Search

Purpose – The purpose of this study is to compare the thermal performance of two flow configurations in corrugated plate heat exchanger (CPHE): vertical flow configuration (CPHEvert.) and diagonal flow configuration (CPHEdiag.). The study aims to determine the differences between these configurations and evaluate their respective thermal performance based on metrics such as heat transfer rates, pressure drop values and flow distribution. Design/methodology/approach – The study compares the thermal performance of two flow arrangements of CPHE using identical geometrical dimensions and test conditions. Computational fluid dynamics (CFD) is employed, and a validated numerical model is used for the investigation. The comparison is based on analyzing the rate of heat transfer and pressure drop data between the two flow arrangements. Findings – The findings indicate that the diagonal flow configuration in CPHEs offers improved flow distribution, enhanced heat transfer performance and lower pressure drop compared to the vertical flow configuration. However, the differences in general in the thermal performance of CPHEvert. and CPHEdiag. are found to be minimal. Originality/value – To the best of the author’s knowledge, this study represents the first attempt to investigate the impact of vertical and diagonal flow configurations on the thermal performance of the CPHE.

The simultaneous flow of gas, oil & water is frequently encountered in pipelines during upstream petroleum operations. The multiphase flow results in different types of flow patterns based on the flow rates of fluids, physical properties and geometry of the flow domain. The flow behavior is characterized based on the governing flow patterns. Hence, the information about the flow patterns, regime maps and resulting pressure loss are important for multiphase flow system design and optimization. The current work is focused on construction of gas, oil and water, three-phase flow regime maps and developing pressure loss prediction correlations for the flow through vertical riser downstream 90° bend. The pipe internal diameter (ID) is 6 inch and the bending radius to pipe diameter ratio is 1. The observed gas-liquid flow patterns are slug, churn, and semi-annular churn flow at the given range of superficial velocities of fluids. The flow pattern data has been used to construct flow regime maps to analyze the variation in flow patterns with flow rates of fluids and compared with the available works in the literature. In addition, the change in pressure loss with respect to flow patterns has been analyzed. Previous models are used for the prediction of pressure loss. However, according to the assessment, the models underpredicted the pressure loss. Based on three-phase pressure loss data, multiple linear regression analysis has been carried out to propose new correlations for pressure loss prediction. Comparison of the calculated and experimental data showed good agreement between the results. The knowledge of flow regime variation and pressure loss correlations can help flow assurance engineers in designing and optimization of multiphase flow systems.

Objectives: Improving emergency department (ED) patient flow has plagued many hospitals worldwide. "Vertical" flow improves throughput by maximizing use of chairs and waiting areas instead of beds. This process, however, is inconsistently described in the literature. The objective of this study was to collate existing evidence of successful vertical care programs. Method: A scoping review was conducted within several databases utilizing key search terms to capture relevant traditional and gray literature. All articles were uploaded into Covidence (n = 1000). After duplicates were removed, remaining abstracts were initially screened by two reviewers (n = 731). Records identified by at least one reviewer subsequently underwent a two‐reviewer full‐text screening for inclusion (n = 46). This process yielded 36 articles. Finally, each record underwent data extraction by two independent study members and any inconsistencies were resolved by a third study member. Extracted data included 21 predetermined variables. Descriptive statistics were used to summarize results. Results: Of the 36 included articles, most were published from the United States (91.7%), after 2014 (55.6%), and as a peer‐reviewed article or abstract/conference proceeding (86.1%). While every article discussed some aspect of vertical flow, most (77.8%) were observational studies. Only half of the studies reported details of staffing and/or physical resources. A variety of challenges and success strategies were described, with several themes identified. Positive outcomes were reported by most articles (86%), although measurement of outcomes varied with the two most common being length of stay (69.4%) and arrival‐to‐provider time (55.6%). Conclusions: The findings of this scoping review provide the first summative report of existing literature on vertical flow processes within the ED setting. Despite different measurable outcomes and varied processes, most articles support the use of vertical flow to improve throughput. [ABSTRACT FROM AUTHOR]

The use of treatment wetlands (TWs) presents particular challenges in regions with sub-zero winter temperatures, due to reduced biological activity and risk of pipe breakage or clogging due to freezing. We studied the vertical temperature distribution in four pilot-scale TWs exposed to winter temperatures in order to determine the impact of operational system parameters and the role of insulation on heat conservation inside the filtering bed. The overall temperature pattern was similar in all wetlands, with a trend of increasing temperature from the surface toward the bottom during the cold season. No freezing was detected in the wetlands despite average daily temperatures as low as −20 °C. Influent water temperature and hydraulic loading had a stronger influence on TW temperatures in winter than air temperature. The vertical distribution of temperatures in TWs is more sensitive to hydraulic loading variation in the percolating operating condition than in the saturated flow with forced aeration configuration. Our results suggest that TW systems can remain operational under cold winter conditions provided the surface is properly insulated by vegetation, mulch and/or snow. HIGHLIGHTS In winter, temperature increases from the surface towards the bottom in vertical flow treatment wetlands.; The vertical distribution of temperatures is more sensitive to hydraulic loading variation in the percolating operating condition than in saturated flow with forced aeration.; Given proper surface insulation, influent water temperature and hydraulic loading have a stronger influence on treatment wetland temperatures in winter than air temperature.; Vertical flow treatment wetlands can remain operational in winter, if the surface is properly insulated by vegetation, mulch and/or snow.;

This work aimed to evaluate the performance of modified vertical flow treatment wetlands (VF-TWs) in terms of depth and medium to assess the effect of the feeding/resting periods and footprint (FP). The modifications were proposed for treating domestic wastewater in rural areas with flow variations such as tourist sites. The experimental setup included six laboratory-scale VF-TWs: (a) normal (VF-N), bed depth 1.0 m, filled with sand and (b) modified (VF-M), bed depth 0.5 m, filled with sand (upper) and zeolite (bottom, saturated). The operation was divided into three phases (3 months each), varying the feeding/resting period and FP: phase I, 5 d/10 d, 2.6 m2/person-equivalent (PE); phase II, 3.5 d/3.5 d, 1.7 m2/PE; and phase III, only feeding no resting, 0.85 m2/PE. Influent and effluent grab samples were taken every 2 weeks. The results showed effective removal (above 60%) of total solids, organic matter, and pathogens for both VF-N and VF-M. Regarding nutrients, VF-M showed a phosphate removal below 60%, but no consistent removal (15–60%) of total nitrogen. Thus, the results suggest that proposed modifications can be an option to be established in tourist sites, but further work should be conducted to improve and optimize total nitrogen removal. HIGHLIGHTS VF-TWs with the proposed modifications (bed depth, feeding/resting period; footprint reduction; zeolite as medium) had effective removal of total solids, organic matter, and pathogens.; VF-TWs with the proposed modifications were shown to be robust and able to cope with flow variations in tourist facilities of rural areas.; Further work should be conducted for consistent nitrogen removal in VF-TWs with the proposed modifications.;

Drastic variation in the thermodynamic properties of supercritical fluids near the pseudo critical point hinders the use of commercial computational fluid dynamics (CFD) software. However, with the increase in computational abilities, along with the use of Artificial Neural Networks (ANN), turbulence heat transfer characteristics of supercritical fluids can be very accurately predicted. In the present work, heat transfer characteristics for a vertically downward flow of carbon dioxide in a pipe are studied for a wide range of heat flux and mass flux values. Firstly, six different turbulent models available in the commercial CFD software - Ansys Fluent are validated against the experimental results. The k-? Standard model with enhanced wall treatment is found to be the best-suited turbulence model. When experimental results were validated in CFD, an average error of 1% in the bulk fluid temperature and 2% in the wall temperature were recorded. Further, K-? Standard Turbulence Model is used in CFD for parametric analysis to generate the data for ANN studies. Mass flux range of 238 to 1038 kg/m2s, and heat flux range of 26 kW/m2 to 250 kW/m2 are used to generate 81,432 data samples. These samples were fed into the ANN program to develop an equation that can predict the heat transfer coefficient. It was found that ANN can predict the heat transfer coefficient for the considered range of values within the absolute average relative deviation of 2.183 %. [ABSTRACT FROM AUTHOR]

This work investigates three laboratory-scale vertical flow-constructed wetlands (VFCWs) for treating a secondary effluent of wastewater under arid conditions to investigate the efficiency of two plants Canna indica and Typha latifolia in mono and mixed culture. The VFCWs were operated under hydraulic load (0.057 m3/m2d) and 5 days retention time. The results indicated no significant differences (P > 0.05) between the mono and mixed cultures. The C. indica gives the best efficiency of pollutant removal as COD (71.34%), NO2− (69.34%), and PO43− (69.67%). The uptake of TSS (83.98%) was best in the case of mixed culture. The mean percentages of BOD5 were convergent for mono and mixed culture, and it exceeds 89.80% in mixed culture. The mean percentages in NH4+ (98.69%) in mixed culture, elimination of NO2−, and the increase in the concentration of NO3− in the treated effluent showed the presence of nitrification in the VFCWs units. The two plant species exhibit high efficiency in the elimination of pollution compared to the unplanted control, with a slight superiority in the mixed culture. Therefore, it can be concluded that the application of these plants can be effective in arid conditions. HIGHLIGHTS Study of some plant species (comparison) in the field of water treatment in arid regions.; Comparison of monoculture and mixed.; Helps in the prevention of pollution.; Low-cost treatment solution for the rural areas.; Helps to optimize the design of the treatment units in arid regions.;

This study analyzed the effect of lightweight aggregates made of fly ash from sewage-sludge thermal treatment (FASSTT LWA) on the effectiveness of phosphorus removal from wastewater in vertical constructed wetlands (CWs), depending on FASSTT LWA content in the CW filling and hydraulic loading rate. It was performed over 13 weeks using 15 lysimeters prepared as double-layer systems. An upper layer was made of FASSTT LWA above the gravel layer with different thicknesses of FASSTT LWA (CW 0 cm: only gravel; CW 12 cm, CW 25 cm; CW 50 cm, and CW 100 cm: only FASSTT LWA). Each filling variant was repeated three times. Wastewater with a mean phosphorus concentration of 7.43 mgP/L was fed to the lysimeters once a day. The hydraulic loading rates tested were 3.0, 5.0, and 7.0 mm/d. Both the increased FASSTT LWA content in the CW filling and the decreasing hydraulic loading rate were found to boost the effectiveness of phosphorus removal in the treated wastewater. Constructed wetland filled in 100 % with FASSTT LWA ensured a reduction in phosphorus concentration below 2.0 mg P/L at all hydraulic loading rates tested. [ABSTRACT FROM AUTHOR]

The motion of elongated gas bubbles in vertical pipes has been studied extensively over the past century. A number of empirical and numerical correlations have emerged out of this curiosity; amongst them, analytical solutions have been proposed. A review of the major results and resolution methods based on a potential flow theory approach is presented in this article. The governing equations of a single elongated gas bubble rising in a stagnant or moving liquid are given in the potential flow formalism. Two different resolution methods (the power series method and the total derivative method) are studied in detail. The results (velocity and shape) are investigated with respect to the surface tension effect. The use of a new multi-objective solver coupled with the total derivative method improves the research of solutions and demonstrates its validity for determining the bubble velocity. This review aims to highlight the power of analytical tools, resolution methods and their associated limitations behind often well-known and wide-spread results in the literature. [ABSTRACT FROM AUTHOR]

• This study was conducted to evaluate the hydraulic performance of GCL overlaps. • Na-B GCLs consisting of different geotextile combinations were tested. • Test were conducted with saline solutions at 20 to 500 kPa confining stress. • The GCL overlaps permeated with saline solutions had horizontal flow. • The horizontal flow through GCL overlaps reduced at higher confining stress. Hydraulic conductivity of the overlap region of two needle-punched sodium bentonite (Na-B) geosynthetic clay liners (GCLs) permeated with CaCl 2 solutions under confining stresses of 20, 100, 250, and 500 kPa were evaluated. One of the GCLs consisted of a uniform layer of Na-B encapsulated between a nonwoven (NW) and a woven (W) geotextile, and the other one consisted of NW geotextiles on both sides. Supplemental bentonite was placed within the overlap region. Experiments were conducted with 10, 20, and 50 mM CaCl 2 solutions representing dilute and aggressive leachates. The results indicate that in most of the scenarios there is a possibility that the flow is not completely vertical (meaning flow passes through the overlap region horizontally). As the confining stress increased, the horizontal flow through the overlap region for GCLs reduced effectively when permeated with deionized water and 10 mM CaCl 2 solution, whereas the reduction of horizontal flow was limited to 20 mM and 50 mM CaCl 2 solutions. [ABSTRACT FROM AUTHOR]

Electrochemical machining (ECM), an advanced manufacturing technology, is widely used in aero-engine blades machining. In traditional ECM, the electrolyte flows through the inter-electrode gap (IEG), generating hydrogen bubbles and heat, which affect the conductance and thus influence the machining quality. This paper focuses on the effect of bubble movement on the flow field and the machining quality of ECM. A novel vertical flow mode of electrolyte is proposed according to the bubbles dynamics analysis. Multi-physical fields simulations of blade ECM using vertical and horizontal flows were carried out. With an initial gas void fraction, flow rate, and temperature at the inlet of 0, 19.7 m/s, and 302.65 K, respectively, in both flow modes, the vertical flow reduces the gas void fraction, flow rate, and temperature at the outlet by 2.4%, 0.4 m/s, and 0.6 K, and increases the conductance by 0.47 S/m. Thus, the vertical flow of the electrolyte is beneficial in reducing the gas void fraction and controlling the temperature rise, while enhancing the conductance. Then, the corresponding experiments using a vertical flow were carried out. The maximum machining deviation ranges from 3.4 to 75.6 μm and surface roughness Ra < 0.35 μm. The machining quality is high and the variation observed in the experiments is consistent with the simulation results, the validity and correctness of the simulations are verified. Thus, the vertical flow mode proposed in this paper is appropriate, can be used for other complex structures in ECM. [ABSTRACT FROM AUTHOR]

The utilization of hybrid-constructed wetland systems has recently expanded due to more rigorous municipal wastewater discharge and also complex wastewaters treated in hybrid-constructed wetlands (HCWs). A lab-scale two-stage experimental setup of vertical flow followed by horizontal flow hybrid-constructed wetland (VFHCW-HFHCW) configuration was built. First-stage vertical flow hybrid-constructed wetland reactor with the surface area was 1963.49 cm2 and second-stage horizontal flow hybrid-constructed wetland reactor with the surface area was 2025 cm2. The HCW unit was planted with two type plants: Calibanus hookeri and Canna indica (Cannaceae). Influent Municipal wastewater flow rate 112.32 l/day, hydraulic loading rate (HLR) 0.55 m/day, and hydraulic retention time of 1 day. The efficiency was evaluated in municipal wastewater quality improvement and physico-chemical analysis in our laboratory. The removal rate after the second-stage horizontal flow of BOD3 at 27 °C, COD, TSS, TP, NH3-N, and NO3-N reached 92.75%, 89.90%, 85.45%, 88.83%, 99.09%, and 96.05%, respectively. The results shown after both stage hybrid-constructed wetland VFHCW-HFHCW, treated effluent of Municipal wastewater produced high-quality effluent which may be reused in gardening, agriculture, and flushing in toilet purpose according to Bureau of Indian Standards (BIS) code for practices. However, in the future, hybrid-constructed wetlands could be standards design criteria developing and enhancing the performance standards and economic meets both to make more popular technology of the hybrid-constructed wetland (HCW). [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the technological reliability and to forecast the efficiency of wastewater treatment in a constructed wetland wastewater treatment plant (CW WWTP) in long-term operation. The research was conducted at a facility which in the mechanical part had a 3-chamber settling tank and the biological stage consisted of 4 constructed wetland beds with horizontal sewage flow, planted with common reed (Phragmites australis). During 12 years of the study, the WWTP was hydraulically loaded up to 97.7% of the designed mean daily inflow, equal to Qd,av. = 116 m3/d. The study showed that despite the high degree of reduction of such parameters as biochemical oxygen demand (BOD5) (90.0%), chemical oxygen demand (COD) (88.4%) and total suspended solids (TSS) (93.5%) the achieved reliability with respect to the limit values determined by the Weibull distribution model amounted to 48%, 62% and 77% for BOD5, COD and TSS, respectively. In the case of biogenic parameters, the technological reliability with respect to permissible values was 3% for total nitrogen and 13% for total phosphorus. Based on the performed analysis, it was concluded that the analyzed technological system did not guarantee the concentrations of pollutants in treated wastewater to reach the admissible levels defined in the related Polish legal act. In order to increase the efficiency of pollutants removal in the discussed wastewater treatment plant, the application of additional constructed wetland bed with vertical sewage flow (VF) preceding the horizontal beds (HF) was suggested. [ABSTRACT FROM AUTHOR]

In this paper, the “sonar percolation detection or logging” technology, which has emerged recently, is questioned from the aspects of test principle and calculation method, and the serious problems of this technology are pointed out. It is considered that sonar technology can not be used for seepage testing.

The use of biochar in constructed wetlands for domestic wastewater treatment is gradually being acclaimed by environmentalists due to its high specific surface area and porosity. In this study, the effectiveness of corn cob biochar (CCB) and rice husk biochar (RHB) in vertical flow constructed wetlands vegetated with Echinochloa pyramidalis was studied with sand as common reference material. The filters were fed with primarily treated domestic wastewater at a hydraulic loading rate of about 350 L/m2/day for 6 months. Water samples were collected monthly for physicochemical and bacteriological analysis and plant growth assessed every two weeks throughout the study. Biochar filters were highly performant in wastewater improvement with no significant differences between the biochar types. Both biochars were more efficient than sand in the removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD), true colour, total suspended solids (TSS) and total dissolved solids (TDS). However, sand filters performed better in the reduction of nutrients. All wetlands showed positive plant growth though the plants did not significantly affect the performance of the different filters for most parameters. However, a better plant growth was observed in the CCB filters. The study shows that CCB and RHB can effectively replace sand as substrates in constructed wetlands for wastewater treatment. HIGHLIGHTS Valorisation of crop wastes through biochar production.; Biochar filters are less effective in the removal of nutrients compared to sand.; Significant organic matter removal in vegetated constructed wetlands.; Significant reduction of bacteriological parameters regardless of substrate type.; Biochar substrates promote the growth of Echinochloa pyramidalis.;

• The available heat transfer correlations for supercritical CO 2 are evaluated. • New correlations for supercritical CO 2 in vertical up/downward tubes are developed. • 12720 data points are predicted with a mean absolute relative error of 20.10%. • The effects of different parameters on heat transfer are discussed. • It is the only predictive model validated over such a wide range of parameters. Supercritical CO 2 is a promising working fluid for many industrial applications. To improve the performances of relevant components and systems, the prediction of the heat transfer of supercritical CO 2 is an important research topic. General explicit heat transfer correlations of supercritical CO 2 for upward and downward flows heated in circular tubes were established using the genetic programming (GP) method. A total of 12720 experimental data points from 22 publications were collected to develop the models. The data included hydraulic diameter from 0.0992 to 22 mm, bulk temperature from -6.0 to 134.5°C, pressure from 7.44 to 10.50 MPa, mass flux from 50 to 4834 kg•(m2•s)−1, heat flux from 2.9 to 748 kW•m−2 and wall temperature from 6.4 to 368.2°C. The database was divided into four parts according to the flow direction and the relationship between the bulk temperature and the pseudo-critical temperature. The developed correlations considered various non-dimensional parameters as the independent variables to reflect the effects of supercritical properties, flow acceleration and buoyancy on the heat transfer. The results showed that the proposed correlations had excellent accuracy with a mean absolute relative error (MARE) of 20.10% based on prediction with the iterated wall temperature. The developed correlations outperformed the existing correlations in the literature. Compared to other correlations, the trend analysis indicated that these newly developed correlations could appropriately present the physics sense when the condition parameters varied. [ABSTRACT FROM AUTHOR]

Abstract—The problem of vertical flow stability in an oil reservoir with a gas cap is considered, when the oil flow obeys the Brinkman equation. Boundary conditions at the moving boundary of the gas-oil interface are derived and a basic solution is obtained. The normal mode method is used to study the stability of the gas–oil interface. The obtained dispersion equation is investigated. Conditions for flow stability are found for all values of the parameters, and it is shown that, in the linear approximation, the growth rate of short-wave perturbations tends to zero with increasing wave number. [ABSTRACT FROM AUTHOR]

Based on Barron’s equal strain consolidation theory of sand-drained ground and Gibson’s one-dimensional large strain consolidation theory, and considering the well resistance of drains, the variation of radial permeability coefficient and the vertical flow, a more general governing equation of large strain consolidation of sand-drained ground is established and solved by using the finite difference method. The correctness of the numerical solution is verified by comparing with the existing consolidation model and small- strain analytical solution. Using the numerical solution, the large strain consolidation behaviors of sand-drained ground are investigated. The analyses show that the well resistance of drains can reduce the consolidation rate of sand-drained ground. But when the permeability coefficient of drains increases to a certain value, the well resistance of drains can be ignored. The variation pattern of radial permeability coefficient has a great influence on the consolidation rate of sand-drained ground. The consolidation rate is faster under the parabolic pattern than that the linear pattern. The vertical flow accelerates the consolidation rate of sand-drained ground, when the radius ratio is small, and the influence of the vertical flow on the consolidation rate should be considered. The larger the ratio of compression index to permeability index is, the slower the consolidation rate of sand-drained ground will be.

This study analyzed the effect of lightweight aggregates made of fly ash from sewage-sludge thermal treatment (FASSTT LWA) on the effectiveness of phosphorus removal from wastewater in vertical constructed wetlands (CWs), depending on FASSTT LWA content in the CW filling and hydraulic loading rate. It was performed over 13 weeks using 15 lysimeters prepared as double-layer systems. An upper layer was made of FASSTT LWA above the gravel layer with different thicknesses of FASSTT LWA (CW 0 cm: only gravel; CW 12 cm, CW 25 cm; CW 50 cm, and CW 100 cm: only FASSTT LWA). Each filling variant was repeated three times. Wastewater with a mean phosphorus concentration of 7.43 mgP/L was fed to the lysimeters once a day. The hydraulic loading rates tested were 3.0, 5.0, and 7.0 mm/d. Both the increased FASSTT LWA content in the CW filling and the decreasing hydraulic loading rate were found to boost the effectiveness of phosphorus removal in the treated wastewater. Constructed wetland filled in 100 % with FASSTT LWA ensured a reduction in phosphorus concentration below 2.0 mg P/L at all hydraulic loading rates tested.

Constructed wetlands are a kind of sewage treatment technology that requires simple equipment and low energy consumption. Intermittent influent vertical-flow constructed wetlands (VFCW) provide good pollutant control and are widely used. In order to clarify the mechanism of vertical flow constructed wetland in controlling pollutants, this study established a VFCW experimental system to investigate the removal rates of hydraulic load on CODCr, NH4-N, TN and TP. For the removal effect of pollutants, different factors included retention time, water inlet flow rate, water inlet cycle, and water distribution method were analyzed respectively. The experimental results revealed that the hydraulic load had the greatest impact on pollutant removal in the intermittent water intake system. The removal rates of CODCr, NH4-N and TN all increased with hydraulic load, and which had a tendency to increase first and then decrease. The optimal hydraulic load was 200 mm/d, at which the removal rates of CODCr, NH4-N and TN were 88.5%, 48.5% and 52.5%, respectively. Too short or too long a hydraulic retention time was not conducive to pollutant removal. The best hydraulic retention time was about 2 days, at which the removal rates of CODCr, NH4-N and TN were 89%, 48% and 53%, respectively. Increasing the water flow rate and the uniformity of water distribution can help improve CODCr, NH4-N and TN removal rates and the wetland utilization rate and processing load. [ABSTRACT FROM AUTHOR]

The existing well test models ignore vertical flow in the thick multi-layered reservoirs and cannot analyze the difference in physical properties and production contribution of each layer. T h is paper extends the Kazemi model to present a physical model for triple- porosity carbonate reservoir, and further establishes a three-dimensional flow model for multi-layer fault-controlled karst reservoirs considering wellbore storage and skin. The finite difference technique is used to numerically solve the proposed model. The typical flow regimes are analyzed. The interlayer formation coefficient ratio (βm) and interlayer storage capacity ratio ယm) are defined to analyze the main controlling factors of stratified production. Results show that: before the pressure wave propagates to the boundary, the stratified production contribution is approximately equal to ယm when the pressure wave propagates to the boundary to form a pseudo-steady flow, the stratified production contribution is approximately equal t o ယm the skin factor Sm makes the stratified production contribution approximately equal to βm no longer, and the layer with the larger Sm has a lower production contribution. However, the skin and wellbore storage have no effect on the stratified production in the pseudo-steady flow regime. Finally,the proposed model is used to interpret the pressure build up data of typical wells in Shunbei Oilfield, and to analyze the differences in physical properties and production contribution of each layer,which is of guiding significance for formulating a reasonable production plan. [ABSTRACT FROM AUTHOR]

Modeling of turbulence heat transfer for supercritical fluids, using computational fluid dynamics (CFD) software, is always challenging due to the drastic property variations near the critical point. The use of artificial neural networks (ANNs) along with numerical methods has shown promising results in predicting heat transfer coefficients of heat exchangers. In this study, the accuracy of four different turbulent models available in the commercial CFD software--ansysfluent is investigated against the available experimental results. The k-ε Re-normalization group (RNG) model, with enhanced wall treatment, is found to be the best-suited turbulence model. Further, K-ε RNG turbulence model is used in CFD for parametric analysis to generate the data for ANN studies. A total of 1,34,698 data samples was generated and fed into the ANN program to develop an equation that can predict the heat transfer coefficient. It was found that, for the considered range of values, the absolute average relative deviation is 3.49%. [ABSTRACT FROM AUTHOR]

A vertical subsurface flow constructed wetland (VSSFCW) and a free surface flow constructed wetland (FSFCW) were set for the objective of comparison the performance of two systems in order to make a decision of the better one for future installation of wastewater treatment system and power generation. Both of the constructed wetlands were planted with Cyperus Alternifolius. During the observation period (19 days or 456 hours), environmental conditions such as pH, temperature, total chemical oxygen demand (COD), phosphate (PO4), nitrate (NO3) ,total suspended solids (TSS), total dissolved solids (TDS), Pb, Cu, and Cd removal efficiencies of the systems were determined. According to the results, final removal efficiencies for the VSSF and FWSF, respectively, were: COD (94.3% and 94.3%),PO4 (84.3% and 75.3%), NO3 (100% and 100%), TSS (96.8% and 85.6%), Pb (65.8% and 81.4%), Cu (more than 94.7% and 89.4%), Cd (85.7% and 88%). The treatment performances of the VSSF were better than that of the FWSF with regard to the removal of suspended solids and nutrients. In FWSF systems, electricity generation performed better than VSSF of 31.4 mV especially with batch system during one wastewater feed is loaded among all of the nineteen days with maximum voltage of 33.7 mV and decreased gradually as oxygen depletion in cathode chamber and less metabolism processes has occurred.

Accumulation of liquids in gas-condensate reservoirs may lead to a vertical flow of liquid caused by density difference in the presence of gravity. In this paper, the effect of this vertical flow on the prediction of production data has been investigated. To achieve this goal, a single-layer synthetic cylindrical reservoir is considered and, the flows are simulated with and without vertical direction grid blocks with two lean and rich fluids. The governing equations of the so-called Modified Black-Oil (MBO) model are solved in a cylinder sector using the open-source Matlab Reservoir Simulation Toolbox (MRST). When the vertical flow is taken into consideration, the results show that gravity may lead to migration of liquid condensates to lower regions and the production rates decrease as a consequence of wellbore partially blockage especially for the rich fluid. In addition, gravity may cause a non-linear effect on the flow behavior and increase in the condensates production rates. All results are also obtained for three values of critical liquid condensate saturation to show the effect of this parameter on the production. It has been shown that neglecting the vertical flow may cause significant errors in the result of production, i.e. up to 25% when the fluid is rich and the critical condensate saturation is 0.15. To generalize the effect of the reservoir thickness, dimensional analysis is carried out which yields a similarity parameter. The findings of this study can help for a better understanding of near well flow in gas-condensate reservoirs. Based on this study, in applications in which the reservoir gas is rich in condensate and the thickness of the reservoir layer or the vertical permeability is high enough, it is recommended that the gravity effect is taken into account by enough grid points in the vertical direction in each layer.

Here, we describe a SERS-based vertical flow assay as a platform technology suitable for point-of-care (POC) diagnostic testing. A capture substrate is constructed from filter paper embedded with spherical gold nanoparticles (AuNPs) and functionalized with an appropriate capture antibody. The capture substrate is loaded into a filtration device and connected to a syringe to rapidly and repeatedly pass the sample through the sensor for efficient antigen binding. The antigen is then labeled with a SERS-active detection probe. We show that only a few Raman reporter molecules, exclusively located adjacent to the plasmonic capture substrate, generate detectible signals. To maximize the signal from underutilized Raman reporter molecules, we employ a secondary signal enhancing probe that undergoes antibody-directed assembly to form plasmonic core-satellites. This facile enhancement step provides a 3.5-fold increase in the signal and a detection limit of 0.23 ng/mL (1.6 pM) for human IgG. This work highlights the potential to rationally design plasmonic architectures using widely available and reproducible spherical AuNPs to achieve large SERS enhancements for highly sensitive POC diagnostics.

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, we focused on the modeling and optimization of the purifying power of the vertical filter filled with pozzolana, using the response surface methodology, which is based on the study of the main factors, their effects, and their interaction. Therefore, we applied a rotary and uniform-centered composite plane to three factors while evaluating three responses, namely: the chemical oxygen demand abatement rate, electrical conductivity, turbidity, and discoloration. The contours of iso-response enabled us to define the optimal conditions, in terms of residence time and volume of treated water which are respectively, tsj = 806 min, V = 2 L, and for a reduction greater than 70% of the four responses measured. [ABSTRACT FROM AUTHOR]

Vertical flow has an important effect on consolidation rate of ultra-soft soil, but the influence law and influence level on the degree of large-strain consolidation have not been quantitatively evaluated. Based on the negative axisymmetric large strain consolidation (NALSC) model, the variation laws of calculation error of consolidation degree ignoring vertical flow with consolidation time and strain are studied under different values of H/re (ratio of soil thickness to influence radius), w0/wL (ratio of initial water content to liquid limit) and kh/kv (ratio of horizontal permeability coefficient to vertical permeability coefficient). Taking 10% as the error threshold, the H/re values ignoring vertical flow are given, and the difference between them in the theories of large-strain and small-strain is discussed. The results show that the effect of vertical flow on degree of stress consolidation (Up) is greater than degree of strain consolidation (Us). The H/re values neglecting the effect of vertical flow on the degree of consolidation in large-strain theory are less than those in small-strain theory. The calculation errors affected by vertical flow decrease with the increase of H/re and kh/kv. Error of Us affected by vertical flow decreases, whereas error of Up increases with the increase of w0/wL. The effect of vertical flow on the degree of consolidation is greater when well resistance is considered. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, an investigation of heat transfer characteristics at supercritical pressure fluid flowing in a uniformly heated vertical tube has been carried out. In order to reduce thermal emissions and increase thermal efficiency, supercritical boilers were developed at various sizes. Above supercritical pressure, the distinction of liquid and gas phases disappears. This dispenses with the problem of critical heat flux and dry out phenomenon which occurs in subcritical pressure. However, the study of heat transfer behavior above supercritical pressure is indeed required due to the heat transfer deterioration operation at high heat flux to mass flux ratio. In the present work, numerical simulation has been employed in order to inquire about the effect of various parameters such as heat flux to mass flux ratio, diameter and pressure that causes heat transfer deterioration. Shear Stress Transport k-ω model has been applied in all the computations. It is observed that the metal temperature predicted by numerical simulation is more accurate than the empirical correlations available in the literature. A Visual Basic Program has also been developed to assess the empirical correlations in the context of predicting metal temperature under 5280 different operating conditions. Tube sizes of 10, 15 & 20 mm inner diameter with 4 m length, the pressure between 225 and 280 bar and heat flux to mass flux ratio between 0.27 and 0.67 have been chosen to explore the effect of diameter, pressure and heat flux respectively.

Abstract Constructed wetlands (CWs) are simple low-cost wastewater treatment units that use natural process to improve the effluent water quality and make it possible for its reuse. In the present study, a comparison is made between horizontal subsurface flow (HSSF-CW) and vertical flow (VFCW) constructed wetland in effectively post-treating the effluents from the secondary biological treatment system. Locally available plants, viz. Pennisetum pedicellatum and Cyperus rotundus, which are abundantly available in the Western Ghats, were used in the wetland. A pilot-scale study was undertaken in National Institute of Technology, Karnataka Campus. The experiments were conducted at two hydraulic retention times, i.e., 12 h and 24 h. The experimental study was carried out in February 2018 to May 2018. Concentration-based average removal efficiencies for HSSF-CW and VFCW were BOD, 77% and 83%; COD, 60% and 65%; NH4 +–N, 67% and 84.47%; NO3–N, 69% and 66.75%; and PO4–P, 85% and 90%, respectively. VFCW showed a better overall removal efficiency than HSSF-CW by 7.14%. Thus, constructed wetland can be considered as a sustainable alternative to the tertiary conventional treatment of domestic wastewater, thus making it possible for reuse.

Vertical flow immunoassays (VFIAs) are considered potential point-of-care testing (POCT) devices compared to lateral flow assays due to their ability to analyze a comparatively large sample volume and ease of multiplexing. However, VFIA devices are limited by low analytical sensitivity when coupled with a visual colorimetric signal. Herein, we carefully analyzed key parameters that accounted for the proper functionality of VFIA that can be modified to enhance the overall sensitivity of VFIA. In particular, we focused on improving the stability of conjugate pads impregnated with capture antibodies, maintaining a controlled flow rate to ensure higher analyte reactivity with capture antibodies, and enhancing the absorption efficiency. The results showed that air-drying of conjugate pads in the presence of 5% (w/v) lactose significantly improved the stability of antibodies during long-term storage. Integration of dissolvable polyvinyl alcohol (PVA) membrane of optimal concentration as a time-barrier film into the sensor delayed the flow of samples, thereby increasing the biorecognition interaction time between immunoreagents for the formation of immuno-complexes, which in turn led to higher sensitivity of the assay. Furthermore, the employment of an absorbent pad with higher water holding capacity significantly reduced the non-specific binding of immunocomplexes, thereby reducing the possibility of false-negative results.

In this study, the simulation results of four vertical flow wetland systems using the HYDRUS Wetland Module are presented. The four wetland systems comprise three single-stage pilot scale systems and one full-scale two-stage system. The main difference between these systems is the filter media used, referred to as fine media, i.e., sand with a grain size distribution 0.063–4 mm, or coarse media, i.e., sand with grain size distributions between 1–4 mm, respectively. The water-flow simulation of each system is carried out using the single porosity van Genuchten-Mualem model. A good match between measured and simulated volumetric effluent flow rates could be achieved for all wetland systems. For reactive transport simulations, the CW2D biokinetic model was applied. First, simulations were run using the standard CW2D parameter set. For some systems, adjustments of the parameter set were needed in order to avoid unlimited bacteria growth. To better fit measured COD, NH4-N, and NO3-N effluent concentrations, adjustments of few parameters of the standard parameter set were required. The results show that for the VF wetlands with fine sand, no adjustments of the CW2D standard parameter set were needed, while for systems with coarser filter media as the main layer, the standard parameter set had to be adjusted to match simulated and measured effluent concentrations.

Bacteria are frequently studied due to their involvement in pollutants transformation processes during wastewater treatment. In this study, the treatment efficiency, bacteria densities and their vertical profile were investigated in pilot-scale vertical flow constructed wetlands (VFCW) planted with different plant species under a tropical climate in west Africa. Five beds were planted with local plant species, i.e., Andropogon gayanus, Chrysopogon zizanioides, Echinochloa pyramidalis, Pennisetum purpureum and Tripsacum laxum, while one bed remained unplanted. These species have been rarely used in CWs while some (e.g., T. laxum) are tested for the first time. After a 7-month trial, bacteria densities were measured in substrate samples separated into six layers along the bed depth. Plants presence enhanced the bacterial density and VFCW efficiency; the removal rates of organic matter (90.9–95.9%; COD and 95.2–98.5%; BOD5), nitrogen (74.3–84%; TN and 76–84%; NH4-N) and phosphorus (77.4–96.9%; PO4-P) were higher by 5.9–24.1% compared to the control bed, providing an overall excellent treatment performance for a single-stage VFCW system. Small numbers of anaerobic bacteria were obtained in the VFCWs, explaining the low-to-zero NO3-N removal, except for the VFCWs with T. laxum and P. purpureum. Aerobic bacteria decreased from the upper to bottom layers from 17.4 to 0.1 × 106 CFU/g in the planted beds, while anaerobic bacteria increased from 0.1 to 2.1 × 106 CFU/g. Anaerobic bacteria were more abundant in the unplanted than in the planted beds. The total bacteria count was dominated by aerobic bacteria, and decreased from the surface towards the bottom. Overall, the VFCW with P. purpureum demonstrated the highest efficiency, indicating that this design is an effective and sustainable nature-based solution for wastewater treatment in a tropical climate.

Sediment microbial fuel cell (SMFC) is a simple and low-cost wastewater treatment technique that uses natural plants to treat a variety of contaminates. It is able to improve the wastewater quality and make it possible for reuse and producing energy along with the treatment process. In the present study, a comparison has been made between five aquatic and semi-aquatic plants, Juncus, Schoenoplectus triqueter, Phragmites australis, Typha latifolia, Cyperus alternifolius, in order to detect the optimal plant in wastewater treatment to generate energy. Vertical flow constructed wetland adopted in feeding the SMFC with Al-Rustumiya crude wastewater. Samples of the treated wastewater were taken every 3 d. The results showed a maximum reduction in chemical oxygen demand with a value of 91.4%, 90.4%, 86.6%, 73.3%, and 72.3% for S. triqueter, T. latifolia, P. australis, Juncus, and C. alternifolius, respectively, and total suspended solids value of 86%, 80%, 79.6%, 78.4%, and 64%, and PO4 values of 70.8%, 66.6%, 66.6%, 62.5%, and 58.3% for P. australis, S. triqueter, C. alternifolius, T. latifolia, and Juncus, respectively. For NO3 removals were 81.4%, 80.9%, 80.9%, 80%, and 66.6% for C. alternifolius, T. latifolia, P. australis, S. triqueter, Juncus, and respectively. Heavy metals were removed as to be non-detected by the testing device from the first sampling process after initial values of 0.07 ± 0.01 ppm for Pb, 0.04 ± 0.02 ppm for Cu, 0.02 ± 0.01 ppm for Cd. The initial pH was 7.9 ± 0.02 and decreased to the minimum possible value of 6.7 ± 0.08 for C. alternifolius electricity generation performed better in Cyperus and P. australis and reached the maximum output of 43 ± 4 mV and 34 ± 3.1 mV on the third day of operation. The findings illustrate that all of the used species were proficient accumulator plants for phytoremediation of these pollutants and could be arranged ascendingly, P. australis, C. alternifolius, S. triqueter, T. latifolia, Juncus. [ABSTRACT FROM AUTHOR]

This study presents the performance of a hybrid constructed wetland (Bp(VF + HF)2:1) system which consists of an unsaturated vertical flow (VF) unit followed by a saturated down-flow unit simulating horizontal flow (HF) with HF/VF area ratio of 0.5 and influent bypass to the HF unit. Treating synthetic wastewater simulating municipal wastewater, optimum total nitrogen (TN) removal (57%) was reached at 39% bypass and surface loading rate (SLR) of 33 g BOD5/m2 day and 9.7 g TN/m2 day (overall system). On the other hand, treating actual municipal wastewater, the system reached 63% TN removal at 30% bypass and SLR of 18 g BOD5/m2 day and 4.7 g TN/m2 day. Surface removal rates reached 5.5 and 3.0 g TN/m2 day for synthetic and municipal wastewater. Surface nitrification rate in the VF unit was in the range of 5.0–7.4 and 3.6–3.8 g N/m2 day for synthetic and municipal wastewater, respectively, indicating a large effect of wastewater characteristics on the nitrification process. Infiltration rate in the VF unit remained high and far from clogging risk. Overall greenhouse gas emissions were 0.11 (N2O) and 0.41 (CH4) g/m2 day which corresponded to emissions factors (relative to total organic carbon and TN influent) of 0.7% (N2O) and 3.6% (CH4). Compared with a similar system with a different HF/VF area ratio of 2.0, organic matter and nitrogen removal efficiency was similar, but surface removal rates were about 3 times higher. [ABSTRACT FROM AUTHOR]

A vertical subsurface flow constructed wetland (VSSFCW) and a free surface flow constructed wetland (FSFCW) were set for the objective of comparison the performance of two systems in order to make a decision of the better one for future installation of wastewater treatment system and power generation. Both of the constructed wetlands were planted with Cyperus Alternifolius. During the observation period (19 days or 456 hours), environmental conditions such as pH, temperature, total chemical oxygen demand (COD), phosphate (PO4), nitrate (NO3), total suspended solids (TSS), total dissolved solids (TDS), Pb, Cu, and Cd removal efficiencies of the systems were determined. According to the results, final removal efficiencies for the VSSF and FWSF, respectively, were: COD (94.3% and 94.3%),PO4 (84.3% and 75.3%), NO3 (100% and 100%), TSS (96.8% and 85.6%), Pb (65.8% and 81.4%), Cu (more than 94.7% and 89.4%), Cd (85.7% and 88%). The treatment performances of the VSSF were better than that of the FWSF with regard to the removal of suspended solids and nutrients. In FWSF systems, electricity generation performed better than VSSF of 31.4 mV especially with batch system during one wastewater feed is loaded among all of the nineteen days with maximum voltage of 33.7 mV and decreased gradually as oxygen depletion in cathode chamber and less metabolism processes has occurred. [ABSTRACT FROM AUTHOR]

It was evaluated the performance of French vertical flow constructed wetlands of different configurations, for the treatment of domestic residual water in the Tarn Department in France. Likewise, the functioning of these systems, at the mesocomos level, for the removal of emerging contaminants in the tertiary treatment of the effluent of a municipal plant in Izúcar de Matamoros, Mexico was evaluated, comparing two species of macrophytes, Phragmites australis and Typha latifolia. The results obtained in the Tarn show that these systems achieve high removal rates of organic matter and nitrogen, with a stable operation over time. In Izúcar de Matamoros, when comparing the two macrophytes, were observed slightly better results of organic load and some organic micropollutants removal for Typha latifolia, with turbidity values that approach the value established for urban public use water accordingly to Mexican regulations. [ABSTRACT FROM AUTHOR]

In recent years, paper-based Surface-enhanced Raman spectroscopy (SERS) substrates have received extensive attention in the field of rapid analysis. However, obtaining quantitative SERS results is still challenging because of the inferior uniformity originating from the irregular morphology of the filter paper. In this work, a novel paper-fluidic SERS sensor was developed and its in-depth applications in the real-word quantitative analysis of contaminants in complex matrices were demonstrated. In particular, the Au@Ag core-shell nanospheres were labeled with an internal standard molecule to successfully normalize the fluctuation of the SERS signal caused by the microstructure of the filter paper, which could significantly improve the detection accuracy and accomplish the SERS quantitative analysis. In addition, a facile and robust strategy for the fabrication of a paper-based SERS sensor, which uses a dropper and mask to transfer the nanoparticle monolayers, was developed. This convenient and flexible approach effectively achieved a precise patterned assembly of nanoparticles on the filter paper. Furthermore, the paper-fluidic SERS sensor was fabricated by cutting and packaging for two detection modes, i.e., lateral-flow and vertical-flow, which generates the functionalization of the paper-based SERS substrate. Both detection modes integrated sample pretreatment and sample enrichment with SERS detection were applied to accurately detect the pesticide thiram in a complex sample of orange juice with pulp. In summary, this paper-fluidic SERS sensor with a simple preparation process and integrated functions is an ideal candidate for real sample analysis without pretreatment. Image 1 • Internal standard method was used to improve the uniformity of paper-based sensor and complete SERS quantitative analysis. • A facile strategy was developed with aid of dropper and mask to achieve precise assembly of nanoparticles on filter paper. • Lateral-flow and vertical-flow detection modes were applied to accurately measure the pesticide in orange juice with pulp. [ABSTRACT FROM AUTHOR]