Academic literature on the topic 'Reversible energy flows'
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Journal articles on the topic "Reversible energy flows":
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Zhao, Yang, Chi-Chiu Ma, Lai-Ho Wong, GuanHua Chen, ZhiPing Xu, QuanShui Zheng, Qing Jiang, and Allen T. Chwang. "Quasi-Reversible Energy Flows in Carbon-Nanotube Oscillators." Journal of Computational and Theoretical Nanoscience 3, no. 5 (October 1, 2006): 852–56. http://dx.doi.org/10.1166/jctn.2006.027.
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Devine, Sean. "Algorithmic Entropy and Landauer’s Principle Link Microscopic System Behaviour to the Thermodynamic Entropy." Entropy 20, no. 10 (October 17, 2018): 798. http://dx.doi.org/10.3390/e20100798.
Abstract:
Algorithmic information theory in conjunction with Landauer’s principle can quantify the cost of maintaining a reversible real-world computational system distant from equilibrium. As computational bits are conserved in an isolated reversible system, bit flows can be used to track the way a highly improbable configuration trends toward a highly probable equilibrium configuration. In an isolated reversible system, all microstates within a thermodynamic macrostate have the same algorithmic entropy. However, from a thermodynamic perspective, when these bits primarily specify stored energy states, corresponding to a fluctuation from the most probable set of states, they represent “potential entropy”. However, these bits become “realised entropy” when, under the second law of thermodynamics, they become bits specifying the momentum degrees of freedom. The distance of a fluctuation from equilibrium is identified as the number of computational bits that move from stored energy states to momentum states to define a highly probable or typical equilibrium state. When reversibility applies, from Landauer’s principle, it costs k B l n 2 T Joules to move a bit within the system from stored energy states to the momentum states.
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Cartas-Fuentevilla, R., and A. Olvera-Santamaria. "Deforming the theory λϕ4 along the parameters and fields gradient flows." International Journal of Modern Physics A 30, no. 02 (January 20, 2015): 1550008. http://dx.doi.org/10.1142/s0217751x15500086.
Abstract:
Considering the action for the theory λϕ4 for a massive scalar bosonic field as an entropy functional on the space of coupling constants and on the space of fields, we determine the gradient flows for the scalar field, the mass and the self-interaction parameter. When the flow parameter is identified with the energy scale, we show that there exist phase transitions between unbroken exact symmetry scenarios and spontaneous symmetry breaking scenarios at increasingly high energies. Since a nonlinear heat equation drives the scalar field through a reaction-diffusion process, in general the flows are not reversible, mimicking the renormalization group flows of the c-theorem; the deformation of the field at increasingly high energies can be described as nonlinear traveling waves, or solitons associated to self-similar solutions.
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Salter, S. H., J. R. M. Taylor, and N. J. Caldwell. "Power conversion mechanisms for wave energy." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 216, no. 1 (June 1, 2002): 1–27. http://dx.doi.org/10.1243/147509002320382103.
Abstract:
It is easy to make a device that will respond vigorously to the action of sea waves. Indeed, it is quite hard to make one that will not. However, the conversion of the slow, random, reversing energy flows with very high extreme values into phase-locked synchronous electricity with power quality acceptable to a utility network is very much harder. This paper describes a range of different control strategies of varying degrees of sophistication and then describes possible conversion equipment for high-pressure oil and water and low-pressure air. Like many renewable energy sources, waves would benefit from some form of energy storage, particularly if they are to be used in weak island networks. Flywheels, gas accumulators, submerged oil/vacuum accumulators, thermal stores and reversible fuel cells are discussed, with emphasis on the coupling hardware. This leads on to a description of a new type of hydraulic machine with digital control which has been specially designed for high efficiency and flexible control of multiple erratic sources. An explanation of the rather low performance of air turbines in the random air flows caused by sea waves suggests the need for a variable-pitch version of the Wells turbine and the design of a reciprocating-flow wind-tunnel with recirculating energy recovery in which it could be tested.
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Devine, Sean. "Landauer’s Principle a Consequence of Bit Flows, Given Stirling’s Approximation." Entropy 23, no. 10 (September 30, 2021): 1288. http://dx.doi.org/10.3390/e23101288.
Abstract:
According to Landauer’s principle, at least kBln2T Joules are needed to erase a bit that stores information in a thermodynamic system at temperature T. However, the arguments for the principle rely on a regime where the equipartition principle holds. This paper, by exploring a simple model of a thermodynamic system using algorithmic information theory, shows the energy cost of transferring a bit, or restoring the original state, is kBln2T Joules for a reversible system. The principle is a direct consequence of the statistics required to allocate energy between stored energy states and thermal states, and applies outside the validity of the equipartition principle. As the thermodynamic entropy of a system coincides with the algorithmic entropy of a typical state specifying the momentum degrees of freedom, it can quantify the thermodynamic requirements in terms of bit flows to maintain a system distant from the equilibrium set of states. The approach offers a simple conceptual understanding of entropy, while avoiding problems with the statistical mechanic’s approach to the second law of thermodynamics. Furthermore, the classical articulation of the principle can be used to derive the low temperature heat capacities, and is consistent with the quantum version of the principle.
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Attou, A., and L. Bolle. "Integral formulation of balance equations for two-phase flow through a sudden enlargement Part 1: Basic approach." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 211, no. 5 (May 1, 1997): 387–97. http://dx.doi.org/10.1243/0954406971522132.
Abstract:
A general expression of irreversible losses related to two-phase flows through a sudden enlargement is derived from basic balance equations (mass, momentum and energy). The need to take into account void fraction and quality changes is emphasized for some one-fluid flows. From a comparison with several experimental results, it is concluded that a void fraction decrease downstream of the enlargement must be considered in order to predict satisfactorily pressure variations on the basis of the momentum balance procedure. When expressed in the form of a fraction of reversible pressure recovery, dissipation losses appear to depend strongly on the quality. Their minimum value is observed for a larger quality value when the pressure of the system is increased.
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Peters, Michael H. "Nonequilibrium Entropy Conservation and the Transport Equations of Mass, Momentum, and Energy." Energies 14, no. 8 (April 14, 2021): 2196. http://dx.doi.org/10.3390/en14082196.
Abstract:
Nonequilibrium statistical mechanics or molecular theory has put the transport equations of mass, momentum and energy on a firm or rigorous theoretical foundation that has played a critical role in their use and applications. Here, it is shown that those methods can be extended to nonequilibrium entropy conservation. As already known, the “closure” of the transport equations leads to the theory underlying the phenomenological laws, including Fick’s Law of Diffusion, Newton’s Law of Viscosity, and Fourier’s Law of Heat. In the case of entropy, closure leads to the relationship of entropy flux to heat as well as the Second Law or the necessity of positive entropy generation. It is further demonstrated how the complete set of transport equations, including entropy, can be simplified under physically restrictive assumptions, such as reversible flows and local equilibrium flows. This analysis, in general, yields a complete, rigorous set of transport equations for use in applications. Finally, it is also shown how this basis set of transport equations can be transformed to a new set of nonequilibrium thermodynamic functions, such as the nonequilibrium Gibbs’ transport equation derived here, which may have additional practical utility.
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Tiwari, Ravi Nath, Alberto Traverso, and Federico Reggio. "Performance assessment of a reversible Tesla machine." E3S Web of Conferences 414 (2023): 03002. http://dx.doi.org/10.1051/e3sconf/202341403002.
Abstract:
It is well known that bladeless or Tesla turbomachinery, which was invented by Nikola Tesla in 1913, has several distinct features, such as reversibility of operation, which includes expander as well as compressor operation, just by reversing the rotational speed, provided that the statoric channels are purposely designed. Despite their potential application to a variety of fields, such as energy harvesting, automotive, light aircraft, and food processing, especially for low volumetric flows, Tesla machines have not found yet a specific market niche. In fact, at small size, it is estimated that the Tesla machinery does not change performance significantly, while conventional bladed machines are subject to significant efficiency reduction because of mechanical tolerances, thus matching the Tesla relatively low performance. Therefore, Tesla machines can become the fluid machinery of choice for small-size applications, thanks to their competitive performance at that size, simple construction, and reversible operation. A key objective of this paper is to numerically study Tesla devices in both expander and compressor modes with air as the working fluid. As a consequence of the high losses due to rotor and stator interactions, statorless (volute) configurations are investigated here, showing superior performance in both direct and indirect modes of operation. With reference to a laboratory prototype under construction, this paper presents the numerical design results, which predict the peak isentropic efficiencies of 63.5% and 57.5%, for the expander and compressor mode of operation, respectively. Actual prototype is expected to match those performance, apart from leakage and ventilation losses, not included in the numerical analysis.
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Jesudason, Christopher G. "Simulation Algorithm That Conserves Energy and Momentum for Molecular Dynamics of Systems Driven by Switching Potentials." Mathematical Problems in Engineering 2009 (2009): 1–14. http://dx.doi.org/10.1155/2009/215815.
Abstract:
Whenever there exists a crossover from one potential to another, computational problems are introduced in Molecular Dynamics (MD) simulation. These problem are overcome here by an algorithm, described in detail. The algorithm is applied to a 2-body particle potential for a hysteresis loop reaction model. Extreme temperature conditions were applied to test for algorithm effectiveness by monitoring global energy, pressure and temperature discrepancies in an equilibrium system. No net rate of energy and other flows within experimental error should be observed, in addition to invariance of temperature and pressure along the MD cell for the said system. It is found that all these conditions are met only when the algorithm is applied. It is concluded that the method can easily be extended to Nonequilibrium MD (NEMD) simulations and to reactive systems with reversible, non-hysteresis loops.
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Bratianu, Constantin, and Ruxandra Bejinaru. "The Theory of Knowledge Fields: A Thermodynamics Approach." Systems 7, no. 2 (March 29, 2019): 20. http://dx.doi.org/10.3390/systems7020020.
Abstract:
The emergence of knowledge economy and knowledge management revealed the need for reconsidering the concept of knowledge in a larger framework than that created by philosophers from ancient times. While the epistemology as a theory of knowledge and justification considers knowledge as a justified true belief, experts in knowledge management consider knowledge as a strategic resource. The new economic interpretation of knowledge as a strategic resource and a key contributor to achieving a competitive advantage generated a search of new metaphors to supply the attributes needed in constructing the new framework of understanding and operating with a working concept of knowledge in management. The most widespread knowledge metaphors are based on analogies with stocks, flows, and stock-and-flows. These metaphors induce, beyond some useful attributes, the Newtonian mechanics paradigm which is limited by the properties of linear spaces and reversible processes. The purpose of this paper is to show how we can enrich the theory of knowledge by introducing the concepts of knowledge fields and knowledge dynamics based on metaphorical thinking and the thermodynamics principles. The focus of our research is the energy metaphor which considers energy as a source semantic field. The main outcome of the present research is that knowledge can be considered as a field, which is manifesting in different forms like energy. This thermodynamics framework opens new directions for research in knowledge management, decision-making and leadership.
Dissertations / Theses on the topic "Reversible energy flows":
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Merhy, Ghimar. "Contribution à la modélisation, la commande et l'optimisation des flux énergétiques : application à la gestion de recharge des véhicules électriques." Electronic Thesis or Diss., Amiens, 2020. http://www.theses.fr/2020AMIE0042.
Abstract:
Vu que le secteur du transport est directement impliqué dans les émissions gigantesques de gaz à effet de serre et la pollution mondiale globale, l'électrification des véhicules a récemment surgi comme étant une solution efficace aux catastrophes environnementales contemporaines. Face à l'impossibilité de stockage d'électricité en grandes quantités, et en vue d'ajuster en permanence l'offre d'électricité à la demande, il faudrait développer des solutions d'adaptation où les batteries des véhicules électriques (VE) prendraient en charge le stockage et la restitution de l'énergie. Cette étude se focalise sur les systèmes énergétiques impliquant des véhicules électriques utilisés comme moyens de stockage et de restitution d'énergie et sur l'optimisation des flux énergétiques relatifs à ces systèmes. L'étude porte sur les flux énergétiques réversibles entre les véhicules électriques, le réseau et les habitations. Une approche de modélisation et d'optimisation a été développée afin d'apporter une contribution permettant la gestion optimale et efficace des flux énergétiques entre les VE et les infrastructures. Pour ce fait, un système énergétique incluant une maison, un véhicule électrique et la grille est bien défini. La maison est alimentée à partir de sources d'énergie renouvelables et le véhicule sera utilisé comme moyen de stockage ou de restitution d'énergie en fonction de l'offre et de la demande d'électricité. Eventuellement, l'objectif serait d'éliminer l'approvisionnement du réseau de façon à maintenir l'équilibre entre l'offre et la demande d'électricité. Le contrôle des flux énergétiques du véhicule a été élaboré à travers la proposition d'un algorithme d'optimisation multi-objectifs et multi-critères dépendant de l'offre et la demande de l'électricité. Donc, le stockage d'énergie est proposé via une optimisation multi-objectifs des flux d'énergie pénétrant les véhicules électriques à partir du réseau, de la maison ou du bâtiment au cours du processus de recharge, et ceux sortant des véhicules durant la décharge. L'algorithme génétique est utilisé pour calculer les solutions optimales du problème d'optimisation relatif à la décharge. Les fonctions objectifs sont ensuite normalisées et la méthode de la somme pondérée est utilisée avec des poids aléatoires définis selon l'ordre de priorité du décideur dans différents scénarios afin d'aboutir à une solution optimale finale. Les calculs sont également vérifiés et l'optimisation validée grâce au solveur gamultiobj du logiciel Matlab. La marge de différence entre la production et la consommation d'énergie cède souvent la place à un énorme gaspillage. En effet, la production excessive d'énergie serait rejetée, tandis que la production déficiente se traduirait par des compensations coûteuses de l'énergie consommée; d'où la nécessité d'une régulation de l'énergie. Afin de contrôler les flux d'énergie, et visant à atteindre un système équilibré, un algorithme de contrôle et de régulation a été développé. Toutefois, comme l'algorithme permet d'intégrer un nombre infini de véhicules, une amélioration a été proposée de sorte que le nombre de véhicules retenus par la recharge ou la décharge soit minimisé. Ainsi, le transfert d'énergie serait pratique et la consommation de batteries serait réduite. Subséquemment, dans la version améliorée de l'algorithme, les véhicules disponibles subissent une classification selon leur état de charge et la longévité de leur batterie avant d'injecter ou de récupérer leur énergie, dans le but d'obtenir un système équilibré sans détériorer les batteries des véhicules. Par conséquent, les processus de stockage et de restitution d’énergie ont été optimisés grâce à la minimisation du nombre de véhicules chargés ou déchargés. Ainsi a été développée une stratégie de gestion énergétique permettant de contrôler les flux énergétiques établissant une loi de commande bidirectionnelle qui serait une solution d'adaptation de l'offre à la demande d'électricitéThe electric vehicles' usage keeps expanding worldwide for its beneficial environmental purposes. Eventually, vehicles' electrification seems to play a major role in the reduction of toxic greenhouse gases' emissions linked to the transportation sector. However, the chaotic difference margin between the electricity supply and demand still urges for a production/consumption balance that would reconcile both ends. Thus, the adaptation of energy flows to the supply and demand has become a necessity facing the gigantic energy waste related to the electricity storage challenges. Therefore, the batteries of electric vehicles (EV) could be an alternative solution for the storage and the retrieval of energy depending on the supply and demand of electricity. Our research work mostly proposes an energetic strategy based on a multi-objective and multi-criteria optimization algorithm related to the control of the bidirectional energy flows X2V/V2X between the electric vehicles and X (where X represents the grid, home or building depending on the available supply or demand of electric energy. First, the study proposes a control and regulation algorithm aiming to reach a balanced production/consumption system. The balance is mostly acquired through the bidirectional control of the energy flows related to a domestic residence (supplied with renewable sources), electric vehicles (adopted as means of storage and retrieval) and the grid. Then, the defined system's modeling is formulated and a multi-objective optimization of electric vehicles' charging and discharging modes defined by the regulation algorithm is assessed in order to attain an optimal fulfillment of the system's energetic needs. In order to do so, the energy production and consumption are first investigated through defining their reversible energy flows. Consequently, the vehicles' batteries are adopted as means of storage and retrieval depending on the energetic needs for a balanced system where any excess or lack of energy is avoided. The storage and retrieval's optimization is performed using the genetic algorithm method that helps to find optimal solutions for predefined objectives functions related mainly to the state of charge, the vehicle's propulsive energy, the valley energy and the losses. Consecutively, the study's objective functions are normalized and the weighted sum approach is implemented with the use of several case studies. And then, the optimal values resulting from the calculation are computed and verified by simulation using Matlab software. Finally, once the regulation algorithm has been set, and the corresponding optimizations implemented, the algorithm's simulation has been performed. Thus, a convenient control of the reversible energy flows, as well as the energy production and consumption has been confirmed
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Flack, Kyle M. "Two approaches to green chemistry in industrially driven processes: aluminum tert-butoxide as a rate enhancing Meerwein-Ponndorf-Verley reduction catalyst applied to the technological transfer from batch to continuous flow and structural modifications of functionalized trialkylsilylamines as energy efficient carbon dioxide capture solvents." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44802.
Abstract:
Green chemistry principles have been applied to the enhancement of two industrial chemistry problems. An industrially used reaction to form alcohols from aldehydes and ketones, the Meerwein-Ponndorf-Verley reduction, was improved by introducing a new catalyst Al(OtBu)₃. Due to the lower state of aggregation of this catalyst versus the conventional Al(OiPr)₃ catalyst, reduction rates were found to be faster in both pure iPrOH and mixed solvent systems for three model compounds: benzaldehyde, acetophenone, and a complex, chiral ketone, (S)-CMK. This allowed for the successful implementation of two important milestones; lowering the amount of catalyst needed necessary to complete the reactions (an economic benefit and lower waste) and the conversion from traditional batch reactions to continuous flow (a processing benefit) whereby reactions can be scaled-out rather than scaled-up. Another industrially important field of research that was focused on was CO₂ capture. High energy demands from current CO₂ capture methods such as aqueous amine solvents, specifically from coal-fired power plant flue gas, led to the development of non-aqueous reversible ionic liquids based on silylated amines. Structural modifications of the substitution around the silicon atom, the length of the alkyl chain bonding the silicon and amine, branching along the alkyl backbone, and investigating secondary and primary amines within this class of silylated amines were completed. These amines were reacted with CO₂ and the CO₂ capacity, the ionic liquid viscosity, reversal temperature and reaction enthalpy were all considered as a function of structure. In all cases the capacity was found to be not only greater than that of monethanolamine, an industrial standard, but higher than theoretical predictions through the formation of carbamic acid. Viscosity, reversal temperature, and reaction enthalpy were all found to be tunable through structure. These modifications gave significant insight into the necessary direction for optimization of these solvents as energy-efficient replacements of current CO₂ capture technology.
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Kos, Cristoffer, and Kristoffer Hermansson. "BUILDING AND SIMULATING DYNAMIC MODELS OF DISTRICT HEATING NETWORKS WITH MODELICA : Using Matlab to process data and automate modelling and simulation." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-36107.
Abstract:
District heating systems are common in Nordic countries today and accounts for a great portion of the heat demand. In Sweden, total district heating end use in the last years has been around 50 TWh and district heating accounts for roughly 50 % of the total heat demand. Suppliers of district heating must balance demand and supply, often in large and complex networks. Heat propagation can be in the range of hours and it is not known in detail how the heat will propagate during transient conditions. A dynamic model has been developed in OpenModelica and a method for modeling, handling data, simulating and visualizing the results of a district heating network was developed using Matlab as core. Data from Mälarenergi AB, a district heating producer and grid operator, was used for validation of the model. Validation shows that the model works well in predicting heat propagation and temperature distribution in the network and that the model can be scaled up to a large number of heat exchangers and pipes. The model is robust and can handle bi-directional and reversing flows in complex ring structures. It was concluded that OpenModelica together with Matlab is a good combination for creating models of district heating networks, as a high degree of standardization and automation can be achieved. This, together with visualization of the heat propagation, makes it useful for the understanding of the district heating network during transient conditions.Smarta Flöden
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Рєзва, Ксенія Сергіївна. "Удосконалення проточних частин високонапірних оборотних гідромашин на основі чисельного моделювання їх гідродинамічних характеристик." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/40009.
Abstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.17 – гідравлічні машини і гідропневмоагрегати. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2019 р.
Дисертацію присвячено вирішенню науково-практичної задачі удосконалення проточних частин високонапірних оборотних гідромашин за рахунок розробки методів розрахунку та аналізу їх гідродинамічних характеристик. На підставі розгляду тенденцій розвитку гідроенергетики України, з урахуванням ролі високонапірних оборотних гідромашин в об'єднаній енергетичній системі, відмічено актуальність проектування нових проточних частин. Визначено переваги та недоліки існуючих методів дослідження гідродинамічних процесів у проточних частинах оборотних гідромашин. Наведені результати розрахунку гідродинамічних характеристик елементів проточної частини на основі методу осереднених безрозмірних параметрів для оборотних гідромашин ОРО200-В-100 та ОРО500-В-100. Застосована математична модель робочого процесу гідромашини на основі блочно-ієрархічного підходу для проведення дослідження балансу енергії. Визначено вплив геометричних параметрів елементів проточної частини на показники роботи. Проведено чисельне дослідження просторової течії рідини в проточній частині високонапірних оборотних гідромашин за допомогою CFD, що дозволило визначити та візуалізувати картину течії. Складено баланси енергії гідромашин ОРО200-В-100 та ОРО500-В-100. Відмічено, що розподіл втрат по елементам проточної частини нерівномірний: для ОРО200-В-100 найбільшу частину втрат складають втрати в робочому колесі (близько 56 %), для ОРО500-В-100 – втрати у підводі (близько 62 %). Описано основні положення визначення оптимального режиму роботи оборотної гідромашини. Запропоновано та досліджено модифікований підвід для тихохідної оборотної гідромашини ОРО500-В-100, щоб підвищити її енергетичні показники: краще узгоджені елементи ПЧ та гідравлічний ККД збільшився на 2 %.Thesis for granting the Degree of Candidate of Technical sciences in speciality 05.05.17 – Hydraulic machines and hydropneumatic units. – National Technical University "Kharkiv Polytechnic Institute", 2019. The tеhesis is devoted to the solution of the scientific and practical problem of improvement of the water passages of the high-pressure reversible hydraulic due to calculation and analysis their hydrodynamic characteristics. Based on the review of the trends in the development of hydropower engineering in Ukraine and given the role of high-pressure reversible hydraulic machines in the United Power System, it was noted that the designing a new flow parts is topical task. Advantages and disadvantages of the existing methods for research hydrodynamic processes in water passages of reversible hydraulic machines were identified after their analysis. The results of the calculation of the hydrodynamic characteristics of the elements of the water passages based on the method of averaged dimensionless parameters using the example of reversible hydraulic machines OPO200-B-100 and OPO500-B-100 were demonstrated. The mathematical model of the hydraulic machine working process based on a block-hierarchical approach was used to study the energy balance in the turbine and pump modes of hydraulic machines. The influence of the geometrical parameters of the elements of the water passage on the performance was determined: how the angle of flow in the spiral casing (cп ), the height of the wicket gate (b0 D) and the shape of the wicket gate profile influence the value of the coefficient resistance in the wicket gate. A numerical study of the three-dimensional flow of fluid in the water passage of high-pressure reversible hydraulic machines was carried out using the CFD software. This program allows determining the character of the flow and presenting the fields of distribution of velocity components, pressure and streamlines. The balances of energy were compiled: for the OPO200-B-100 in the turbine and pump operation modes, for the OPO500-B-100 in the turbine operation mode. It is noted that the distribution of losses on the elements of the water passage is not uniform: for the OPO200-B-100, the greatest part of the total losses are losses in the runner (about 56%), for OPO500-B-100 - losses in the inlet (about 62%). The main points for determining the optimal operating mode of the reversible hydraulic machine are described. The modified inlet for low-speed high-pressure hydraulic machine OPO500-B-100 was proposed and investigated to increase energy performance of hydraulic machine. The spiral casing was expanded, the number of stay vane blades and wicket gate blades were reduced to 16. As a result of the calculations of the modified inlet, the obtained results showed that the second variant made it possible to better align the elements of the water passage and the hydraulic efficiency increased by 2 %.
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Рєзва, Ксенія Сергіївна. "Удосконалення проточних частин високонапірних оборотних гідромашин на основі чисельного моделювання їх гідродинамічних характеристик." Thesis, Національний технічний університет "Харківський політехнічний інститут", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/40011.
Abstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.05.17 – гідравлічні машини і гідропневмоагрегати. – Національний технічний університет "Харківський політехнічний інститут", Харків, 2019 р.
Дисертацію присвячено вирішенню науково-практичної задачі удосконалення проточних частин високонапірних оборотних гідромашин за рахунок розробки методів розрахунку та аналізу їх гідродинамічних характеристик. На підставі розгляду тенденцій розвитку гідроенергетики України, з урахуванням ролі високонапірних оборотних гідромашин в об'єднаній енергетичній системі, відмічено актуальність проектування нових проточних частин. Визначено переваги та недоліки існуючих методів дослідження гідродинамічних процесів у проточних частинах оборотних гідромашин. Наведені результати розрахунку гідродинамічних характеристик елементів проточної частини на основі методу осереднених безрозмірних параметрів для оборотних гідромашин ОРО200-В-100 та ОРО500-В-100. Застосована математична модель робочого процесу гідромашини на основі блочно-ієрархічного підходу для проведення дослідження балансу енергії. Визначено вплив геометричних параметрів елементів проточної частини на показники роботи. Проведено чисельне дослідження просторової течії рідини в проточній частині високонапірних оборотних гідромашин за допомогою CFD, що дозволило визначити та візуалізувати картину течії. Складено баланси енергії гідромашин ОРО200-В-100 та ОРО500-В-100. Відмічено, що розподіл втрат по елементам проточної частини нерівномірний: для ОРО200-В-100 найбільшу частину втрат складають втрати в робочому колесі (близько 56 %), для ОРО500-В-100 – втрати у підводі (близько 62 %). Описано основні положення визначення оптимального режиму роботи оборотної гідромашини. Запропоновано та досліджено модифікований підвід для тихохідної оборотної гідромашини ОРО500-В-100, щоб підвищити її енергетичні показники: краще узгоджені елементи ПЧ та гідравлічний ККД збільшився на 2 %.Thesis for granting the Degree of Candidate of Technical sciences in speciality 05.05.17 – Hydraulic machines and hydropneumatic units. – National Technical University "Kharkiv Polytechnic Institute", 2019. The tеhesis is devoted to the solution of the scientific and practical problem of improvement of the water passages of the high-pressure reversible hydraulic due to calculation and analysis their hydrodynamic characteristics. Based on the review of the trends in the development of hydropower engineering in Ukraine and given the role of high-pressure reversible hydraulic machines in the United Power System, it was noted that the designing a new flow parts is topical task. Advantages and disadvantages of the existing methods for research hydrodynamic processes in water passages of reversible hydraulic machines were identified after their analysis. The results of the calculation of the hydrodynamic characteristics of the elements of the water passages based on the method of averaged dimensionless parameters using the example of reversible hydraulic machines OPO200-B-100 and OPO500-B-100 were demonstrated. The mathematical model of the hydraulic machine working process based on a block-hierarchical approach was used to study the energy balance in the turbine and pump modes of hydraulic machines. The influence of the geometrical parameters of the elements of the water passage on the performance was determined: how the angle of flow in the spiral casing (cп ), the height of the wicket gate (b0 D) and the shape of the wicket gate profile influence the value of the coefficient resistance in the wicket gate. A numerical study of the three-dimensional flow of fluid in the water passage of high-pressure reversible hydraulic machines was carried out using the CFD software. This program allows determining the character of the flow and presenting the fields of distribution of velocity components, pressure and streamlines. The balances of energy were compiled: for the OPO200-B-100 in the turbine and pump operation modes, for the OPO500-B-100 in the turbine operation mode. It is noted that the distribution of losses on the elements of the water passage is not uniform: for the OPO200-B-100, the greatest part of the total losses are losses in the runner (about 56%), for OPO500-B-100 - losses in the inlet (about 62%). The main points for determining the optimal operating mode of the reversible hydraulic machine are described. The modified inlet for low-speed high-pressure hydraulic machine OPO500-B-100 was proposed and investigated to increase energy performance of hydraulic machine. The spiral casing was expanded, the number of stay vane blades and wicket gate blades were reduced to 16. As a result of the calculations of the modified inlet, the obtained results showed that the second variant made it possible to better align the elements of the water passage and the hydraulic efficiency increased by 2 %.
Books on the topic "Reversible energy flows":
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Tiwari, Sandip. Information mechanics. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198759874.003.0001.
Abstract:
Information is physical, so its manipulation through devices is subject to its own mechanics: the science and engineering of behavioral description, which is intermingled with classical, quantum and statistical mechanics principles. This chapter is a unification of these principles and physical laws with their implications for nanoscale. Ideas of state machines, Church-Turing thesis and its embodiment in various state machines, probabilities, Bayesian principles and entropy in its various forms (Shannon, Boltzmann, von Neumann, algorithmic) with an eye on the principle of maximum entropy as an information manipulation tool. Notions of conservation and non-conservation are applied to example circuit forms folding in adiabatic, isothermal, reversible and irreversible processes. This brings out implications of fluctuation and transitions, the interplay of errors and stability and the energy cost of determinism. It concludes discussing networks as tools to understand information flow and decision making and with an introduction to entanglement in quantum computing.
Book chapters on the topic "Reversible energy flows":
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Singh, Gurwinder, Amandeep Singh Oberoi, Harmesh K. Kansal, and Amrinder Pal Singh. "Electrochemical Hydrogen Storage Within a Modified Reversible PEM Fuel Cell and Its Performance Analysis with Interdigitated and Spiral Micro Flow Channels." In Green Energy and Technology, 155–63. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2279-6_14.
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Metcalfe, Ian S. "The energy balance and temperature effects." In Chemical Reaction Engineering. Oxford University Press, 1997. http://dx.doi.org/10.1093/hesc/9780198565383.003.0009.
Abstract:
This chapter demonstrates how reactors need not be isothermal. It looks at how reaction rate depends upon temperature for different classes of reaction, including irreversible reactions, reversible endothermic reactions, and reversible exothermic reactions. The chapter then formulates the energy balance for given reactors and uses this to investigate the variation of temperature and therefore reaction rate with time or position in the reactor. This, in turn, can be used to calculate reactor volumes and residence times for a given duty. The chapter also considers steady-state multiplicity in continuous stirred tank reactors (CSTRs) and multistage adiabatic plug flow reactor (PFR). For a PFR, there exists an optimum temperature profile or line of maximum reaction rate and it is important to try to approach this path. The chapter discusses two different methods for achieving this: interstage cooling and cold-shot cooling.
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Maczek, Andrew, and Anthony Meijer. "Applications of the molecular partition function." In Statistical Thermodynamics. Oxford University Press, 2017. http://dx.doi.org/10.1093/hesc/9780198777489.003.0003.
Abstract:
This chapter explores how to use the molecular partition function to calculate internal energy and entropy. It highlights the link between the molecular partition function and thermodynamics. Additionally, the chapter notes the relation of β to temperature. It explains the link between the statistical weight of the predominant configuration and thermodynamic entropy. The chapter uses equation diagrams to explain modifications on molecular and internal energies. As the chapter shows, the spacing between successive energy states does not change on heating and stays at a constant volume, which is a defining condition for the internal energy. Thus, an infinitesimal reversible change in a system linked to an infinitesimal flow of heat produces a change in entropy.
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Peters, Luanne L., and Jane E. Barker. "Spontaneous and Targeted Mutations in Erythrocyte Membrane Skeleton Genes: Mouse Models of Hereditary Spherocytosis." In Hematopoiesis, 582–608. Oxford University PressNew York, NY, 2001. http://dx.doi.org/10.1093/oso/9780195124507.003.0051.
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Abstract The red cell outer limiting membrane is critical to all aspects of red cell function. The membrane responds to extracellular signals during erythropoiesis, mediates iron uptake, facilitates carbon dioxide transport, regulates red cell cation and water content, and provides a negatively charged exterior that allows red cells to flow through the circulation without adhering to the endothelial layer of the vasculature. Evidence suggests that the red cell membrane also regulates energy metabolism by reversibly binding the glycolytic enzymes glyceraldehyde 3-phosphate dehydrogenase, aldolase, and phosphofructokinase (Harrison et al., 1991; Low et al., 1993).
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Shklyaev, Oleg E., Raj Kumar Manna, Abhrajit Laskar, Joshua E. Kauffman, Benjamin M. Tansi, Ayusman Sen, and Anna C. Balazs. "Autonomous Photothermally-driven Fluid Pumping and Particle Transport and Assembly." In Out-of-equilibrium Soft Matter, 296–325. The Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/9781839169465-00296.
Abstract:
We review the design of photothermally-driven fluid micropumps that can regulate the assembly and segregation of microparticles in solution. Externally imposed light represents particularly useful energy input since the light source (further enabled with a mask) is easily moved and thus can regulate spatially and temporally coordinated dynamics. Ultraviolet (UV) light sources are used to illuminate regions of a fluid-filled chamber that results in fluid flow throughout the chamber. The light-driven pumping occurs via three different mechanisms: thermal buoyancy, solutal buoyancy, and diffusioosmosis. These pumping mechanisms can operate simultaneously and the combination of two or more mechanisms leads to complex fluid flow patterns. This approach enables systems that allow dynamic control over the motion of immersed microparticles, including the formation and transport of reversible particle assemblies, as well as the segregation and separation of different sized particles in the fluidic chambers. Thus, one device can be used to both separate the particles and drive them to different locations for further processing. This property is particularly useful for analyzing fluids that contain multiple particulate types.
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Williams, R. J. P., and J. J. R. Frausto Da Silva. "Early cellular organisation in anaerobes." In The Natural Selection of the Chemical Elements, 417–62. Oxford University PressOxford, 1996. http://dx.doi.org/10.1093/oso/9780198558439.003.0011.
Abstract:
Abstract Chapter 10 described which elements, compounds and reaction sequences have been selected in order to generate a living system. This was but a descriptive analysis of connected but uncoordinated rates of uptake and reactions in pathways, although it did also show the need for energy coupled to element incorporation. We stressed that the very fact that the chemistry was energised made it more probable that degradation would occur rather than synthesis. Since survival must depend on driving synthesis more efficiently than degradation, a living system cannot just push energy into all syntheses randomly or into reversible catalysed reactions. In order to bias effective over random synthesis and over degradation a considerable degree of organisation is necessary, where organisation implies flow of material and energy in managed dissipative systems (Fig. 11.1). We know that life is only identifiable and has superior survival character because it has organised its own production of a self-protected set of molecules in a cell and this must be examined next. Now, an additional feature that we can show has survival value is that life self reproduces. Reproduction is copying and in biological chemistry implies coded activity. We cannot solve the initial problems of the origin of the whole of this efficient organisation and reproduction in any very convincing way today but we can imagine some possibilities for its beginnings.
Conference papers on the topic "Reversible energy flows":
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Torricelli, Noemi, Lisa Branchini, Andrea De Pascale, Olivier Dumont, and Vincent Lemort. "Optimal Management of Reversible Heat Pump/ORC Carnot Batteries." In ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-82509.
Abstract:
Abstract In the view of reducing the global greenhouse gas emissions it becomes fundamental to exploit the renewable energy sources at their maximum potential by developing effective strategies for their flexible use. Among the available solutions to realize these strategies are the electric energy storages including the innovative Pumped Thermal Energy Storage technology (included in the Carnot battery concept). This can become very interesting in these applications where different energy flows must be handled (both electric and thermal), thanks to the possibility of adding the contribution of a waste heat source, in a thermally integrated energy storage. However, despite the several advantages, the state-of-the-art still lacks experiments and investigation of efficient control strategy for the Carnot battery when inserted into the process. As original contribution to the current literature, this paper presents the off-design model of a reversible Organic Rankine Cycle (ORC)/Heat Pump (HP) Carnot battery configuration with the aim of employing it to simulate the performance of such system and discuss its optimal management when inserted into a generic process. An existing reversible HP/ORC kW-size prototype is considered as reference and its optimal control in both HP and ORC mode under different boundary conditions is assessed.
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Ancona, Maria Alessandra, Michele Bianchi, Lisa Branchini, Andrea De Pascale, Francesco Melino, Saverio Ottaviano, Antonio Peretto, and Chiara Poletto. "Preliminary Investigation of a Combined Heat and Power Reversible-Brayton System Integrated With a Renewable Power Source." In ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/gt2023-103125.
Abstract:
Abstract Pumped Thermal Electricity Storage (PTES) technology is drawing increasing attention as a promising solution to limit the mismatch between the electric demand and the renewable production. In this context, a preliminary model of a reversible Brayton PTES is developed on a commercial software to finalize a comprehensive performance investigation. In the proposed arrangement, the system allows to store the surplus of electric renewable production, by converting it into heat, through an inverse cycle, and then to convert it back into electric energy when needed, through a direct cycle. A systematic analysis comparing two configurations (base and recuperated) of the reversible Brayton system is carried out to assess the performance of the system. Since thermal and electric energy flows are involved, PTES is particularly interesting when adopted to satisfy both thermal and electric demands, in a combined heat and power (CHP) system. To this aim, the system has been simulated when delivering both thermal and electric energy, in different partitioning. Results show that if 25 % of the stored heat is addressed to a thermal user the integrated system can be convenient in terms of saved primary energy, compared to conventional separate production. In case 70 % of the stored heat is delivered to a thermal user and 30 % reconverted into electricity, the maximum investment cost to have a return of the investment in 10 years is assessed to be between 2000 and 5000 €/kW, depending on the configuration.
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Lyall, M. Eric, Paul I. King, and Rolf Sondergaard. "Endwall Loss and Mixing Analysis of a High Lift Low Pressure Turbine Cascade." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68709.
Abstract:
A high lift LPT profile designated L2A is used as a test bed for studying the origin of endwall mixing loss and the role of vortical structures in loss development. It is shown analytically and experimentally that the mixing forces within the endwall wake can be decoupled into either mean flow or turbulent forces, and can be further classified as either reversible or irreversible. Among the irreversible forces, mean flow shear is negligible compared to turbulent shear, suggesting that turbulence dissipation is the dominant cause of loss generation. As a result, the mean flow components of the vortical structures do not generate significant mixing losses. Rather than mixing effects, the mean flow of the vortices cause the suction surface boundary layer to separate inside the passage, thereby generating the large low energy regions typical of endwall flows. Losses are generated as the low energy regions mix out. This vortex separation effect is demonstrated with an experiment using a profile fence and pressure surface modification near the endwall. The findings in this paper suggest that profile modifications near the endwall that suppress suction surface separation may provide loss reductions additive to those that weaken vortical structures, such as endwall contouring.
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Cheng, Li, Chao Liu, Jiren Zhou, Fangping Tang, and Yan Jin. "Three Dimensional Numerical Simulation of Flow Field Inside a Reversible Pumping Station With Symmetric Aerofoil Blade." In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55001.
Abstract:
The pumping station with symmetric aerofoil can achieve reversible pumping function. It can keep high reversible efficiency and its flow coefficient is approaching to normal one. At same time, it has the simple structure and is easy to operate and maintain. The flow inside reversible pumping station is very complex and dominated by three dimensional viscous effects. With the rapid progress of computational fluid dynamics, CFD has become an important tool to help to make full understanding of flow. In order to recognize the characteristic of pumping station, the control volume method is used to simulation the flow filed. The RNG k-ε turbulent model and SIMPLEC algorithm are applied to do analysis. Flow field inside symmetric aerofoil blade and passage of pumping station are analyzed in detail. Some computational data, such as computational contour of sections, streamline of pumping system, flow vectors of blade and pressure contour of blade for two different rotate directional, are given in the paper. On the based of the simulation results, efficiency prediction of the pumping station is applied. By calculating the useful power and the hydraulic efficiency at the 11 different discharge points, capabilities of pumping station are predicted. A set of model pumping station with a 300mm blade are made for test. Using the laboratory test loop of which the total uncertainty of measured efficiency is ±0.39%, the hydraulic performance is evaluated and demonstrated. The numerical performances agree well with experiment data.
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Parisi, Simone, and Fredrik Haglind. "Numerical Analysis of Reversible Radial-Flow Turbomachinery for Energy Storage Applications." In ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/gt2023-101441.
Abstract:
Abstract Decarbonization of energy systems is expected to require significant amounts of energy storage. Among the different technologies studied, thermo-mechanical storage is being considered for long duration storage due to its low cost and limited usage of critical materials. Based on the experience of pumped hydro plants, significant cost savings can be achieved if a single stage reversible compressor-turbine is used for both the charging and discharging of the storage. Due to the modest (< 4.5) pressure ratio involved, low temperature adiabatic compressed air energy storage and pumped thermal energy storage are considered as candidate applications for reversible turbomachinery. This paper presents a numerical analysis of an existing high efficiency centrifugal compressor operating both as a compressor and a turbine using mean-line analysis and steady-state simulations with Reynolds-Averaged Navier-Stokes equations in ANSYS CFX. After validation against experimental data in compressor operating mode, the turbine mode was tested by changing only the inlet and outlet boundary conditions and reversing the direction of rotation. Subsequently, a new stage was designed using conventional procedures developed for compressors and evaluated using computational fluid dynamics simulations. The results indicate that for an up-scaled version of the existing compressor it is possible to reach total-to-total polytropic efficiencies exceeding 86.7% as a compressor and 92.1% as a turbine, which is comparable with the efficiencies of dedicated machines. The new design reaches a polytropic efficiency of 89.4% as compressor and 90.4% as turbine. In both cases the numbers obtained do not include a volute or diffuser cone. Furthermore, the results indicate that there is a compromise between the optimal design for the compressor and turbine mode.
6
Winkler, Wolfgang. "Fuel Cell Hybrids, Their Thermodynamics and Sustainable Development." In ASME 2005 3rd International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2005. http://dx.doi.org/10.1115/fuelcell2005-74157.
Abstract:
The increasing demand on primary energy and the increasing concern on climatic change demand immediately a sustainable development, but still there remain open questions regarding its technical realisation. The second law of thermodynamics is a very simple but efficient way to define the principle design rules of sustainable technologies in minimising the irreversible entropy production. The ideal, but real process chain is defined by a still reversible structure or logic of the process chain—the reversible reference process chain—but consisting of real components with an irreversible entropy production on a certain level. It can easily be shown for energy conversion and for transportation that hybridisation in general can be indeed a measure to meet the reversible process chain and to minimise the entropy flow to the environment. Fuel cells are principal reversible converters of chemical energy and thus a key element within hybridisation. Depending on application, CHP may be a hybridisation step or only a slight improvement. There is a fundamental difference in heating a house or in supplying an endothermic chemical reaction with reaction entropy. The use of heat recovery and isolation is a necessary measure to minimise the entropy flow to the environment and can be described by a reversible reference process as well. The application of reversible reference process chains shows that hybrid systems with fuel cells are a technical feasibility to approach very closely the thermodynamic potential. This development differs from the past where the technical possibilities of materials and manufacturing limited the technology to meet reversibility and thus sustainability.
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Hedayat Mofidi, Seyyed Ali, and Kent S. Udell. "Study of Heat and Mass Transfer in MgCl2/NH3 Thermo-Chemical Batteries." In ASME 2016 10th International Conference on Energy Sustainability collocated with the ASME 2016 Power Conference and the ASME 2016 14th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/es2016-59099.
Abstract:
Intermittency of sustainable energy or waste heat availability calls for energy storage systems such as thermal batteries. Thermo-chemical batteries are particularly appealing for energy storage applications due to their high energy densities and ability to store thermal energy as chemical energy for long periods of time without any energy loss. Thermo-chemical batteries based on a reversible solid-gas (MgCl2 - NH3) reactions and NH3 liquid-gas phase change are of specific interest since the kinetics of absorption are fast and the heat transfer rates for liquid — vapor phase change are high. Thus, a thermo-chemical battery based on reversible reaction between magnesium chloride and ammonia was studied. Experimental studies were conducted on a reactor in which temperature profiles within the solid matrix and pressure and flow rates of gas were obtained during charging processes. A numerical model based on heat and mass transfer within the salt and salt-gas reactions was developed to simulate the absorption processes within the solid matrix and the results were compared with experimental data. The studies were used to determine dominant heat and mass transfer processes within the salt. It is shown that for high permeability materials, heat transfer is the dominant factor in determining reaction rates. However increasing thermal conductivity might decrease permeability and reduce reaction rates. The effect of constraining mass flow rate on the temperature and reaction propagation is also studied. These results show that optimized heat and mass transfer within the solid-gas reactor will lead to improved performance for heating and air conditioning applications.
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Tanaka, Takaharu. "An Investigation on Energy Transfer Mechanism Caused in Rotating Flow Passage of Turbomachinery and Practical Performance Characteristic Curve." In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95441.
Abstract:
Hydraulic energy is constructed from two different kinds hydraulic energies. One is the singled irreversible kinetic hydraulic energy that acts horizontal direction. It produces mass weight flow rate. The other is the un-kinetic reversible potential energy. Potential energy is stored on the fluid particle in the form of coupled (or twined) real and imaginary energies. Typical of real energy is potential energy, which is equivalent to pump and water turbine heads. It is caused by the real gravitational acceleration and directs vertical downward. Real potential head is balanced with the imaginary force, which is caused by the imaginary acceleration whose magnitude is equivalent to real gravitational acceleration but its acting direction is opposed to that, therefore, vertical upward. Therefore, to produce the higher real potential pump head that directs vertical downward, the imaginary centrifugal force, whose acting direction is opposed to real potential head, has to be produced and act on the fluid particle vertical upward as much by the impelling action in the rotating flow passage of centrifugal pump.
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Yazji, Jalal, Hamza Zaidi, Luke Thomas Torres, Christopher Leroy, Alicia Keow, and Zheng Chen. "A Novel Buoyancy Control Device Using Reversible PEM Fuel Cells." In ASME 2019 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/dscc2019-9155.
Abstract:
Abstract Buoyancy control devices are essential to maneuver ROV effectively underwater. Many approaches have been used to tackle this problem such as compressed air ballast which can take in water and eject it using compressed air and the use of high-density foam plates that can be added or removed to increase or decrease the buoyancy. Presented in this paper is a novel approach for buoyancy control, which utilizes the electrolysis and reverse electrolysis capabilities of a reversible polymer electrolyte membrane (PEM) fuel cell to adjust the volume of a small vehicle, and change its depth. Making use of the two processes helps restore some of the energy consumed by the system through the process of reverse electrolysis and also for building a fully-closed system, that is, one that does not require any water or gas flow to the surrounding. Modeling of the device is explained and a proportional-derivative (PD) controller is designed to control it at a certain depth using a single sensor measurement. Experiments validate the controller performance.
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Shen, Jiawei, and Ji Pei. "Energy Loss Evaluation of a Reversible Mixed-Flow Pump Applied to Low-Head Pumped Storage Based on Entropy Production Theory." In The 9th World Congress on Momentum, Heat and Mass Transfer. Avestia Publishing, 2024. http://dx.doi.org/10.11159/enfht24.259.