High Flow Rates Research Articles

Development of CPAP Overlay Interfaces for Efficient Administration of Aerosol Surfactant Therapy to Preterm Infants

Abstract The administration of surfactant aerosol therapy to preterm infants receiving continuous positive airway pressure (CPAP) respiratory support is highly challenging due to small flow passages, relatively high ventilation flow rates, rapid breathing and small inhalation volumes. To overcome these challenges, the objective of this study was to implement a validated computational fluid dynamics (CFD) model and develop an overlay nasal prong interface design for use with CPAP respiratory support that enables high efficiency powder aerosol delivery to the lungs of preterm infants when needed (i.e., on-demand) and can remain in place without increasing the work of breathing compared with a baseline CPAP interface. Realistic in vitro experiments were first conducted to generate baseline validation data, and then the CFD model, once validated, was used to explore key design parameters across a range of preterm infant nose-throat geometries and aerosol delivery conditions. The most important factors for efficient aerosol delivery were shown to be (i) maintaining the aerosol delivery flow rate below the tracheal flow rate (to minimize CPAP line loss) and (ii) concentrating the aerosol within the first portion of the inhalation waveform. An optimized design was shown to deliver approximately 37–60% of the nominal dose through the system and to the lungs with low intersubject variability (1050–2200 g infants) across two modes of device actuation (automated and manual) with room for further improvement. Ergonomic curvatures and streamlining of the prong geometries were also found to reduce work of breathing and flow resistance compared with a commercial alternative. Graphical Abstract

Artificial Neural Network For Predictive Modeling of Quinoline Insolubles in Pitch in A Steel Industry: Quality and Sustainability

Objective: The objective of the present work was the development of an intelligent system based on artificial neural networks, supervised and with batch learning, to predict the quinoline insoluble quality (IQ) parameter of tar, using a set of data from a steel industry. Theoretical Framework: Tar, derived from coal tar, is widely used in the production of anodes for the aluminum industry, and its quinoline insoluble (IQ) content is a crucial parameter, influenced by factors such as coal mixing, coking parameters and heat treatment. IQ forecasting is challenging due to the complexity of the processes involved. To address this question, artificial neural networks (ANNs) have been applied to predict the IQ of tar, taking advantage of its ability to handle complex, nonlinear systems. Method: In this study, a feedforward RNA model was used, trained with the Levenberg-Marquardt algorithm. The model has been configured with two hidden layers and the tansig activation function. The training was carried out with real data from polymerization reactors, including variables such as level, temperature, nitrogen rate, feed flow rate of the polymerizers and tar IQ. The network was configured with 2000 interactions and 20 neurons in the hidden layer, obtaining a training error (MSE) of 1x10-20. Results and Discussion: The analysis of the results revealed that temperature and nitrogen flow have the greatest influence on the IQ of the pitch, with higher temperatures and higher flow rates resulting in a higher IQ. Research Implications: ANN modeling is effective in predicting and optimizing industrial processes, especially in the analysis of large volumes of data and complex systems, contributing to quality control in pitch production and the improvement of industrial processes. Originality/Value: The main contribution of this work lies in the demonstration of the ability of artificial neural networks to accurately model the content of Quinoline Insolubles (IQ) of the pitch, even in the face of the significant dispersion observed in the input data. This finding is particularly relevant because the high variability of the data often poses a challenge for traditional predictive models. The precision achieved by the neural network, therefore, proves the feasibility and potential of this approach to overcome the limitations inherent to the complexity of the pitch production process and optimize its control, opening new perspectives for the steel industry

Parametric optimization of abrasive waterjet machining for aluminum 7075/boron carbide/zirconium silicate hybrid composites

In the present work, an attempt was made to study the machining characteristics of Hybrid Metal Matrix Composites (HMMCs) using Abrasive Waterjet Machining (AWJM). For preparing the composites, Aluminum alloy 7075 is cast with boron carbide (B4C) and zirconium silicate (ZrSiO4) reinforcement by the method of stir casting. Experimental investigation of the machining parameters on Depth of Cut (DoC), Material Removal Rate (MRR), and Surface Roughness (SR) was done. The independent parameters include Abrasive Mesh Size (AMS), Abrasive Flow Rate (AFR), Water Jet Pressure (WJP), and Traverse Rate (TR). The results of experiments reveal that low TRs increase SR, while short AMSs, high flow rates, and large WJPs increase DoC and MRR. Surface maps made by SEM exposed information about the surface texturing and the material removal processes. It was found that the optimal DoC was achieved at an AMS 80#, AMS of 340 g/min, WJP of 200 MPa, and TR of 60 mm/min for both unreinforced Al and the composite of Al + 5% B4C + 5% ZrSiO4. The results enable the development of proper AWJM procedures for HMMCs to ensure better surface finish and workability. From the experiments, it was observed that while smaller mesh sizes and greater AFR will improve MRR and DoC, it can at the same time have a negative effect on the overall performance of Kerf Taper angle (KT) and Surface Roughness (SR).

Renal pelvis pressure and flowrate with a multi-channel ureteroscope: invoking the concept of outflow resistance.

Understanding renal pelvis pressure (PRP) during ureteroscopy (URS) has become increasingly important. High irrigation rates, desirable to maintain visualization and limit thermal dose, can increase PRP. Use of a multi-channel ureteroscope (m-ureteroscope) with a dedicated drainage channel is one strategy that may facilitate simultaneous low PRP and high flowrate. We sought to define the relationship between PRP and flowrate across a range of different outflow resistance scenarios with an m-ureteroscope versus a single-channel ureteroscope (s-ureteroscope). The m- or s-ureteroscope was placed into the pelvis of a validated silicone kidney-ureter model. Trials were conducted at irrigation pressures (50-150 cmH20) and five different outflow resistance scenarios simulated with catheters of different lengths and diameters. PRP was measured with a fiber optic pressure sensor positioned in the renal pelvis. Flowrate was determined by measuring the mass of drainage fluid over 60s. PRP was lower with the m-ureteroscope than the s-ureteroscope when equivalent flowrates were delivered (i.e. 34 vs. 82 cmH20 respectively with 15ml/min irrigation in a high outflow resistance scenario). Flowrate was higher with the m-ureteroscope than the s-ureteroscope when equivalent irrigation pressures were applied (i.e. 28 vs. 14ml/min respectively with irrigation pressure 150 cmH20 in a high outflow resistance scenario). The m-ureteroscope has improved pressure-flow dynamics imparting important clinical benefits. More importantly, this approach to framing ureteroscopy in the context of pressure-flow relationships related by resistance values allows quantification of ureteroscopy within a deterministic system, which can be used to streamline future device development and technological innovation.

Implications of non-native metal substitution in carbonic anhydrase - engineered enzymes and models.

The enzyme carbonic anhydrase has been intensely studied over decades as a means to understand the role of zinc in hydrating CO2. The naturally occurring enzyme has also been immobilized on distinct heterogeneous platforms, which results in a different hybrid class of catalysts that are useful for the adsorption and hydration of CO2. However, the reusability and robustness of such natural and immobilized systems are substantially affected when tested under industrial conditions, such as high temperature and high flow rate. This led to the generation of model systems in the form of metal-coordination complexes, metal-organic frameworks, metallo-peptide self-assembled supramolecules and nanomaterials that mimic the primary, and, to some extent, secondary coordination sphere of the active site of the natural carbonic anhydrase enzymes. Furthermore, the effects of zinc-substitution by other relevant transition metals in both the naturally occurring enzymes and model systems has been reported. It has been observed that some other transition metal ions in the active site of carbonic anhydrase and its models can also accomplish similar activity, established by various reaction probes and ideas. Herein, we present a comprehensive highlight about substituting zinc in the active site of the modified enzymes and its biomimetic model systems with non-native metal ions and review how they affect the structural orientation and reactivity towards CO2 hydration. In addition, the utility of artificially engineered carbonic anhydrases towards a number of non-natural reactions is also discussed.

Instability mechanism and a fractal theory-based relative permeability model of immiscible two-phase displacement in rough fractures

The two-phase displacement in rock fractures is a critical scientific challenge in deep energy development projects, characterized by the intricate and dynamic flow patterns resulting from the complex fracture geometry and mutual interference between the two-phase fluids. The present study involves the construction of a three-dimensional rough fracture fine model using the fast Fourier transform and Gaussian distribution method. The phase field-finite element method is employed to simulate the dynamic displacement of water-oil flow and the evolution of the water-oil interface, aiming to investigate the impact of roughness, aperture, and wettability on the viscous fingering pattern observed in rough fractures. The numerical results indicate that the immiscible two-phase displacement presents a viscous fingering pattern at a high flow rate. Moreover, the greater the roughness is, the higher the number of fingering is, and the more volatile the change in displacement velocity is. The width of the wet-phase flow channel increases proportionally with the fracture aperture increasing. Furthermore, the morphology of immiscible two-phase interface within fractures is also influenced by the wetting angle, and the fingering, bifurcation, and crushing phenomena appear in the oil-wet state with the strong displacement interface instability. Finally, a fractal model of relative permeability for waterflooding in rough fractures is proposed based on the cubic law of flow and fractal dimension of aperture distribution, which has been validated through comparison with numerical results.

Flow control of blade-end oscillating jets on corner separation in a high-load compressor cascade

Based on unsteady numerical simulation, the feasibility of utilizing a fluid oscillator to generate oscillating jets for relieving the compressor cascade's corner separation was investigated. First, at design incidence angle, the optimal jet position is located where corner separation is not fully developed (74% axial chord length). Jets at more upstream and downstream positions are less effective due to premature dissipation of jet effects and the occurrence of high corner losses, respectively. The effectiveness of separation control through jet injection increases with higher jet mass flow rates, and the scheme with 0.66% relative jet flow rate exhibits a wide effective jet position range. However, excessively low jet flow rates are sensitive to jet position selection, while excessively high jet flow rates lead to significant mixing losses, resulting in high overall field losses and reduced engineering applicability. Second, the optimal jet scheme remains consistent at both design and high incidence angles and exhibits effective control at other off-design incidence angles. Finally, the oscillating jet suppresses the spanwise development of wall vortex and passage vortex within the blade passage by injecting high-momentum flow. Moreover, proper orthogonal decomposition analysis indicates that the oscillating jet redistributes the modal energy of the original flow field, exciting the vortex structures into high-frequency, small-scale oscillations at the jet frequency. Meanwhile, the oscillating jet primarily facilitates momentum exchange through strong mixing with passage vortex, wall vortex, and concentrated separation vortex, ultimately mitigating corner separation and reducing corner loss.

Numerical simulation on the effect of impeller radial gap on hemodynamics and hemocompatibility of a centrifugal blood pump

Impeller radial gap is one of important parts within a blood pump, which may affect the hemodynamics and hemocompatibility. In this study, computational fluid dynamics method was performed to evaluate the impact of radial gap sizes. The volume of scalar shear stress decreased with radial gap sizes increasing. On the contrary, the residence time increased with radial gap sizes increasing, especially in the bottom gap. The hemolysis index and platelet activation status at three flow rates decreased with the increase of radial gap sizes. Compared with the hemolysis index when the radial gap size was 0.6 mm, the hemolysis index for the radial gap of 1.0 mm decreased by 27.6%, 25.4% and 21.1% from low flow rate to high flow rate, respectively. Similarly, the platelet activation status for the radial gap of 1.0 mm decreased by 13.0%, 11.5% and 9.1%, respectively. As a novelty, this study revealed that radial gap sizes can significantly influence the blood pump hemocompatibility, especially at low flow rate. In addition, the hemolysis performance can be more affected by radial gaps than that on thrombosis risk.

Applying Photoelectric Sand Meter for Monitoring of Suspended Solid Matter in Rivers

River ecosystems are integral to sustainable environmental development, playing a crucial role in understanding suspended solid matter (SSM) transport dynamics and soil conservation. Accurate monitoring of SSM concentrations in watersheds is foundational for these studies. This research introduces and evaluates a novel HHSW·NUG-1 photoelectric sand meter, specifically designed for SSM measurement. Its reliability was validated at three hydrological stations, including Xiaolangdi. The instrument, based on light scattering principles, is optimized for environments with high SSM loads and rapid flow rates. Laboratory tests indicate a measuring range of 0 to 730 kg/m3, and field trials show effective operation within 0 to 375 kg/m3, meeting the monitoring needs of hydrological stations. Through comparative analysis of measurement data, we established conversion relationships for various SSM concentration ranges, confirming that the instrument’s system error is less than 1%. The photoelectric sand meter adheres to standards outlined in the “Guidelines for SSM Test in Rivers”, demonstrating stability in reliability, calibration methods, observation accuracy, real-time monitoring, data storage, and continuous operation. For optimal use, adherence to relevant hydrological instrument standards is recommended, particularly in stations requiring SSM analysis. Standard sampling and calibration of conversion coefficients should be conducted, and proper sensor installation is crucial to avoid interference from flow conditions. In conclusion, the HHSW·NUG-1 optoelectronic sand meter exhibits stable and reliable performance in practical applications, with broad potential for rapid deployment in other river hydrological stations.

Performance Evaluation of Rain Hose Irrigation System for Enhancing Water Productivity in Kerala, India

A field experiment was conducted to evaluate the performance of rain hose irrigation system in terms of discharge variation, moisture distribution, and uniformity coefficient at different operating pressures. The study revealed a linear relationship between operating pressure and discharge for rain hose irrigation system. Specifically, at pressures of 0.5 and 1.0 kg cm- ², increased pressure correlated well with higher soil moisture content along with 20% to 23% increase in moisture with greater water-infiltration depth. The distribution of moisture was found to be more uniform at higher pressures, achieving a uniformity coefficient of 74%. This uniformity was enhanced in the multilateral rain hose irrigation system with reduced spatial variation as compared to the single lateral system. As operating pressure increased, discharge per unit length also showed an increase, alongside the throw distance. The rain hose system is particularly advantageous for closely-spaced and shallow-rooted crops like onion, groundnut, and leafy green vegetables, ensuring consistent and high flow rates. The study suggested that regulating operating pressure is crucial for optimizing soil moisture levels, as higher pressures lead to deeper water infiltration. Notably, at a pressure of 1.5 kg cm- ², the system performed the best, yielding the optimum results for irrigation efficiency. In summary, the rain hose irrigation system proved effective at higher operating pressures, providing a reliable method for achieving uniform water distribution and adequate soil moisture for crops, which is essential for effective irrigation management.

Simulation study of two-phase flow in branched horizontal wells

Natural gas hydrate reservoirs have low permeability and uneven distribution, necessitating multiple branches for effective commercial development. Due to cost and technical constraints, multi-branch horizontal wells typically forgo packers in previously drilled sections, relying instead on intelligent completion technologies and flow control devices. This paper investigates the complex multiphase flow of drilling fluid and rock cuttings in horizontal annular spaces during the drilling of multi-branch wells. A simplified model and the Euler model are used to analyze how different drilling fluid flow rates and rheological properties affect rock cutting transport. Results show that while increasing flow rates reduces the volume fraction of rock cuttings and enhances fluid return speed, the increase in apparent viscosity diminishes. Therefore, excessively high flow rates are not economically beneficial. In multi-branch drilling, higher flow rates are necessary to minimize rock cutting invasion from active to previously drilled sections, primarily influenced by yield stress and consistency coefficient. The study concludes that while ensuring dynamic shear forces, efforts should focus on increasing yield stress and consistency coefficient to manage rock cutting invasion effectively.

Ionization Characteristics of Glycan Homologues in Various Modes of Electrospray.

Fluorescence labeled glycan homologous mixtures were quantified using fluorescence and then used to evaluate ionization performances in electrospray ionization at micro, nano, and femto flow modes. nanoESI produced higher (2+ and 3+) charged ions adducted with sodium and calcium. In comparison, femtoESI was found to favor the generation of [M + H]+ ions against metal adducts, even with nonvolatile salts up to 1 mM for NaCl and 100 μM for CaCl2. For labeled glucose homopolymer (GHP) glycans, nanoESI and femtoESI had 0.81 and 3 nM detection limits, respectively. With LC separation and a much higher flow rate, conventional microflow ESI detected all glycans with 10-fold lower concentrations. Overall, nanoESI had the optimum uniformity in the relative ionization efficiency (RIE). When summing up intensities of analyte ions formed with all charge carriers, the RIE of the midsized glycans (10 to 16 glucose units) appear to be uniform (RIE 95%-105%). For the smaller (1-5 glucose units) glycan components, femtoESI provided better uniformity than nanoESI and conventional ESI. For the labeled IgG N-glycans, the impact of chemical structure on the ionization efficiency was revealed by the strong correlation between their RIE trends in different ionization modes.

An Acidic Media Pump with Ga‐Based Liquid Metal

AbstractMicropumps have an important influence on the field of microfluidics, with particular interest in pumps based on liquid metal that operate without mechanical moving parts. While previous research has primarily focused on pumping alkaline media, this article aims to advance the field by demonstrating a liquid metal pump suitable for acidic environments. A key strategy involves reducing the interfacial tension between the liquid metal and the surrounding solution through the addition of surface‐active anions (I−). Theoretical analysis first evaluates the effectiveness of this approach. These experimental results confirm that increasing KI concentrations leads to a decrease in interfacial tension, enabling the deformation and actuation of liquid metal droplets at lower voltages compared to acidic media alone. Subsequently, an acidic media pump is constructed, and various parameters influencing its performance are examined, including acidity, iodide anion concentration, voltage, frequency, and droplet volume. This research offers strategies for developing liquid metal pumps with high flow rates and low energy consumption, thereby expanding the application potential of liquid metal in microfluidics.

Experimental Investigation of a Regenerative Kalina Cycle for Electrical Power Generation Using Waste Heat

Kalina cycle is a thermodynamic power cycle uses any waste heat source (low temperature source) to generate electrical power or cooling. Many versions of Kalina cycle exist. In this paper a regenerative Kalina version is designed and constructed. The cycle consists of the following main components: heat recovery vapor generator (HRVG), separator, turbine, condenser, throttling valve, mixer (absorber), heat exchanger and pump. The heat exchanger is used to heat the working fluid coming from the pump before entering the HRVG by the hot saturated liquid (weak solution) coming from the separator. The cycle uses aqua ammonia mixture as the working fluid with different ammonia concentrations. The effect of many operating conditions on cycle performance is studied such as ammonia (NH3) mass fraction (range from 0.85-0.89), low pressure (range from 2-4 bar), and maximum pressure (range from 20-40 bar). The dryness fraction (DF) at separator entrance is kept at 0.3. The results show that the highest thermal efficiency obtained is 12.9% at Pmax=35 bar, Pmin=2 bar, and x=0.85. The highest value of the net power is 0.367 kW at x=0.89 at turbine inlet pressure of Pmax=20 bar. The highest value of exergy efficiency is 28.5% at Pmax=35 bar, Pmin=2 bar. It is noticed that the highest exergy destruction is in the heat recovery vapor generator (HRVG) which is about 48% due to high temperature heat exchange process and low mass flow rate. The exergy destruction is larger at Pmax=35 and x=0.89 than the exergy destruction at Pmax=20 bar and x=0.89.

Numerical Modeling of a Primary Heat Exchanger in sCO2 Power Cycles for Thermal Energy Storage Systems

Abstract Renewable energy sources are the key for long-term decarbonization of energy. However, the intermittent nature of renewables does not always meet the energy demand in the electrical grid. Thus, electrical heated thermal energy storage systems (TES) coupled with sCO2 power cycles are investigated at Helmholtz-Zentrum Dresden-Rossendorf as a possible solution to balance this mismatch. In this study, a printed circuit heat exchanger (PCHE) is considered as candidate for the 1 MW primary heat exchanger, given the mechanical challenge induced by drastic pressure difference between the hot fluid of the TES and the cold fluid of the power cycle. The present work consists of two parts, one elaborates a one-dimensional (1D) model in order to optimize the PCHE regarding the pump power required to compensate the pressure loss. It was found that the hot fluid coming from the TES accounts for 80% of the total pump power after optimization because of its low density and its high mass flow rate. Furthermore, three-dimensional simulations by computational fluid dynamics (CFD) were done and compared to the results from the 1D model to ensure its validity. It was observed that the results from the 1D model and the CFD simulations are consistent, with a slight potential deviation in the calculation of the pressure profile.

Maximum Magnitude of Induced Earthquakes in Rate and State Friction Framework

Abstract We analyze the evolution of the rupture radius and maximum magnitude (Mmax) of injection-induced earthquakes on faults obeying rates and state friction. We define the radii of two different slip modes, aseismic (Ra) and seismic slip (Rs), and derive an expression for maximum magnitude evolution. If the flow rate is sufficiently high, the seismic moment grows with the scaled injection volume, Qt/wS, as M∼Cf(Qt/wS)3/2, in which Cf depends on the initial stress level, S is storage coefficient, and w is the thickness of the reservoir. These findings are confirmed using numerical simulations conducted with varied initial states. The simulations show that Rs behaves as a rupture arrest radius and Ra behaves as the minimum possible radius of aseismic creep at a given injection volume. The Mmax evolution curve can be steeper if the fault is slightly critically stressed. A high-flow rate results in frequent seismic events, starting at relatively low-injected volume, which helps track the evolution of Mmax, providing a way to anticipate the risk of a large event. Conversely, a low-flow rate allows for a larger volume injection without seismic events but may lead to sudden large events without precursory events.

Physics-based numerical evaluation of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) in the Upper Jurassic reservoir of the German Molasse Basin

Abstract. Concepts of High-Temperature Aquifer Thermal Energy Storage (HT-ATES) (> 50 °C) are investigated in this study for system application in the Upper Jurassic reservoir (Malm aquifer) of the German Molasse Basin (North Alpine Foreland Basin). The karstified and fractured carbonate rocks exhibit favourable conditions for conventional geothermal exploitation of the hydrothermal resource. Here, we perform a physics-based numerical analysis to further assess the sustainability of HT-ATES development in the Upper Jurassic reservoir. With an estimated heating capacity of approx. 19.5 MW over half a year, our approach aims at determining numerically the efficiency of heat storage under the in situ Upper Jurassic reservoir conditions and projected operation parameters. In addition, the hydraulic performance of the HT-ATES system is further evaluated in terms of productivity and injectivity index. The numerical models build upon datasets from three operating geothermal sites at depths of approx. 2000–3000 m TVD, located in a subset of the reservoir dominated by karst-controlled fluid fluxes. Commonly considered as a single homogeneous unit, the 500 m thick reservoir is subdivided into three discrete layers based on field tests and borehole logs from the three considered sites. The introduced vertical heterogeneity with associated layer-specific enhanced permeabilities allows to examine potentially arising favourable heat transfer, and in combination with the facilitated high operation flow rates (100 kg s−1) to evaluate thermal recoveries in the multilayered reservoir. All simulations account for fluid density and viscosity variation based on thermodynamically consistent equations of state (EOS). Computation results reveal that the reservoir layering induces preferential fluid and heat migration primarily into the high-permeability zone, while thermal front propagation into the lower permeable rock matrix is inhibited. The simulations further display a gradual temperature increase in the warm wellbore and its surrounding host rock, and a consequent progressive improvement in the heat recovery efficiency. Despite the elevated permeability that may trigger advective heat losses, heat recovery factor values range from approx. 0.7 over the first year of operation to over 0.85 after 10 years of operation. An additional scenario is examined with fluid injection solely in the high permeable zone, in order to quantify potential enhancement in the recovery efficiency by omitting fluid injection in the lower-permeability layers where heat propagation is diminished. This is due to the geometrical shape of the thermally perturbed rock volume as heat losses occur during thermal equilibration between injected fluid and reservoir rock, as well as at the contact-surface area between propagating thermal front and adjacent rock matrix. Results suggest that under the stratified reservoir configuration, additionally constrained by the selected spatial distribution of rock properties, heat storage performed only into the upper high-permeability zone corresponds to an improved thermal performance. Simulation results further indicate that density-induced buoyant fluxes, which would considerably decrease thermal efficiencies are inhibited in the system, and the prevailing heat transport mechanism is forced convection.

Assessment of Two Crosslinked Polymer Systems Including Hydrolyzed Polyacrylamide and Acrylic Acid-Hydrolyzed Polyacrylamide Co-Polymer for Carbon Dioxide and Formation Water Diversion Through Relative Permeability Reduction in Unconsolidated Sandstone Formation.

One of the most challenging aspects of manipulating the flow of fluids in subsurfaces is to control their flow direction and flow behavior. This can be especially challenging for compressible fluids, such as CO2, and for multiphase flow, including both water and carbon dioxide (CO2). This research studies the ability of two crosslinked polymers, including hydrolyzed polyacrylamide and acrylic acid/hydrolyzed polyacrylamide crosslinked polymers, to reduce the permeability of both CO2 and formation water using different salinities and permeability values and in the presence of crude oil under different injection rates. The result showed that both polymers managed to reduce the permeability of water effectively; however, their CO2 permeability-reduction potential was much lower, with the CO2 permeability reduction being less than 50% of the water reduction potential in the majority of the experiments. This was mainly due to the high flow rate of the CO2 compared to the water, which resulted in significant shearing of the crosslinked polymer. The crosslinked polymers' swelling ratios were impacted differently based on the salinity, with the maximum swelling ratio being 9.8. The HPAM polymer was negatively affected by the presence of crude oil, whereas increasing salinity improved its performance greatly. All in all, both polymers had a higher permeability reduction for the formation water compared to CO2 under all conditions. This research can help improve the applicability of CO2-enhanced oil recovery and CO2 storage in depleted oil reservoirs. The ability of the crosslinked polymers to improve CO2 storage will be a main focus of future research.

Comparison of Ammonia Removal from Ground Water in Attached Growth Process Using Over-burnt Brick with Suspended Growth Process without Any Media

Rising amount of ammonia in groundwater is rising problem in groundwater of Kathmandu. This has led to various diseases like blue baby syndrome to arise. So, it is necessary for efficient and safe removal of ammonia from drinking water. Since the physical-chemical system includes the major disadvantages of high operation and maintenance cost, the biological nitrification system can only be a good alternative to remove ammonia from ground water. Hence, an attempt is done in this research to treat ammonia contaminated water by biological nitrification process. Three reactors were constructed in series with media of over-burnt brick and other three in series were constructed without media. The study was carried out for five different flow rates of 10, 14.4, 18.8, 27.6 and 38.8 ml/min. Based on laboratory test the efficiency of these five different flow rates was plotted and conclusions were reached. Achievement of continuously increasing efficiency, which reached to 95–100% in the reactor provided with over-burnt media; reflects a success in the assumption that the over-burnt brick is good media to be used in bio filters for nitrification. The reactors with media have more efficiency than reactors without media. An average efficiency of 56.48% for reactors with media and 37.55% for reactors without media was observed for all the flows. The difference of 18.72± 0.2 was found between reactor with media and reactor without media in both series and single reactor. Low flow rates showed better ammonia removal than flow rates with higher flow rates such that a hydraulic retention time of 7.29 hour per reactor can be taken as design criteria for nitrification using over-burnt brick as media.

Numerical investigation and thermal optimization of low-inductance ring-shaped film capacitors with integrated cooling structure for electric vehicle

The advancement of motor controllers for electric vehicles is increasingly focusing on higher power density, efficiency, and miniaturization. Consequently, there is a growing demand for film capacitors that offer not only lower stray inductances but also enhanced high-temperature resistance capabilities. While existing research dedicated to mitigating the stray inductances of film capacitors, studies that address both the capacitors’ stray inductances and the thermal managements remain relatively scarce. Therefore, this paper proposes for the first time a low-inductance ring-shaped capacitor, utilizing an integrated cooling structure to reduce the capacitor’s thermal resistance and enhance its high-temperature tolerance. Firstly, the stray inductances and heat dissipation performances of both ring-shaped and conventional square-shaped capacitors, each with identical capacitances, are compared using Q3D and FLUENT simulations, the results demonstrate that the ring-shaped capacitor exhibits lower stray inductance and superior heat dissipation performance. Then an integrated cooling structure is proposed for the ring-shaped capacitor with the aim of diminishing its thermal resistance and augmenting its tolerance to high temperature. Utilizing FLUENT conjugate heat transfer simulation, the impacts of key factors within the cooling structure such as inlet flow rate, inlet temperature, and ambient temperature on the capacitor’s maximum temperatures are investigated, and the optimal inlet flow rate and inlet temperature are determined by multi-objective optimization. The findings reveal that increasing the inlet flow rate reduces the maximum temperature, although the cooling effect becomes less significant at higher flow rates, leading to increased energy consumption and operating costs. Moreover, the ambient temperature has the largest impact on the capacitor temperature, followed by the inlet temperature. The optimized integrated cooling structure achieves approximately a 73.93% reduction in thermal resistance and lowers the maximum temperature of the ring-shaped capacitor by about 72.24%.