The subject of this work is the analysis of the Frictional Pressure Drop of Two-Phase Flows, in particular for Gas/Vapour-Liquid systems during Evaporation or Adiabatic Flow. The principal aims of the thesis are to clean-up, organise and analyse the experimental data already detected at the Multiphase Lab of the Department of Energy. The data regard the Flow Boiling of two refrigerants, R22 and R134a, and the Adiabatic Flow of an Air-Water mixture. The Evaporation happens at 5°C and every types of flow are developed inside Horizontal Smooth tubes, with an internal diameter of 8.92 mm. The idea is the creation of a Database which will include the measurements of R1234ze, at the same operating conditions, which will be taken in the near future at the Multiphase Lab. The thesis aims to compare the Frictional Pressure Drop correlations available in literature with the actual experimental data, in order to find the most suitable type of model. In this way, an Historical Literature review is done, searching the possible approaches for this purpose, starting from the oldest (1946) to the newest (2020). The selected approaches are compared and the most suitable ones for the Evaporation, Adiabatic and both type of flows are presented. In addition, for the Evaporation flow, an analysis of the flow pattern is made, in order to find the most suitable correlations for each flow pattern and to apply the flow pattern dependent method. Finally, an original approach is proposed and compared with the existing correlations.
Il presente lavoro riguarda l’analisi della caduta di pressione (per attrito) di flussi bifase, Gas/Vapore-Liquido in particolare, in Evaporazione o in flusso Adiabatico. L’obiettivo principale della tesi è pulire, organizzare e analizzare i dati sperimentali già rilevati al Multiphase Lab del Dipartimento di Energia. I dati riguardano l’Ebollizione di due refrigeranti, R22 e R134a, e il flusso Adiabatico di una miscela Aria-Acqua. L’Evaporazione avviene a 5°C e ogni tipo di flusso è sviluppato all’interno di tubi lisci orizzontali, con un diametro interno di 8.92 mm. L’obiettivo è la creazione di un Database che includa anche le misurazioni di R1234ze, le quali verranno rilevate nell’imminente futuro al Multiphase Lab. Il presente lavoro si prefigge lo scopo di confrontare le correlazioni sulle cadute di pressione per attrito presenti in letteratura con i dati sperimentali disponibili, in modo tale da trovare il modello più appropriato. In questo modo un’analisi di letteratura “storica” sulle correlazioni è stata effettuata, partendo dalla più vecchia (1946) fino alla più recente (2020). Gli approcci selezionati sono confrontati e i migliori per Evaporazione, flusso Adiabatico ed entrambi sono riportati. In aggiunta, per l’Evaporazione, viene effettuata un’analisi dei Flow Pattern, in modo tale da trovare le correlazioni migliori per ciascun regime e applicare approcci dipendenti dal tipo di flusso. Infine, un approccio originale viene proposto e confrontato con le esistenti correlazioni.
Evaluation of two-phase frictional pressure drop for gas/vapour-liquid flows
Benini, Marco
2019/2020
Abstract
The subject of this work is the analysis of the Frictional Pressure Drop of Two-Phase Flows, in particular for Gas/Vapour-Liquid systems during Evaporation or Adiabatic Flow. The principal aims of the thesis are to clean-up, organise and analyse the experimental data already detected at the Multiphase Lab of the Department of Energy. The data regard the Flow Boiling of two refrigerants, R22 and R134a, and the Adiabatic Flow of an Air-Water mixture. The Evaporation happens at 5°C and every types of flow are developed inside Horizontal Smooth tubes, with an internal diameter of 8.92 mm. The idea is the creation of a Database which will include the measurements of R1234ze, at the same operating conditions, which will be taken in the near future at the Multiphase Lab. The thesis aims to compare the Frictional Pressure Drop correlations available in literature with the actual experimental data, in order to find the most suitable type of model. In this way, an Historical Literature review is done, searching the possible approaches for this purpose, starting from the oldest (1946) to the newest (2020). The selected approaches are compared and the most suitable ones for the Evaporation, Adiabatic and both type of flows are presented. In addition, for the Evaporation flow, an analysis of the flow pattern is made, in order to find the most suitable correlations for each flow pattern and to apply the flow pattern dependent method. Finally, an original approach is proposed and compared with the existing correlations.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/173972