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Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime
Thesis (PhD)--University of Pretoria, 2017.
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| Language: | English |
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University of Pretoria
2018
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| _version_ | 1867613463629529088 |
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| access_status_str | Open Access |
| author2 | Dirker, Jaco |
| author_browse | Dirker, Jaco |
| author_facet | Dirker, Jaco |
| collection | Thesis |
| dc_rights_str_mv | © 2018 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. |
| description | Thesis (PhD)--University of Pretoria, 2017. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/66230 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:36:33.236Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/66230 Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime Dirker, Jaco u27229573@tuks.co.za Meyer, Josua P. Ndenguma, Dickson Daniel UCTD Heat transfer Pressure drop Annuli Non-uniform Internal wall temperatures Transition flow regime Engineering, built environment and information technology theses SDG-07 SDG-07: Affordable and clean energy Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-13 SDG-13: Climate action Thesis (PhD)--University of Pretoria, 2017. It is common practice to design heat exchangers that are operated in either the laminar or the turbulent flow regime and not in the transition flow regime. This could mainly be due to a lack of knowledge on the behaviour in the transition flow regime for several reasons. However, due to factors such as design constraints, heat exchangers may indeed operate in the transition flow regime. An experimental study was conducted to determine the lower and upper Reynolds number limits of the transition flow regime, and the characteristics of the heat transfer coefficients and friction factors for annular passages with different geometric dimensions. The inner wall of the annular passage had different degrees of non-uniform temperature, while the outer wall was insulated. Both heated and cooled flow applications with water as fluid (cold fluid and hot fluid respectively) were investigated. The isothermal condition investigation was also conducted for pressure drop. Four horizontal concentric counter-flow tube-in-tube heat exchangers with conventional inlet geometries were considered to obtain the required data. The hydraulic diameters of the test sections were 26.2 mm, 23 mm, 20.2 mm and 17 mm, their respective annular diameter ratios were 0.327, 0.409, 0.386 and 0.483 and their length-to-hydraulic ratios were 193, 221, 251 and 299 respectively. The flow was both hydrodynamic and thermally developing. Test data of laminar, transition and turbulent flow regimes was collected. However, the transition flow regime was the main area of interest for this study. The transition flow regime was found to exhibit either mixed or forced convection types. Average heat transfer coefficients were obtained for both heating and cooling cases, while friction factors were obtained for heating, cooling and isothermal conditions. Uncertainties in the friction factor and Nusselt number were on average below 5.6% and 10.5%, respectively. The geometric size of the annular passage, degree of wall temperature uniformity and direction of the heat flux (heating and cooling cases of annular fluid) had a significant influence on the heat transfer coefficients, friction factors and Reynolds number span of the transition flow regime. New correlations for predicting the transition flow regime Reynolds number spans, Nusselt numbers and friction factors were developed for the transition flow regime and predicted most of the data to within +-10%. mi2025 Mechanical and Aeronautical Engineering PhD Unrestricted SDG-07: Affordable and clean energy SDG-09: Industry, innovation and infrastructure SDG-13: Climate action 2018-08-17T09:42:44Z 2018-08-17T09:42:44Z 2005/03/18 2017 Thesis Ndenguma, DD 2017, Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime, PhD Thesis, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/66230> A2018 http://hdl.handle.net/2263/66230 en © 2018 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. application/pdf University of Pretoria |
| spellingShingle | UCTD Heat transfer Pressure drop Annuli Non-uniform Internal wall temperatures Transition flow regime Engineering, built environment and information technology theses SDG-07 SDG-07: Affordable and clean energy Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-13 SDG-13: Climate action Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime |
| title | Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime |
| title_full | Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime |
| title_fullStr | Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime |
| title_full_unstemmed | Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime |
| title_short | Heat transfer and pressure drop in annuli with non-uniform internal wall temperatures in the transition flow regime |
| title_sort | heat transfer and pressure drop in annuli with non uniform internal wall temperatures in the transition flow regime |
| topic | UCTD Heat transfer Pressure drop Annuli Non-uniform Internal wall temperatures Transition flow regime Engineering, built environment and information technology theses SDG-07 SDG-07: Affordable and clean energy Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-13 SDG-13: Climate action |
| url | http://hdl.handle.net/2263/66230 |