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Analysis of an evaporator with single horizontal circular micro-tube using FC-72 as working fluid for electronic cooling applications
No full textFlow boiling in micro-channels is one of the most efficient methods for heat rejection in electronics, necessitating proper system design. Numerical simulations are the most suitable tool for this purpose, with most literature focusing on CHF situations, while few studies address conditions bellow it. This paper presents a parametric analysis of an evaporator with a horizontal circular micro-tube, maintaining a fixed outlet quality, using numerical simulation. The simulation employs a one-dimensional steady-state model with FC-72 as the working fluid, considering both subcooled liquid and two-phase lengths, computed using theoretical equations and correlations. The effects of inner tube diameter, heat flux, inlet pressure, and subcooling level on key evaporator design parameters are discussed in detail. Results indicate that to minimize hydraulic pumping power, fluid temperature difference, and inlet temperature are required, the evaporator should operate with the lowest heat flux (50kW∙m-2), the largest inner tube diameter (1.3mm), the highest subcooling level (30K), and the lowest inlet pressure (2bar). Under these conditions, hydraulic pumping power can be reduced by up to 86%. Furthermore, to achieve the minimum fluid temperature difference along the tube (approximately 4.9K) and avoid CHF situation, operation with the lowest subcooling level (5K) is necessary. Finally, the ratio of the heat flux to the critical heat flux, q"/CHF, increases with rising inlet pressure and subcooling level, and/or decreasing inner tube diameter. The minimum q"/CHF ratio of 43.9% was obtained at pin=2bar, q"=50kW∙m-2, D=0.9mm, and ΔTsub=5K. These findings provide insights into optimal design parameters for evaporators in micro-electronics cooling applications
Chemistry and relevant thermophysical properties of Pb84.3Li15.7 liquid solutions: Updated view and identification of new and coherent values
Get PDFThe liquid breeding blanket concept of a fusion reactor is based on the employment of the eutectic Lead-Lithium solution (LLE), where Lithium, enriched in 6Li, has the purpose of regenerating Tritium by reacting with neutrons, while Lead enhances the process acting as neutrons multiplier. Anyway, despite the huge interest on this binary system, LLE is not characterized yet by a fully consolidated description of its basic thermophysical properties and, in many cases, the spread of values reported so far in literature remains still significant. The purpose of this paper is hence to check again the many data available in literature, with a special attention to the ones more recently published, trying to explain and solve their inhomogeneity. Taking into account the general features of the Pb-Li interaction and particularly the not ideal behaviour of the Pb-Li liquid solutions, the following thermophysical properties of the LLE are dealt in detail: specific heat; density and volumetric thermal expansion coefficient; thermal conductivity and diffusivity; electrical resistivity; Sieverts' constant of Hydrogen. Based on the deep analysis of all the reported experimentation and through the adoption of several comparison criteria, the most trustable correlation is sought for each of the above properties; additionally, when a robust correlation couldn't be retrieved, a new, optimized, one has been proposed, capable also to foresee correctly the effect of small composition variations and to assure the internal coherence among linked properties. Specific heat and density values resulted at the end accurately described and not needing for additional experimentation; thermal properties and electrical resistivity can be evaluated with decent confidence, even if their uncertainty could be somehow reduced by future investigations; for Sieverts' constant it has not possible yet to identify a unique, trustable correlation, anyway the range of values correctly assumed up to 900K has been significantly restricted
Measurements of jet quenching using semi-inclusive hadron+jet distributions in pp and central Pb-Pb collisions at sNN =5.02 TeV
Get PDFThe ALICE Collaboration reports measurements of the semi-inclusive distribution of charged-particle jets recoiling from a high transverse momentum (high pT) charged hadron, in pp and central Pb-Pb collisions at center-of-mass energy per nucleon-nucleon collision sNN=5.02 TeV. The large uncorrelated background in central Pb-Pb collisions is corrected using a data-driven statistical approach which enables precise measurement of recoil jet distributions over a broad range in pT,chjet and jet resolution parameter R. Recoil jet yields are reported for R=0.2, 0.4, and 0.5 in the range 7<140 GeV/c and π/2<Δφ<π, where Δφ is the azimuthal angular separation between hadron trigger and recoil jet. The low-pT,chjet reach of the measurement explores unique phase space for studying jet quenching, the interaction of jets with the quark-gluon plasma generated in high-energy nuclear collisions. Comparison of pT,chjet distributions from pp and central Pb-Pb collisions probes medium-induced jet energy loss and intra-jet broadening, while comparison of their acoplanarity distributions explores in-medium jet scattering and medium response. The measurements are compared to theoretical calculations incorporating jet quenching
Multiplicity dependence of charged-particle intra-jet properties in pp collisions at √s = 13 TeV
No full textThe first measurement of the multiplicity dependence of intra-jet properties of leading charged-particle jets in proton–proton (pp) collisions is reported. The mean charged-particle multiplicity and jet fragmentation distributions are measured in minimum-bias and high-multiplicity pp collisions at center-of-mass energy s = 13 TeV using the ALICE detector. Jets are reconstructed from charged particles produced in the midrapidity region (|η|<0.9) using the sequential recombination anti-kT algorithm with jet resolution parameters R = 0.2, 0.3, and 0.4 for the transverse momentum (pT) interval 5–110 GeV/c. The high-multiplicity events are selected by the forward V0 scintillator detectors. The mean charged-particle multiplicity inside the leading jet cone rises monotonically with increasing jet pT in qualitative agreement with previous measurements at lower energies. The distributions of jet fragmentation function variables zch and ξch are measured for different jet-pT intervals. Jet-pT independent fragmentation of leading jets is observed for wider jets except at high- and low-zch values. The observed “hump-backed plateau” structure in the ξch distribution indicates suppression of low-pT particles. In high-multiplicity events, an enhancement of the fragmentation probability of low-zch particles accompanied by a suppression of high-zch particles is observed compared to minimum-bias events. This behavior becomes more prominent for low-pT jets with larger jet radius. The results are compared with predictions of QCD-inspired event generators, PYTHIA 8 with Monash 2013 tune and EPOS LHC. It is found that PYTHIA 8 qualitatively reproduces the jet modification in high-multiplicity events except at high jet pT. These measurements provide important constraints to models of jet fragmentation
Nonlinear lower hybrid wave equations in collisional tokamak plasmas
Get PDFA new set of coupled integro-differential nonlinear lower hybrid (LH) wave equations is derived within the framework of a kinetic theory coupled to the Maxwell equations to study the parametric instabilities (PIs) produced by LH waves in collisional tokamak plasma. Previous models of nonlinear LH wave equations have been significantly improved. The wave equations derived overcome the limits and incorrectness of the standard theory of the PI in inhomogeneous plasma. They allow us to treat the full spectrum in the parallel and poloidal wavenumber of the coupled LH power wave, diffraction effects and possible cascade phenomena, which are elements of the nonlinear LH physics ignored in the standard PI theory. Numerical solutions of the new nonlinear LH wave equations are proposed. The relevant LH frequency spectra produced by PI are calculated, exhibiting characteristic features of PI observed in LH experiments. It is shown that the LH sideband amplification can be overestimated by orders of magnitude by the standard theory of PI. A benchmark of the new model is provided for spatially homogeneous plasmas. The role of the collisions for PI has been assessed. We demonstrate that previous analyses significantly overestimated their stabilization effect
Economic and Environmental Impact Analysis of Innovative Peeling Methods in the Tomato Processing Industry
Get PDFPeeling is a key step in the industrial production of canned peeled tomatoes, vital for optimizing efficiency, yield, product quality, waste reduction, and environmental impact. This study presents a comparative assessment of the economic and environmental impacts of adopting innovative peeling technologies, including infrared (IR), ohmic heating-assisted lye (OH-lye), and ultrasound-assisted lye (US-lye) peeling, relative to conventional steam and lye peeling methods. Focusing on a medium-sized Italian tomato processor, the impacts of these methods on productivity, water and energy consumption, wastewater generation, and environmental footprint using Life Cycle Assessment (LCA) methodology, were evaluated. Findings indicated that adopting IR, OH-lye, and US-lye methods enhanced peelability (ease of peeling > 4.5) and increased production capacity by 2.6–9.2%, while reducing solid waste by 16–52% compared to conventional steam and lye methods. LCA results showed IR as the most environmentally favorable method, followed by steam, OH-lye, and US-lye, with conventional lye peeling being the least sustainable. OH-lye and IR methods also significantly reduce water and energy use, while US-lye shows higher demands in these areas. Additionally, OH-lye and IR methods require little or no NaOH, minimizing chemical consumption and wastewater production, which offers notable environmental and cost advantages. Overall, this preliminary study underscores economic and environmental potential for novel peeling technologies, encouraging industry consideration for adoption
Self-assembled monolayers of reduced graphene oxide for robust 3D-printed supercapacitors
Get PDFHerein, additive manufacturing, which is extremely promising in different sectors, has been adopted in the electrical energy storage field to fabricate efficient materials for supercapacitor applications. In particular, Al2O3-, steel-, and Cu-based microparticles have been used for the realization of 3D self-assembling materials covered with reduced graphene oxide to be processed through additive manufacturing. Functionalization of the particles with amino groups and a subsequent "self-assembly" step with graphene oxide, which was contextually partially reduced to rGO, was carried out. To further improve the electrical conductivity and AM processability, the composites were coated with a polyaniline-dodecylbenzene sulfonic acid complex and further blended with PLA. Afterward, they were extruded in the form of filaments, printed through the fused deposition modeling technique, and assembled into symmetrical solid-state devices. Electrochemical tests showed a maximum mass capacitance of 163 F/g, a maximum energy density of 15 Wh/Kg at 10 A/g, as well as good durability (85% capacitance retention within 5000 cycles) proving the effectiveness of the preparation and the efficiency of the as-manufactured composites
Sviluppo e testing di un sistema WIM con sensori in fibra ottica FBG
Get PDFIn questo rapporto si presenta il lavoro svolto per lo sviluppo di un sistema WIM (weight-in-motion) finalizzato alla pesatura dinamica di veicoli pesanti, basato su piastre flettenti in acciaio strumentate con sensori in fibra ottica FBG (Fiber Gragg Grating). Il lavoro svolto ha considerato sia il design e la realizzazione del prototipo della struttura meccanica, sia lo sviluppo sistemistico del sistema di acquisizione e lo sviluppo integrale degli algoritmi di analisi dei dati. Per la realizzazione della struttura sono state eseguite preliminari attività di caratterizzazione dei componenti in laboratorio, mediante prove meccaniche e cicli di aging accelerato in camera climatica su provini in acciaio strumentati. In particolare, le misure di caratterizzazione hanno considerato il confronto comparativo fra sensori FBG con diversa tipologia di coating, al fine di determinare quella più appropriata con riferimento all’efficienza e durabilità della funzione di trasferimento della deformata dalla piastra al sensore. Per lo sviluppo degli algoritmi sono state implementate e comparate procedure di analisi implementabili a basso livello ed in tempo reale su microprocessore di modesta potenza di calcolo. In particolare, è stata definita ed ottimizzata la procedura di decodifica del segnale dei sensori FBG corrispondente al passaggio dei veicoli, con sviluppo dell’algoritmo più opportuno per la riduzione dell’errore nella determinazione del peso dinamico del veicolo in transito. Il sistema sviluppato è stato validato con la realizzazione di un sito dimostratore su sede stradale all’interno del C.R. ENEA Trisaia, eseguendo campagne di prove con transiti controllati di veicoli pesanti. I risultati hanno permesso di testare il sistema prototipale e di acquisire dati idonei alla definizione di interventi migliorativi per la realizzazione di sistema idoneo ad installazione su viabilità autostradale.This report presents the work carried out for the development of a WIM (weight-in-motion) system aimed at the dynamic weighing of heavy vehicles, based on steel bending plates instrumented with fiber optic sensors FBG (Fiber Gragg Grating). The work carried out considered both the design and the prototype realization of the mechanical structure, and the systemic development of the acquisition system and the integral development of data analysis algorithms. For the realization of the structure, preliminary characterization activities of the components were carried out in the laboratory, through mechanical tests and accelerated aging cycles in the climatic chamber on instrumented steel specimens. In particular, characterization measures considered the comparative comparison between FBG sensors with different coating types, to determine the most appropriate one for the efficiency and durability of the deformation transfer function from the plate to the sensor. For the development of algorithms procedures implementable at low-level and in real-time on microprocessors of modest computing power have been implemented and compared. In particular, the procedure to decode the signal of the FBG sensors corresponding to the passage of vehicles has been defined and optimized, with the development of the most appropriate algorithm for reducing the error in the determination of the dynamic weight of the vehicle in transit. The developed system has been validated with the realization of a demonstration site on the road inside the C.R. ENEA Trisaia, performing test campaigns with controlled transits of heavy vehicles. The results made it possible to test the prototype system and to acquire data suitable for the definition of improvements for the construction of a system suitable for installation on highways
Nuclear analyses for the integration of ITER equatorial Port 2
No full textThe present work is devoted to nuclear analyses in support of the ITER diagnostic Equatorial Port 2 (EP#2) integration. ITER EP #2 is a diagnostic port based on the long-modular Diagnostic Shielding Module (DSM) housing the following systems: Disruption Mitigation System (DMS) in DSM#1 and #3 and X-Ray Crystal Spectroscopy Core (XRCS-Core) in DSM#2. Ensuring adequate radiation shielding is a major challenge since the diagnostic systems require several apertures from the Vacuum Vessel (VV) through the Port Interspace (PI) and up to the Port Cell (PC). In the present study, a three-dimensional MCNP model of EP#2 has been developed, starting from the latest design available from Preliminary Design Review stage (PDR), and successively integrated into the reference 40° ITER C-Model. Comprehensive nuclear analyses have been carried out employing the D1SUNED v3.1.4 code based on the MCNP Monte Carlo transport code. Relevant nuclear quantities during and at the end of plasma operations have been evaluated: i.e., neutron and gamma fluxes and energy spectra along the port from the Diagnostic First Wall (DFW) up to the Bio-Shield Plug (BP), nuclear heating, neutron damage, helium and tritium production, and shutdown dose rate. This analysis allowed the identification of potentially critical areas, and therefore, the implementation of additional shielding options aimed at reducing the neutron streaming and mitigating of the radiation field in the PI region. In this work, the results of the analyses are presented and discussed. Some solutions to mitigate nuclear loads and to improve the shielding in PI area are proposed and their impact has been assessed. Finally, some recommendations for the optimization of the design of EP#2 are provided as well
International fuel performance study of fresh fuel experiments for PCMI effects during RIA experiments
No full textThis paper presents the results of High-burnup Experiments for Reactivity-initiated Accident (HERA) Modeling & Simulation (M&S) exercise. The HERA project under the Nuclear Energy Agency (NEA) Second Framework for Irradiation Experiments (FIDES-II) program is focused on studying Light Water Reactor (LWR) fuel behavior during Reactivity-Initiated Accident (RIA) conditions. The Part I M&S cases are based on a series of tests in the Transient Reactor Test (TREAT) facility in the United States and the Nuclear Safety Research Reactor (NSRR) in Japan. The purpose of this work is to evaluate the test design to accomplish its goals in establishing clearer understanding of the effects of power pulse width during RIA conditions. The blind predictions using various computational tools have been performed and compared amongst to interpret the behaviors of high burnup fuels during RIA. While many international participants evaluate the thermal–mechanical behavior of fuel rod under different conditions, a considerable scatter of outputs comes out for the cases due to the disparity between codes in predicting mechanical behaviors. In general, however, the results of thermal–mechanical analysis elaborate that nominal design conditions the shorter pulse width tests in NSRR should cause cladding failures while the TREAT tests appear to have more split prediction of failure or not. Furthermore, the sensitivity analysis varying key testing parameters reveals the considerable effect of power pulse width and total energy deposition on prediction of fuel rod failure