Academic literature on the topic 'Closed Thermal Cycles'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Closed Thermal Cycles.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Closed Thermal Cycles"
1
Garcia, Ramon. "Contributions on Closed System Transformations Based Thermal Cycles." British Journal of Applied Science & Technology 4, no. 19 (January 10, 2014): 2821–36. http://dx.doi.org/10.9734/bjast/2014/10074.
Full text
2
Ferreiro Garcia, Ramon, and Dr Jose Carbia Carril. "Analysis of a thermal cycle that surpass Carnot efficiency undergoing closed polytropic transformations." JOURNAL OF ADVANCES IN PHYSICS 15 (February 19, 2019): 6165–82. http://dx.doi.org/10.24297/jap.v15i0.8029.
Full textAbstract:
This research work deals with a feasible non-regenerative thermal cycle, composed by two pairs of closed polytropic-isochoric transformations implemented by means of a double acting reciprocating cylinder which differs basically from the conventional Carnot based thermal cycles in that:
-it consists of a non condensing mode thermal cycle
-all cycle involves only closed transformations, instead of the conventional open processes of the Carnot based thermal cycles,
-in the active processes (polytropic path functions), as heat is being absorbed, mechanical work is simultaneously performed, avoiding the conventional quasi-adiabatic expansion or compression processes inherent to the Carnot based cycles and,
-during the closed polytropic processes, mechanical work is also performed by means of the working fluid contraction due to heat releasing.
An analysis of the proposed cycle is carried out for helium as working fluid and results are compared with those of a Carnot engine operating under the same ratio of temperatures. As a result of the cycle analysis, it follows that the ratio of top to the bottom cycle temperatures has very low dependence on the ideal thermal efficiency, but the specific work, and, furthermore, within the range of relative low operating temperatures, high thermal efficiency is achieved, surpassing the Carnot factor.
3
Dumitrașcu, Gheorghe, Michel Feidt, and Ştefan Grigorean. "Finite Physical Dimensions Thermodynamics Analysis and Design of Closed Irreversible Cycles." Energies 14, no. 12 (June 9, 2021): 3416. http://dx.doi.org/10.3390/en14123416.
Full textAbstract:
This paper develops simplifying entropic models of irreversible closed cycles. The entropic models involve the irreversible connections between external and internal main operational parameters with finite physical dimensions. The external parameters are the mean temperatures of external heat reservoirs, the heat transfers thermal conductance, and the heat transfer mean log temperatures differences. The internal involved parameters are the reference entropy of the cycle and the internal irreversibility number. The cycle’s design might use four possible operational constraints in order to find out the reference entropy. The internal irreversibility number allows the evaluation of the reversible heat output function of the reversible heat input. Thus the cycle entropy balance equation to design the trigeneration cycles only through external operational parameters might be involved. In designing trigeneration systems, they must know the requirements of all consumers of the useful energies delivered by the trigeneration system. The conclusions emphasize the complexity in designing and/or optimizing the irreversible trigeneration systems.
4
Rogalev, Nikolay, Andrey Rogalev, Vladimir Kindra, Olga Zlyvko, and Pavel Bryzgunov. "Review of Closed SCO2 and Semi-Closed Oxy–Fuel Combustion Power Cycles for Multi-Scale Power Generation in Terms of Energy, Ecology and Economic Efficiency." Energies 15, no. 23 (December 5, 2022): 9226. http://dx.doi.org/10.3390/en15239226.
Full textAbstract:
Today, with the increases in organic fuel prices and growing legislative restrictions aimed at increasing environmental safety and reducing our carbon footprint, the task of increasing thermal power plant efficiency is becoming more and more topical. Transforming combusting fuel thermal energy into electric power more efficiently will allow the reduction of the fuel cost fraction in the cost structure and decrease harmful emissions, especially greenhouse gases, as less fuel will be consumed. There are traditional ways of improving thermal power plant energy efficiency: increasing turbine inlet temperature and utilizing exhaust heat. An alternative way to improve energy efficiency is the use of supercritical CO2 power cycles, which have a number of advantages over traditional ones due to carbon dioxide’s thermophysical properties. In particular, the use of carbon dioxide allows increasing efficiency by reducing compression and friction losses in the wheel spaces of the turbines; in addition, it is known that CO2 turbomachinery has smaller dimensions compared to traditional steam and gas turbines of similar capacity. Furthermore, semi-closed oxy–fuel combustion power cycles can reduce greenhouse gases emissions by many times; at the same time, they have characteristics of efficiency and specific capital costs comparable with traditional cycles. Given the high volatility of fuel prices, as well as the rising prices of carbon dioxide emission allowances, changes in efficiency, capital costs and specific greenhouse gas emissions can lead to a change in the cost of electricity generation. In this paper, key closed and semi-closed supercritical CO2 combustion power cycles and their promising modifications are considered from the point of view of energy, economic and environmental efficiency; the cycles that are optimal in terms of technical and economic characteristics are identified among those considered.
5
Dumitrascu, Gheorghe, Michel Feidt, and Stefan Grigorean. "Closed Irreversible Cycles Analysis Based on Finite Physical Dimensions Thermodynamics." Proceedings 58, no. 1 (September 11, 2020): 37. http://dx.doi.org/10.3390/wef-06905.
Full textAbstract:
The paper develops generalizing entropic approaches of irreversible closed cycles. The mathematical models of the irreversible engines (basic, with internal regeneration of the heat, cogeneration units) and of the refrigeration cycles were applied to four possible operating irreversible trigeneration cycles. The models involve the reference entropy, the number of internal irreversibility, the thermal conductance inventory, the proper temperatures of external heat reservoirs unifying the first law of thermodynamics and the linear heat transfer law, the mean log temperature differences, and four possible operational constraints, i.e., constant heat input, constant power, constant energy efficiency and constant reference entropy. The reference entropy is always the entropy variation rate of the working fluid during the reversible heat input process. The amount of internal irreversibility allows the evaluation of the heat output via the ratio of overall internal irreversible entropy generation and the reference entropy. The operational constraints allow the replacement of the reference entropy function of the finite physical dimension parameters, i.e., mean log temperature differences, thermal conductance inventory, and the proper external heat reservoir temperatures. The paper presents initially the number of internal irreversibility and the energy efficiency equations for engine and refrigeration cycles. At the limit, i.e., endoreversibility, we can re-obtain the endoreversible energy efficiency equation. The second part develops the influences between the imposed operational constraint and the finite physical dimensions parameters for the basic irreversible cycle. The third part is applying the mathematical models to four possible standalone trigeneration cycles. It was assumed that there are the required consumers of the all useful heat delivered by the trigeneration system. The design of trigeneration system must know the ratio of refrigeration rate to power, e.g., engine shaft power or useful power delivered directly to power consumers. The final discussions and conclusions emphasize the novelties and the complexity of interconnected irreversible trigeneration systems design/optimization.
6
Shen, Qiang, Chang Lian Chen, Fei Chen, Qi Wen Liu, and Lian Meng Zhang. "Thermal Shock Behavior of Calcia Stabilized Zirconia Ceramics with Porosity Gradient Structure." Materials Science Forum 631-632 (October 2009): 435–40. http://dx.doi.org/10.4028/www.scientific.net/msf.631-632.435.
Full textAbstract:
Porous calcia stabilized zirconia ceramics (CSZC) with closed pores were presurelessly sintered by adding different contents of zirconia hollow balls. CSZC FGM with porosity gradient structure was then fabricated by laminating five layers with designed contents of zirconia hollow balls. The porosity, microstructure, and bending strength of the obtained CSZC samples were characterized. The results show that the hollow balls distribute uniformly and are well bonded with the matrix, and the porous structure is mainly composed of closed pores. The porosity of the CSZC increases linearly from 5.7 % to 31.6 % when the content of zirconia hollow balls increases from 0 % to 30 %, and the bending strength decreases rapidly from 297 MPa to 30 MPa. The thermal shock behavior of the CSZC and FGM was evaluated using air-quenching technique. It is shown that the residual bending strength of the quenched samples increases after several quenching cycles, and the samples are damaged by thermal shock after eight thermal cycles because of the production of monoclinic zirconia. FGM samples with porosity gradient structure can endure above twelve thermal shock cycles and exhibits better thermal shock resistance.
7
Burugupally, Sindhu Preetham. "Evaluation of a Combustion-Based Mesoscale Thermal Actuator in Open and Closed Operating Cycles." Actuators 8, no. 4 (October 23, 2019): 73. http://dx.doi.org/10.3390/act8040073.
Full textAbstract:
A combustion-based mesoscale thermal actuator is proposed and its performance is studied in both open and closed cycle operations using a physics-based lumped-parameter model. The actuator design is unique as it implements a free-piston complaint architecture where the piston is free to move in a linear direction. Our objective is to study the actuator behavior in both the cycles to help identify the benefits and highlight the differences between the two cycles. The actuator is modeled as a spring-mass-damper system by taking an air standard cycle approach. Three observations are reported: (1) for nominal heat inputs (140 J/cycle), the actuator can produce large displacement strokes (16 cm) that is suitable for driving mesoscale robots; (2) the efficiency of the actuator depends on the heat input; and (3) for a specific heat input, both the open and closed cycles operate differently—with different stroke lengths, peak pressures, and thermal efficiencies. Our study reveals that the performance metrics of the actuator make it an ideal candidate for high speed, large force, and large displacement stroke related applications.
8
Itoh, Y. Z., and H. Kashiwaya. "A Study of Cyclic Thermal Straining in a Welded Joint, Using a Closed-Loop, Servo-Controlled Testing Machine." Journal of Pressure Vessel Technology 114, no. 4 (November 1, 1992): 422–27. http://dx.doi.org/10.1115/1.2929249.
Full textAbstract:
For investigating the origin of residual stresses in welded joints, the transient thermal stresses in a carbon-manganese-silicon steel (JIS SM41B), a cast martensitic stainless steel (JIS SCS5), an austenitic stainless steel (JIS SUS304), and a titanium alloy (Ti-6Al-4V) were investigated by subjecting round bar specimens, in which both ends were fixed, to thermal of cycles. The specimens were heated in air by high-frequency induction. The cyclic thermal straining tests were conducted for the case of a single thermal cycle and the case of multiple thermal cycles, using a closed loop, servo-controlled testing machine. The experimental results made clear that the transient thermal stress behavior was dependent on metallurgical effects, such as phase transformations, strain hardening, the Bauschinger effect, etc. The effects on phase transformation on the transient thermal stress behavior of SCS5 and SM41B were especially remarkable. However, the effects of phase transformations on the residual stresses due to the thermal straining cycle were negligible in SM41B and not observed in both SUS304 and Ti-6Al-4V. The residual stresses tended to increase with increase of the peak temperature of thermal cycles in SM41B, SUS304 and Ti-6Al-4V. However, when the peak temperature increased above 600°C in SCS5, the residual stress rapidly decreased and became compressive because of the expansion due to the martensite transformation. This study led to the conclusion that the transient thermal stresses for various peak temperatures could easily be obtained by an incremental step test using a single specimen and that this incremental step test could simply estimate the residual stress character of butt-welded joints.
9
Amann, Charles A. "Applying Thermodynamics in Search of Superior Engine Efficiency." Journal of Engineering for Gas Turbines and Power 127, no. 3 (June 24, 2005): 670–75. http://dx.doi.org/10.1115/1.1804537.
Full textAbstract:
Historically, a succession of thermodynamic processes has been used to idealize the operating cycles of internal combustion engines. In this study, the 256 possible combinations of four reversible processes—isentropic, isothermal, isochoric, and isobaric—are surveyed in search of cycles promising superior thermal efficiency. Regenerative cycles are excluded. The established concept of the air-standard cycle, which mimics the internal combustion engine as a closed-cycle heat engine, is used to narrow the field systematically. The approach relies primarily on graphical interpretation of approximate temperature-entropy diagrams and is qualitative only. In addition to identifying the cycles offering the greatest efficiency potential, the compromise between thermal efficiency and mean effective pressure is addressed.
10
Khaliq, A. "Finite-Thermal Reservoir Effects on Ecologically Optimized Closed Regenerative Joule-Brayton Power Cycles." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 220, no. 5 (July 11, 2006): 425–34. http://dx.doi.org/10.1243/09576509jpe189.
Full textDissertations / Theses on the topic "Closed Thermal Cycles"
1
Agrawal, Nitin. "Design and characterization of convective thermal cyclers for high-speed DNA analysis." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1060.
Full text
2
Vijayaraj, K. "Thermal Turbomachinery Design for Closed Thermal Cycles and Multiple Fluids." Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4640.
Full textAbstract:
Closed-cycle gas turbines can complement conventional power conversion systems due to their potential for improved efficiencies, compact system layouts, and the ability to exploit non-fossil fuel energy sources which leads to low carbon emissions. Moreover, they can be adopted for distributed power generation applications. This thesis provides an understanding of the true essence of closed-cycle gas turbines with a focus on the development of turbomachinery design methodologies. The methodologies have been applied for the radial turbomachinery design (small-scale power range) for supercritical Brayton cycles and other thermal cycles such as air cycle, organic Rankine cycle, cryogenic cycles, and steam Rankine cycle.
The thesis begins with an elaborate review of the potential of closed-cycle gas turbines. Thermodynamic analysis has been carried out for the recuperated closed Brayton cycle with and without intercooling employing different working fluids. It has shown that the supercritical carbon dioxide gives considerably higher efficiencies at mild turbine inlet temperatures of 400-700°C and helium can be considered at higher temperatures of above 800°C. The closed Brayton cycle turbomachinery designs with multiple fluids have been brought together uniquely on two charts, one in absolute scale (∆H-M-D) and other in non-dimensional scale (NS-DS) by carrying out a detailed survey of the closed-cycle gas turbine plants and concept designs, which can aid in the design of turbines and compressors for different applications.
Turbomachinery design can have two approaches. The first one is scaling a benchmark design for different fluids catering to a particular application. The second one is a thorough step-by-step meanline design methodology for both turbines and compressors for any new application. Turbomachinery development through scaling a good benchmark design using the power of similitude to adapt it to the different working fluids employed in various thermal cycles can save considerable amount of time and provide a quick solution with good performance. The scaling methodology has been used for the development of radial turbomachinery for a 50 kW supercritical carbon dioxide (SCO2) power plant. The CFD simulations along with experimental results have confirmed that the scaling technique is quite good. The radial inflow turbine had an isentropic efficiency of 77 % from the CFD simulation at the design point with SCO2 fluid. The torque coefficients, flow coefficients, and the efficiencies determined from the CFD simulations for the turbine, when superimposed on the benchmark turbine experimental curves, showed good agreement. The efficiencies for the compressor from CFD with SCO2 fluid were lower compared to the experimental efficiencies of the benchmark compressor, but the curves showed the same trend. The highest CFD efficiency of 77.2 % was obtained at a flow coefficient of around 0.46. Experiments were carried out for the developed turbine and compressor assembly using air as the fluid (aeroloop) to mainly observe the vibrations at high speeds. The assembly had run-up to a maximum speed of 70000 rpm. The turbine flow coefficients from the aeroloop experiment were not far away from the simulation and the NASA benchmark data. The compressor flow coefficient zone from the experiment coincided with the flow coefficient zone of open-type boundary condition simulation results of the compressor with air as the fluid. Also, the absolute plot of speed vs. mass flow rate for the compressor in the aeroloop test matched well with the open boundary type CFD simulation results.
The thesis has also presented a scaling procedure to develop turboexpanders from a benchmark air turbine having experimental characteristics. It has been applied for the design of turboexpanders for supercritical carbon dioxide (SCO2) Brayton cycle, R143a organic Rankine cycle, and helium cryogenic cycle. The dimensionless iso-Mach number characteristic curves and efficiency curves of the SCO2 turbine, helium turbine, and R143a turbine determined from the CFD simulations were superimposed on the experimental characteristics of the benchmark turbine. There was good conformance between both, which proved that the proposed scaling methodology can be adopted for the turboexpander design.
Detailed meanline design procedures were proposed in this thesis for radial inflow turbine and centrifugal compressor using specific speed and specific diameter parameters so that the design can be started from scratch for a new application. These were used for the development of a turbo-compressor for the 2 kW air cycle machine for DARE (DRDO) which is employed in aircraft cooling. The radial inflow turbine had an isentropic total efficiency of 85.6 %. The centrifugal compressor designed based on the proposed methodology had an isentropic total efficiency of 76 %. Another design of centrifugal compressor which was carried out in a different approach had attained an efficiency of 78.6 %.
Radial turbomachinery design for a 1 MW supercritical carbon dioxide power plant has been presented in which the radial turbine is designed using the proposed 1-D meanline design methodology and the centrifugal compressor is designed using the scaling school of thought. Numerical simulations showed isentropic total efficiencies of 91% for the radial inflow turbine and 77.25 % for the centrifugal compressor at the design point.
The last part of the thesis has discussed the design procedure of an unconventional turbine type called ‘radial outflow turbine’ for a 200 kW steam Rankine cycle and 1 MW supercritical carbon dioxide Brayton cycle. The design point CFD simulation of the 18-stage steam radial outflow turbine showed efficiency close to 75 %. A new zone was identified for the radial outflow turbine in Balje’s specific speed-specific diameter chart. The design point CFD efficiency of the supercritical carbon dioxide radial outflow turbine was 84.6 %.
3
Rovense, Francesco, Franco Furgiuele, Mario Amelio, and Manuel Silva Pèrez. "Study of an unfried closed joule-brayton cycle in a concentrating solar tower plant with a mass flow rate control system." Thesis, 2018. http://hdl.handle.net/10955/1821.
Full textAbstract:
Dottorato di Rocerca in Ingegneria Civile ed Industriale. Ciclo XXXOggigiorno, la domanda di energia primaria è aumentata, raggiungendo un incremento del 62.5% rispetto a 20 anni fa. La necessità di risorse rinnovabili ha spinto le politiche governative di tutto il mondo a incoraggiare lo sviluppo di nuovi sistemi di produzione di energia. Fra questi vi sono i sistemi a concentrazione solare (CSPs), una tecnologia che concentra la radiazione solare rendendola disponibile, attraverso un fluido termovettore (HTF) come fonte di calore in un ciclo termodinamico di potenza. Il ciclo di potenza più efficiente, come noto, è quello Joule-Brayton, che in configurazione chiusa consente l'utilizzo di HTF diversi; inoltre, è possibile lavorare in condizioni di pressione elevate, con alta temperatura operativa ed efficienza di conversione. L’uso dell’aria come fluido di lavoro rende di facile gestione il sistema senza rischi. Inoltre unendo il ciclo chiuso con un sistema CSP, il sistema è totalmente privo di combustione e non essendo necessario l’uso di combustibile, non sono emessi inquinanti. Fra i sistemi CSP, la tecnologia a torre è in grado di poter raggiungere più alte temperature, disponibile quindi nel ciclo Brayton, e per questo motivo è stato considerato il suo uso nelle analisi. La risorsa imprevedibile, rappresentata dalla radiazione solare, richiede un metodo di regolazione per il controllo della potenza generata dall’impianto. In questo lavoro, quindi, è stata analizzata la fattibilità di un ciclo Joule-Brayton chiuso senza combustione, in un impianto solare a concentrazione a torre che utilizza un sistema di controllo della portata massica. Nel ciclo è operato un controllo della temperatura di ingresso della turbina della turbina a gas, quando varia la radiazione normale diretta (DNI) attraverso la regolazione della densità del fluido di lavoro; questa regolazione è attuata attraverso una variazione di pressione di base del ciclo. In questo sistema la turbina gas non cambia la portata volumetrica come anche i triangoli di velocità o i rapporti di pressione, quindi variando la densità del fluido di lavoro, attraverso una variazione di pressione, è possibile regolare la portata massica al fine di controllare la TIT. Controllando la TIT, quindi, è possibile controllare la potenza elettrica prodotta dalla turbina a gas sotto diversi carichi termici del DNI. In questo lavoro, diverse configurazioni, in termini di potenza delle macchine, come anche l’utilizzo di accumulo termico (TES) sono stati analizzate, ponendo particolare attenzione alla progettazione del campo eliostati. I risultati mostrano che l’efficienza globale del ciclo, rimane costante sotto differenti carichi termici dovuti alla radiazione solare, indipendentemente dalla potenza della turbina a gas; l’utilizzo di accumulo permette di aumentare le ore di utilizzo dell’impianto come anche il fattore di utilizzazione (UF). L’analisi economica, effettuata attraverso il metodo del Levelised Cost of Electricity (LCoE) ha reso possibile ottenere un valore del multiplo solare (SM) differente rispetto ai valori tipici usati. In fine è stata considerata l’applicazione in micro scala di questo tipo di impianto, al fine di confrontarlo con un sistema commerciale esistente.
Università della Calabria.
Books on the topic "Closed Thermal Cycles"
1
A, Hall Carsie, and Lewis Research Center, eds. Thermal state-of-charge in solar heat receivers. [Cleveland, Ohio]: National Aeronautics and Space Administration, Lewis Research Center, 1998.
Find full text
2
A, Hall Carsie, and Lewis Research Center, eds. Thermal state-of-charge in solar heat receivers. [Cleveland, Ohio]: National Aeronautics and Space Administration, Lewis Research Center, 1998.
Find full text
3
Alexander, Dennis. 2 kWe Solar Dynamic Ground Test Demonstration Project. [Washington, DC]: National Aeronautics and Space Administration, 1997.
Find full text
4
Alexander, Dennis. 2 kWe Solar Dynamic Ground Test Demonstration Project. [Washington, DC]: National Aeronautics and Space Administration, 1997.
Find full text
5
Alexander, Dennis. 2 kWe Solar Dynamic Ground Test Demonstration Project. [Washington, DC]: National Aeronautics and Space Administration, 1997.
Find full text
6
National Aeronautics and Space Administration (NASA) Staff. Conceptual Design Study of a Closed Brayton Cycle Turbogenerator for Space Power Thermal-To-Electric Conversion System. Independently Published, 2018.
Find full textBook chapters on the topic "Closed Thermal Cycles"
1
Haseli, Yousef. "Irreversible engines—Closed cycles." In Entropy Analysis in Thermal Engineering Systems, 85–102. Elsevier, 2020. http://dx.doi.org/10.1016/b978-0-12-819168-2.00007-6.
Full text
2
Avery, William H., and Chih Wu. "Open-Cycle OTEC." In Renewable Energy from the Ocean. Oxford University Press, 1994. http://dx.doi.org/10.1093/oso/9780195071993.003.0012.
Full textAbstract:
The historical development leading to the proposal by Claude to generate power by producing steam in flash evaporation of warm seawater has been discussed in Chapter 2. In this chapter, the thermodynamic fundamentals of the open-cycle concepts are discussed, leading to a detailed review of state of the art and commercial prospects of the process. There are several variations on the standard OTEC open-cycle (OC) system. The three major variations are “hybrid cycle” (Bartone, 1978), “mist lift cycle” (Ridgway, 1977), and “foam lift cycle” (Beck, 1975; Zener et al., 1975). These are advanced concepts that offer certain attractive features and are being investigated. The three cycles will be discussed in Sections 5.3, 5.4, and 5.5, respectively. The standard OTEC open cycle is discussed in the following. The modest but nearly steady temperature difference that exists between the warm surface water and the much colder water at great depth in some tropical regions of the world has attracted the attention of many thermodynamicists from the time that these temperature differences were first observed. From the thermodynamicist’s view, any significant temperature difference can be used to produce power. The open or Claude cycle is the forerunner of various OTEC cycles. The open cycle refers to the use of seawater as the working fluid. A schematic diagram of the system, which comprises a flash evaporator, vapor expansion turbine and generator, steam condenser, noncondensables-removing equipment, and deaerator, is shown in Fig. 5-1 (Chen, 1979). The cycle is a basic Rankine cycle for converting thermal energy of the warm surface water into electrical energy. In the cycle, the warm seawater is deaerated and then passed into a flash evaporation chamber, where a fraction of the seawater is converted into low-pressure steam. The steam is passed through a turbine, which extracts energy from it, and then exits into a condenser. This cycle derives the name “open” from the fact that the condensate is not returned to the evaporator as in the “closed” cycle. Instead, the condensate can be used as desalinated water if a surface condenser is used, or the condensate is mixed with the cooling water and the mixture is discharged back into the ocean.
3
"Thermal reactors." In Closed Nuclear Fuel Cycle with Fast Reactors, 317–28. Elsevier, 2022. http://dx.doi.org/10.1016/b978-0-323-99308-1.00032-5.
Full text
4
Avery, William H., and Chih Wu. "Closed-Cycle OTEC Systems." In Renewable Energy from the Ocean. Oxford University Press, 1994. http://dx.doi.org/10.1093/oso/9780195071993.003.0011.
Full textAbstract:
The Rankine closed cycle is a process in which beat is used to evaporate a fluid at constant pressure in a “boiler” or evaporator, from which the vapor enters a piston engine or turbine and expands doing work. The vapor exhaust then enters a vessel where heat is transferred from the vapor to a cooling fluid, causing the vapor to condense to a liquid, which is pumped back to the evaporator to complete the cycle. A layout of the plantship shown in Fig. 1-2. The basic cycle comprises four steps, as shown in the pressure-volume (p—V) diagram of Fig. 4-1. 1. Starting at point a, heat is added to the working fluid in the boiler until the temperature reaches the boiling point at the design pressure, represented by point b. 2. With further heat addition, the liquid vaporizes at constant temperature and pressure, increasing in volume to point c. 3. The high-pressure vapor enters the piston or turbine and expands adiabatically to point d. 4. The low-pressure vapor enters the condenser and, with heat removal at constant pressure, is cooled and liquefied, returning to its original volume at point a. The work done by the cycle is the area enclosed by the points a,b,c,d,a. This is equal to Hc–Hd, where H is the enthalpy of the fluid at the indicated point. The heat transferred in the process is Hc–Ha Thus the efficiency, defined as the ratio of work to heat used, is: . . . efficiency(η)=Hc–Hd/Hc–Ha (4.1.1) . . . Carnot showed that if the heat-engine cycle was conducted so that equilibrium conditions were maintained in the process, that the efficiency was determined solely by the ratio of the temperatures of the working fluid in the evaporator and the condenser. . . . η=TE–Tc/TE (4.1.2) . . . The maximum Carnot efficiency can be attained only for a cycle in which thermal equilibrium exists in each phase of the process; however, for power to be generated a temperature difference must exist between the working fluid in the evaporator and the warm-water heat source, and between the working fluid in the condenser and the cold-water heat sink.
5
Cerezo Acevedo, Estela, Jessica G. Tobal Cupul, Victor M. Romero Medina, Elda Gomez Barragan, and Miguel Angel Alatorre Mendieta. "Analysis and Development of Closed Cycle OTEC System." In Ocean Thermal Energy Conversion (OTEC) - Past, Present, and Progress. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.90609.
Full text
6
Hanlon, Robert T. "Sadi Carnot." In Block by Block: The Historical and Theoretical Foundations of Thermodynamics, 329–67. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198851547.003.0030.
Full textAbstract:
Carnot sought to better understand the performance of the Cornish engine for the benefit of France. His ground-breaking analysis involved new theories on thermal efficiency, maximum work, and closed-cycle operation. Carnot proposed an ideal heat engine that achieved the best possible efficiency, regardless (surprisingly) of the nature of the working substance. Unfortunately, embedded deep inside Carnot’s powerful analysis was a single major flawed assumption: the caloric theory of heat in which heat is treated as a conserved quantity.
7
Pérez-de-Tejada, Hector, and Rickard Lundin. "Vortex Dynamics in the Wake of Planetary Ionospheres." In Vortex Dynamics - From Physical to Mathematical Aspects [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.101352.
Full textAbstract:
Measurements conducted with spacecraft around Venus and Mars have shown the presence of vortex structures in their plasma wake. Such features extend across distances of the order of a planetary radius and travel along their wake with a few minutes rotation period. At Venus, they are oriented in the counterclockwise sense when viewed from the wake. Vortex structures have also been reported from measurements conducted by the solar wind-Mars ionospheric boundary. Their position in the Venus wake varies during the solar cycle and becomes located closer to Venus with narrower width values during minimum solar cycle conditions. As a whole there is a tendency for the thickness of the vortex structures to become smaller with the downstream distance from Venus in a configuration similar to that of a corkscrew flow in fluid dynamics and that gradually becomes smaller with increasing distance downstream from an obstacle. It is argued that such process derives from the transport of momentum from vortex structures to motion directed along the Venus wake and that it is driven by the thermal expansion of the solar wind. The implications of that momentum transport are examined to stress an enhancement in the kinetic energy of particles that move along the wake after reducing the rotational kinetic energy of particles streaming in a vortex flow. As a result, the kinetic energy of plasma articles along the Venus wake becomes enhanced by the momentum of the vortex flow, which decreases its size in that direction. Particle fluxes with such properties should be measured with increasing distance downstream from Venus. Similar conditions should also be expected in vortex flows subject to pressure forces that drive them behind an obstacle.
8
Couto, Luíza Camargos, Maria Clara Martins Avelar, Vitória Bernardes, and Lamara Laguardia Valente Rocha. "Inhalation of Toxic Gases in the Kiss Nightclub Disaster: an Example of Inhalation Injury from Indoor Fires." In COLLECTION OF INTERNATIONAL TOPICS IN HEALTH SCIENCE- V1. Seven Editora, 2023. http://dx.doi.org/10.56238/colleinternhealthscienv1-003.
Full textAbstract:
The Kiss Nightclub disaster, which occurred on January 27, 2013, in Santa Maria, Brazil, had an impact both on a national and global scale, as it was an accident with 230 immediate fatalities and can be compared to other indoors fires. In addition to bodily burns, inhalation injuries stood out, that is, thermal injuries of the airway, chemical injuries and intoxication by toxic gases. Carbon monoxide and cyanide are the main toxic gases produced in indoor fire situations and are formed from the incomplete combustion of hydrocarbons and carbonaceous and nitrogenous materials, respectively. While carbon monoxide, at high concentrations in the blood, promotes a shift of the oxyhemoglobin curve to the left and a consequent hypoxia condition, cyanide blocks the respiratory cycle, activating anaerobic respiration and evolving to an excessive production of lactic acid, which can lead the victim to death. Considering that in the accident of Santa Maria 169 individuals were hospitalized in a critical condition, it is necessary to understand the consequences and pathophysiology of inhalation injuries, being that the focus of this narrative review is the knowledge about poisoning by toxic gases. Moreover, it is essential to discuss proper diagnosis and treatment, in order to improve the prognosis of future victims of new fires in closed environments. Therefore, having knowledge about the potential causes of indoor fires helps in the prevention of similar disasters to the one that happened in the Kiss Nightclub.
9
Quante, Markus, and David O’C Starr. "Dynamic Processes in Cirrus Clouds: A Review of Observational Results." In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0021.
Full textAbstract:
Local dynamical processes are a key factor determining the microphysical characteristics and typically heterogeneous macroscopic structure of cirrus cloud fields. The internal and background flow fields are correspondingly heterogeneous, albeit only weakly turbulent in most instances, as is discussed here. Nucleation processes and ice crystal growth and habit are intrinsically governed by the local temperature and humidity (saturation ratio) conditions that, in turn, are strongly regulated by the intensity and duration of local updrafts and downdrafts. The microphysical result of equivalent lift by a 50cm/s updraft over a cell width of 200m is quite different from that by a 0.5 cm/s updraft over a 2-km width, even though the overall mass fluxes are equivalent. The great degree of horizontal structure seen in fallstreaks emanating from cirrus likely reflects corresponding variability in microphysical properties, primarily ice crystal size, resulting from variability in the dynamical conditions in the ice-crystal-generating layer. The ice fallout process is a first-order effect in determining overall cloud ice water path. Entrainment of noncloudy environmental air and internal mixing processes are other dynamical aspects that likely play a significant role in cloud life cycle. Dynamical processes provide an important coupling between cirrus cloud microphysical and radiative processes, as described in chapter 18 and illustrated in figure 17.1. Cirrus cloud microphysical properties and macroscopic structure strongly affect the overall radiative properties of a cirrus cloud field and thus the important radiative effect of cirrus in the climate system. Knowledge of the dynamical processes influencing cloud macrophysical properties and microphysical structure is important to understanding the origin of these characteristics. Moreover, cloud-resolving models of cirrus cloud systems must be evaluated in these respects due to the importance of cloud dynamical processes in determining overall cloud properties. Dynamical processes in cirrus are linked to the state of the background flow field that, in general, is characterized by significant wind shear and a stable thermal stratification. Gravity waves are ubiquitous and occur over a range of scales. Upper tropospheric turbulence tends to occur intermittently in patches, likely a result of sporadic shear generation (Kelvin-Helmholtz instabilities) or breaking gravity waves. Turbulent mixing in stratified shear flows is a notoriously difficult subject, and advances in its description have been obtained only recently (e.g., Fernando 1991; Schumann and Gerz 1995; Vanneste and Haynes 2000).
10
Whiteman, C. David. "Diurnal Mountain Winds." In Mountain Meteorology. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195132717.003.0019.
Full textAbstract:
Diurnal mountain winds develop over complex topography of all scales, from small hills to large mountain massifs and are characterized by a reversal of wind direction twice per day. As a rule, winds flow upslope, up-valley, and from the plain to the mountain massif during daytime. During nighttime, they flow downslope, down-valley, and from the mountain massif to the plain. Diurnal mountain winds are strongest when skies are clear and winds aloft are weak. Diurnal mountain winds are produced by horizontal temperature differences that develop daily in complex terrain. The resulting horizontal pressure differences cause winds near the surface of the earth to blow from areas with lower temperatures and higher pressures toward areas with higher temperatures and lower pressures. The circulations are closed by return, or compensatory, flows higher in the atmosphere. Four wind systems comprise the mountain wind system, which carries air into a mountain massif at low levels during daytime and out of a mountain massif during nighttime. The slope wind system (upslope winds and downslope winds) is driven by horizontal temperature contrasts between the air over the valley sidewalls and the air over the center of the valley. The along-valley wind system (up-valley winds and down-valley winds) is driven by horizontal temperature contrasts along a valley’s axis or between the air in a valley and the air over the adjacent plain. The cross-valley wind system results from horizontal temperature differences between the air over one valley sidewall and the air over the opposing sidewall, producing winds that blow perpendicular to the valley axis and toward the more strongly heated sidewall. The mountain-plain wind system results from horizontal temperature differences between the air over a mountain massif and the air over the surrounding plains, producing large-scale winds that blow up or down the outer slopes of a mountain massif. The mountain-plain circulation and its upper level return flow are not confined by the topography but are carried over deep layers of the atmosphere above the mountain slopes. Because diurnal mountain winds are driven by horizontal temperature differences, the regular evolution of the winds in a given valley is closely tied to the thermal structure of the atmospheric boundary layer within the valley, which is characterized by a diurnal cycle of buildup and breakdown of a temperature inversion.
Conference papers on the topic "Closed Thermal Cycles"
1
Beniwal, Ravi, Kapil Garg, Sarit Kumar Das, and Himanshu Tyagi. "PARAMETRIC ANALYSIS BETWEEN CLOSED AIR OPEN WATER (CAOW) AND CLOSED WATER OPEN AIR (CWOA) HDH CYCLES." In 5-6th Thermal and Fluids Engineering Conference (TFEC). Connecticut: Begellhouse, 2021. http://dx.doi.org/10.1615/tfec2021.ens.036676.
Full text
2
Kusterer, Karsten, René Braun, Norbert Moritz, Takao Sugimoto, Kazuhiko Tanimura, and Dieter Bohn. "Comparative Study of Solar Thermal Brayton Cycles Operated With Helium or Argon." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94990.
Full textAbstract:
Concentrating Solar Power (CSP) plants often use Rankine cycles operated with water/steam as energy conversion cycles. Since the solar central receiver technology could provide receiver fluid outlet temperatures higher than 900°C, open and closed gas turbine technologies become a promising alternative. Closed solar Brayton cycles operating with appropriate fluids can reach similar or higher thermal efficiencies than water/steam Rankine cycles but have the advantage of less consumption of fresh water. This paper presents the results of a comparative thermodynamic and process study of closed solar thermal Brayton cycles operated with Helium or Argon as working fluids. The main components of the cycles are two axial compressors with an intercooler, a recuperator and one axial turbine. The solar heat is fed in by a central receiver technology. It is assumed that the transferred heat to the cycles is constant and the turbine inlet temperature is 900°C. A first one-dimensional design approach for both cycles is performed based on the results of the thermodynamic considerations. The major parameters like stage types, number of stages, rotational speed, etc. are determined and discussed. The thermodynamic and process investigation results for the described closed Brayton cycles show that thermal efficiencies over 46% can be established for both fluids. The design considerations show that both cycles are feasible, but with respect to design dimensions the Argon based cycle can be built up with fewer stages and more compact, if compared to the Helium cycle.
3
Watson, Darren T., and Ian Ritchey. "Thermodynamic Analysis of Closed Loop Cooled Cycles." In ASME 1997 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/97-gt-288.
Full textAbstract:
Closed loop steam cooling schemes have been proposed by a number of manufacturers for advanced Combined Cycle Gas Turbine (CCGT) power plant (see for example Corman (1996) and Briesch et al. (1994)) asserting that thermal efficiencies in excess of 60% (LHV) are achievable combined with significant improvements of ∼15% in specific power (see Corman (1995)). In understanding the efficiency advantage however, the relative performance of each cooling system (subject to the same practical constraints and technology levels) is a better indicator then the absolute value. Assessment of the performance of such novel schemes generally involves a detailed numerical analysis of an integrated cycle which may often prevent validation of the results or obscure an understanding of the physical basis for the claimed improvements. Here, to overcome this, a group of simplified expressions are defined for the variation of each cycles efficiency due to cooling which show where the differences come from. These expressions are based simply on a calculation of the marginal increase in heat rejected, to the environment from the cycle, due to an increase in the level of cooling. After these relationships are validated using detailed heat balance calculations they are used to compare the main cooling options, namely open loop air, closed loop air and closed loop steam when subject to the same practical constraints and assumptions. Based on these results it is proposed that the relative advantage of closed loop cooling may not be as significant as previously thought. Furthermore, it is shown that the closed loop cooling efficiency gain is heavily dependent on the performance and reliability of substantial Thermal Barrier Coatings (TBCs). Finally, although the majority of recent interest in closed loop cooling schemes has focused upon CCGT plant, there are other systems where the benefits of closed loop steam cooling appear to be greater, in particular cycles involving steam injected gas turbines. Such a cycle is analysed here with a number of advanced cooling options.
4
Bethapudi, Sasank Viswanath, N. Rajalakshmi, and K. S. Dhathathreyan. "PEMFC Stack Activation Through Thermal Management." In ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology collocated with the ASME 2013 Heat Transfer Summer Conference and the ASME 2013 7th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fuelcell2013-18203.
Full textAbstract:
Activation of PEM fuel cell stack is an important factor in setting peak power of stack before its steady operations. Several methods of activation for larger capacity stacks involve operation of the stacks initially at low voltages under highly humidified conditions and at high temperatures. This is expected to improve proton conductivity of the membrane. For large area cells this method can create hot spots due to high current and non-uniform temperature distribution. Hence, an alternative approach for activating PEMFC stack at low current for vehicular applications has been investigated in this study. Conventional stack activation requires continuous supply of coolant. However for vehicular applications, a closed loop thermal management system is required. During the course of developing such a close loop thermal management system for transportation application, we have identified that the same system can be used in activating a PEM fuel cell stack. In the present study a 5kW PEMFC stack, operating on dry reactants, has been activated using a closed loop thermal management system. The activation has been carried out over a period of 620 minutes with 6 start/stop cycles. Through the start stop cycles the power delivered by the stack steadily increased from 2.5kW, to 5kW. Further, heat developed inside the fuel cell, as removed by the coolant water, has been studied and there is a proportional increase in the overall heat removed by the coolant to the total power delivered by the fuel cell. The start stop cycles are regulated based on the single cell voltages and stack temperature. Each cycle is stopped when the stack temperature reaches a set temperature of 50°C. The advantage of this procedure is that it will result in long life of the fuel cell stack, uniform membrane equilibration, and will avert hot spot generation in the electrodes at low cell potential.
5
Tacconi, Jacopo, Wilfried Visser, and Dries Verstraete. "Potential of Semi-Closed Cycles for UAV Propulsion." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-92066.
Full textAbstract:
Abstract Conventional Brayton cycles have demonstrated to be significantly less efficient than alternative propulsion systems (spark ignition, diesel, fuel cells, etc.) for low power output applications, such as for small size UAVs. The gas turbine performance could be enhanced through the introduction of heat exchangers, with the consequent increase of the overall engine weight. Semi-closed cycles have documented advantages of higher thermal efficiency and degree of compactness than traditional intercooled-recuperated open cycles. This paper discusses advantages and applicability of semi-closed cycles to a small gas turbine, designed for a medium altitude UAV mission. In particular, size and altitude effects have been accounted in the performance evaluation of two different semi-closed cycle arrangements designed for an output shaft power of 100 hp (74.57 kW). Resultant performance has been compared with equivalent simple recuperated and intercooled-recuperated open cycles. Furthermore, a final engine performance comparison has been made with data obtained from a similar analysis performed on a larger engine, with a power output of 300 hp (223.71 kW) and designed for an extremely high altitude UAV application. While promising results have been obtained for the larger case study, where semi-closed cycles have demonstrated superior performance and higher engine compactness than conventional solutions, similar trends have not been displayed for the smaller engines, as consequence of the strong size effects observed in the turbomachinery performance. For the 100 hp engine the semi-closed cycles are slightly outperformed by the open cycle engines.
6
Frate, Guido Francesco, Luigia Paternostro, Lorenzo Ferrari, and Umberto Desideri. "Off-Design of a Pumped Thermal Energy Storage Based on Closed Brayton Cycles." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-60185.
Full textAbstract:
Abstract The growth of renewable energy source requires reliable, durable and cheap storage technologies. In this field, the Pumped Thermal Energy Storage (PTES), is drawing some interest as it appears not to be affected by geographical limitations and use very cheap materials. PTES is less efficient than pumped hydro and batteries, but it could achieve satisfactory efficiencies, show better economic performance and be characterized by negligible environmental impacts. A PTES stores the electric energy as thermal exergy in solid packed beds, by operating two closed Brayton cycles, one for charging and the other one for discharging. Although PTES thermodynamical behavior is well understood, the interaction between the components is rarely investigated. This study investigates the impact of packed-bed behavior on turbomachines operating conditions. In this way, PTES off-design and part-load performance are estimated. A control strategy especially suited for closed Brayton cycles, i.e. the inventory control, is used to control the system. As it resulted, PTES is characterized by an excellent part-load performance, which might be a significant advantage over the competing technologies. However, the off-design operation induced by the packed-bed thermal behavior might significantly reduce the system performance and, in particular, that of the discharge phase.
7
Kusterer, Karsten, René Braun, Norbert Moritz, Gang Lin, and Dieter Bohn. "Helium Brayton Cycles With Solar Central Receivers: Thermodynamic and Design Considerations." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68407.
Full textAbstract:
Concentrated Solar Power (CSP) technologies are considered to provide a major contribution for the electric power production in the future. Several technologies for such kind of power plants are already in operation. Parabolic troughs, parabolic dishes, Fresnel multi-facet reflectors or heliostats in combination with a central receiver are applied for concentration of the solar irradiation. The energy conversion cycles usually are water/steam cycles (Rankine cycles), but also open gas turbine cycles (Brayton cycle) or combined cycles are possible. One option is to apply closed Brayton cycles using fluids like carbon dioxide or helium. With respect to commercial considerations, the main parameter driving the decision on which cycle to apply for energy conversion is the thermal efficiency of the process. This is due to the fact, that in case of a power plant without additional fuel supply, no fuel costs have to be considered to determine the levelized electricity costs (LEC). Thus, in the first place the capital costs determine the LEC. In CSP plants one main driver for the capital costs are the heliostats and the mirror size, which are necessary to generate the desired amount of electric power. The necessary solar aperture area directly depends on the thermal efficiency of the energy conversion cycle. In this paper different closed Helium Brayton Cycles for application with solar central receivers are analyzed thermodynamically. The thermodynamic calculations are performed by application of a self-developed thermodynamic calculation software, which considers the real gas properties of the fluid. The software calculates the cycle’s thermodynamic diagrams (e.g. T-s-, h-s-diagrams) and determines its efficiency. The results show that thermal efficiencies of approximately 46.6% (and higher) can be reached with a Helium Brayton Cycle. One important parameter is the turbine inlet gas temperature, which is not less than 900 °C. This means that the pressurized receiver for this technology has to bear even higher temperatures. Furthermore, the paper deals with design considerations for compressor and turbine within the closed Helium Brayton Cycle. Based on dimensionless parameters, the major parameters like stage types, number of stages, rotational speed etc. are determined and discussed.
8
Enge, Yngvil O., Manfred Wirsum, and Hans E. Wettstein. "The Potential of Recuperated Semiclosed CO2 Cycles." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90888.
Full textAbstract:
Semi-closed cycles are characterized by firing a fuel with technically pure oxygen. The combustion gases mainly consist of CO2 and H2O. The use of the exhaust heat of the turbine in a steam bottoming cycle is the most common approach to achieve a sufficient thermal efficiency. In this paper it is shown that a semi-closed CO2 cycle with thermal recuperation avoids the complexity of a bottoming steam cycle and at the same time adds the potential of supercharging the cycle to high pressure. This allows both a very high power density and a discharge of fairly clean CO2 under sufficiently high pressure, which may be used directly or after separation of parasitic gases for enhanced oil recovery or other kind of disposal methods. We show in this paper preliminary cycle calculations, the optimization of pressure ratio, pressure level, turbine inlet temperature and recuperator assumptions. The real gas properties influence the cycle optimization and especially the temperature match within the recuperator.
9
Aoki, S., K. Uematsu, K. Suenaga, H. Mori, and H. Sugishita. "A Study of Hydrogen Combustion Turbines." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-394.
Full textAbstract:
A hydrogen combustion turbine system has been proposed by Mitsubishi Heavy Industries, LTD. which is the Closed Circuit Cooled Topping Recuperation Cycle (CCCTR cycle) and is part of a Japanese government sponsored program WE-NET (“World Energy Network”). This cycle is composed of closed Brayton and Rankine cycles. The efficiency of this cycle is more than 60% HHV (Higher Heat Value) with a power capacity of 500MW. This cycle was selected as the most suitable for hydrogen combustion turbine used for industrial power plant by the Japanese government. A closed circuit steam cooling system has been proposed to cool vanes and blades of the high temperature turbine (HIT) which has inlet temperature of 1700°C and inlet pressure of 45bar. This paper presents the comparisons of the thermal efficiency and the feasibility of components between the CCCTR cycle and other cycles.
10
Amann, Charles A. "Applying Thermodynamics in Search of Superior Engine Efficiency." In ASME 2002 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/icef2002-483.
Full textAbstract:
Historically, a succession of thermodynamic processes has been used to idealize the operating cycles of internal combustion engines. In this study, the 256 possible combinations of four reversible processes – isentropic, isothermal, isochoric, and isobaric – are surveyed in search of cycles promising superior thermal efficiency. Regenerative cycles are excluded. The established concept of the air-standard cycle, which mimics the internal combustion engine as a closed-cycle heat engine, is used to narrow the field systematically. The approach relies primarily on graphical interpretation of approximate temperature-entropy diagrams and is qualitative only. In addition to identifying the cycles offering the greatest efficiency potential, the compromise between thermal efficiency and mean effective pressure is addressed.
Reports on the topic "Closed Thermal Cycles"
1
Analysis of Recompression-Regeneration sCO 2 Combined Cycle Utilizing Marine Gas Turbine Exhaust Heat: Effect of Operating Parameters. SAE International, July 2022. http://dx.doi.org/10.4271/2022-01-5059.
Full textAbstract:
Gas turbines are fast being explored to replace the existing steam or diesel-based power packs to propel marine transportation. Marine gas turbines have already come to power high-speed marine vessels transporting perishable goods as well as high-speed naval fleets. This article investigates the potential of gas turbine to be made hybrid with supercritical recompression-regeneration carbon dioxide (CO2) cycle drawing thermal energy from the exhaust of marine gas turbines. The recompression unit acts as the topping cycle and the regeneration unit acts as the bottoming cycle of the proposed combined supercritical CO2 (sCO2) cycle. The cycle has a maximum temperature of 530°C and supercritical pressure of 20 MPa. The proposed sCO2 powerplant is compact because of the smaller size of the turbomachinery, owing to the low specific volume of working fluid in the supercritical range. The proposed combined cycle is analyzed for different operating conditions including maximum temperature, minimum temperature, and cycle pressure ratio. The thermal efficiency of the proposed sCO2 cycle is 30.77% and efficiency of the hybrid cycle (including marine GT) is 58.17%, i.e., enhancement in thermal efficiency of the marine vessel power pack by 18.6%. Further the power output of the gas turbine-sCO2 hybrid cycle is enhanced by nearly 23.5% to 45.7 megawatts (MW). The second law of thermodynamic efficiency of the proposed combined cycle is close to 52.5%. The proposed hybrid gas turbine-sCO2 cycle has immense potential to replace the aging propulsion systems of existing marine vessels as the proposed power cycle is greener and more compact.