1. Αποθετήριο Παραδοτέων Υποτρόφων Δράσεων ΕΣΠΑ Τριτοβάθμιας Εκπαίδευσης 2017-2023
2. Όλο το Αποθετήριο
3. Υποψήφιοι διδάκτορες

Τύπος:	Διδακτορική διατριβή
Τίτλος:	Design and modeling of printed - circuit heat exchangers and centrifugal compressors for supercritical carbon dioxide
Εναλλακτικός τίτλος:	Σχεδιασμός και μοντελοποίηση εναλλακτών θερμότητας τύπου τυπωμένου κυκλώματος και φυγοκεντρικού συμπιεστή για κύκλους ισχύους με υπερκρίσιμο διοξείδιο του άνθρακα
Συγγραφέας:	[EL] Γκούντας, Απόστολος
Επιβλέπων διατριβής:	[EL] Σταματέλλος, Αναστάσιος[EN] Stamatelos, Anastassios [EL] Κάλφας, Ανέστης[EN] Kalfas, Anestis
Συμβουλευτική επιτροπή:	[EL] Χαραλάμπους, Γεώργιος[EN] Charalampous, Georgios
Ημερομηνία:	19/11/2020
Περίληψη:	The closed loop Brayton cycle using supercritical carbon dioxide (s-CO2) is a promising technology for waste heat recovery and power production. This thesis presents the design and performance modeling of the most critical cycle components, namely the printed-circuit heat exchangers and the centrifugal compressor. The attainable limits of recompression Brayton cycle efficiency, using supercritical carbon dioxide, are investigated. A comprehensive study on the design and modeling of printed-circuit heat exchangers and the centrifugal compressor is used to achieve this goal. A case study of a thermodynamic analysis is used for a power cycle with a thermal load of 600 MW. The results indicate that thermal efficiency figures exceeding 46% are possible for a turbine inlet temperature of 830 K. The supercritical carbon dioxide varies abruptly its properties, particularly close to the critical point. Therefore, a split cycle with recompression is used to reduce the entropy generation. The design of heat exchangers based on the printed-circuit technology are investigated. The components are modeled by using a one-dimensional segmental analysis, three-dimensional computational fluid dynamics analysis and experimental methods. The limits of attainable heat exchanger effectiveness and their effect on the total efficiency are investigated. The performed analysis validated by experimental data, suggests a high effectiveness design for the high-temperature recuperator.The pressurized conditions of the supercritical carbon dioxide and the two-phase risk approaching the critical region, point the need to investigate the centrifugal compressor design and operation. Both direct and inverse problems are solved. The direct design problem is solved for a tested centrifugal compressor. The inverse problem is solved in order to obtain the compressor geometry that meets the necessary thermodynamic conditions. An iterative one-dimensional design model has been developed, aiming to estimate through the compressor efficiency. A computational fluid dynamics analysis is used, in order to investigate the flow field in the compressor, taking into account the real gas effects. The two-phase flow at the compressor inlet is examined, in view of identifying the local flow acceleration at the impeller leading edge. Moreover, the effect of tip clearance on the compressor performance and its impact on possible condensation is investigated. It has been shown that when tip clearance increases from 1% to 5% (1 mm) of blade height, condensation occurs at the leading edge tip. The compressor performance map is derived and the condensation investigation leads to a limited operational range in order to ensure supercritical flow throughout the cycle.The high-temperature recuperator with 99% effectiveness should lead to 0.1% cycle efficiency improvement. Moreover, the designed compressor’s operational range is limited to a 30% of the initial range for low rotational speed and to a 25% for higher rotational speeds.
Γλώσσα:	Αγγλικά
Τόπος δημοσίευσης:	Βόλος, Ελλάδα
Σελίδες:	198
Θεματική κατηγορία:	[EL] Μηχανική ενέργειας[EN] Energy Engineering and Power Technology [EL] Επιστήμη Μηχανολόγου Μηχανικού[EN] Mechanical Engineering
Λέξεις-κλειδιά:	Υπερκρίσιμο CO2; Κλειστός κύκλος Brayton; Εναλλάκτες θερμότητας; Φυγοκεντρικός συμπιεστής
Κάτοχος πνευματικών δικαιωμάτων:	Apostolos A. Gkountas
Διατίθεται ανοιχτά στην τοποθεσία:	https://www.didaktorika.gr/eadd/handle/10442/45657
Σημειώσεις:	This research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Strengthening Human Resources Research Potential via Doctorate Research” (MIS5000432), implemented by the State Scholarships Foundation (ΙΚΥ).
Εμφανίζεται στις συλλογές:	Υποψήφιοι διδάκτορες