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Power cycles running on carbon dioxide at supercritical pressure and temperature were introduced in the late ninety-sixties but, after a warm welcome to the theoretical performance announced, they were later abandoned in favour of standard combustion gas turbines. Nevertheless, the technology was brought forward about a decade ago and has since captured significant attention from the scientific and industrial community. The number of publications has risen exponentially and there are several experimental projects under development today. The performances of these cycles have been deeply analysed in literature, proving to be theoretically competitive.
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Cp,sCO2= ˙m·cp,sCO2
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1Simple Recuperated R1
2T ranscritical CO2R1
3Hot day R1IC
4Allam R1IC
5Intercooling I I R1IC
6Brayton C O2GT R1IC
7Reheating II R1RH
8Split E xpansion R1RH
9Matiant R1I C RH
10 Allam +RH R1I C RH
11 F orced Cooler R1IC RH
12 DEM O R1IC RH
13 P reheating R1SF H
14 SEJ R1SF E
15 Inter Recuperated R2
16 Recompression R2SF C
17 BAS R2SF C
18 P recompression R2IC
19 Recuperated CP OC R2IC
20 P artial Cooling R2IC S F C
21 Intercooling I R2IC S F C
22 Reheating I R2RH SF C
23 Double Reheated Recompression R2RH SF C
24 Driscoll R2S F H
25 REC 2R2SFC SF H
26 T urbine Split Flow I R2SF H E
27 T urbine Split Flow I I R2SF H E
28 T urbine Split Flow I II R2SF H E
29 RC EJ R2S F C S F E
30 Recompression +IC +RH R2I C RH SFC
31 P artial Cooling +RH R 2IC RH SF C
32 MC E J R2IC SF C SF E
33 Double Recompression R3SFC
34 P artial Cooling w/ Impr. Recuperation R3IC S F C
35 Cascade R3S F C S F HE
36 REC 3R3SFC SF H
37 Schroder T urner R3IC RH S F C S F E
38 Quasi combined R3IC RH S F C S F HE
39 Rankine w/ Reheat RH
40 Rankine w/ ejector SF C SF H
41 CP OC IC
42 T CO IC RH
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1Simple Recuperated R1T opping
2Simple Recuperated +RH +I C R1IC RH T opping
3Recompression R2SF C Topping
4P artial Cool ing R2IC SF C T opping
5P artial Cool ing +RH R2IC RH SF C T opping
6sCO 2ORC I I R3SFC Topping
7sCO 2ORC I II R3SF C Topping
8sCO 2ORC I V R3IC S F C SF H T opping
9Brayton Simple B ottoming
10 iso Brayton Simple B ottoming
11 Simple Recuperated R1Bottoming
12 Hot Day R1IC B ottoming
13 P reheating R1SF H Bottoming
14 T riple Heating R1S F H Bottoming
15 Dual Expansion R1SF HE Bottoming
16 Combined Recompression and P reheating R1SF C SF H Bottoming
17 P recompression R2I C Bottoming
18 Recompression R2SF C Bottoming
19 P artial Recuperation R2S F HE Bottoming
20 Cascade I R2SF H E B ottoming
21 Cascade I I R2SF H E B ottoming
22 Dual Stage R2SF H E B ottoming
23 Cascade I +I C R2IC S F HE Bottoming
24 Cascade I I +IC R2I C SF H E Bottoming
25 Composite Bottoming II R2SF C SF HE Bottoming
26 Composite Bottoming II I R2SF C SF H E Bottoming
27 Cascade I II R2IC S F H SF HE Bottoming
28 T hree S tage R3SF H E B ottoming
29 Bottoming recompression with Reheat R3RH SF C Bottoming
30 Composite Bottoming I R3SF C SF H E Bottoming
31 Composite Bottoming IV R3RH SF C SF H E Bottoming
32 Simple Recuperated +Recompression R1+(R2SF C )Bottoming
33 Recompression +P reheating (R2SF C)+(R1S F H)B ottoming
34 P recompression +P reheating (R2IC)+(R1S F H)B ottoming
35 sCO2+T C O2R1 + Simple Bottoming
36 RCO2 + T C O2 (R2S F C) + S imple T opping +B ottoming
37 P eregrine T urbine Simple Nested
38 Recuperated P eregrine T ur bine R1SF H N ested
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Pmin Tmin Pmax Tmax ηth
1Simple Recuperated
2T ranscritical CO 2
3Hot day
4Allam
5Intercooling II
6Brayton CO2GT
7Reheating II
8Split E xpansion
9Matiant
10 Allam +RH
11 F orcedC ooler
12 DEM O
13 P reheating
14 SEJ
15 Inter Recuperated
16 Recompression
17 BAS
18 P recompression
19 Recuperated C P OC
20 P artial Cooling
21 Intercooling I
22 Reheating I
23 Double Reheated Recompression
24 Driscoll
25 REC 2
26 T urbine S plit F l ow I
27 T urbine S plit F l ow I I
28 T urbine S plit F l ow I II
29 RC EJ
30 Recompression +IC +RH
31 P artial Cooling +RH
32 MC EJ
33 Double Recompression
34 P artial Cooling w/ I mproved Recup.
35 Cascade not declared
36 REC 3
37 Schroder T ur ner
38 Quasi combined
39 Rankine w/ Reheat
40 Rankine w/ ej ector
41 CP O C
42 T CO
P[M P a]T[C]
sCO2Pmin Tmin Pmax Tmax ηth,sC O2ηth,overall
1Simple Recuper ated T opp. ORC
2Simple Recuper ated +RH +IC T opp. ORC n.d.
3Recompression T opp. ORC
4P artial C ooling T opp. O RC 49.7 52.3
5P artial C ooling +RH T opp. ORC n.d.
6sCO2ORC I I T opp. ORC
7sCO2ORC I II Topp. ORC
8sCO2ORC I V T opp. ORC
9Brayton Bott. ST n.d. 41
10 iso Brayton B ott. GT n.d.
11(a)Simple Recuperated Bott. GT n.d.
11(b)Simple Recuper ated B ott. MC F C
12 Hot Day Bott. GT n.d.
13 P reheating B ott. GT
14 T riple H eating Bott. GT n.d.
15 Dual Expansion Bott. GT n.d.
16 Combined Recompr. and P reh. Bott. GT n.d. n.d.
17 P recompression B ott. GT n.d.
18(a)Recompression B ott. GT
18(b)Recompression B ott. MC F C
19 P artial Recuperation Bott. GT n.d.
20 Cascade I B ott. GT n.d.
21 Cascade I I B ott. GT n.d.
22 Dual Stage B ott. GT n.d.
23 Cascade I +I C Bott. GT n.d.
24 Cascade I I +IC Bott. GT n.d.
25 Composite Bott. II Bott. GT
26 Composite Bott. III B ott. GT
27 Cascade I II Bott. GT n.d.
28 T hree S tage Bott. GT
29 Bott. Recompr. w/ RH Bott. GT
30 Composite Bott. I Bott. GT
31 Composite Bott. IV Bott. GT
32 Simple Recuperated +Recompr. Bott. GT
33 Recompression +P reheating Bott. GT
34 P recompression +P reheating B ott. GT
35 sCO2T C O2Bott. M CF C
36 RCO2 + T C O2T opp. +Bott.
37 P eregrine T ur bine Nes. GT n.d.
38 Recuperated P eregr ine T urbine Nes. GT n.d.
P[M P a]T[C]
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... The recompression Brayton cycle is shown in Figure 1. To select suitable supercritical cycle structures, a lot of research was carried out during the period, with over 40 structures studied [5]. In 2015, Sulaiman's research found that a system with a re-compressor has advanced performance compared to the simple system, regeneration system, pre-compression system, partial cooling system, segmented expansion system, and other structures [6]. ...
... The recompression Brayton cycle is shown in Figure 1. To select suit supercritical cycle structures, a lot of research was carried out during the period, with 40 structures studied [5]. In 2015, Sulaiman's research found that a system with a re-c pressor has advanced performance compared to the simple system, regeneration sys pre-compression system, partial cooling system, segmented expansion system, and o structures [6]. ...
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Detailed thermodynamic, exergoeconomic, and multi-objective analysis are performed for a supercritical recompression Brayton cycle in which the advanced working medium mixture of nitrous oxide and helium (N2O–He) is utilized for power generation. The thermodynamic and exergoeconomic models are propitious based on the standard components’ mass and energy conservation, exergy balance equation, and exergy cost calculation equation. An investigation of the sensitivity parametric is considered for judging the impact of crucial decision variable parameters on the performance of the proposed Brayton cycle. The proposed cycle’s performance is evaluated by systematic analysis of the thermal efficiency (ηth), exergy efficiency (ηex), total cost rate (C.total), levelized cost of electricity (LCOE), and the total heat transfer area (Atotal). Furthermore, multi-objective optimization is adopted from the viewpoint of the first and second laws of exergoeconomics to find the optimum operating parameters and to improve the circular’s exergoeconomic performance. The final results illustrate that the optimization calculation is based on the fact of the exergoeconomics method; the whole system produces electrical power of 0.277 MW with C.total of USD 18.37/h, while the ηth, ηex, Atotal, and LCOE are 49.14%, 67.29%, 165.55 m2 and USD 0.0196/kWh, respectively. It is concluded that the work exergy destruction for the reactor and turbine is higher than that of other components; then, after the multi-objective optimization analysis, the ηth and ηex improved by 2.08% and 5.07%, respectively, and the C.total, Atotal, and LCOE decreased by 13.99%, 0.01%, and 5.13%, respectively.
... Figure 7 shows the plant layout of a recompression s-CO2 power cycle coupled with a solar particle receiver. The recompression s-CO2 plant layout was chosen due to its simplicity and reasonably good efficiency [21,35]. This cycle is highly recuperative and consists of a low-temperature (LTR) and high-temperature heat exchanger (HTR). ...
... Figure 7 shows the plant layout of a recompression s-CO 2 power cycle coupled with a solar particle receiver. The recompression s-CO 2 plant layout was chosen due to its simplicity and reasonably good efficiency [21,35]. This cycle is highly recuperative and consists of a low-temperature (LTR) and high-temperature heat exchanger (HTR). ...
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This paper investigates and compares several highly efficient thermodynamic cycles that are suitable for coupling with particle-in-tube fluidized-bed solar receiver technology. In such a receiver, high-temperature particles are used as both a heat transfer fluid and a storage medium. A dense particle suspension (DPS) is created through an upward bubbling fluidized-bed (UBFB) flow inside the receiver tubes, which constitutes the “particle-in-tube” solar receiver concept. Reaching higher temperatures is seen as a key factor for future cost reductions in the solar plant, as this leads to both higher power conversion efficiency and increased energy storage density. Three advanced thermodynamic cycles are analyzed in this work: the supercritical steam Rankine cycle (s-steam), supercritical carbon dioxide cycle (s-CO2) and integrated solar combined cycle (ISCC). For each one, 100% solar contribution, which is considered the total thermal input to the power cycle, can be satisfied by the solar particle receiver. The main findings show that the s-CO2 cycle is the most suitable thermodynamic cycle for the DPS solar plant, exhibiting a net cycle efficiency above 50% for a moderate temperature range (680–730 °C). For the other advanced power cycles, 45.35% net efficiency can be achieved for the s-steam case, while the efficiency of the ISCC configuration is limited to 45.23% for the solar-only operation mode.
... Supercritical carbon dioxide (sCO 2 ) is used in a wide range of industries [1][2][3] for refrigeration [4], power generation [5][6][7][8][9], and thermal management [10]. Near its critical point (P ¼ 7.38 MPa and T ¼ 31.0 ...
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An exhaustive review was undertaken to assemble all available correlations for supercrit-ical CO 2 in straight, round tubes of any orientation, with special attention paid to how the wildly varying fluid properties near the critical point are handled. The assemblage of correlations, along with subsequent discussion, is presented from a historical perspective , starting from pioneering work on the topic in the 1950s to the modern day. Despite the growing sophistication of sCO 2 heat transfer correlations, modern correlations are still only generally applicable over a relatively small range of operating conditions, and there has not been a substantial increase in predictive capabilities. Recently, researchers have turned to machine learning as a tool for next-generation heat transfer prediction. An overview of the state-of-the-art predicting sCO 2 heat transfer using machine learning methods, such as artificial neural networks, is also presented.
... Aerospace applications, and in particular liquid oxygen rocket engines and cooling systems, have largely promoted research on real gas flows. In recent decade, more attention has been focused on high-pressure combustion of reactants exhibiting real gas behaviour with regard not only to the renewed interest in space exploration, but also its application in electric power generation, as in advanced supercritical CO 2 gas turbine cycles (designed to operate at 300 bar) [1], organic Rankine cycles and diesel engines. In such applications, the flow can be far away from ideal thermodynamics and the different fluid behaviour has to be accounted for by means of real gas equations of state and specific models for molecular transport properties [2]. ...
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... When the residuals for all monitored variables in Eqs. (3) to (8) are less than 1×10 -6 , the numerical result is considered to be converged. ...
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The heat transfer and flow characteristics of supercritical CO2 (SCO2) in a vertical tube under axially and circumferentially non-uniform heat-flux conditions are numerically studied with average heat flux ranging from 150 kW·m-2 to 210 kW·m-2 and mass flux ranging from 400 kg·m-2 ·s-1 to 700 kg·m-2 ·s-1 , and the influences of buoyancy on the flow and heat transfer characteristics are evaluated. Compared with uniform heat-flux condition, SCO2 exhibits more complex flow and heat transfer performance under non-uniform heat-flux conditions. The non-uniform distribution of the axial heat flux leads to 1.2% to 20.5% increase in the overall heat transfer coefficient, while more serious local heat transfer deterioration is observed, and the fluid bulk temperature corresponding to the trough of the local bulk heat transfer coefficient is 1.6 K to 3.3 K higher than that under the axially uniform heating especially for the high mass flux. Reducing the heat flux and increasing Reynolds number could alleviate the local heat transfer deterioration. The buoyancy effect changes the flow structure, resulting in the difference of turbulence level near the wall and the development of the momentum and thermal boundary layer under non-uniform heat-flux conditions, which is closely related to the heat transfer behaviour of SCO2. Bo* could well predict the buoyancy effect in a vertical tube under different non-uniform heat-flux conditions. Compared with upward flow, downward flow could effectively alleviate heat transfer deterioration and reduce wall temperature gradient especially for axially non-uniform heat-flux condition. The present work could be helpful for the understanding of SCO2 heat transfer mechanism and provide guideline for the design and optimisation of supercritical fluids-based system and components. (J. Guo). 2 Key words: supercritical CO2 (SCO2), non-uniform heat-flux condition, buoyancy effect, numerical simulation, heat transfer, solar energy, heat exchanger. Nomenclature a acceleration, m· s-2 Bo * non-dimensional buoyancy parameter, cp specific heat at constant pressure, kJ· kg-1 ·K-1 D diameter, mm g gravity, m· s-2 G mass flux, kg· m-2 ·s-1 Gr * Grashof number h heat transfer coefficient, kW· m-2· K-1 H enthalpy kJ· kg-1 k turbulence kinetic energy, m 2 ·s-2 L heated length or distance from the position where heating starts, m P Pressure, MPa Pk production of turbulence energy, kg· m-1 ·s-3 Pr Prandtl number q heat flux, kW· m-2 r radial coordinate, mm R tube radius, mm Re inlet Reynolds number T temperature, K Tpc pseudocritical temperature, K v velocity, m· s-1 x, y, z x, y, z directions 3 y + non-dimensional distance from the wall Greek symbols  volume expansion coefficient, K-1  circumferential angle, degree  thermal conductivity, W· m-1 ·K-1  dynamic viscosity, Pa· s t turbulent viscosity, Pa· s  kinematic viscosity, m 2 ·s-1  density, kg· m-3  standard deviation of the Gaussian distribution  shear stress, Pa  energy dissipation, W· m-3
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Supercritical CO2 has important applications in the fields of power cycle generation systems and carbon capture, utilization and storage (CCUS). The venting equipment represents a fundamental pressure-relief method for the purpose of depressurizing sections of those systems for inspection, maintenance or repair. The extremely low temperatures, dry ice blockage and overpressurization will appear in the system due to the throttling and expansion effect during venting. Meanwhile, the released CO2 may cause the exposure for the high density gaseous CO2, solid CO2 particles and cryogenics to the people in the venting area. The study of flow characteristics during CO2 venting is absolutely essential for assessing the hazard probability of dry ice formation and the blockage of relief valves during emergency or routine operational venting. In this paper, the theoretical analysis and experimental tests were conducted to study the throttle and expansion characteristics through the elbow, valve and orifice during straight vertical venting of supercritical CO2 with a 258 m long, 233 mm inner diameter pipeline system. The pressures and temperatures inside the main pipe and vent pipe, and the temperatures near field region were recorded during venting. After the valve was opened, the pressure in the vent pipe rose rapidly, and the rising range decreased with the decrease of the distance from the orifice. The temperature drops of CO2 were obvious after supercritical CO2 passed through the bend, the valve and the orifice. The supercritical CO2 in the main pipe changed into gas-liquid two-phase, and the liquid CO2 were produced in the vent pipe due to the throttling expansion effect. The CO2 temperature near the orifice were in quasi steady state after reaching the lowest value due to the continuous vaporization of liquid-phase CO2 and sublimation of dry ice particles, accompanied by the air entrainment process.
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The excellent thermo-physical and chemical properties of CO2 suggest its employment as a working fluid in power sectors owing to several benefits over the steam cycle. The present review emphasizes the potential prospects of supercritical CO2 power cycles in terms of its current status and advancement of its components. This is continuing investigation towards the attainment of safe operation at such high working pressures and temperatures. Numerous studies on supercritical CO2 (sCO2) power cycles in various layouts (standalone and combined) are reported with the major findings applicable for different energy sectors. The current state art of the experimental facilities with CO2 power cycle working under trans-critical/supercritical states in various research institutes is elucidated. For initial commercialization, these facilities provide a pathway for operational demonstration and control strategies. The enhancement in thermo-hydraulic performance and effectiveness of recuperators demands the execution of innovative and advanced techniques in conventional recuperators. Printed circuit heat exchangers are considered to be the most pertinent recuperators which possess the inimitable properties of augmented efficiency, impressive against withstanding higher temperature/pressure and especially their ample performance during operating conditions despite the drastic variations in thermophysical properties of supercritical fluid. The improvement in thermo-hydraulic performance of conventional recuperators after incorporating the novel geometric configurations has been extensively reviewed in this study. Moreover, the impact of non-linear variation of thermodynamic properties of supercritical fluid on efficiency, performance and stability of turbomachineries (centrifugal compressor and gas turbines) has also been broadly demonstrated through the recent experimental and numerical investigations. This research article certainly will contribute towards the development of future power generation by clean energy technologies to subside the alarming energy crisis. This article will also contribute to the development of renewable and sustainable energy sectors.
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Concentrated Solar Power (CSP) is an electricity generation technology that concentrates solar irradiance through heliostats onto a small area, the receiver, where a heat transfer medium, currently a fluid (HTF), is used as heat carrier towards the heat storage and power block. It has been under the spotlight for a decade as one of the potential or promising renewable and sustainable energy technologies. Using gas/solid suspensions as heat transfer medium in CSP has been advocated for the first time in the 1980′s and this novel concept relies on its possible application throughout the full CSP plant, i.e., in heat harvesting, conveying, storage and re-use, where it offers major advantages in comparison with the common heat transfer fluids such as water/steam, thermal fluids or molten salt. Although the particle suspension has a lower heat capacity than molten salts, the particle-driven system can operate without temperature limitation (except for the maximum allowable wall temperature of the receiver tubes), and it can also operate with higher hot-cold temperature gradients. Suspension temperatures of over 800 °C can be tolerated and achieved, with additional high efficiency thermodynamic systems being applicable. The application of high temperature particulate heat carriers moreover expands the possible thermodynamic cycles from Rankine steam cycles to Brayton gas cycles and even to combined electricity generating cycles. This review paper deals with the development of the particle-driven CSP and assesses both its background fundamentals and its energy efficiency. Among the cited systems, batch and continuous operations with particle conveying loops are discussed. A short summary of relevant particle-related properties, and their use as heat transfer medium is included. Recent pilot plant experiments have demonstrated that a novel bubbling fluidized bed concept, the upflow bubbling fluidized bed (UBFB), recently adapted to use bubble rupture promoters and called dense upflow fluidized bed (DUFB), offers a considerable potential for use in a solar power tower plant for its excellent heat transfer at moderate to high receiver capacities. For all CSP applications with particle circulation, a major challenge remains the transfer of hot and colder particles among the different constituents of the CSP system (receiver to storage, power block and return loop to the top of the solar tower). Potential conveying modes are discussed and compared. Whereas in solar heat capture, bubbling fluidized beds, particle falling films, vortex and rotary furnaces, among others, seem appropriate, both moving beds and bubbling fluidized beds are recommended in the heat storage and re-use, and examined in the review. Common to all CSP applications are the thermodynamic cycles in the power block, where different secondary working fluids can be used to feed the turbines. These thermodynamic cycles are discussed in detail and the current or future most likely selections are presented. Since the use of a back up fuel is recommended for all CSP systems, the hybrid operation with the use of alternative fuel back-up is also included in the review. The review research is concluded by scale-up data and challenges, and provides a preliminary view into the prospects and the overall economy of the system. Market prospects for both novel concentrated solar power are expected to be excellent. Although the research provided lab- and pilot-scale based design methods and equations for the key unit operations of the novel solar power tower CSP concept, there is ample scope for future development of several topics, as finally recommended.
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The use of organic refrigerants or supercritical CO2 (sCO2) as a working fluid in closed loop power cycles has the potential to revolutionise power generation. Thermodynamic cycle efficiency can be improved by selecting bespoke working fluids that best suit a given combination of heat source and heat sink temperatures, but thermal efficiency can be maximised by pairing this with a custom made turbine. This work describes the development and design of a new 100kW thermal laboratory-scale test loop at the University of Queensland. The loop has capabilities for characterising both simple and recuperated refrigerant and sCO2 organic Rankine cycles in relation to overall cycle performance and for the experimental characterisation of radial inflow turbines. The aim of this facility is to generate high quality validation data and to gain new insight into overall loop performance, control operation, and loss mechanisms that prevail in all loop components, including radial turbines when operating with supercritical fluids. The paper describes the current test loop and provides details on the available test modes: an organic Rankine cycle mode, a closed loop Brayton cycle mode, and heat exchanger test mode and their respective operating ranges. The bespoke control and data acquisition system has been designed to ensure safe loop operation and shut down and to provide high quality measurement of signals from more than 60 sensors within the loop and test turbine. For each measurement, details of the uncertainty quantification in accordance with ASME standards are provided, ensuring data quality. Data from the commissioning of the facility is provided in this paper. This data confirms controlled operation of the loop and the ability to conduct both cycle characterisation tests and turbomachinery tests.
Conference Paper
At Sandia National Laboratories (SNL), The Nuclear Energy Systems Laboratory / Brayton Lab has been established to research and develop subsystems and demonstrate the viability of the closed Brayton cycles (CBC), and in particular, the recompression CBC. The ultimate objective of this program is to have a commercial-ready system available for small modular reactors. For this objective, R&D efforts must demonstrate that, among other things, component and the system behavior is understood and control is manageable, and system performance is predictable. Research activities that address these needs include investigating system responses to various anticipated perturbations, and demonstrating that component and system performance is understood. To these ends, this paper presents system response to a perturbation, and turbomachinery performance results during steady state operation. A long duration test, with an extensive period at steady state, was completed in the simple CBC configuration. During this period, a cooling perturbation was initiated. Data from this test are presented and evaluated to explain the sequence of events following the perturbation. It was found that a cascading series of events ensued, starting with the fluid condensing effect of the cooling perturbation. The explanation of events emphasizes the highly interactive and nonlinear nature of CBC’s. The comparisons of measured and predicted turbomachinery performance yielded excellent results and give confidence that the predictive methods originally envisioned for this system work well. Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
Conference Paper
As the demand to develop more efficient energy systems increases, ways to generate power from waste heat are under investigation. The supercritical carbon dioxide recovery cycle (S-CO2 cycle) has been considered a viable candidate as a bottoming cycle for “waste heat to power” (WHP) applications, such as the utilization of gas turbine outlet heat. One major limitation to the system is that the S-CO2 cycle operates at a low expansion ratio, which leads to a higher turbine outlet temperature. This waste heat should be recuperated in order for the overall cycle efficiency to increase. Such limitation leads to a larger recuperator, higher volume flow rate, lower temperature gradient at the heater, and more complex cycle layouts for WHP applications. These constraints ultimately lead to the increase of hardware costs, which can degrade economics of the system. To solve the existing problems regarding the use of S-CO2 cycle for WHP applications, the possibility of using an isothermal compressor in place of a conventional compressor in a simple Brayton cycle is investigated. This solution, named the iso-Brayton cycle, though the compressor technology is still under development, seems promising because it does not require an additional heat exchanger as one of the cycle components. Furthermore, the compressing work is minimized during an isothermal compression process. To analyze the cycle performance of the iso-Brayton cycle, it is compared with a reference cycle, the simple recuperated Brayton cycle. The parameters of cycle net efficiency and cycle net work (or net usable work) are calculated using the KAIST-CCD in-house code.
Conference Paper
Three supercritical carbon dioxide (CO2) power cycle experimental loops have been developed in Korea Institute of Energy Research (KIER) from 2013. As the first step, a 10 kWe-class simple un-recuperated Brayton power cycle experimental loop was designed and manufactured to test its feasibility. A 12.6 kWe hermetic turbine-alternator-compressor (TAC) unit which is composed of a centrifugal compressor, a radial turbine and the gas foil bearings was manufactured. The turbine inlet design temperature and pressure were 180 °C and 130 bar, respectively. Preliminary operation was successful at 30,000 RPM which all states of the cycle existed in the supercritical region. Second, a multi-purpose 1 kW-class test loop which operates as a transcritical cycle at a temperature of 200 °C was developed to concentrate on the characteristics of the cycle, control and stability issues of the cycle. A high-speed turbo-generator was developed which is composed of a radial turbine with a partial admission nozzle and the commercial oil-lubricated angular contact ball bearings. Finally, a 60 kWe-class Brayton cycle is being developed which is composed of two turbines and one compressor to utilize flue-gas waste heat. As the first phase of development, a turbo-generator which is composed of an axial turbine, a mechanical seal and the oil-lubricated tilting-pad bearings was designed and manufactured. Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
Article
Renewable energy technologies based on solar energy concentration are important alternatives to supply the rising energy demand in the world and to mitigate the negative environmental impact caused by the extensive use of fossil-fuels. In this work, a thermodynamic model based on energy and exergy analyses is developed to study the transient behavior of a Concentrated Solar Power (CSP) supercritical CO2 plant operating under different seasonal conditions. The system analyzed is composed of a central receiver, hot and cold thermal energy storage units, heat exchangers, a recuperator, and three-stage compression and expansion subsystems with intercoolers between compressors and reheaters between turbines, respectively. From the exergy analysis, the recuperator, the hot thermal energy storage, and the solar receiver were identified as the main sources for exergy destruction with more than 70.0% of the total lost work in the plant. These components offer an important potential to improve the system performance via design optimization. With reference parameters, the system reaches efficiencies of about 18.3%. These efficiencies are increased with a combination of improved design parameters, reaching values of between 26.0% and 29.4%, depending on the season, which are relatively good for CSP plants.