Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: In this study, one and two-dimensional models are developed for the evaluation of
the thermal performance of a delugeable flat tube bundle to be incorporated in the
second stage of an induced draft hybrid (dry/wet) dephlegmator (HDWD) of a
direct air-cooled steam condenser (ACSC). Both models are presented by a set of
differential equations. The one-dimensional model is analysed analytically by
using three methods of analysis which are: Poppe, Merkel, and heat and mass
transfer analogy. The two-dimensional model is analysed numerically by means
of heat and mass transfer analogy method of analysis whereby, the governing
differential equations are discretised into algebraic equations using linear upwind
differencing scheme. The two-dimensional model’s accuracy is verified through a
comparison of the two dimensional solutions to one dimensional solutions.
Satisfactory correlation between the one and two-dimensional results is reached.
However, there is a slight discrepancy in the solutions, which is mainly due to the
assumptions made in one-dimensional model. The effect of tube height, tube
pitch, tube width, deluge water mass flow rate, frontal air velocity, steam, and air
operating conditions on the heat transfer rate and air-side pressure drop for both
wet and dry operating modes are investigated. The long tube height, large tube
width, small tube pitch, and high frontal air velocity are found to increase the tube
bundle’s performance. However, this performance is associated with a high airside
pressure drop. The performance of the deluged flat tube bundle is found to be
less sensitive to the changes in the deluge water mass flow rate and air operating
conditions. Furthermore, the best configuration of a delugeable flat tube bundle is
identified through a comparison to round tube bundle presented by Anderson
(2014). The performance of the round tube bundle is found to be around 2 times,
and 1.5 times of that of flat tube bundle, when both bundles operate as an
evaporative and dry air-cooled condenser respectively. / AFRIKAANSE OPSOMMING: In hierdie studie is een en twee-dimensionele modelle ontwikkel vir die
evaluering van die termiese prestasie van 'n benatbare plat buis bundel in die
tweede stadium van 'n geïnduseerde ontwerp hibriede (droë / nat ) deflegmator
van 'n direkte lugverkoelde stoom kondensator. Beide modelle is aangebied deur
'n stel van differensiaalvergelykings. Die een-dimensionele model is analities
ontleed deur die gebruik van drie metodes van analise wat: Poppe, Merkel, en die
hitte en massa-oordrag analogie. Die twee-dimensionele model is numeries
ontleed deur middel van hitte en massa-oordrag analogie metode van analise
waardeur , die regerende differensiaalvergelykings gediskretiseer in algebraïese
vergelykings met behulp van lineêre windop differensievorming skema. Die tweedimensionele
model se akkuraatheid is geverifieer deur 'n vergelyking van die
twee dimensionele oplossings te een dimensionele oplossings. Bevredigende
korrelasie tussen die een en twee-dimensionele resultate bereik word. Maar daar is
'n effense verskil in die oplossings, wat is hoofsaaklik te wyte aan die aannames
wat gemaak in een-dimensional model. Die effek van buis hoogte, buis
toonhoogte, buis breedte, vloed water massa-vloeitempo, frontale lug snelheid,
stoom, en in die lug werktoestande op die hitte oordrag snelheid en lug - kant
drukval vir beide nat en droë maatskappy modi word ondersoek. Die lang buis
hoogte, groot buis breedte, klein buisie toonhoogte, en 'n hoë frontale lug snelheid
gevind die buis bundel se prestasie te verhoog. Tog is hierdie prestasie wat
verband hou met 'n hoë lug - kant drukval. Die prestasie van die oorstroom plat
buis bundel gevind word minder sensitief vir die veranderinge in die vloed water
massa-vloeitempo en lug werktoestande. Verder is die beste opset van 'n
benatbare plat buis bundel geïdentifiseer deur 'n vergelyking met ronde buis
bundel aangebied deur Anderson (2014). Die prestasie van die ronde buis bundel
gevind word om 2 keer, en 1.5 keer van daardie plat buis bundel , wanneer beide
bundels funksioneer as 'n damp en droë lugverkoelde kondensor onderskeidelik.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97151 |
| Date | 03 1900 |
| Creators | Angula, Ester |
| Contributors | Reuter, H. C. R., Stellenbosch University. Faculty of Engineering. Dept of Mechanical and Mechatronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 114 pages : illustrations |
| Rights | Stellenbosch University |
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