bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chloride Salt Systems for High Temperature Thermal Energy Storage: Properties and Applications
Authors: Myers Philip D. , Bhardwaj Abhinav , Goswami D. Yogi , Stefanakos Elias 
Published: October 2015

There is substantial potential to increase the operating temperatures of concentrating solar power (CSP) plants, thereby increasing the Carnot efficiency. Coupled with viable thermal energy storage (TES) strategies, this would bring us closer to achieving the goals of the U.S. Department of Energy Sunshot Initiative. Current TES media employ molten inorganic salts (namely, nitrate salts) for thermal storage, but they are limited in application to lower temperatures: generally, below 600°C. While sufficient for parabolic trough power plants, these materials are inadequate for use with the higher operating temperatures achievable in solar power tower-type CSP plants. For these higher temperatures, chloride salts are more ideal candidate storage media, either for sensible heat storage in the molten salt (e.g, a dual-tank storage arrangement) or for sensible and latent heat thermal energy storage (LHTES) as phase change materials (PCMs). Their melting points and those of their eutectic mixtures cover a broad range of potential operating temperatures, up to and including 800.7°C, the melting point of pure NaCl.
This paper examines these salt systems and presents relevant properties and potential applications in high temperature (>400°C) utility scale solar thermal power generation. A preliminary screening of pure chloride salts based on available literature yields a list of promising candidate salts. Eutectic mixtures of these salts are also considered; the eutectic systems were modeled using the thermodynamic database software, FactSage. Thermophysical properties (melting point, latent heat) are summarized for each salt system. Radiative properties are also addressed, since at these temperatures, thermal radiation can become a significant mode of heat transfer. Candidate containment materials and strategies are discussed, along with the attendant potential for corrosion. Finally, cost data for these systems are presented, allowing for meaningful comparison among these systems and other materials in the context of utility scale thermal energy storage units.
Performance of a Multi-Cell MgCl2/NH3 Thermo-Chemical Battery During Recharge and Operation
Authors: Udell Kent S. , Kekelia Bidzina , Fan Peng , Zhou Chengshang , Fang Zhigang 
Published: October 2015

The development of thermal energy storage technologies to match sustainable energy production is of interest. A prototype of a multi-cell thermochemical battery consisting of connected cells containing MgCl2 salt, and additional air-cooled or air-heated cells containing liquid ammonia of varying quality, was constructed and tested. Each of the 17 cells contained thermocouple probes at three different axial locations within the cylindrical cells. Heat transfer rates, pressures, and ammonia condensation and vaporization rates were measured.
Three tests were run. In the first test, the hot bed containing 10 cells was heated using cartridge heaters, driving vaporous ammonia from the salt phase once sufficient salt temperatures were reached. The evolved gaseous ammonia was condensed in an additional 7 empty air-cooled cells. Once the recharging cycle was complete, a valve in the ammonia vapor line connecting the cold and hot beds was closed, allowing indefinite storage of cooling or heating capacity. The second operational test involved the opening of the valve while simultaneous air-cooling the hot bed cells and air-heating the cold bed cells. Heating rates and cooling rates to/from air forced through the hot bed and cold bed, respectively, were monitored to gauge HVAC performance. The second recharge was performed by using a air/air heat exchanger that captured waste heat from an automobile engine exhaust manifold and transferred it to air that was re-circulated through the hot bed array. Temperatures, pressures, heating rates, cooling rates, and cell array heat transfer specifications are reported.
Measurement of Particulate Flow in Discrete Structure Particle Heating Receivers
Authors: Khayyat A. W. , Knott R. C. , Nguyen C. L. , Golob M. C. , Abdel-Khalik S. I. , Jeter S. M. , Al-Ansary H. A. 
Published: October 2015

Conventional central receiver power tower plants typically use steam or molten salts as the heat collection medium. Recently, attention has returned to using solid particulates in a particle-heating receiver (PHR). In this project we are interested in discrete structure PHR that includes structures, such as an array of wire mesh protrusions in our current design, to increase the residence time of particles falling through the receiver. The meshes should be sized to accommodate the falling particles without exposing too much mesh to concentrated radiation, which might degrade collection efficiency and expose the mesh material to high temperature thermal degradation. The experiment described in this paper was implemented to measure the appropriate exposed length of such discrete porous structures for a PHR.
Particulates are introduced to the model PHR from a perforated plate distributor. As detailed in the body of the paper, a laser and photosensor (responding in units of lux) are used at positions 546 mm and then 1111 mm downstream from the perforated plate to measure the transparency of the flow in a vertical plane across the receiver. The laser light forms a vertical sheet, and its intensity is measured by the photosensor on the opposite side of the receiver. By comparing the lux data with and without particles flowing, the transparency of the particulate curtain can be determined. Different mesh counts have been tested and compared, and plotted for comparison. This research is useful for designers to use when planning a PHR and will inform the proper length of wire meshes to use. This paper reports the results obtained so far including a standard error propagation analysis.
Acoustic Emission Minimization in a Wind Turbine Using Trip-Wires and Owl-Wing-Serrations
Authors: Madadnia Jafar , Nurdin Muhammad Fauzan 
Published: October 2015

Acoustic noises emitted from wind turbine blades should be reduced to an acceptable level for the uptake of wind energy in buildings and in the urban environment. This paper reports on effectiveness of, Owl-wing-serrations (OWS), two-dimensional trip-wires, and Active-noise-cancellation (ANC) in minimization of aerodynamic noises in a micro model turbine. The OWS and trip wires were attached to the blade leading edges and trailing edges in the wind turbine. The model was operated in the fan mode as a single row. Combined effects of OWS and ANC were also tested in a counter rotating double-row Fan. Air velocity (m/s), shaft-revolution (rpm); electric-power (W), amplitude of acoustic noise (dB) and its Centre frequency (CF in Hz) were measured at a reference location, for a number of spacing. Experimental results were plotted in the forms of dB vs. Tip Speed Ratio (TSR), dB vs. CF, and Efficiency or Coefficients of Performance COP vs. TSR.
It was noticed that
• In the single row operations, 3mm trip wires and OWS attached to blades have influenced on the emitted aerodynamic noises. OWS reduced dB and increased Cf more than the trip-wires. For example, at a fixed TSR, amplitude of noise (dB) decreased with trip wires or OWS with the lowest dB occurring with the OWS alone. At a fixed dB, Centre frequency (Cf) increased with the highest frequency Cf occurring with OWS alone. Minor changes in efficiency (COP) were noticed with the trip wires or Owl-wing serrations. It may suggest that larger eddies are converted into small turbulences with lower amplitudes and higher frequencies.
• Active-noise-cancellation (ANC) in the double row operation affected acoustic noises as spacing/gap between the counter-rotating rows changed. At a fixed TSR, dB decreased in the double row operations in comparison with the single-row operations, the reduction in dB increased at higher TSR. At a fixed dB, Centre frequency (Cf) increased by 100% with the highest frequency Cf occurring at the spacing of 50mm. Efficiency or COP decreased by 50% when ANC was implemented with a minor change due to spacing between rows.
• Combined effects of OWS and ANC were moderate comparing to ANC alone, reducing both dB and COP by around 35% while doubling Cf as compared to the single raw fan conditions. The minimum dB and maximum Cf occurred at the gap/spacing of 50mm. No significant change was noticed at COP with combined OWS and ANC.
Investigation of Gas Diffusion Layer Properties Using X-Ray Microtomography
Authors: Hasanpour Sadegh , Phillion Andre , Hoorfar Mina 
Published: October 2015

An essential part of proton exchange membrane fuel cells (PEMFCs) is the gas diffusion layer (GDL), which provides pathways for by-products to be removed from PEMFCs. One of the main properties of GDLs is porosity. The two widely used experimental methods for finding the porosity of GDLs are mercury intrusion porosimetry (MIP) and method of standard porosimetry (MSP). In addition to these methods, the porosity of GDLs can be calculated based on the high resolution 3D images that are acquired using X-ray microtomography (μXCT) as shown in recent studies (e.g., [7,12]). Despite the general success of using μXCT to measure GDL porosity, different porosity values have been reported for similar GDLs.
These variations are due to different assumptions made for determining the surface of the sample, and hence, its external dimensions. In this research, current methods used for calculating porosity of GDLs from μXCT images are discussed, and a new surface identification method based on a rolling ball algorithm is introduced. The main advantage of this new method is that variations in surface topology or roughness are taken into account when calculating porosity. The new method is not only applicable to GDLs, but can be applied to characterize a wide range of highly porous media.
Molten Carbonate Fuel Cells as Means for Post-Combustion CO2 Capture: Retrofitting Coal-Fired Steam Plants and Natural Gas-Fired Combined Cycles
Authors: Spinelli Maurizio , Campanari Stefano , Romano Matteo C. , Consonni Stefano , Kreutz Thomas G. , Ghezel-Ayagh Hossein , Jolly Stephen , Di Nitto Matthew 
Published: October 2015

The state-of-the-art conventional technology for post combustion capture of CO2 from fossil-fuelled power plants is based on chemical solvents, which requires substantial energy consumption for regeneration. Apromising alternative, available in the near future, is the application of Molten Carbonate Fuel Cells (MCFC) for CO2 separation from post-combustion flue gases. Previous studies related to this technology showed both high efficiency and high carbon capture rates, especially when the fuel cell is thermally integrated in the flue gas path of a natural gas-fired combined cycle or an integrated gasification combined cycle plant. This work compares the application of MCFC based CO2 separation process to pulverized coal fired steam cycles (PCC) and natural gas combined cycles (NGCC) as a ‘retrofit’ to the original power plant.
Mass and energy balances are calculated through detailed models for both power plants, with fuel cell behaviour simulated using a 0D model calibrated against manufacturers’ specifications and based on experimental measurements, specifically carried out to support this study. The resulting analysis includes a comparison of the energy efficiency and CO2 separation efficiency as well as an economic comparison of the cost of CO2 avoided under several economic scenarios. The proposed configurations reveal promising performance, exhibiting very competitive efficiency and economic metrics in comparison with conventional CO2 capture technologies. Application as a MCFC retrofit yields a very limited (<3%) decrease in efficiency for both power plants (PCC and NGCC), a strong reduction (>80%) in CO2 emission and a competitive cost for CO2 avoided (25–40 €/ton).
A One-Dimensional Modelling Approach for Planar Cylindrical Solid Oxide Fuel Cell
Authors: Marra Dario , Sorrentino Marco , Pianese Cesare , Mennella Antonio 
Published: October 2015

In this paper a 1-D steady-state model of a planar cylindrical Solid Oxide Fuel Cell (SOFC) is described. The SOFC 1-D model developed has been applied for both co-flow and counter-flow configurations. The computational domain selected is a symmetrical single cell slice with an angle of twenty degrees (i.e. one eighteen of the entire cell). The cell has been divided into computational units in the radial direction, for each of them energy, mass and electrochemical conservation equations have been solved. The cell is considered non-adiabatic with heat conduction inside the solid material and convective-radiative heat transfer mechanism between the outer section and the surrounding gases. Moreover, at the cell outlet the residual fuel mixes with the surrounding gases and is completely burnt (afterburning).
The 1-D model has been verified making use of literature data generated from 3-D model of a planar cylindrical SOFC. The results obtained confirmed the good performance of the model developed and its applicability in a computational framework for the development of either control or diagnosis algorithm.
Fuel-Cell and Electrolysis By-Product D2O Improves Third Way to Mitigate CO2
Authors: Schenewerk William Ernest 
Published: October 2015

Rapid atomic power deployment may be possible without using fast breeder reactors or making undue demands on uranium resource. Using by-product D2O and thorium-U233 in CANDU and RBMK piles may circumvent need for either fast breeder reactors or seawater uranium.
Atmospheric CO2 is presently increasing 2.25%/a (2.25 percent per year) in proportion to 2.25%/a exponential fossil fuel consumption increase. Roughly 1/3 anthropologic CO2 is removed by various CO2 sinks. CO2 removal is modeled as being proportional to 50-year-earlier CO2 amount above 280 ppm-C.
Water electrolysis produces roughly 0.1 kg-D20/kWa. Material balance assumes each electrolysis stage increases D2O bottoms concentration times 3. Except for first electrolysis stage, all water from hydrogen consumption is returned to electrolysis. D2O enrichment from water electrolysis is augmented by using the resulting Hydrogen and Oxygen in fuel cells. Condensate from hydrogen consumption returns to the appropriate electrolysis stage. Fuel cell condensate originally from reformed natural gas may augment second-stage feed.
Previously, recycling only hydrogen from combustion back to upper electrolysis stages allowed a 5%/a atomic power expansion. Using fuel-cells to augment upper-stage electrolysis enrichment increases atomic power expansion from 5%/a to 6%/a. Implementation of this process should start by 2020 to minimize peak atmospheric CO2 concentration to 850 ppm-C.
Atomic power expansion is 6%/a, giving 45000 GW by 2100. World primary energy increases at the historic rate of 2.25%/a, exceeding 4000 EJ-thermal/a by 2100. J-electric ∼ 3J-thermal. CO2 maximum is roughly 850 ppm-C around year 2100. CO2 declines back below 350 ppm-C by 2250 if the 50-year-delay seawater sink remains effective. The 15-year global temperature rise hiatus is apparently caused by convective heat transfer into seawater. Presumably convective CO2 transfer into seawater also occurs by the same mechanism. Each decade rapid atomic power expansion is delayed results in a 100 ppm increase in maximum atmospheric CO2 concentration. 50 TW dispatchable CSP (concentrated solar power), including 2 TWa storage, costs 1600 trillion USD and covers two Australias.
High Temperature Intrinsically Safe Nuclear Reactor
Authors: McDaniel Robin J. 
Published: October 2015

Small Modular Reactor (SMR) technologies have been recently included by the DOE as clean energy, a low carbondioxide emitting “alternative energy” source. The objective of this paper is to further the discussion of intrinsically safe nuclear reactors in the context of passive safety design principles and introduction of a novel conceptual reactor design. After a multiple year research study of past fast neutron reactor designs and recent reactor proposals, the following design is the result of analysis of the best concepts discovered.
An improved fast reactor of the liquid metal cooled type including a core configuration allowing for only two operational states, “Power” or “Rest”. The flow of the primary cooling fluid suspends the core in the “Power” state, with sufficient flow to remove the heat to an intermediate heat exchanger during normal operation. This design utilizes the force of gravity to shut down the reactor after any loss of coolant flow, either a controlled reactor shut down or a Loss of Coolant Accident (LOCA) event, as the core is controlled via dispersion of fuel elements. Electromagnetic pumps incorporating automatic safety electrical cut-offs are employed to shutdown the primary cooling system to disassemble the core to the “Rest” configuration due to a loss of secondary coolant or loss of ultimate heat sink. This design is a hybrid pool-loop pressurized high-temperature reactor unique in its use of a minimum number of components, utilizing no moving mechanical parts, no rotating seals, and no control rods.
This defines an elegantly simple Gen IV intrinsically safe nuclear reactor. [Advanced Small Modular Reactor (aSMR)]
Stator Cooling Water System Instrumentation
Authors: Bauer Thomas , Svoboda Mat , Chetwynd Russell J. 
Published: October 2015

Large turbo- and hydro-generators are directly cooled with high purity water for efficient heat transfer from the coils. Plant operators, engineers and chemists don’t get a lot of experience with troubleshooting, as operation can be trouble free for decades. However, when a problem arises, it can happen rapidly. The reason is often plugging of the stator cooling water system (SCWS) copper hollow conductors. This can result in forced outages or major generator failures and can occur within weeks — or years — after first indication. Thus, proper instrumentation will support plants to early detect a malfunctioning cooling water system and can provide sufficient time to take effective corrective actions.
The focus is on how both the SCWS and its internal instrumentation, along with enhanced monitoring techniques, can help facilitate a more proactive approach to manage corrosion effects such as hollow conductor plugging. Different basic OEM supplied instrumentation for both high- and low-oxygen systems are discussed and benefits thereof are outlined as well as “state-of-the-art” instrumentation is presented. Industry examples are demonstrating the benefit of proper instrumentation as early detection of copper oxide plugging prevented power plants from forced outages and costly rewinds. Subsequently, full cooling capacity was restored by online removal of the copper oxides.
Numerical Prediction of a Multistage Centrifugal Pump Performance With Stationary and Moving Mesh
Authors: Nocente Alessandro , Arslan Tufan , Nielsen Torbjørn K. 
Published: October 2015

The present work reviews a comparison between calculations of a steady and unsteady three dimensional (3D) flow past the diffuser channels of a centrifugal pump. The commercial software ANSYS Fluent has been used. The considered domain is one of the three stages, since each has exactly the same design.
In the first part, simulations are carried out at the best efficiency point (BEP) both steady and transient state, single phase flow and four different turbulence models. Results are compared with the performance report from the manufacturer. In the second part, only the realizable k-ε turbulence model has been taken into account. The simulations have been repeated for different mass flows and the results were again compared with the data from the manufacturer.
The comparison performed in the first part shows that integral quantities results are not sensibly influenced by the turbulence model. The comparison at different mass flow shows that the steady state simulations demonstrated to be a good approximation of the transient state, always containing the error within an acceptable limit. The minor computational effort needed makes it attractive to be used for further investigations which will involve two-phase flow studies on the same pump.
Increase of Operational Safety of Tilting-Pad Journal Bearings by Extraction of Hot Oil at the Trailing Edge
Authors: Kukla Sebastian , Buchhorn Nico , Bender Beate 
Published: October 2015

A theoretical study is presented with the main objective on the operational safety parameters (minimum film thickness and maximum pad temperature) and thermomechanical deformations of a ø500 mm rocker pad tilting-pad journal bearing (TPJB) for application in large turbo machinery. It can be described by the following specifications: Five pads, 0.23 nominal preload, 60% offset, 56° pad arc angle, 350 mm pad length and 1.28‰ relative bearing clearance. Theoretical investigations are carried out for circumferential speeds up to 78 m/s and static loads up to 3.60 MPa.
The simulation tool simultaneously solves both Reynolds and energy equations for the oil film (3D temperature distribution) on the one hand and computes thermomechanical deformations of the pad on the other hand. The simulations are conducted for a single pad and are supported by boundary conditions taken from experiments. The results with regard to static bearing characteristics and pad deformation show good agreement with experiments.
The impact of axial pad arching on operational safety parameters and load-carrying capacity are shown and compared to experimental results. It is shown that the axial deviation in film thickness Δh can be even higher than the minimum film thickness hmin. This leads to reduced hydrodynamic pressure build-up towards the axial edges and therefore significantly decreased safety parameters or load-carrying capacity.
In order to reduce pad crowning, radial bores through the pad body are modelled to simulate the extraction of hot oil from the trailing edge. In the simulation, the hot oil is used to heat up the back of the pad for a decrease of radial temperature gradients and thus pad arching. It is shown that by extracting 0.4 l/s of hot oil, a decrease in axial pad crowning from Δh = 47μm to Δh = 26μm can be achieved and that this leads to a decrease of 7.8 K in maximum temperature and an increase of 5 μm in minimum film thickness respectively a gain of load-carrying capacity of 0.4–0.6 MPa.