Initial Flow Rate Research Articles

Numerical simulations and experimental verification of the thermal performance of phase change materials in a tube-bundle latent heat thermal energy storage system

• Thermal performance of tube-bundle LHTS studied numerically and experimentally. • Charging and discharging are studied using lauric acid and water as PCM and HTF. • Three HTF initial temperatures and flow rates are examined. • PCM charging and discharging results were superior in comparison with double pipe LHTS. • Charging and discharging time was shortened by 85.3% and 82.5% respectively. Theoretical simulation and experimental validation of a new design tube-bundle latent-heat thermal storage (LHTS) working under solar-thermal application conditions was performed. A laboratory-scale experimental test rig was designed and tested for charging and discharging processes by using lauric acid and water as a phase-change material (PCM) and heat-transfer fluid (HTF), respectively. Six equal size tubes with 2 cm diameter and 45 cm length were clamped together with a central diameter tube for carrying the HTF. The temperature of the PCM during charging and discharging in the tubes in the bundle was measured radially. A 3D numerical model using ANSYS FLUENT was developed to simulate the time-dependent liquid fraction, temperature, and stored power of the PCM. The simulation was conducted after the successful validation with the experimental results at different HTF inlet temperatures (70 °C, 75 °C, and 80 °C) and (10 °C, 15 °C, and 20 °C) for charging and discharging processes, respectively, as well as with different Reynolds numbers (750, 1250, and 1750) for both processes. Although the design of the proposed LHTS was very simple, the results revealed that it has a superior thermal performance and fast charging and discharging period when compared to a double-pipe LHTS. Accordingly, the time was shortened by about 85.3% and 82.5% for charging and discharging processes, respectively.

Application of extracorporeal membrane oxygenation in critically ill pregnant women

To investigate the safety and effectiveness of extracorporeal membrane oxygenation (ECMO) in emergency treatment of critically ill pregnant women. Clinical data of 8 pregnant women with severe cardiopulmonary dysfunction during the perinatal period treated by ECMO in the department of intensive care unit (ICU) of Nanjing Drum Tower Hospital, the Affiliated Hospital to Nanjing University Medical School from September 2017 to November 2020 were retrospectively analyzed. For the 8 pregnant women, the mean age was (32.5±6.3) years old. Body weight was (73.5±8.1) kg. Gestational age was (31.0±4.4) weeks. Acute physiology and chronic health evaluation II (APACHE II) score was 13.0±6.6, and sequential organ failure assessment (SOFA) score was 8.3±3.8. Among them, 5 pregnant women suffered from severe pneumonia and were treated with venous-venous ECMO (VV-ECMO). Another 3 pregnant women with heart failure underwent venous-arterial ECMO (VA-ECMO). The initial ECMO flow rate was set to 2.0-3.0 L/min. Then the highest flow rate was (3.1±0.6) L/min, and the average ECMO running time was (174±36) hours. The length of ICU stay was (16.0±5.4) days. Six pregnant women (5 with severe pneumonia and 1 with peripartum cardiomyopathy) successfully evacuated from ECMO and survived. Two pregnant women with pulmonary hypertension showed poor prognosis. In total, seven babies survived. Two of them were delivered after ECMO evacution, and one underwent emergency cesarean section with ECMO support. In another case, the fetus could not be delivered due to under-gestational weeks. During this period, there were no serious bleeding complications. One pregnant woman developed heparin-induced thrombocytopenia and thrombosis (HITT), then she received another anticoagulant treatment. One pregnant woman got sequential anticoagulation therapy for 3 months on account of thrombosis in the puncture vessel. ECMO has played an active role in the rescue of critically ill pregnant women. For those with reversible severe cardiopulmonary dysfunction, it is necessary to evaluate the application of ECMO as early as possible to improve the survival rate of mothers and infants.

Concentration of aqueous solutions of low-volatile liquids in a falling film with evaporation into a cross-gas flow

The article presents the results of the investigation of the process of concentrating solutions of low-volatile liquids in a flowing film under the conditions of evaporation in the cross-flow of neutral gas. The purpose of the study was to establish the features of solution composition change along the film length. The study was carried out using the developed mathematical model with experimental determination of model parameters: heat and mass transfer coefficients. It was found that at the beginning of the film, the change in the concentration of the solution has a character close to linear, and then the concentration sharply increases until the solvent evaporates completely. It was shown that this pattern of change in the composition of the solution is related to the distribution of the temperature of the solution along the length of the film. The intensity of the concentration process increases with decreasing initial flow rate of the solution and its initial concentration as well as with increasing initial temperature of the solution, initial temperature of the gas and temperature of the surface of the wall along which the film flows. The concentration intensity decreases with an increase in the velocity of the gas entering the space above the film. Comparison of the calculation results concerning aqueous glycerol solution with the experimental data showed their good agreement. The data obtained in the article allow calculating the height of the film concentrator nozzle at which a given concentration of the solution is provided.

The starting rate for high-flow nasal cannula oxygen therapy in infants with bronchiolitis: Is clinical judgment enough?

To determine whether in infants with bronchiolitis admitted to a pediatric intensive care unit (PICU) the starting rate for high-flow nasal cannula (HFNC) therapy set by the attending physicians upon clinical judgment meets patients' peak inspiratory flow (PIF) demands and how it influences respiratory mechanics and breathing effort. We simultaneously obtained respiratory flow and esophageal pressure data from 31 young infants with moderate-to-severe bronchiolitis before and after setting the HFNC rate at 1 L/kg/min (HFNC-1), 2 L/kg/min (HFNC-2) or upon clinical judgment and compared data for PIF, respiratory mechanics, and breathing effort. Before HFNC oxygen therapy started, 16 (65%) infants had a PIF less than 1 L/kg/min (normal-PIF) and 15 (45%) had a PIF more than or equal to 1 L/kg/min (high-PIF). Normal-PIF-infants had higher airway resistance (p < .001) and breathing effort indexes (e.g., pressure rate product per min [PTP/min], p = .028) than high-PIF-infants. Starting the HFNC rate upon clinical judgment (1.20-2.05 L/kg/min) met all infants' PIFs. In normal-PIF-infants, the clinically judged flow rate increased PIF (p = .081) and tidal volume (p = .029), reduced airway resistance (p = .011), and intrinsic positive end-expiratory pressure (p = .041), whereas, in both high-PIF and normal-PIF infants, it decreased respiratory rate (p < .001) and indexes of breathing effort such as PTP/min (in normal-PIF infants, p = .004; in high-PIF infants, p = .001). The 2 L/kg/min but not 1 L/kg/min rate induced similar effects. The wide PIF distribution in our PICU population of infants with bronchiolitis suggests two disease phenotypes whose therapeutic options might differ. An initial flow rate of nearly 2 L/kg/min meets patients' flow demands and improves respiratory mechanics and breathing effort.

Productivity Analysis of Volume Fractured Wells under Different Working Systems

The volume fracturing technique has been widely used to improve the productivity of ultralow-permeability reservoirs. This paper presents a new semianalytical model to simulate the pressure transient and production behaviour of finite conductivity vertical fractured wells with stimulated reservoir volume (SRV) in heterogeneous reservoirs. The model is based on the five-linear flow model, the Warren-Root model, and fracture conductivity influence function. The model is validated by comparing its results with a numerical model. One novelty of this model is its consideration of three different kinds of production prediction models. Constant rate, constant pressure, and compound working systems are taken into account. This paper illustrates the effects of the SRV size and shape, mobility ratio, initial flow rate, limiting wellbore pressure, and hydraulic fracture parameters under different working systems. Results show that the SRV and parameters of fractures have a significant influence on long-term well performance. Moreover, the initial rate can extend the constant rate period by 418%, and limiting wellbore pressure can effectively improve the cumulative recovery rate by 23%. Therefore, this model can predict long-term wells’ behaviour and provide practical guiding significance for hydraulic fracturing design.

Development of molecular imprinting-based smart cryogels for selective recognition and separation of serum cytochrome-c as a biochemical indicator

The recognition and detection of proteins has an important role in the fields of biochemistry and medicine in term of diagnosis and prognosis. In this study, molecularly imprinted cryogel (MIP) was synthesized for the selective recognition of Cytochrome-c (Cyt-c) by cryopolymerization techniques with the lanthanide-chelate approach using (MAAP)2-Ce(III) as complex functional monomer and Cyt-c as a template protein. The incorporation of template with monomer was characterized by near- infrared (Near-IR) spectroscopy. The binding capacity was optimized in accordance with numerous experimental parameters including pH, initial Cyt-c concentration, flow rate, temperature and ionic strength. As a result, the maximum binding capacity reached to 98.33 mg g−1 in a buffer system with a pH of 6.0. Beside of the excellent reusability performance of prepared MIP, it was successfully applied to separation of template Cyt-c in the existence of hemoglobin (Hb) and myoglobin (Mb) chosen as interfering proteins. The relative selectivity constants of the Cyt-imprinted polymer were determined as 13.84 for the Cyt/Mb pair and 16.05 for the Cyt/Hb pair. Consequently, a high selectivity, simple and cheap strategy for efficient separation of proteins was provided with this novel MIP cryogel.

Effect of an entrapped air pocket on hydraulic transients in pressurized pipes

The current research focuses on the analysis of different dynamic effects of an air pocket located at mid-pipe length on transient pressures based on experimental data. Different flow rates and air pocket volumes are analysed. Several features are identified in the pressure-head signal associated with the air pocket: initial pressure drop, higher maximum overpressure peaks, increased pressure wave damping and delay. These features result from the superposition of pressure waves associated with the entrapped air contraction and expansion. Smaller air pockets generate minor reflections, whereas larger air-pockets tend to disperse and artificially attenuate maximum pressures. Video recording images of the air pocket during the transient event allow observation of two types of behaviour: one associated with lower transients, characterized by an air pocket volume variation with a clear air–water interface; and another one associated with more severe transients in which air mixes with water. Finally, there is a critical air pocket volume, independent of the initial flow rate, that leads to the highest overpressures.

Short lifespans of serpentinization in the rocky core of Enceladus: Implications for hydrogen production

The discovery of a liquid ocean on Saturn's small moon Enceladus and evidence of modern hydrothermal activity provide an unexpected new environment in which to expand the search for life. However, as with the age of the moons themselves, the age of the liquid ocean and any hydrothermal activity therein remains an area of debate. Based on physical and chemical observations from the Cassini mission we can apply known mineral dissolution rates, estimated water-rock ratios from Enceladus' density, and variable water flow rates within the rocky core to constrain durations of active serpentinization. On this basis we developed a 1-D reactive transport model to compare the effect of initial olivine percentage, grain size, temperature, and flow rate on timespans of primary olivine alteration in a rocky core the size and density of Enceladus'. In most cases, olivine alteration and precipitation of hydrous secondary minerals results in a water-limited alteration regime. An alteration front that propagates in the direction of water flow then controls the overall rate of olivine alteration. Of the parameters explored, high initial olivine percentages and slow fluid flow rates were the strongest predictors of long serpentinization times, while temperature and grain size had a smaller effect. The annual global H2 production rate in all model cases (> 1 × 1012 mol yr−1) is several orders of magnitude greater than the minimum H2 release rate calculated from the observed H2 in Enceladus' plume (1 × 109 mol yr−1), suggesting that any ongoing active serpentinization processes in the core are likely nearing completion. The longest timescales indicate the potential for olivine alteration and H2 production for up to ~75 Myr, consistent with weathering rates of terrestrial peridotite massifs. If the H2 produced from Enceladus is sourced from primary mineral alteration, these results suggest that hydrothermal activity in the core of Enceladus may have developed only very recently – even as recent as within the past 100 Myr.

Investigation of the transport characteristics of Pb(II) in sand-bone char columns.

Pb(II) leakage from batteries, dyes, construction materials, and gasoline threaten human health and environmental safety, and suitable adsorption materials are vitally important for Pb(II) removal. Bone char is an outstanding adsorbent material for water treatment, and the effectiveness in Pb(II) removing need to be verified. In this paper, the transport characteristics of Pb(II) in columns filled with a sand and bone char mixture were studied at the laboratory scale, and the influences of the initial concentration, column height, inlet flow rate, and competing ion Cu(II) on Pb(II) adsorption and transport were analyzed. The Thomas and Dose-Response models were used to predict the test results, and the mechanisms of Pb(II) adsorption on bone char were investigated. The results showed that the adsorption capacity of the bone char increased with increasing column height and decreased with increasing initial Pb(II) concentration, flow rate, and Cu(II) concentration. The maximum adsorption capacity reached 38.466 mg/g and the saturation rate was 95.8% at an initial Pb(II) concentration of 200 mg/L, inlet flow rate of 4 mL/min, and column height of 30 cm. In the competitive binary system, the higher the Cu(II) concentration was, the greater the decreases in the breakthrough and termination times, and the faster the decrease in the Pb(II) adsorption capacity of the bone char. The predicted results of the Dose-Response model agreed well with the experimental results and were significantly better than those of the Thomas model. The main mechanisms of Pb(II) adsorption on bone char include a surface complexation reaction and the decomposition-replacement-precipitation of calcium hydroxyapatite (CaHA). Based on selectivity, sensitivity, and cost analyses, it can be concluded that bone char is a potential adsorbent for Pb(II)-containing wastewater treatment.

Prospective artificial lift equipment for shale oil production from the Bazhenov formation

The article provides an analysis of shale oil production and artificial lift equipment world market for choosing the optimal method for oil production from the Bazhenov formation. The result of the analysis is the identification of prospective complexes of artificial lift (wellhead and downhole) equipment that meet the following conditions:&#x0D; • artificial lift equipment is used in operating conditions that are similar to those, which planned for the Bazhenov formation development: for wells with a long horizontal wellbore and multi-stage hydraulic fracturing; conditions similar to the Bazhenov formation in terms of the depth of the deposit, production volumes (production curve, initial flow rates, gas-oil ratio (GOR), reservoir temperature, etc ).;&#x0D; • the properties of the produced fluid are similar to the Bazhenov formation reservoir fluid (light oil, GOR increase over production time, water cut drop over time, etc.&#x0D; Analysis includes wellhead equipment, downhole equipment, and control stations for wellhead and downhole equipment.&#x0D; Based on the analysis results, the main selection criteria are given, a comparative analysis of the main types of artificial lift equipment is carried out, and promising types of artificial lift for oil production from the Bazhenov formation are identified.

Retarding frosting of an air source heat pump by using vapor-bypassed evaporation technique

• Vapor-bypassed evaporation is firstly used to retard frosting for ASHP applications. • A tested ASHP system that contains two operation modes is established. • Frosting characteristics of the two operation modes are investigated in detail. • Vapor-bypassed evaporation is more suitable for high heating capacity conditions. This paper presents a comparative experimental study on the frosting characteristics of an air source heat pump system that contains two operation modes, i.e., the vapor-bypassed evaporation (VB) mode and the conventional operation (CO) mode. For VB mode, a phase separator is installed inside the evaporator refrigerant circuit to bypass vapor refrigerant, which can increase the average evaporation temperature for retarding frosting by reducing refrigerant pressure drop and decreasing the area of refrigerant inferior heat transfer coefficient region (mist flow region). According to the experimental results, under H2 condition (indoor: 20/15 °C; outdoor: 2/1 °C), as the initial refrigerant mass flow rate ranges 35–45 g / s , the VB mode yields 4.30–7.06% lower frost mass, 3.9–7.3% higher average heating capacity and 6.4–10.8% higher coefficient of performance (COP) over CO mode with the frosting duration of 60 min. Moreover, under H3 condition (indoor: 20/15 °C; outdoor: -7/-8 °C), the frosting duration is set as 100 min, and the VB mode obtains 9.67% lower frost mass, 7.0% higher average heating capacity and 13.3% higher COP over CO mode. Generally, the vapor-bypassed evaporation technique has a great application potential in retarding frosting and improving performance of an air source heat pump system especially under high heating capacity or low ambient temperature conditions.

Packed bed column adsorption of phenol onto corn cob activated carbon: linear and nonlinear kinetics modeling

In the present study, linear and nonlinear regression analysis for packed bed column adsorption of phenol onto corn cob activated carbon was investigated. The activation of the corn cob provided the activated carbon with enhanced surface area and micropore volume of 903.7 m2/g and 0.389 cm3/g respectively. The analysis of the physical properties of the corn cob activated carbon (CCAC) revealed that it contained 33.47% of fixed carbon, 5.82% of ash content, 18.01% of volatile matter, 0.63 g/mL of bulk density, 5.50% of moisture content, and a pH of 6.30. SEM images indicated the presence of interspatial pores within the matrix of the adsorbent, while the FTIR analysis revealed that the major functional groups in CCAC were alkanol, alkanes, alkyls, carboxylic acids, ethers, esters, and nitro compounds. The effect of the process parameters influencing the dynamic adsorption process was investigated at flow rates (9–18 mg/min), initial phenol concentration (100-300 mg/L), bed height (5–10 cm), and particle size (300-800 µm). The breakthrough time and adsorption capacity increased with an increase in bed height but decreased with an increase in flow rate, initial phenol concentration, and particle size. At optimum conditions of bed height 10 cm, initial phenol concentration, 100 mg/L, flow rate, 9 mL/min, and particle size 300 µm, the adsorption capacity at breakthrough (qb), adsorption capacity at saturation (qs), volume of effluent treated at saturation (Veff,s), length of mass transfer zone (MTZ), adsorbent exhaustion rate (AER), fractional bed utilization (FBU) factor, Reynolds number (Re), Sherwood number (Sh), and the percentage phenol removal (Ys) were 2.143 mg/g, 8.570 mg/g, 12.96 L, 7.50 cm, 30.86 g/L, 0.25, 17.93, 28.85, and 66.13% respectively. The linear and nonlinear regression analysis of the Thomas, Adams-Bohart, and Wolborska models fitted better with the experimental data than the Yoon–Nelson model. Generally, the nonlinear regression proved to be a better tool for dynamic adsorption model analysis as the model parameters generated by the technique have a better correlation with the experimental data when compared to those obtained via linear regression. Conclusively, this study has shown that CCAC can successfully be used for the removal of phenol from aqueous solutions. It also demonstrated that the modeling approach significantly affects the outcome of the analysis of dynamic adsorption systems.

Air stripping pre-treatment process to enhance biogas production in anaerobic digestion of chicken manure wastewater

Anaerobic digestion is typically applied for water and air pollution control and energy recovery from chicken manure wastewater. Unfortunately, high nitrogen content of the chicken manure could be prohibitive to efficient anaerobic digestion. In this study, air stripping was employed as a pre-treatment process for ammonia removal from a chicken manure wastewater. Laboratory-scale experiments of air striping were conducted at various temperatures, initial pH values, air flow rates, and stripping times. The experimental results showed that the high ammonia removal efficiencies of more than 80% could be achieved from the air stripping process operating at the initial pH, temperature, and air flow rate of 11, 80 °C, and 4.0 L/min, respectively. The ammonia removal kinetics were found to fit with the first-order reaction. Bio-methane potential tests suggested that air stripping pre-treatment of the chicken manure wastewater resulted in about 25% increase in biogas production.

Hydraulics analysis of the U-tubing effect in a riserless drilling system

As a newly developed marine drilling technology, riserless drilling (RD) shows obvious advantages for use in deep-water and ultra-deepwater petroleum resources exploitation. However, the available published hydraulic analysis models for RD are rare or imperfect, especially regarding the lack of accounting for the out-of-hole time. To analyse the actual flow characteristics of drilling mud in an RD system after the surface mud pumping is complete, this paper presents a new hydraulic simulation model of the U-tubing effect. The specific calculation methods of pressure loss in the drilling string and the wellbore annulus at different flow regimes (turbulent flow, transition flow, and laminar flow) are provided based on the Herschel-Bulkley (HB) rheological model. A case study shows that a critical volumetric flow rate (CVFR) exists for a specific RD system to just cause the standpipe pressure to become zero. Only when the initial pump circulation rate is greater than the CVFR can it ensure the normal operation of the RD. Otherwise, the fluid mud level inside the drilling string will drop, resulting in the u-tubing effect. In the first few seconds after the surface pump is shut down, the wellbore transient flow rate is influenced strongly by the initial circulation rate. When the initial flow rate is less than the CVFR, the transient flow rate is accelerated during the first few seconds, which is not the expected behaviour. The influence of the drilling string size, fluid density and rheological parameters of the drilling fluid on the transient flow rate and the Bottom Hole Pressure (BHP) are also considered. The results proved that the smaller values of the rheological parameters are beneficial for reducing the fluctuation of the BHP during the U-tubing process.

Justification of the parameters and operating modes of the disinfecting system

Increasing yields is an important task for our country. This is possible due to removing the tip of the shoot, which stimulates the potential of the plant itself, and such products can be sold as organic since no other chemicals are used to increase yields. When the shoot tip is removed, a wound is formed through which pathogens can enter. To reduce the likelihood of plant contamination, the device provides a system for applying a disinfectant solution (hydrogen peroxide) to the knife blade. The settings of the injector are taken into account. When choosing a spray gun, it is necessary to take into account the average working pressure, equal to P = 0.28 MPa, which provides a solution flow rate щa Q = 0.8 l • min-1 with a nozzle diameter of 0.1 mm. These requirements can be met by spray guns of caliber 04 or 05. At a spray angle of 800, the recommended spray angle is 300; the mounting distance is 0.3 m below the plane of rotation of the cut-off wheel. The initial flow rate of the liquid of 17.33 m • s-1 will provide stable droplet formation, providing the recommended dispersion of the solution of 150-200 microns.

Electrochemical mineralization of abattoir wastewater with continuous system

This study aims to determine the effects of initial pollutant concentration level (1/1–1/4), flow rate (10–40 mL/min), NaCl concentration (0.1–1 M), pH (3–9) and current density (4.73–23.67 mA/cm2) parameters on the removals of total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color for economic treatment of cattle-abattoir wastewater using mesh-type Ti/Pt anodes with continuous EO system. Total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color analyses were carried out according to photometric method, catalytic oxidation method, closed reflux colorimetric method, nitrogen cell test method and platinum–cobalt method, respectively. The effluent chloride levels were analyzed according to the argentometric titration method. According to results, all operational parameters had an impact on removal efficiencies but the most effective parameters on energy consumption were NaCl concentration and applied current density. Although two possible system conditions were determined according to removal efficiencies the operating conditions with the lowest energy consumption are considered to be optimal. The optimum operating conditions were determined as NaCl concentration of 1 M, CD of 4.73 mA/cm2, initial pH of 7.03, reaction temperature of 25 °C and FR of 10 mL/min. Under these conditions removal efficiencies (%) for total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color were found as; 98.28, 93.03, 97.44, 95.53 and 99.80, respectively. The energy consumption values were calculated as 2.42 kWh/kg COD and 19.43 kWh/m3. The approximate cost to treat 1 m3 wastewater was calculated as $ 6.43. The kinetic behavior abided by a pseudo-first-order model.

Influence of asphaltene inhibitors on asphaltene deposition in the porous media

This article deals with organic asphaltene deposition in the reservoir rock, for crude oil having high asphaltene content and high apparent viscosity. The crude oil is characterized using thermal analysis through the thermogravimetric method. Crude oil is blended with heptane and flooded through the formation core at 55°C and 200-1200 psi pressure. With the rise in flow pressure, asphaltene precipitation became more significant with about four hundred times fall in the initial flow rate (flow rate at 200 psi) of crude oil at 1200 psi pressure. Phthalic acid and turpentine oil are used as asphaltene inhibitors for this crude oil. These asphaltene inhibitors are easy to procure, required less dosage for asphaltene dissolution and are relatively less toxic as compared to the other organic solvents used frequently as asphaltene inhibitor in oil industries. The asphaltene inhibitors are injected into the crude oil and flowed through the pores of the core. It is found that the crude oil treated with phthalic acid resulted in 88.23% increment its flow rate as compared to the turpentine oil, suggesting significant organic asphaltene dissolution in the formation rock.

Treatment of simulated printing and dyeing wastewater using ozone microbubble

Owing to its widespread and persistent usage, methylene blue (MB) is an environmental substance, mostly found in the printing and dyeing industry that raises concerns in the environment recently by posing significant threat to human life and the ecosystem as a whole. Thus, there is the need to effectively manage and treat the wastewater from these industries before reaching to the available water sources. Ozonation treatment is very efficient in treating printing and dyeing wastewater (MB) and can be greatly improved by using micro-bubble technology. Microbubble dissolution is an effective way to improve the rate of ozone mass transfer. To discover these properties, a method was used to improve the mass transfer of ozone microbubbles, which was used to effectively treat simulated printing and dyeing wastewater. We investigated the effects of pH, water temperature, ozone flow, and other conditions on the dissolution and attenuation properties of ozone in methylene blue microbubble solutions. Treatment of simulated printing and dyeing wastewater (methylene blue) was investigated under various initial pH and ozone flow rates. A catalytic exhibition was performed towards the decolorization of methylene blue (MB) concentrations and the corresponding COD removal efficiency. Ozone depletion and pH levels played key roles in MB degradation. Under high pH level of 11.01, the rate of removal of COD was 93.5%. Ozone dosage also has direct effect on COD removal efficiency and decolorization. Higher ozone flow rates, 0.4 L/min and 0.5 L/min recorded more than 94% degradation of COD thus very effective and efficient. Also, ozone flow rates 0.3 L/min, 0.4 L/min and 0.5 L/min with initial pH, 7.03, 6.63 and 6.36 decreased to 3.43, 3.49 and 3.44 after reaction processes which clearly shows that with high ozone dosage, pH reduces considerably.

EXPERIMENTAL STUDY OF HEAT EXCHANGE FROM A STEAM-GAS MIXTURE DURING HEAT TRANSFER THROUGH A RIBBED SURFACE

This article deals with the problem of heat energy transfer from a steam-gas mixture with a constant temperature of 220 °C. An experimental study of the transfer of heat energy from a steam-gas mixture by a recuperative heat exchanger with a ribbed surface at the industrial enterprise “PULP Invest”, located at the production site of the industrial park Technopolis “Khimgrad” in Kazan, is presented. The design of a heat exchanger with a ribbed surface is described. The finned surface of the recuperative heat exchanger allowed intensifying the transfer of heat flow, due to the appearance of turbulent vortices of the vapor-gas medium when it moves between the transversely arranged fins. For a heated heat carrier, water was used, which in the future is planned to be used for technological and economic needs. This paper presents the experimental method and measuring instruments. During the experiments, the initial temperature of the cold coolant (water) varied from 28.8 to 31.9 °C. The series of experiments included 7 experiments with a different volume flow of water from 60 to 120 liters/hour. The initial volume flow rate was 60 l/h, the flow rate change step was 10 l/h. The results of the studies showed that the time of the output of the studied parameters: temperature head, heat flow and heat transfer coefficient to the stationary mode was 265 s. When entering the stationary mode with a volume flow rate of cold coolant in the range from 60 to 120 l/h, the temperature head varied from 32.2 to 63 °C, the heat flow varied from 4.1 to 4.5 kW, the heat transfer coefficient varied in the range of 24.4-27.9 W/(m2 · K). The obtained results allowed establishing that the heat transfer coefficient is inversely proportional to the thermal resistance of the vapor-gas phase.

Network community structure and resilience to localized damage: Application to brain microcirculation

In cerebrovascular networks, some vertices are more connected to each other than with the rest of the vasculature, defining a community structure. Here, we introduce a class of model networks built by rewiring Random Regular Graphs, which enables reproduction of this community structure and other topological properties of cerebrovascular networks. We use these model networks to study the global flow reduction induced by the removal of a single edge. We analytically show that this global flow reduction can be expressed as a function of the initial flow rate in the removed edge and of a topological quantity, both of which display probability distributions following Cauchy laws, i.e. with large tails. As a result, we show that the distribution of blood flow reductions is strongly influenced by the community structure. In particular, the probability of large flow reductions increases substantially when the community structure is stronger, weakening the network resilience to single capillary occlusions. We discuss the implications of these findings in the context of Alzheimers Disease, in which the importance of vascular mechanisms, including capillary occlusions, is beginning to be uncovered. Statement of significance“Occlusions of capillary vessels, the smallest blood vessels in the brain, are involved in major diseases, including Alzheimers Disease and ischemic stroke. To better understand their impact on cerebral blood flow, we theoretically study the vessel network response to a single occlusion. We show that the reduction of blood flow at network scale is a function of the initial blood flow in the occluded vessel and of a topological quantity, both of which have broad distributions, that is, with significant probabilities of extreme values. Using model networks built from Random Regular Graphs, we show that the presence of communities in the network (subparts more connected to each other than with the rest of the vasculature) yield a broader distribution of the topological quantity. This weakens the resilience of brain vessel networks to single capillary occlusions, which may contribute to the pathogenicity of capillary occlusions in the brain”.