bluuebunny/crossref_metadata_2025 huggingface dataset:
Circuit and systems architectures and performance evaluation of AMR magnetometers
Authors: Χατζηγεωργίου Νεοκλής
Published: July 2024

Τα μαγνητικά πεδία και η μέτρησή τους είναι ένα σημαντικό κομμάτι της ανθρώπινης εξέλιξης. Η πλοήγηση στις θάλασσες και στους ωκεανούς βασίστηκε για πολλά χρόνια στη μαγνητική πυξίδα. Από την άλλη οι μαγνητικοί τομογράφοι, ένα απαραίτητο εργαλείο για απεικόνιση των μαλακών ιστών στην ιατρική, βασίζονται στις διαφορετικές ιδιότητες του κάθε υλικού όταν αυτό εκτίθεται σε μαγνητικό πεδίο. Για τους πιο πάνω λόγους κρίθηκε σκόπιμο να εξεταστεί η δυνατότητα συνεισφοράς στον τομέα των μαγνητικών μετρήσεων και των μαγνητικών αισθητήρων. Στα πλαίσια συνεισφοράς στον τομέα μαγνητικών αισθητήρων επελέγη η τεχνολογία μαγνητικού αισθητήρα τύπου ανισοτροπικής μαγνητικής-αντίστασης AMR (Anisotropic Magneto-Resistor) για μια πληθώρα λόγων. Όμως οι δύο κύριοι λόγοι της πιο πάνω επιλογής είναι πρώτον το ότι οι αισθητήρες τύπου AMR έχουν συμπαγές μέγεθος και κατά δεύτερον ο τρόπος κατασκευής τους είναι συμβατός με την τεχνολογία κατασκευής ολοκληρωμένων κυκλωμάτων (IC). Επιπλέον, ο αισθητήρας τύπου AMR είναι διαθέσιμος σε διακριτή μορφή στο εμπόριο και χρησιμοποιείται ευρέως. Παρά την ευρεία χρήση του αισθητήρα τύπου AMR, φαίνεται ότι μέχρι στιγμής η συμπεριφορά του δεν είχε μελετηθεί εις βάθος. Για να καταλήξουμε στην επιλογή του αισθητήρα τύπου AMR έγινε πρώτα μια εκτενή βιβλιογραφική έρευνα καθώς και μελέτη άλλων τεχνολογιών αισθητήρων που χρησιμοποιούνται για τη μέτρηση του μαγνητικού πεδίου. Για τις τεχνολογίες μαγνητικών αισθητήρων αφιερώθηκε ένα μεγάλο μέρος της βιβλιογραφικής ανασκόπησης. Το υπόλοιπο μέρος της αναφέρεται στα φυσικά φαινόμενα που διέπουν τη συμπεριφορά των μαγνητικών υλικών που χρησιμοποιούνται στους μαγνητικούς αισθητήρες.Η διδακτορική αυτή διατριβή εντρυφεί στη συμπεριφορά του αισθητήρα τύπου AMR. Ο αισθητήρας τύπου AMR που χρησιμοποιήθηκε είναι ο HMC100x (HMC1001 και HMC1002) της Honeywell. Για τη μελέτη της συμπεριφοράς του πιο πάνω αισθητήρα αναπτύχθηκαν διάφορα κυκλώματα και πειραματικές διατάξεις. Εξετάστηκε και χαρακτηρίστηκε η συμπεριφορά του αισθητήρα HMC100x σε συνεχόμενα μαγνητικά πεδία. Αναπτύχθηκε μαθηματικό και κυκλωματικό μοντέλο για τη συμπεριφορά του σε υψηλές συχνότητες, λόγω των προβλημάτων αστάθειας του κλειστού βρόχου σε υψηλές συχνότητες. Η αστάθεια αυτή οφείλεται στον τρόπο της επίπεδης κατασκευής του υπό μελέτη αισθητήρα AMR. Επιπλέον, εξετάσθηκε ο χρόνος απόκρισης του αισθητήρα σε παλμούς ρεύματος υψηλής συχνότητας. Οι παλμοί αυτοί χρησιμοποιούνταν για την επαναπόλωση του αισθητήρα. Στη συνέχεια, βασιζόμενοι στα προηγούμενα αποτελέσματα της μελέτης, αναπτύχθηκε μία νέα αρχιτεκτονική μέτρησης, η οποία έχει ως σκοπό τη βελτίωση της απόκρισης του εν λόγω αισθητήρα. Τέλος, αναπτύχθηκαν τρία κυκλώματα βασιζόμενα σε αυτήν τη νέα αρχιτεκτονική. Τα κυκλώματα αυτά επιβεβαίωσαν και πειραματικά τη σωστή και αποτελεσματική λειτουργία της νέας αρχιτεκτονικής στην απόκριση του αισθητήρα.
Μελέτη του σχηματισμού αναδυόμενων παραπροϊόντων απολύμανσης του νερού υπό την επίδραση της κλιματικής αλλαγής
Authors: Κοζάρη Αργυρή
Published: July 2024

Η κλιματική αλλαγή επιδρά στην ποσότητα και ποιότητα των υδάτινων πόρων. Η συνεχής αύξηση της θερμοκρασίας, η άνοδος της στάθμης της θάλασσας, οι εκτεταμένες περίοδοι ξηρασίας και οι ακραίες βροχοπτώσεις είναι κύριοι παράγοντες που επηρεάζουν τη διαθεσιμότητα και την ποιότητα των υδάτινων πόρων. Αυτά τα ακραία φαινόμενα οδηγούν στην αύξηση εξωτερικών και εσωτερικών πρόδρομων ενώσεων στις δεξαμενές νερού και κατά συνέπεια επηρεάζουν τον σχηματισμό παραπροϊόντων απολύμανσης (DBPs). Στόχος αυτής της διατριβής είναι η διερεύνηση του σχηματισμού αναδυόμενων DBPs (eDBPs) υπό συνθήκες που προκαλούνται από την κλιματική αλλαγή. Για το λόγο αυτό, επιλέχθηκαν τέσσερις διαφορετικές περιπτώσεις συνθηκών που επιφέρει η κλιματική αλλαγή σε επιφανειακά νερά: α) άνοδος της στάθμης της θάλασσας, β) επίδραση των έντονων βροχοπτώσεων που οδηγούν σε πλημμυρικά φαινόμενα, γ) αύξηση κυανοβακτηριακής μάζας στο επιφανειακό νερό και δ) εμπλουτισμός του επιφανειακού νερού με χουμικές ενώσεις. Οι ενώσεις-στόχοι ήταν αλογονοακετονιτρίλια (HANs), αλογονοακεταμίδια (HAcAms), αλογονονιτρομεθάνιο (TCNM) και αλογονομένες κετόνες (HKs). Η χλωρίωση και η χλωραμίνωση επιλέχθηκαν ως μέθοδοι απολύμανσης υπό διαφορετικές δόσεις (5 και 10 mg/L) και χρόνους επαφής (24 και 72 ώρες). Τα αποτελέσματα έδειξαν αύξηση στον σχηματισμό των eDBPs και αλλαγές στο προφίλ τους. Η άνοδος της στάθμης της θάλασσας οδήγησε σε αυξημένες συγκεντρώσεις βρωμιωμένων ειδών. Τα πλημμυρικά φαινόμενα οδήγησαν σε εκτεταμένο σχηματισμό του χλωροακεταμιδίου και του βρωμοχλωροακετονιτριλίου. Η αύξηση κυανοβακτηριακής μάζας ενίσχυσε το σχηματισμό των HAcAms και του TCNM, ενώ ο εμπλουτισμός του νερού από χουμικές ενώσεις οδήγησε σε εκτεταμένο σχηματισμό των HANs. Παράλληλα, παρατηρήθηκαν αλλαγές στην κυτταροτοξικότητα και τη γονιδιοτοξικότητα των δειγμάτων. Χρησιμοποιώντας τα δεδομένα που προέκυψαν από τις παραπάνω πειραματικές διαδικασίες, αναπτύχθηκαν γραμμικά και μη γραμμικά μοντέλα πρόβλεψης σχηματισμού για τα εξεταζόμενα παραπροϊόντα χλωρίωσης λαμβάνοντας υπόψη ως ανεξάρτητες μεταβλητές τις φυσικοχημικές παραμέτρους του νερού και τις συνθήκες χλωρίωσης. Επίσης στο πλαίσιο της διατριβής, πραγματοποιήθηκαν αναλύσεις για τον έλεγχο της παρουσίας των εξεταξόμενων eDBPs σε δείγματα πόσιμου νερού στο πολεοδομικό συγκρότημα της Θεσσαλονίκης για δύο χρονικές περιόδους (χειμερινή – θερινή) και εκτιμήθηκε η συνεισφορά τους στην τοξικότητα σε σχέση με τα θεσμοθετημένα ΤΗΜs.
Novel Deep Learning Application: Recognizing Inconsistent Characters on Pharmaceutical Packaging
Authors: Koponen Jarmo , Haataja Keijo , Toivanen Pekka
Published: July 2024

Background Machine vision faces significant challenges when applied to text recognition on cardboard packaging particularly due to multiple printing methods, irregular character shapes, and curved packaging surfaces. Methods This research introduces a novel deep learning application for recognizing binarized expiration date and batch code characters printed using multiple printing methods. The method, based on Region-based Convolutional Neural Networks (R-CNN), enables character recognition directly from in the images without the need for extracting handcrafted features. In detail, this approach performs character recognition by using the whole image as input, extracting and learning salient character features directly from the packaging surface images. Results The R-CNN model, with a precision of 91.1% and an F1 score of 80.9%, effectively recognizes manufacturing markings on pharmaceutical packages, with inconsistencies in the characters’ shapes. In a comparative experiment using the same dataset of images, the R-CNN model significantly outperformed Tesseract OCR, achieving much higher precision, recall, and F1 scores. Conclusions The results of this study reveal that the deep learning method outperforms the well-established optical character recognition method in recognizing text characters printed with different printing methods. Presented in this study, the deep learning method recognizes text characters with high precision. It is also suitable for recognizing text printed on curved surfaces, provided proper preprocessing is applied. The problem investigated in the study differs from previous research in the field, focusing on the recognition of texts printed with different printing methods. The research thus fills a gap in text recognition that existed in the research of the field. Furthermore, the study presents new ideas that will be utilized in our future research.
A review on the phytochemistry and biological activities of Curculigo latifolia Dryand ex. W.Aiton
Authors: Taufik Amanina Yusrina , Mohd Yasin Hartini , Ahmad Norhayati , Arai Masayoshi , Ja'afar Fairuzeta
Published: July 2024

Curculigo latifolia Dryand. ex W. T. Aiton, from the genus Curculigo, is a medicinal plant traditionally used to treat numerous illnesses such as fever, stomach aches, jaundice, wounds, and inflammation. C. latifolia is a perennial herb that is widely found in tropical and subtropical regions, such as Southeast Asia, Southern China, Bangladesh, Australia, and the Andaman Islands. This review collates the reported studies on the different aspects of C. latifolia from its plant description, nutritional value, phytochemistry, chemical composition, and pharmacological properties. This review aims to identify gaps in the literature and provide useful references for future work on this plant. Previous studies have shown that C. latifolia contains high mineral contents of calcium, iron, and magnesium, which are essential components of human health. Moreover, the plant is rich in phytochemicals, which play a prominent role in various pharmacological activities. The most common compounds identified included curculigoside, crassifoside I, nyasicoside, and curculigine. C. latifolia demonstrated high antioxidant activity through its ability to scavenge superoxide anions, 1,1–diphenyl–2–picrylhydrazyl (DPPH) and 2,2’-azino–bis(3–ethylbenzthiazoline–6–sulfonic acid) (ABTS) radicals, reducing ferric ions to ferrous complexes, iron chelation, and β –carotene bleaching. It was also shown that the roots, stems, and leaves of C. latifolia were effective in exerting antimicrobial activity against several microbial strains, including Bacillus cereus, Bacillus subtillis, Enterobacter aerogenes, Erwinia sp., Klebsiella sp., Pseudomonas sp., Candida albicans, Salmonella choleraesuis and Staphylococcus aureus. Moreover, the root, fruit, leaf, petiole, and rhizome extracts were found to improve glucose uptake and insulin secretion in diabetic rats, suggesting their antidiabetic potential. C. latifolia presents a wide range of medicinal properties that could make it a promising functional food or source of food supplements to prevent nutrition–related or chronic diseases.
Sacubitril with valsartan, a modern pharmacotherapy in heart failure - a literature review
Authors: Sadłowski Bartosz , Bieganek Paula , Łukaszewicz Stanisław , Pawłowski Piotr , Rybak Julia , Kordialik Jakub , Koćwin Julia , Sarnacka Sandra , Tokarski Michał , Banasiak Angelika
Published: July 2024

Introduction and purpose: Heart failure is one of the most common cardiovascular diseases worldwide. It is an important factor leading to a reduced, health-related quality of life (HRQoL) not only because of its various symptoms but also due to loss of jobs or increase in medical expenses impairing the socioeconomic status of the sick. Nowadays scientists face this problem and are trying to invent specific pharmacotherapy that allows it to extend life and improve its quality. One of the elements of modern pharmacotherapy is the combination of sacubitril with valsartan. This work aims to evaluate the effect of this drug on the length and quality of life of patients with heart failure.Materials and methods: This article is a literature review based on publications from PubMed, Cochrane Library, ClinicalKey released since 2014, keywords included: sacubitril/valsartan; angiotensin receptor–neprilysin inhibitor; ARNI; heart failure.The state of knowledge: The use of sacubitril/valsartan drugs is an established agent used to reduce the risk of death from any cause in all patients with heart failure with reduced ejection fraction, death from cardiovascular causes and the rate of hospitalization due to exacerbation of symptoms. Some study analyses also indicate the utility of using sacubitril/valsartan in HFmrEF and HFpEF to reduce the rate of cardiovascular events and hospitalization because of heart failure.Conclusions: The use of sacubitril/valsartan is recognized to improve prognosis in patients with HFrEF. Evidence supporting its efficacy in the subgroup of patients with mid-range and preserved ejection fraction is still insufficient and requires further investigation.
Potential for surplus-heat-to-power conversion in current and future aluminium production process with off-gas recycling
Authors: Bueie Jonas , Windfeldt Magnus , Andresen Trond
Published: July 2024

Increased utilization of industrial surplus heat can make significant contributions towards reaching energy efficiency and emissions reduction goals. The off-gas from metal production smelters can contain large amounts of thermal energy, and conversion to electric power often appears an enticing prospect. However, the practical potential for exploitation can be significantly reduced from plant processes that are designed considering surplus heat as a waste product to get rid of. This typically makes the heat accessible only at reduced temperatures. The HighEFF research centre for industrial energy efficiency has studied technologies, applications, and cases for surplus heat utilization since its start in 2016. Heat-to-power conversion has been explored in several cases provided by the partner industries from – among others – Norwegian aluminium manufacturers. Centre research activities also include novel production processes and modifications, which has side effects providing very different conditions and constraints for energy recovery. One such process modification is off-gas recirculation, mainly developed to increase concentration of CO2 in the off-gas to improve conditions for CO2 capture in the future, but which also will alter off-gas temperature and recoverable heat as a side effect. This could improve the potential for energy recovery. In this work, the potential for energy recovery is evaluated and compared in four cases – one representing a current aluminium process, and three future process scenarios with flue gas recycling. The simulated heat-to-power conversion is done by applying an organic Rankine cycle (ORC) optimization model to each case. The results indicate significant benefits to energy recovery in the recycling cases. In the case with the highest recycling rate and flue gas temperature, the potential for electric power production increases by 270 % compared to the present-day case. In addition, the reduced work of the main exhaust fans in the recycling cases brings further energy savings on the system level equivalent to 25–50 % of the ORC power output, further increasing overall energy efficiency. From this, some potential synergies between process design, heat-to-power, and thermal integration of other technologies such as CO2-capture are discussed.
COLD ENERGY RECOVERY IN LNG PLANTS WITH ORGANIC RANKINE CYCLE
Authors: Marchiori Gabriele , Giudici Marta , Ruffato Giorgia , Astolfi Marco
Published: July 2024

During the production phase, natural gas (NG) is compressed and chilled to liquid state (liquified natural gas, LNG) for sake of volume reduction, hence to ease transportation. Approximately, 500 kWh of electricity or mechanical power per ton of LNG is needed for LNG compression and refrigeration during the production phase, which makes cold energy exploitation interesting from a thermodynamics point of view. An effective way to harness the cold energy contained in LNG is through an Organic Rankine Cycle system. A Cold Energy Plant (CEP) is an efficient system based on ORC technology which regasifies liquified natural gas and converts the heat absorbed from sea water into electricity by recovering the valuable exergy content of LNG. This solution allows to produce electrical power onsite without any additional external fuel consumption and no emissions at stacks. The CEP is a lowmaintenance and cost-effective solution that can be efficiently applied in the LNG industry to increase energy efficiency and sustainability of operations. The CEP system designed by Exergy achieves high efficiency thanks to the use of the proprietary Exergy Radial Outflow Turbine combined with the Multilevel Condensation Cycle, maximizing the revenue from electricity production. This paper will outline the technical features of a CEP power plant and will present a case study based on a Liquified Natural Gas regassification system engineered to produce Nominal 4 MWe (4000 kWe) net electric power while simultaneously fulfilling the regasification of 180 ton/h (~1 MTPA) of LNG.
Selection of The Optimal Working Fluid in an Organic Rankine Cycle for Waste Heat Recovery Through Multi-Objective Optimization and Decision Making
Authors: Krishna Saha Bipul , Billah Messini El Mouatez , Haque Syed J , Bhat B Aneesh
Published: July 2024

In India, utilising low-temperature waste heat is crucial to improving energy efficiency. The regenerative organic Rankine cycle (ORC) process is a promising waste heat recovery technique in this study. Here, the thermodynamic behaviour of eight working fluids: Butane, Heptane, Hexane, Pentane, Cyclopentane, HexMDiSiloxn (MM), Benzene, and Toluene, was carefully examined. An elite Nondominated sorting genetic sorting algorithm (NSGA-II) was used in Multi-objective Optimization (MOO) to address the incongruent behaviour of thermodynamic performance (exergy efficiency) and economic performance (levelized energy cost, LEC). Every eight working fluids are the subject of MOO studies, and the resulting Pareto optimal fronts are created. Several advanced Pareto ranking techniques are taken into account to choose one ideal solution from the Pareto optimal front. These include Simple additive weighting (SAW), The technique for order of preference by similarity to deal Solution (TOPSIS), Grey relation analysis (GRA), and Multi-attributive border approximation area comparison (MABAC). The most economically advantageous working fluid is chosen using an explicit economic performance assessment index called the Static Investment Payback Period (SIPP). The results show that Pentane is the most economically advantageous working fluid with the shortest SIPP and a medium waste heat temperature range. The findings also imply that any working fluid can be used TOPSIS, SAW, GRA, and MABAC with entropy information considered in this study to recover low-temperature waste heat in the ORC.
DESIGN AND CONSTRUCTION OF A REVERSIBLE ORC TEST RIG FOR GEOTHERMAL CHP APPLICATIONS
Authors: Kaufmann Florian , Schifflechner Christopher , Wieland Christoph , Spliethoff Hartmut
Published: July 2024

for their ability to supply heat or electricity flexibly. While many publications focus on their application in Carnot batteries or domestic systems, geothermal applications got less attention. In geothermal combined heat and power plants, reversible ORCs offer the possibility to generate electricity in times of low heat demand and supply additional heat to a district heating network (DHN) in peak load times. In previous work, the authors showed that this increases plant utilisation and reduces the load of commonly used peak-load gas boilers. This work presents the design and construction of a fully reversible ORC test rig capable of flexible operation as ORC or high-temperature heat pump (HTHP). It extends the state of the art by design and construction of a test rig for experimental validation of a previously untested cycle layout for geothermal applications. The test rig is supplied by a 200 kW hot water heating circuit as a heat source and uses a fully reversible 20 kW twin-screw machine. A closed loop intermediate cooling circuit allows simulating a DHN with varying temperature levels and mass flows during HTHP operation. This paper provides insights into the design methodology and the test rig’s intended operating range and performance. Thus, the paper provides valuable insights for the research community regarding conceptual and experimental activities on reversible ORC systems. Moreover, an in-depth description of the constructed test rig, its components and instrumentation and finally the preliminary control concepts are given. Commissioning and first experimental results are expected in the year 2023.
SHAPE OPTIMIZATION OF A sCO2 CENTRIFUGAL COMPRESSOR STAGE
Authors: Romei Alessandro , Gaetani Paolo , Persico Giacomo
Published: July 2024

The design of a centrifugal compressor for supercritical carbon dioxide (sCO2) power cycle must account for non-ideal gas effects and the possible occurrence of two-phase flows. Shape optimization techniques combined with computational fluid-dynamic (CFD) simulations can produce optimized designs while inherently coping with the peculiar flow characteristics near the thermodynamic critical point. This work presents the first shape-optimization attempt of such non-conventional compressors. The compressor stage includes the impeller and the vaneless diffuser and starts the compression close to the critical point. The impeller blade angle distributions and meridional channel are parameterized with Bezier control points, which grant a local shape control within the optimization routine. The pinch of the vaneless diffuser is optimized as well. The validated CFD solver accounts for both non-ideal effects and two-phase homogeneous flows under the assumption of thermodynamic equilibrium and barotropic fluid. The constrained optimization problem is solved with genetic algorithms. To reduce the computational cost, surrogates for the objective function and constraints are trained over a limited number of CFD results. The surrogate accuracy is improved throughout the optimization process by adding optimal stage geometries to the initial training samples. The optimized geometry shows an appreciable efficiency increase (0.7 percentage points) while delivering the design pressure ratio. Although performing better in the design condition, the operating range of the compressor is altered by optimization. This finding leaves the door open for future optimizations that include both design and off-design operating points in the definition of the objective function and constraints.
ORC technology used in a Heat Removal System for Advanced Nuclear Power Plants
Authors: Lhermet Guillaume , Payebien Benoit , Tauveron Nicolas , Morin Franck
Published: July 2024

This work concerns the design of a specific passive system for an advanced pressurized water reactor (PWR). The system studied is based firstly on passive safety condensers, which are increasingly used in the design of advanced nuclear power plants. These condensers are typically immersed in large water tanks that serve as a heat sink. They are located at a sufficient height to ensure a natural twophase circulation mode. Such a heat removal system can be used for a relatively long period depending on the size of the tank. The present research is based on using a fraction of the energy stored in this volume of boiling water as a heat source for an organic Rankine cycle via an immersed heat exchanger. The electrical energy produced will power various critical components, complementing existing systems. Three unusual issues challenge the use of an ORC in this context: the nature of the hot source (boiling pool water), the low temperature of the hot source (100°C), and the requirement for system reliability and robustness. Apart from these three challenges, the usual constraints associated with ORC systems still exist: maximizing energy performance, using an environmentally friendly fluid and minimizing space requirements. An experimental test bench with a boiling water pool and an ORC with submerged evaporator was built to address the main questions. The first set of results shows the nominal operation of the coupling between the boiling water pool and the ORC when Novec649TM is used as working fluid. The reliability of the system is then studied through the investigation of the immersed evaporator and the implementation of a theoretical model. The theoretical model of the system will be used to scale the system.
Evaluation of the performance of an axial one-stage 10kW turbogenerator through experimental testing
Authors: Klimaszewski Piotr , Klonowicz Piotr , Witanowski Łukasz , Suchocki Tomasz , Lampart Piotr , Ihnatowicz Eugeniusz , Antczak Łukasz , Zaniewski Dawid , Jedrzejewski Łukasz
Published: July 2024

The paper describes the results of experimental research on a prototype one-stage turbo-generator with a nominal power of 10 kW and a rotational speed of 24 000 rpm. The expander at the Institute of Fluid- Flow Machinery, Polish Academy of Sciences was developed as part of the R&D project with Marani company. The unit construction consists of an overhanging rotor and shaft mounted on rolling bearings. The turbo-generator was tested on a specially constructed laboratory test stand in the first stage. Compressed air instead of refrigerant gas (R1233zd) was used. The test results converged with the parameters obtained using the RANS simulation. The convergence for the turbine mass flow was 97% of the value obtained in the CFD model, which is satisfactory. The power generated by the turbogenerator, which was compared at this stage, also achieved satisfactory convergence (95% to 97%) with the calculation model. These tests allowed determine the compliance of the adopted design assumptions and confirmed the correctness of the calculation tools used. The next stage of work was to examine the ORC unit in operating conditions. That stage was aimed at checking the correct work of the machine with the ORC system. The turbine achieved internal efficiency calculated from temperatures at a level slightly lower than that obtained from numerical calculations (total-to-static efficiency). The efficiency was equal to about 73%, and the difference between calculated and measured values do not exceed 0.25 pp. (percentage point). The electric efficiency was about 65% and a maximum electric power output of 6.8 kW was measured.
PERFORMANCE AND ECONOMIC ASSESSMENT OF A THERMALLY INTEGRATED REVERSIBLE HP/ORC CARNOT BATTERY APPLIED TO DATA CENTERS
Authors: Poletto Chiara ,   1,*, 1,  1,  ,, De Pascale Andrea , Ottaviano Saverio , Dumont Olivier , Ancona Maria Alessandra , Bianchi Michele
Published: July 2024

when the contribution of waste heat occurs, resulting in thermally integrated energy storages. In this context, since data centers (DCs) convert almost all the supplied electricity into recoverable waste heat, this work aims at investigating the convenience of integrating a reversible Organic Rankine Cycle (ORC)/Heat Pump (HP) Carnot battery with a DC fed by a photovoltaic power plant. For this purpose, a detailed semi-empirical off-design model of a CB is implemented in a rule-based control strategy to manage the ORC/HP operations in the integrated system. In case of renewable production surplus, the exceeding energy can be stored in the CB through the HP, which is thermally integrated with DC waste heat with the double advantage of operating with a higher coefficient of performance and of reducing the required cooling system power. The stored energy is reconverted through the ORC when the electric demand overcomes the renewable production. A sensitivity analysis varying the storage volume and the energy price has been performed to investigate the influence of such parameters on the integrated system performance. The thermal integration allows to reach roundtrip efficiencies around 37 %, although the very low operating temperatures. The CB intervention results to be economically convenient, especially when the average electricity price is high as it occurred during year 2022. The yearly additional gain, with a storage volume of 10 m3, is assessed to be around 8270 €, and the simple payback period is less than 10 years
Design and Modeling of a Demonstration-scale ORC Cycle for the Liquid Air Combined Cycle
Authors: Pryor Owen M. , Conlon William M. , Rimpel Aaron M. , Venetos Milton J
Published: July 2024

Energy storage is becoming an increasing focus for the future energy markets. One potential hybrid system for ling duration energy storage is the Liquid Air Combined Cycle (LACC). The LACC utilizes excess renewable energy to liquefy and store air during the charge cycle. During its discharge cycle, the system uses the exhaust heat from a conventional combustion turbine and an ORC bottoming cycle to vaporize and superheat the stored air that has been pressurized, which is subsequently expanded to atmosphere through a turbine. During the development of the cycle, it has been identified that the main technologies to advance the cycle are the ORC bottoming cycle machinery and the coupled operation between the liquified air subsystem and the ORC subsystem. This paper presents modeling and simulation of the LACC that involves ORC conditions that fall outside the operating regime of more common applications. Due to the low temperatures of liquified air, the ORC system operates on the order of -70°C for the pump, and the turbine has a pressure ratio around 40. The conceptual design of a demonstration system has been developed that focuses on these challenges in order to advance the overall system.
Pressure profile optimisation of a nozzle for wet-to-dry expansion
Authors: Ogrodniczak Pawel , Sayma Abdulnaser , White Martin T.
Published: July 2024

Wet-to-dry expansion within the nozzle guide vane of an ORC turbine has been proposed as a means to improve the power output of ORC systems for waste-heat recovery (< 250 °C). However, given the rapid fluid acceleration in the stator, the phases can develop significant velocity and temperature disparity due to the density difference and finite rate of interphase heat transfer. Since these factors can significantly affect the phase-change process, wet-to-dry nozzle design techniques must account for non-equilibrium effects. The first part of this paper aims to further validate a previously developed quasi-1D inviscid nozzle design tool that accounts for non-equilibrium effects. The interphase mass, momentum and energy exchange models have been updated using correlations better tailored to evaporating droplet flows, while the drag equation and vapour mass fraction definition have been updated. The validation is performed using nonequilibrium CFD simulations, which, unlike the design model, account for lateral flow variations, viscous and turbulence effects, and secondary momentum forces. The results showed that these effects delay the evaporation, with CFD-predicted outlet vapour mass fraction being about 10 to 15% smaller than predicted by the quasi-1D tool. However, the overall flow behaviour and phase-change pattern were in satisfactory agreement, justifying the use of the design tool for 1D optimisation. In the second part of the paper, the quasi-1D tool is coupled to a gradient-based optimiser to optimise the nozzle pressure profile and enhance evaporation of siloxane MM for expansions with inlet pressure ranging from 450 to 650 kPa, and inlet quality of 0.3. The design variables are the control points of a Bezier curve that defines the shape of the intended nozzle pressure profile. CFD simulations of the optimised geometries indicate a 5.5 to 6.6% increase in the outlet vapour mass fraction, which was raised from 84.9, 88.2 and 90.7% to 90.4, 94.8 and 97.2% for the 450, 550 and 650 kPa inlet pressures respectively. More abrupt expansion in the optimised nozzles resulted in the development of a shock and led to nozzle efficiency deterioration compared to the baseline. This emphasises the need for multi-objective optimisation, which will be conducted in future studies.
Thermodynamic modification of CO2-based combined cooling and power cycle with ejector
Authors: Zhang Yonghao , Shi Lingfeng , Shu Gequn
Published: July 2024

CO2-based combined cooling and power cycle (CCP) has received increasing attentions especially in scenarios with diversified energy desires for its excellent natural properties. In this paper, an ejector is introduced into a conventional CCP system to reduce exergy loss in refrigeration throttling. A refrigerated truck is selected as the typical application scenario. And the simulated results indicate that approximately 28% of the expansion work during throttling can be recovered by the ejector, concurrently saving 0.3kW and 0.7kW compression work with respect to 10.8kW and 6.5kW cooling load under the freezing and refrigeration conditions. To extend the application of CCP system in more general scenarios, the ejector based CCP system is further modified to suit single heat source conditions. Two modified ejector based CCP systems namely ME-CCP-I and ME-CCP-II are proposed to recover waste energy from the compressor discharge. The adaptations to various heat source and refrigerating temperature are comprehensively studied. And the results demonstrate the ME-CCP-II system will be more suitable for air-conditioning scenarios while the ME-CCP-I system is advanced in freezing scenarios. In addition, recovering waste energy from the compressor discharge contributes great to the total energy efficiency of the CCP system as well as the heat transfer in regeneration process. With the mass split ratio increased from 0.1 to 0.9, the total energy efficiency of the ME-CCP-I system can raise from 0.27 to 0.64 and the relative enhancement is ranging from 1.26% to 11.86% versus the baseline system. Meanwhile, the ME-CCP-I system can reduce 48.6% irreversible loss in the heat regeneration process versus the baseline one when the same amount of exhausted energy after expansion is recovered
SELECTION OF SUITABLE WORKING FLUID AND STORAGE MATERIAL FOR ORC COUPLED WITH THERMAL ENERGY STORAGE
Authors: Sowa Dawid , Daniarta Sindu , Kolasiński Piotr
Published: July 2024

Some low-temperature energy sources (e.g., waste or solar heat) tend to be intermittent, and the heat supply from such sources may fluctuate over time. This kind of heat could be utilized using organic Rankine cycle (ORC) to generate electricity. Moreover, the increase in their reliability may be possible thanks to the application of thermal energy storage (TES), in which surplus thermal energy may be accumulated in the storage material. This energy can then be used in these periods of time when the heat source is not available or its output is limited. In this way, energy generation may be levelled. In some cases, a wide range of operating conditions and a variety of working fluids that are used in ORC systems mean that the choice of TES material may be difficult, since there are several types of TES materials, and each analysed case can give different material selections. Because of that, optimizing TES that is connected to the ORC system can be an interesting scientific challenge. Therefore, the aim of this study is to present the selection of proper working fluid-TES material pairs for different working conditions applied to a model of the ORC system coupled with TES. Various configurations of the ORC-TES system were investigated, taking into account differences between latent and sensible TES, and both for simple and recuperated cycles. The results obtained show that the combination of ORC with TES is promising for application in intermittent and fluctuating heat sources.
DECISION-MAKING MATRIX FOR THE SELECTION OF MIXTURE IN ORC APPLICATION
Authors: Combaluzier William , Tauveron Nicolas , Beaughon Michel , Serafino Aldo
Published: July 2024

ORC is an established and affordable technology to convert efficiently low/medium grade thermal energy to power. The choice of the working fluid is critical to the performance of the ORC. The use of zeotropic mixtures as a cycle working fluid could lead to an efficiency enhancement, thanks to the nonisothermal phase change occurring at both the condenser and the evaporator. Therefore, there has been a growing interest for mixtures, which are often studied by the means of optimization algorithms or thermodynamic calculations that lead to interesting results (Bederna et al., 2021, Lecompte et al., 2014). This work proposes an alternative approach. A selection methodology is used to conduct a preliminary screening to optimize the mixture choice in accordance with the targeted objectives. This methodology is applied to study cyclopentane-based mixtures. For this purpose, a large list of criteria is considered to achieve improved safety, maximized performances, ORC using more environmentally friendly fluids and respecting heat exchangers sizing while following specific technical constraints. Among these criteria, the temperature glide should be carefully taken into account: indeed, it is directly linked to the fractionating risk, which must be prevented for the good functioning of the cycle. Performing this study prior to the classical energetic analysis reduces the risk of exploring mixtures of incompatible or irrelevant fluids. This whole analysis yields a decision-making matrix, gathering selection criteria, relevant properties, and cycle performances. By adapting the different threshold of these criteria, this methodology is adaptable to large-scale ORC applications.
Prediction of the ideal maximum operational temperature of hydrocarbon and HFCs as working fluids of organic Rankine cycle power plants based on transition state theory
Authors: Yu Wei , Liu Chao , Ban Xijie , Li Zhirong , Yan Tianlong
Published: July 2024

The use of organic working fluids in organic Rankine cycle (ORC) power plants may lead to thermal decomposition, which can negatively impact system performance and safety. Therefore, it is essential to determine the safe operating temperature range of the working fluids. In this paper, a simplified theoretical method based on the transition state theory is proposed to predict the ideal maximum operational temperature of working fluids. This method involves considering the initial decomposition reaction of the working fluids and calculating the total reaction rate of the initial decomposition using the transition state theory. By setting an acceptable decomposition rate, the ideal maximum operational temperature of the working fluid can be determined. Using this method, the total reaction rate constants of several typical hydrocarbon and hydrofluorocarbon working fluids, including n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, HFC-245fa, HFC-134a, HFC-125, HFC-236fa, HFC- 227ea, HFC-143a, and HFC-152a, were obtained in the temperature range of 300~700K. The predicted maximum operational temperatures were in good agreement with most experimental results. Furthermore, by analyzing the branch ratio of each initial decomposition path of these working fluids, it was found that C-C bond cleavage contributed mainly to the decomposition of hydrocarbons, while the removal of HF and C-C bond cleavage contributed mainly to the decomposition of HFCs. As the CC bond breakage paths and HF removal reaction paths have high branching ratios (>99%), only considering these reactions in the reaction rate calculation can greatly reduce the calculation cost without significantly impacting the prediction accuracy.
MAPPING THE TECHNO-ECONOMIC POTENTIAL OF NEXTGENERATION CSP PLANTS RUNNING ON TRANSCRITICAL CO2-BASED POWER CYCLES
Authors: Rodríguez-deArriba Pablo , Crespi Francesco , Pace Sara , Sánchez David
Published: July 2024

Although the thermodynamic potential of transcritical/supercritical CO2-based power cycles for next generation Concentrated Solar Power plants has been already confirmed in literature, further investigation to assess the actual feasibility of this technology from a techno-economic standpoint is needed. In fact, large uncertainty is found when it comes to the estimation of the CAPEX and OPEX of the power block, and the same can be said for the solar subsystem when high Turbine Inlet Temperatures are considered (>700 ºC). Bearing this in mind, this paper presents a methodology to map the techno-economic potential of nextgeneration Concentrated Solar Power plants running on CO2-based mixtures, with the final aim to identify the threshold (breakeven) costs of the main subsystems enabling a clear gain in terms of Levelised Cost of Electricity with respect to state-of-the-art steam-based CSP. Two different systems are studied which differ in the composition and peak temperature of the Heat Transfer Media: a SoA molten salts system operating at a TIT of 550 ºC (Gen I) and a solid particle system with TIT=700 ºC (Gen II). An integrated platform able to simulate all CSP plant subsystems and perform hourly calculations is built in Matlab employing Artificial Neural Networks to simulate the solar field, ensuring extremely high computational speed. To overcome the high uncertainty in terms of cost estimation, a two-step analysis is developed: firstly, the CAPEX of the entire plant is calculated assuming correlations from literature, except for the power block, whose estimate brings about the largest uncertainty. As a result, the minimum power block cost allowing a LCoE lower than a certain target is identified. Secondly, an inverse methodology is applied, setting the power block cost and assessing the minimum CAPEX of the solar subsystem. As a result, a map is obtained showing the target CAPEX to be accomplished by sCO2+CSP if a clear reduction of the LCoE of this technology is to be achieved.
THERMODYNAMIC FEASIBILITY OF A PUMPED THERMAL ENERGY STORAGE DRIVEN BY OCEAN TEMPERATURE GRADIENT
Authors: Ghilardi Alessandra , Baccioli Andrea , Frate Guido Francesco , Ferrari Lorenzo
Published: July 2024

The significant future penetration of variable renewable energy, necessary to decarbonize power production, will require energy storage to stabilize the electric grids. Electrochemical batteries may not be the best solution for all energy storage needs due to their limited lifetimes, performance degradation and use of critical raw materials. Pumped thermal energy storage (PTES) is an attractive solution since it does not suffer from the abovementioned limitations and might be preferable for long-duration applications. Particularly Thermally Integrated-PTES (TI-PTES), exploiting an external heat source during the charging or discharging phase, represents a significant improvement of this technology regarding the round-trip efficiency . Several TI-PTES systems have been proposed using solar and geothermal energy or industrial waste heat. This paper introduces a novel TI-PTES concept exploiting the temperature difference between the surface and deep oceanic Water in tropical areas. The system comprises a vapour compression chiller, a phase change material (PCM) cold storage, and an organic Rankine cycle. During the charging phase, the chiller operates between the cold seawater and the thermal storage, converting electric energy into a cooling effect. In these conditions, the chiller Energy efficiency ratio (EER) is in the range of 4.6 - 9.0 due to the deep seawater's low temperature. During the discharge phase, the organic Rankine cycle operates between the hot surface and the storage to produce electricity. Results show that the round-trip efficiency ranges from 0.30 to 0.52 depending on the fluids adopted in chiller and ORC and PCM storage temperature, making the investigated technology a promising alternative to other long-duration storage technologies.
Inna lokalność
Authors: Aleksandrowicz Joanna
Published: July 2024

THE OTHER LOCALITY: RETURNS TO THE COUNTRYSIDE IN THE RECENT SPANISH CINEMAThe article concerns returns to rural theme which are characteristic for Spanish cinema of the last decade and can be understood as an expression of the search for a local identity. In many narrations is also present plot motif of the return, connected with stories of characters torn between affection for little homeland and desire or necessity of leaving it. Unlike previous films, images of the country are far removed from idealisation and folkloristic clichés, as well as from black legend about poverty and backwardness, while the specificity of autonomous communities is manifested in regional languages and landscapes. In many stories about local communities directors reveal boarder problems, like changing the character of agricultural areas or depopulation of villages, which applies especially to interior called empty Spain (España vacía). This realistic presentation contrasts with magical realism, which isn’t result of the stranger’s gaze but is connected with specificity of the countryside seen from the perspective of its inhabitants and directors who come from there.
Nowe (eko)Kino Galisyjskie
Authors: Boguszewicz Maria
Published: July 2024

NEW GALICIAN (ECO)CINEMA: LANDSCAPE AND IDENTITYThe term “New Galician Cinema,” coined in 2010, remains prevalent in academic and everyday discourse. However, a growing number of voices question its applicability to recent works by Galician directors. This article aims to assess the established criteria for defining New Galician Cinema, reevaluating them in light of selected directors under this label. Additionally, it proposes a fresh perspective on the term. By referencing other “small cinemas” on the Iberian Peninsula, I highlight the distinctiveness of Galician cinema, particularly its innovative approach to landscape. Examining films by Lois Patño, Diana Toucedo, Oliver Laxe, and Álvaro Gago from a phenomenological standpoint, I explore the interplay between the community/individual and its/their natural surroundings. Ultimately, I position New Galician Cinema within the current trends of independent world cinema, characterizing it as a form of ecocinema.
Wielogłos portugalskiego Południa
Authors: Golemo Karolina
Published: July 2024

MULTI-PART VOICES OF THE PORTUGUESE SOUTH: CANTE ALENTEJANO IN CONTEMPORARY INTERPRETATIONS
The article presents cante alentejano (a multi-part singing form from Alentejo) as a manifestation of cultural identity of the inhabitants of the Portuguese region. It succinctly illustrates the origins and development process of the genre, as well its present situation. The transformations of cante (in terms of its definition, practice, promotion, and „use”) are shown in relation to the contemporary socio-cultural realities of the region. The article also addresses the references to cante alentejano in the works of contemporary artists who are active nationally and internationally, recognized by a wide audience, and originating from other musical traditions (e.g., fado or pop). The article also indicates possible directions for further research on this cultural phenomenon.
Andora – pirenejskie księstwo na styku kultur
Authors: Żebrowski Jerzy
Published: July 2024

Brak abstraktu dla tego artykułu.
Self-Guided Approximate Linear Programs: Randomized Multi-Shot Approximation of Discounted Cost Markov Decision Processes
Authors: Pakiman Parshan , Nadarajah Selvaprabu , Soheili Negar , Lin Qihang
Published: July 2024

Approximate linear programs (ALPs) are well-known models based on value function approximations (VFAs) to obtain policies and lower bounds on the optimal policy cost of discounted-cost Markov decision processes (MDPs). Formulating an ALP requires (i) basis functions, the linear combination of which defines the VFA, and (ii) a state-relevance distribution, which determines the relative importance of different states in the ALP objective for the purpose of minimizing VFA error. Both of these choices are typically heuristic; basis function selection relies on domain knowledge, whereas the state-relevance distribution is specified using the frequency of states visited by a baseline policy. We propose a self-guided sequence of ALPs that embeds random basis functions obtained via inexpensive sampling and uses the known VFA from the previous iteration to guide VFA computation in the current iteration. In other words, this sequence takes multiple shots at randomly approximating the MDP value function with VFA-based guidance between consecutive approximation attempts. Self-guided ALPs mitigate domain knowledge during basis function selection and the impact of the state-relevance-distribution choice, thus reducing the ALP implementation burden. We establish high-probability error bounds on the VFAs from this sequence and show that a worst-case measure of policy performance is improved. We find that these favorable implementation and theoretical properties translate to encouraging numerical results on perishable inventory control and options pricing applications, where self-guided ALP policies improve upon policies from problem-specific methods. More broadly, our research takes a meaningful step toward application-agnostic policies and bounds for MDPs.

This paper was accepted by Chung Piaw Teo, optimization.

Supplemental Material: The online appendix and data files are available at https://doi.org/10.1287/mnsc.2020.00038 .