del Pozo, Carlos ArnaizAlvaro, Angel JimenezCasano, Juan Jose RoncalCloete, Schalk...
17页
查看更多>>摘要：Cryogenic air separation units (ASU) are the predominant method for delivering high-purity pressurized O2 at large capacities to relevant industrial processes。 This study presents an exergoeconomic assessment of the integration of two-phase expanders (TPE) in two ASU configurations with (1) intermediate liquid oxygen pumping followed by gaseous O2 compression and (2) total liquid oxygen pumping to the delivery pressure。 A comprehensive exergy analysis showed that TPE integration in the latter resulted in exergy efficiency increase of 1。1%-points and specific power consumption (SPC) reduction 15。5 kWh/ton (-4。4%)， while for the former， the exergy efficiency increase amounted to 1。8%-points with 17。9 kWh/ton (-5。2%) lower SPC。 A complete thermodynamic mapping for the different cases was presented。 From an economic perspective， total liquid pumping reached levelized cost of oxygen reductions of 1。68 euro/ton (-4。7%)， while in the configuration with gas compressors it was limited to only 0。45 euro/ton (-1。2%)， relative to analogous ASU configurations with JouleThomson valve expansion。 The total liquid pumping scheme with TPE presented a cost reduction of 4。3 euro/ton (-11。2%) relative to the gaseous O2 compression counterpart。 N2 by-product monetization can further improve the plant economic performance。 Based on this assessment， integration of reliable TPE technology for incremental efficiency gains of pressurized O2 production in ASUs presents a promising opportunity to profitably contribute to energy efficiency and decarbonization goals。
查看更多>>摘要：The deep-sea natural gas resources are safely and efficiently sent to the energy market through the offshore liquefied natural gas (LNG) industry chain， which provides a feasible idea for the utilization， development， storage and transportation of deep-sea natural gas fields。 The offshore LNG industry chain includes production equipment (LNG-FPSO， LNG Floating Production Storage and Offloading Unit， also known as FLNG) and receiving equipment (LNG-FSRU， LNG Floating Storage and Regasification Unit)。 Due to the influence of sea conditions， the key cryogenic heat exchangers in LNG-FPSO and LNG-FSRU have the problem of insufficient heat transfer caused by uneven distribution of multiphase flow， which affects the performance index of liquefaction and gasification process。 In this work， the visualization experimental device and numerical simulation model of falling film flow in LNG-FPSO and multiphase flow of intermediate medium in LNG-FSRU have been established， based on the sloshing platform system， camera and processing system， VOF two-phase flow model and dynamic grid technology。 The measures are put forward to improve the offshore adaptability of multiphase flow in offshore LNG industry chain。 When the anti-sloshing angle of the cover plate is 15 degrees， the liquid fluctuation index (FI) is small and the anti-sloshing resistance is good。 The optimal number of transverse anti-sloshing separators is 3， and the anti-sloshing partition number required for unit axial length is 7。5。
查看更多>>摘要：Self-regulating high temperature superconducting (HTS) flux pump is a promising candidate for realizing the quasi-persistent current mode operation of closed-loop HTS magnets。 To characterize its performance and optimize accordingly， in this work， we have established a model in Matlab/Simulink。 The effectiveness of the model has been validated based on the data obtained from the previous experimental counterpart。 The calculated results show that this model is able to reproduce the experimental results with a satisfactory agreement。 Based on the exploration of the model， we found that the charging performance of self-regulating HTS flux pump is mainly dependent on a range of typical design considerations， including the length of HTS bridge， the applied frequency of power source， the coupling coefficient of magnetic couplers， as well as the scale of HTS coils。 Additionally， we proved that the charging speed can be accelerated and the saturated load current will correspondingly increase with the appropriate system parameters。 The results obtained by this work provide some useful references for further optimization design of self-regulating HTS flux pump devices。
查看更多>>摘要：Under disturbances， superconductors may experience sudden， most undesirable phase transitions (quench) from superconducting to normal conducting state。 Quench may lead to damage or even to catastrophic conductor failure。 A superconductor is stable if it does not quench。 In this paper， superconductor stability provides a methodical background for numerical investigations of the time dependence of phase transitions。 Finite Element and Monte Carlo methods are applied to multi-filament， BSCCO 2223 and to thin film， coated YBaCuO 123 superconductors。 Focus is on (i) transient temperature distributions under multi-component internal heat transfer (solid conduction and， in thin films， radiation)， on (ii) a suggested operator method to solve the completeness problem of radiative transfer， and (iii) on time dependence of the order parameter obtained from a quantum-mechanical model。 Explanation of the localizability of disturbances and their impacts in thin films are additional problems。 These investigations shall contribute to improve understanding the physics behind the stability problem， in particular if under disturbances the material is already close to a phase transition。 Traditional stability models cannot provide this information。
查看更多>>摘要：Super-conducting cables are an enabling technology for energy applications such as large magnetic-confinement nuclear fusion machine， and a promising key player in the power transmission of the next future， both in AC and DC conditions。 While the thermal-hydraulic analysis of forced-flow superconducting cables for fusion application can only rely on commercial or proprietary numerical tools， such kind of tools for power transmission cables are not even available。 Within the framework of Open Science， set as a priority by the European Commission in Horizon Europe， the novel software OPEN Super Conducting Cables (OPENSC2) has been developed to grant the entire research community the possibility to simulate thermal-hydraulic transients in forced-flow superconducting cables for energy applications。 A Test-Driven Development has been adopted for the OPENSC2 within an object-oriented approach。 Following the TDD approach， three test cases are considered of paramount interest for the OPENSC2 development， deriving the set of characteristics that the target object-oriented tool should comply with， and namely: 1) a heat slug propagation along an ITER-like 2-region cable-in-conduit conductor， with a thousand of mm-size low-critical-temperature superconducting (LTS) strands， cooled by supercritical helium (SHe); 2) the heat diffusion across the cross section of a twisted-slotted-core cable-in-conduit conductor， with high-critical-temperature (HTS) superconducting tapes， for fusion application， cooled by SHe and 3) the nominal operation of a single-phase HTS High-voltage， Direct Current power cable， with a 2-cryostat configuration and 2 different fluids adopted as primary coolant and thermal shield。 In the object-oriented OPENSC(2 )the class "conductor " is defined， where each Conductor Object (CO) is the combination of different lower-level objects (both fluid and solid components) instantiated by the class。 The choice of each component drives the automatic selection of the appropriate physical equation(s) in the code， as well as the possible interactions between them。 Thermo-physical properties of different materials and cryogens can be attributed to the components of a conductor objects， taken form open datasets。 A user-friendly GUI allows setting and monitoring the simulations while running。 The software is tested in the three case studies targeted in the TDD， to show eventually how it allows modeling the three test cases presented here。 The Verification and Validation of the CO methods performed through benchmarks against the 4C code is also presented and discussed。
查看更多>>摘要：In the present study， corona inception voltage in liquid nitrogen under standard lightning impulse voltage (SLIV) and oscillatory impulse voltages were studied using fluorescent fiber sensor。 A single discharge signal is observed near the peak of the applied SLIV。 The amplitude of the fluorescent signal is high with positive polarity than under negative polarity。 At higher voltages， the magnitude of the fluorescence signal increases and it shifts towards the rising edge of the applied voltage。 Under unidirectional oscillatory impulse voltage (UOIV) and sinusoidal bidirectional oscillatory impulse voltage (SBOIV) conditions， Corona discharge occurs around the peak of the first cycle。 When the applied voltage is increased， the discharges occur in the subsequent cycles。 Under switching impulse voltage (SIV)， corona discharge is noticed at the rising edge in positive polarity， whereas in negative polarity， it is observed at the falling edge。 The corona discharge inception voltage (CDIV) is determined to be highest under Unidirectional Oscillating Lightning Impulse (UOLI) and lowest under SI。 The negative polarity exhibits more temporal spread than the positive polarity under oscillating impulse voltages。
查看更多>>摘要：A small-scale liquid helium cryogenic system has been designed for cooling the superconductive single-flux quantum circuits。 With a special double inner cylinders structure and a PID control system， automatic control of the liquid helium level could be achieved。 The cooling capacity recovered structure was added to the cold shield of the system in order to reduce the heat leakage of the system。 Besides， A special composite magnetic shielding structure was designed to ensure the circuits working in an extremely low magnetic environment。 Experiments were conducted to test the thermal performance and the magnetic shielding efficiency of the liquid helium cryogenic system。 The results show that the storage time of the liquid helium is about 2 days with about 110 coaxial cables and the magnetic flux density at the chip location is below 5 nT at the temperature of 4。2 K。
查看更多>>摘要：The single-screw extruder is used for the continuous formation of solid rod of hydrogen ice and its isotopes。 The extruded rod， further， requires to be cut into pellets and injected into the magnetically confined， hot plasma for the fuelling of long-pulse fusion reactors。 An extruder is capable to produce and continuously supply the pellets at a frequency of 1-40 Hz。 The design and development of a solid hydrogen screw-extruder system require a study of the visco-plastic behaviour of solid hydrogen and its effects on the pressure and speed of the extruder。 A CFD tool (Polyflow) from ANSYSTM is employed to estimate the characteristics of the pressure developed by the extruder at different rotational speed of the screw。 In the simulations， different Shear Stress Models developed by various researchers are implemented and the results of the same are investigated systematically for Single-Screw Hydrogen Extruder。 The results obtained from these simulations are validated with the experimental results on single screw extruder from literature。
查看更多>>摘要：SPIRAL2 is a superconducting LINAC subject to cryogenic thermoacoustic oscillations occurring in its valves boxes。 4 years of monitoring and experimental investigations with thousands of datasets turned these unwanted effects into an opportunity to study and understand thermoacoustics in a complex environment such as a real life accelerator。 Without digging deep into Rott's thermoacoustics theory， thoroughly shown in other works， this paper describes the instrumentation and the methods that prepare more advanced modeling of these phenomena either to damp or to harness the energy of cryogenic thermoacoustics。
查看更多>>摘要：The cryogenic sliding induced surface deformation and tribological behavior of TA2 pure titanium were investigated in the present work。 Friction and wear tests under dry sliding condition at room and cryogenic temperatures were conducted separately。 An external cryogenic device was designed to produce a steady cryogenic environment through liquid nitrogen during the sliding process。 Microstructure of subsurface under beneath the worn surface were detected by Optical Microscope (OM)， Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM)。 The results showed that sliding at room temperature induced a severe plastic deformation (up to 50 mu m in depth)， while the deformation layer was converted to a work-hardening layer (10 mu m) and a gradient microstructure was formed under cryogenic sliding condition。 Sliding at cryogenic temperature induced the formation of dislocation walls and alpha phase sub-grains， which hindered the dislocation motion during sliding process and was responsible for the decrease of plastic deformation。 Furthermore， the refinement of alpha phase grains in this hardening layer could be attributed to the strain accumulation and severe local deformation at cryogenic temperature。 With the effects of subsurface deformation， wear rate of TA2 samples was decreased by up to 66% under cryogenic sliding condition。 The wear mechanism followed the general characteristics of oxidation and adhesive wear under dry sliding wear condition at room temperature。 Under cryogenic sliding， a successive tribological behavior consisting of strain concentration， cracks generation and propagation， and fatigue fracture can be induced by the formation of work-hardening layer in the subsurface of the sample。
NSTL
Elsevier