Cascade Design Research Articles

Efficiency of a Compressor Heat Pump System in Different Cycle Designs: A Simulation Study for Low-Enthalpy Geothermal Resources

The development of district heating systems results in a search for alternative heat sources. One of these is low-enthalpy geothermic energy, more available than traditional geothermal energy. However, utilization of these resources is difficult, due to the low quality of the produced heat. To utilize them, the heat pump system can be used. Such a system was designed for this case study of a city in a region of the Polish Lowlands. The data necessary for the design came from the project of the borehole and operational parameters of the existing heating plant. Four heat pump-cycle designs were proposed, modeled, and simulated using Ebsilon software. Afterward, the designs were optimized to achieve maximum coefficient of performance (COP) value. As a result of the simulation, the efficiency of each design was determined and the seasonal COP value was calculated with the annual measured heat demand of the plant. The system based on the cascade design proved the most efficient, with a seasonal COP of 7.19. The seasonal COP for the remaining basic, subcooling, and regenerator variants was 5.61, 3.73, and 5.60, respectively. The annual heat production of the designed system (22,196 MWh) was calculated based on the thermal power of the designed system and historical demand data. This paper presents a simulation methodology for assessment of the efficiency and feasibility of a heat pump system in district heating.

A Data-Based Policy Model for Intelligent Turbine Cascade Design

The study of intelligent design methods is becoming a hot topic for the design of turbine cascades. This paper proposes a data-based policy model to achieve intelligent design. To gain a high-quality policy model, empirical equations and "space extending + elitism" are adopted to dynamically optimize database. This guarantees the quality of the model. Compared to traditional optimization design approaches, the proposed method relies on less human experience to design a turbine cascade. Ten different turbine cascades are used to verify this method. Results show that, aerodynamic performance of the cascades redesigned is either the same as or better than that of the traditional cascades. The computing time is reduced by more than one order of magnitude compared to a "CFD + optimization algorithm" or "surrogate model + optimization algorithm" method. With the advantages in computing time and intelligence, the proposed novel method shows the possibility of replacing traditional design methods.

Single-tank storage versus multi-tank cascade system in hydrogen refueling stations for fuel cell buses

Many countries in Europe are investing in fuel cell bus technology with the expected mobilization of more than 1200 buses across Europe in the following years. The scaling-up will make indispensable a more effective design and management of hydrogen refueling stations to improve the refueling phase in terms of refueling time and dispensed quantity while containing the investment and operation costs. In the present study, a previously developed dynamic lumped model of a hydrogen refueling process, developed in MATLAB, is used to analyze tank-to-tank fuel cell buses (30–40 kgH2 at 350 bar) refueling operations comparing a single-tank storage with a multi-tank cascade system. The new-built Aalborg (DK) hydrogen refueling station serves as a case study for the cascade design. In general, a cascading refueling approach from multiple storage tanks at different pressure levels provides the opportunity for a more optimized management of the station storage, reducing the pressure differential between the refueling and refueled tanks throughout the whole refueling process, thus reducing compression energy. This study demonstrates the validity of these aspects for heavy-duty applications through the technical evaluation of the refueling time, gas heating, compression energy consumption and hydrogen utilization, filling the literature gap on cascade versus single tank refueling comparison. Furthermore, a simplified calculation of the capital and operating expenditures is conducted, denoting the cost-effectiveness of the cascade configuration under study. Finally, the effect of different pressure switching points between the storage tanks is investigated, showing that a lower medium pressure usage reduces the compression energy consumption and increases the station flexibility.

Multi-Objective Optimization Design for a Novel Parametrized Torque Converter Based on an Integrated CFD Cascade Design System

Advanced cascade design theories and methods are crucial to the rapid development of torque converters. Therefore, the study proposed a new parametric design method for a hydrodynamic torque converter cascade. The method is embodied by using a cubic non-uniform rational B-splines (NURBS) open curve and closed curve, respectively, to carry out the parametric design of the unit blade camberline and unit blade thickness distribution, and the curvature of the designed blade curve is continuous. Then, the author developed batch and script files in the Isight platform for a fully automated integrated design of the hydrodynamic torque converter, including cascade parametric modeling, meshing, computational fluid dynamics (CFD) simulation, post-processing, and optimization design. A three-dimensional cascade integrated optimization design system of the hydrodynamic torque converter is established with CFD technology as the bottom layer design, a control file as the middle layer, and an optimization algorithm as the top layer drive. Finally, multi-objective optimization was carried out for the key cascade parameters (camberline peak height). Compared with the original blade, the optimized NURBS blade increased by 7.207% in high-efficiency region width (Gη), and the optimized blade increased by 2.673% in peak efficiency (ηmax) to meet the actual engineering requirements. The new parametric design method of the blade shape and the integrated optimization design system of a three-dimensional cascade of torque converter proposed in this paper significantly reduces the design costs and shortens the design cycle of the torque converter, which will provide a valuable reference for engineers of turbomachinery.

Geological aspect analysis for micro hydro power plant site selection based on remote sensing data

<span>Geological characters analysis is essential for micro hydropower plant (MHP) development planning. This paper presents an analysis of the geological aspect to determine the layout of MHP components based on remote sensing data as part of a solution to addressing power shortages in Sungai Are District, South Ogan Komering Ulu Regency, South Sumatra Province. Remote sensing and topographic map were extracted to identify the potential site. The topographic map and geological analysis were used to calculate the potential of electrical energy and the geological hazard risk, particularly floods and landslides. The results of the study identified four potential sites. Site 1 (Luas River, Ulu Danau Village) and site 3 (Putih River, Gintung Village) are suitable for MHP with a low cost of construction. Site 2 (Pecah Pinggan Village) and site 4 (Simpang Luas Village) are prone to flooding and landslides that makes it suitable for MHP but with a high cost of construction. Based on the geological aspect analysis, it is possible to optimize the hydropower capacity, by adding the volume of water flow from several nearby tributaries channeled into the hydropower flow system through civil construction engineering or by making a cascade design on the tailrace water flow.</span>

Temporal search persistence, certainty, and source preference in dentistry: Results from the National Dental PBRN

The primary goal of this paper was to investigate an old question in a new way: what are the search patterns that professionals demonstrate when faced with a specific knowledge gap? We examine data from a cascading survey question design that captures details about searching for information to answer a self-nominated clinical question from 1027 dental professionals enrolled in the National Dental Practice Based Research Network. Descriptive and conditional logistical regression analysis techniques were used. 61% of professionals in our sample choose informal sources of information, with only about 11% looking to formal peer reviewed evidence. The numbers of professionals turning to general internet searches is more than twice as high as any other information source other than professional colleagues. Dentists with advanced training and specialists are significantly more likely to consult peer-reviewed sources, and women in the sample were more likely than men to continue searching past a first source. Speed/availability of information may be just as, or in some cases, more important than credibility for professionals' search behavior. Additionally, our findings suggest that more insights are needed into how various categories of professionals within a profession seek information differently.

Glucose Induces Heme Leakage and Suppresses H2O2 Uptake of Chloroperoxidase in the Asymmetric Hydroxylation of Ethylbenzene

AbstractAs a basic feedstock for both natural life and chemical production, glucose is converted into various chemicals upon the help of peroxidase cascades composed of glucose oxidase (GOx) and peroxidases. However, little is known about the glucose effect on the structure and activity of peroxidases in a non‐natural environment. We report herein that glucose deactivates chloroperoxidase (CPO) used in the asymmetric hydroxylation of ethylbenzene into (R)‐1‐phenylethanol. Through both experiment and molecular simulation, we discover that glucose deactivates CPO through hydrophobic interaction with heme and hydrogen bonding with Glu183. These interactions lead to heme leakage and the reduction of H2O2 uptake thereby undermining the CPO activity. The mechanism appears generically applicable to other hemeproteins such as horseradish peroxidase, hemoglobin, and myoglobin. These findings may open new avenues for the design of peroxidase cascades for applications ranging from better diagnosis of diabetes to green synthesis of chemicals by direct functionalization of C−H bonds.

Optimal design of separation cascades using the whale optimization algorithm

High-fidelity simulation tools are required to treat isotope separation cascades. In the present work, a multi-objective optimization method based on Whale Optimization Algorithm, WOA, is developed to obtain the optimal parameters of recycling cascades for separating the binary mixture of isotopes. Detail treatment and simulation of isotope separation phenomena are critical in the economic aspect. The WOA is a novel meta-heuristic algorithm which imitates the bubble-net hunting strategy used by humpback whales in looking for food. In this analysis, the WOA is implemented for benchmark functions and its capabilities demonstrated; in the next step, it is enforced for main real problems such as isotope separation cascades to minimize the total number of centrifuges and flow rates in the process. The optimization results are evaluated against other well-known schemes. It is revealed the outcomes of WOA are in good agreement with those obtained by the conventional methods.

Unmasking the Hidden Carbonyl Group Using Gold(I) Catalysts and Alcohol Dehydrogenases: Design of a Thermodynamically-Driven Cascade toward Optically Active Halohydrins

A concurrent cascade combining the use of a gold(I) N-heterocyclic carbene (NHC) and an alcohol dehydrogenase (ADH) is disclosed for the synthesis of highly valuable enantiopure halohydrins in an aqueous medium and under mild reaction conditions. The methodology consists of the gold-catalyzed regioselective hydration of easily accessible haloalkynes, followed by the stereoselective bioreduction of the corresponding α-halomethyl ketone intermediates. Thus, a series of alkyl- and aryl-substituted haloalkynes have been selectively converted into chloro- and bromohydrins, which were obtained in good to high yields (65–86%). Remarkably, the use of stereocomplementary commercial or made-in-house overexpressed alcohol dehydrogenases in Escherichia coli has allowed the synthesis of both halohydrin enantiomers with remarkable selectivities (98 → 99% ee). The outcome success of this method was due to the thermodynamically driven reduction of the ketone intermediates, as just a small excess of the hydrogen donor (2-propanol, 2-PrOH) was necessary. In the cases that larger quantities of 2-PrOH were applied, higher amounts of other by-products (e.g., a vinyl ether derivative) were detected. Finally, as an extension of this cascade transformation and exploration of the synthetic potential of chiral halohydrins, the synthesis of both enantiomers of styrene oxide has been developed in a one-pot sequential manner in very high yields (88–92%) and optical purities (97 → 99% ee).

The Design and Optimization of Square Cascades by Go and Pso Algorithms to Provide Fresh Fuel for a Nuclear Power Reactor

The Design and Optimization of Square Cascades by Go and Pso Algorithms to Provide Fresh Fuel for a Nuclear Power Reactor

Preface

This special volume contains the proceedings of the “International on-line workshop SPLG: Modern problems in the physics of separation in nuclear fuel cycle” held on June 29, 2021. This meeting was organized by Institute of Nanoengineering in Electronics, Spintronics and Photonics of National Research Nuclear University (MEPhI) in accordance of the solution of the International Organizing Committee of the workshop “Separation Phenomena in Liquids and gases” (SPLG) instead of the planned full-scale meeting SPLG-2021 in Moscow.This event has offered a platform in bringing together experts and young specialists to exchange their ideas and achievements in research of physical processes connected with separation of isotopes in nuclear fuel cycle. We focus on this problem because production of the enriched uranium with high efficiency together with reprocessing and utilization of the spent fuel are of special interest. Solution of these problems makes the nuclear power really pure and “green”. Centrifugal and laser separation traditionally appeared in the center of interest. Design of the separation cascades for reprocessing of the spent fuel is one of the hot spots in the nuclear energy. The existing cascades are not efficient enough for the separation of the reprocessed uranium, which has artificial isotopes such as 232U, 233U in addition to natural ones. New ideas are requested here.Fresh ideas are also valuable in the general theory of cascades for separating multi-component mixtures of stable isotopes. Development of unique approaches to separate lead, molybdenum, tungsten, zinc, boron, and other isotopes is of great importance for nuclear power as well as for other applications such as fundamental research, medicine, industry.The program of the meeting consists of oral invited lectures of the leading experts on selected topics and numerous posters. The main topics of the meeting are the following:• physics of separation processes in strong centrifugal field;• problem of cascading of the separation units in different applications;• physics of the laser separation;• physics of other methods of separation.The meeting attracted specialists from 9 countries. 80 participants have registered during the meeting. The interest demonstrated by specialists from all over the world shows that two year gap between SPLG meetings is sufficient for generation of new ideas and achievements interesting for separation community. We hope that next SPLG meeting will be already in full-scale format.Guest EditorProfessor Sergey V. BogovalovHead of the International Laboratory of Extremal HydrodynamicsNational Research Nuclear University MEPhI, RussiaList of Organizing Committee are available in this pdf.

Design of a green chemoenzymatic cascade for scalable synthesis of bio-based styrene alternatives

We present the strategic development of a synthetic onepot two-step process for the manufacture of acetyl-protected hydroxystyrenes from phenolic acid substrates using environmentally benign (bio)catalysts in an eco-friendly solvent.

Observer Design for ODE-PDE Cascade with Lipschitz ODE Nonlinear Dynamics and Arbitrary Large PDE Domain

This paper deals with observer design for systems constituted of an Ordinary Differential Equation (ODE), containing a Lipschitz function of the state, and a linear Partial Differential Equation (PDE) of diffusion-reaction heat type. In addition to nonlinearity, system complexity also lies in the fact that no sensor can be implemented at the junction point between the ODE and the PDE. Boundary observers providing state estimates of the ODE and PDE do exist but their exponential convergence is only ensured under the condition that either the Lipschitz coefficient is sufficiently small or the PDE domain length is sufficiently small. Presently, we show that limitation is removed by using two connected observers and implementing one extra sensor providing the PDE state at an inner position close to the ODE-PDE junction point. The measurements provided by both sensors are used by the first observer which estimates, not only the PDE state, but also its spatial derivative along the PDE subdomain located between both sensor positions. Using these estimates, the second observer determines estimates of the ODE state and the remaining PDE states. All state estimates are shown to be exponentially convergent to their true values.

Synthesis of silver and gold nanoparticles-enzyme-polymer conjugate hybrids as dual-activity catalysts for chemoenzymatic cascade reactions.

Novel hybrids containing silver or gold nanoparticles have been synthesized in aqueous media and at room temperature using enzymes or tailor-made enzyme-polymer conjugates, which directly induced the formation of inorganic silver or gold species. The choice of pH, protein, or bioconjugate strongly affected the final metallic nanoparticles hybrid formation. Using Candida antarctica lipase (CALB) in a solution, nanobiohybrids containing Ag2O nanoparticles of 9 nm average diameter were obtained. The use of tailor-made bioconjugates, for example, the CALB modified with dextran-aspartic acid polymer (Dext6kDa), resulted in a nanobiohybrid containing smaller Ag(0)/Ag2O nanoparticles. In the case of nanobiohybrids based on gold, Au(0) species were found in all cases. The Au-CALB hybrid contained spherical nanoparticles with 18 nm average diameter size, with a minor range of larger ones (>100 nm) while the AuNPs-CALB-Dext6kDa hybrid was formed by much smaller nanoparticles (9 nm, minor range of 22 nm), and also nanorods of 20-30/40-50 nm length. Using Thermomyces lanuginosus lipase (TLL), apart from the nanoparticle formation, nanoflowers with a diameter range of 100-200 nm were obtained. All nanobiohybrids maintained (dual) enzymatic and metallic activities. For instance, these nanobiohybrids exhibited exquisite dual-activity for hydrolysis/cycloisomerization cascades starting from allenic acetates. By merging the transition metal reactivity with the inherent lipase catalysis, allenic acetates directly converted to the corresponding O-heterocycles in enantiopure form catalysed by AgNPs-CALB-Dext6kDa, taking advantage of a kinetic resolution/cyclization pathway. These results showed the high applicability of these novel hybrids, offering new opportunities for the design of novel reaction cascades.

Research on design and numerical optimization of bowed-twisted-swept cascade of low aspect ratio hydraulic turbine

The bowed-twisted-swept modeling technology of three-dimensional blade has been widely used in the gas impeller machinery and achieved good results. This paper introduces the two-dimensional flow theory and the bowed-twisted-swept modeling ideology into hydraulic turbine design. Simultaneously combined with the popular NSGA-II multi-objective optimization algorithm, a complete set of hydraulic turbine cascade design method was proposed. Taking the last-stage low aspect ratio hydraulic cascade of Ф175 type turbine as an example, the parametric model of this cascade was reconstructed by a high-precision automatic bridge coordinate measuring machine. The multi-objective optimization design of three-dimensional modeling of cascade was completed with the single-stage turbine output torque, efficiency and pressure drop as the objective targets. Finally the influence of the bowed-twisted-swept modeling technology on the hydraulic turbine performance was explored in detail by a professional rotating machinery CFD software. Numerical analysis shows that the twisted blade design achieves a 1.5 times increase in torque and 2 to 4 times increase in pressure diff at same working condition. Moreover, when bowing optimization design and sweeping optimization design are applied on the twisted blade individually, the output torque and the stage efficiency of the hydraulic turbine are respectively improved, and when both two methods are simultaneously applied on the twisted blade, it is beneficial to reduce the pressure drop loss. However, it is noticeable that when the bowed-swept modeling technology used in a straight blade using almost have no effect on the turbine performance.

Enhancing continuous reactive crystallization of lithium carbonate in multistage mixed suspension mixed product removal crystallizers with pulsed ultrasound

In this work, pulsed ultrasound was used to facilitate steady-state reactive crystallization and increase the final yield and productivity of lithium carbonate in continuously operated single and multistage mixed suspension mixed product removal (MSMPR) crystallizers. Experimental analyses of the stirred tank MSMPR cascade were performed to investigate the effects of ultrasound field, residence time and temperature which contributed to the steady-state yield, crystal size distribution and crystal morphology. The results show that pulsed ultrasound can not only significantly enhance the reaction rate, but also help to improve the particle size distribution and the crystal habit. Subsequently, a population balance model was developed and applied to estimate the final yield of the continuous process of the lithium bicarbonate thermal decomposition reaction coupling lithium carbonate crystallization. The consistency of the final yield between the experiments and the simulations proved the reliability of the established model. Through the experimental and simulation analyses, it is demonstrated that the use of pulsed ultrasound, higher final stage temperature, MSMPR cascade design and appropriate residence time help to achieve higher yield and productivity. Furtherly, based on the conclusion drawn, pulsed ultrasound enhanced three-stage MSMPR cascaded lithium carbonate continuous crystallization processes were designed, and the maximum productivity of 44.0 g/h was obtained experimentally.

A new algorithm for simulation of the functional symmetric and asymmetric cascades

Design of cascade based on operational functions of a single machine is an important goal in the isotope separation theory. By recognizing the behavior of gas in a centrifuge machine, a cascade with desirable properties and parameters can be designed. In the classical theory of multistage separation installation, it has been shown that in an ideal cascade (no mixing) the total number of separation elements flow is minimal, and accordingly, the maximum separation work unit (SWU) of the cascade occurs. In the practical form, the cut and separation factors may assume to be dependent on the feed flow. Using specific functional parameters, the algorithm, design the functional cascades (DFUNCAS), can design the functional symmetric and asymmetric cascades. DFUNCAS can design a cascade with stated waste and product concentration. Furthermore, the program can design symmetric and asymmetric cascades. In this work, four test cases were considered and the results show that the DFUNCAS can design any kind of cascade accurately.

A new extended state observer for uncertain nonlinear systems

Extended state observer (ESO) is a class of high-gain observers and a powerful tool for output feedback control of uncertain nonlinear systems. In this paper, we propose a new ESO design technique which is based on cascading a series of first-order ESOs. Benefited from the cascade design, saturations can be inserted into the observer internal variables to limit the maximal implemented gain. The convergence of the new ESO with a class of nonlinear gain functions is established, and it is shown that adopting appropriate nonlinear gain mechanisms leads to improvement in measurement noise tolerance. What is more, the new ESO based output feedback control has stronger uncertainty estimation and compensation capability than the standard ESO based output feedback control. Specifically, the proposed approach only relies on the knowledge of the control direction of the uncertain nonlinear system. Finally, the obtained results are applied to suppress the wing rock motion of a slender delta wing.

Optimization of a conical cascade using invasive weed optimization (IWO) algorithm for multi-component systems: Investigation of the effect of feed flow on the separation factor of centrifuge machines in the cascade by DSMC method

One of the desirable properties that can be mentioned in the design of a cascade is to maximize the amount of separation work for the minimum number of machines so that the input feed does not exceed its maximum amount. For this purpose, the dilute gas area and part of the continuums area inside gas centrifuge are considered as the computational area for calculating the mass source. The mass source is calculated by direct simulation Monte-Carlo (DSMC) method. Based on the separation parameters obtained from the proposed flow function, the optimum cascade design was performed using the invasive weed optimization (IWO) algorithm. The results show that by considering the exact effect of feed by DSMC method in the Onsager equation, with increasing the separation parameters in a centrifuge machine, for a certain amount of separation in the product and waste streams in an optimal cascade, fewer centrifuge machines were obtained.

Optimal design of membrane cascades for gaseous and liquid mixtures via MINLP

Given the growing concern of reducing CO2 emissions, it is desirable to identify, for a given separation carried out through a membrane cascade, the optimum design that yields the lowest power demand. Nevertheless, designing a membrane cascade is challenging since, there are often multiple feasible configurations that differ in their energy consumption and cost. In this work, we develop a Mixed Integer Non-linear Program (MINLP) that, for a given binary separation, which may be either liquid or gaseous, finds the cascade and its operating conditions that minimize power requirement. To model the separation at each membrane in the cascade, we utilize the analytical solution of a system of differential and algebraic equations derived from the crossflow model and the solution–diffusion theory. We provide numerical evidence which shows that our single-stage membrane model accurately predicts experimental data. The resulting membrane model is non-convex and, even state-of-the-art solvers struggle to prove global optimality of the cascades and the operating conditions identified. In this paper, we derive various cuts that help with relaxation quality and, consequently, accelerate convergence of branch-and-bound based solvers. More specifically, we demonstrate, on various examples, that our cuts help branch-and-bound solvers converge within 5% optimality gap in a reasonable amount of time and such a tolerance level was not achieved by a simple formulation of the membrane model. The proposed optimization model is an easy-to-use tool for practitioners and researchers to design energy efficient membrane cascades.