Qualitative analysis of flow patterns : two-phase flow condensation at low mass fluxes and different inclination angles

dc.contributor.advisorMeyer, Josua P.en
dc.contributor.emailu13294980@tuks.co.zaen
dc.contributor.postgraduateKombo, Rainahen
dc.date.accessioned2017-07-13T13:28:50Z
dc.date.available2017-07-13T13:28:50Z
dc.date.created2017-04-26en
dc.date.issued2016en
dc.descriptionDissertation (MSc)--University of Pretoria, 2016.en
dc.description.abstractA great deal of work has been conducted on in-tube condensation in horizontal and vertical smooth tubes. The available literature points to mechanisms governing two-phase condensation heat transfer coefficients and pressure drops, which are directly linked to the local flow pattern for both horizontal and inclined configurations. However, the work has been limited to flow pattern observations, heat transfer, pressure drops and void fractions for both horizontal and inclined tubes at high mass fluxes. No work has been conducted on the analysis of the observed flow patterns and the effect of temperature difference between the average wall temperature and average saturation temperature for different inclination angles at mass fluxes of 100 kg/m2.s and below. The purpose of this study is to carry out a qualitative analysis of flow patterns, and show the effect of temperature difference on the heat transfer coefficient for inclination angles from +90° (upward flow) to -90° (downward flow) at mass fluxes below 100 kg/m2.s. An experimental set-up provided the measurements for the two-phase condensation of R-143a in a smooth tube with an inside diameter of 8.38 mm and a length of 1.5 m. The mass fluxes were 25 kg/m2.s to 100 kg/m2.s, the saturation temperature was 40 °C and the mean qualities were 0.1 to 0.9. A high-speed camera was used to visually analyse and determine the flow patterns for both the inlet and the outlet of the test section. Through the results, eight flow patterns were observed: stratified-wavy, stratified, wavy, wavy-churn, intermittent, churn, annular and wavy-annular. The maximum heat transfer was observed for downward flow between inclination angles of -15° and -30°. The Thome-Hajal flow pattern map correctly predicted horizontal flow patterns, but failed to predict most of the inclined flow patterns. Various flow pattern transitions were identified and proposed for all the investigated inclination angles in this study. Finally, the heat transfer coefficient was found to be dependent on quality, mass flux, temperature difference and inclination angle.en_ZA
dc.description.availabilityUnrestricteden
dc.description.degreeMScen
dc.description.departmentMechanical and Aeronautical Engineeringen
dc.description.librarianmi2025en
dc.description.sdgSDG-09: Industry, innovation and infrastructureen
dc.description.sdgSDG-12: Responsible consumption and productionen
dc.identifier.citationKombo, R 2016, Qualitative analysis of flow patterns : two-phase flow condensation at low mass fluxes and different inclination angles, MSc Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/61303>en
dc.identifier.otherA2017en
dc.identifier.urihttp://hdl.handle.net/2263/61303
dc.language.isoenen
dc.publisherUniversity of Pretoriaen
dc.rights© 2017 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.en
dc.subjectUCTDen
dc.subjectTwo-phase flowen
dc.subjectHeat transfer coefficienten
dc.subjectFlow patternen
dc.subjectLow mass fluxen
dc.subject.otherEngineering, built environment and information technology theses SDG-09
dc.subject.otherSDG-09: Industry, innovation and infrastructure
dc.subject.otherEngineering, built environment and information technology theses SDG-12
dc.subject.otherSDG-12: Responsible consumption and production
dc.titleQualitative analysis of flow patterns : two-phase flow condensation at low mass fluxes and different inclination anglesen_ZA
dc.typeDissertationen

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