identify slug immune-related genes against nematodes. Comparison of gene expression levels between the whole bodies of a nematode-infected slug (N-S) and an uninfected control slug (C-S) revealed that there were a total of 39,380 regulated unigenes, of which 3084 (3%) were upregulated and 6761 (6%) were downregulated at greater than 2-fold change (FC > 2) in the nematode-infected slug. To further investigate the biological functions of differentially expressed genes (DEGs), gene ontology (GO) and functional enrichment analysis were performed to map the DEGs to terms in the GO, eukaryotic ortholog groups of proteins (KOG) and Kyoto Encyclopedia of Genes and Genome Pathway (KEGG) databases. Among these DEGs, approximately 228 genes associated with immunity or immune-related pathways were upregulated 2-fold or more in the N-S compared to C-S. These genes include toll, Imd, JNK, scavenger receptors (SCRs), C-type lectins (CTLs), immunoglobulin-like domains, and JAK/STAT63 signaling pathways. From the RNA-seq results, we selected 18 genes and confirmed their expression levels by qRT-PCR. Our findings provide insights into the immune response of slugs during nematode infection. These studies provide fundamental information that will be valuable for the development of new methods of pest slug control using pathogenic nematodes in the field.
High viscosity oil/air slug flow is investigated both experimentally and theoretically. The behaviour with three different oils, whose viscosities range from 0.037Pa s to 0.804Pa s, is investigated ...in a horizontal pipe with 0.022m I.D. and 9m length. A statistical approach is adopted during the tests so to collect a meaningful amount of data and to build the probability density functions for slug lengths. A new correlation to model their dependence on superficial gas velocity is introduced. The length correlation along with a corrected version of the Nicklin (1962) correlation is used as an input into a developed mechanistic model, which is able to predict the pressure drops along the slug unit. The Modified Two Fluid model (Ullmann and Brauner, 2006) is used as closure relation for shear stresses in the stratified region. The model is validated against the pressure drop data obtained from performed experiments showing good accordance with them and providing detailed pieces of information about the mechanics of the flow regime.
•New experimental data on elongated bubble velocities and pressure drops are presented.•Slug length statistics are analysed and the related PDFs are built from experimental data.•A new slug length correlation for horizontal highly viscous oil/air flow is introduced.•A mechanistic model is developed, which is able to predict the pressure drops along the slug unit.
•Feasibility investigation of N2 alternating CO2 injection for improving CO2 storage and oil production.•Analysis of mobility adjustment by N2 slug during continuous CO2 injection.•Comparison of gas ...channeling phenomenon, gas swept area, EOR, and CO2 storage of different gas injection methods at a field scale.•Recommendation of potential oil reservoirs suitable for NAC technology.
The feasibility of N2 alternating CO2 injection was investigated for improving CO2 storage and oil production. Schemes of continuous CO2 injection and N2 alternating CO2 injection were evaluated using laboratory experiments and numerical simulation. According to the core flooding experiments, the CO2 storage factor and enhanced oil recovery of N2 alternating CO2 flooding were 2.1% and 7.1% lower than continuous CO2 injection. The larger the N2 slug volume in N2 alternating CO2 injection, the lower the EOR and CO2 storage factor due to the reduction of CO2 concentration in the gas phase and CO2 solubility in oil and water. However, the N2 slugs in N2 alternating CO2 injection significantly reduced mobility differences between different flowing zones, and thus can increase the gas swept area in an oil reservoir. The gas swept area of the oil reservoir under N2 alternating CO2 injection mode is 1.78 times that of continuous CO2 injection, resulting in a 44% higher cumulative oil production. Besides, the scheme of N2 alternating CO2 injection was optimized and resulted in 19.6% more CO2 storage than continuous CO2 flooding at a field scale. This study provides valuable experimental and theoretical support for improving CO2 storage and oil production in an oil reservoir.
•Five different passive micro-mixers (μ-Mx) were used for a reaction.•Slug (SF), parallel (PF), drop (DrF) and dispersed (DiF) flow regimes were observed.•PF, generated under specific conditions, ...decreases interphase mass transfer.•At a given flow rate, the μ-Mx impact the flow regime and energy dissipation rate.•Within DrF/DiF, the μ-Mx performed similarly for a given energy dissipation rate.
The flow regimes and mass transfer rates in five complex micro-reactors with different mixing mechanisms were investigated using the two-phase alkaline hydrolysis of 4-nitrophenyl acetate. n-Butanol and toluene were used as organic solvents. Using n-butanol in curvature-based micro-mixers, the flow regime evolved from slug to parallel to drop/dispersed flow with increasing flow rates. In obstacle-based micro-mixers, no parallel flow was observed. Using toluene, no parallel flow was observed for all reactors. The conversion of 4-nitrophenyl acetate was found to be strongly dependent on the flow regime. In slug and parallel flow, the conversion generally decreased with an increase in flow rate whereas it typically increased in drop flow and was constant or slightly decreased in dispersed flow. The different micro-mixers were compared using the overall volumetric mass transfer coefficient, Korga, which was primarily a function of the rate of energy dissipation within the dispersed flow regime. The geometry itself impacts the resulting flow regime and rate of energy dissipation at a given flow rate. The micro-reactors were then compared using modified Damköhler’s numbers. Curvature-based reactors were found to be inadequate for liquid–liquid reactions under the studied conditions, as they favor parallel flow patterns and yield relatively low interphase mass transfer rates.
