Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: The coating thermal conductivity, the effective coated-tube thermal conductivity and
the coating factor of three artificial protective coatings (APCs) applied to condenser
tubes are experimentally evaluated. This testing broadens the limited available knowledge
of these coatings, which is necessary for effective condenser refurbishment and
operation. The coatings are applied to 25.4 mm brass tubes at thicknesses of 44, 46,
50, and 130 μm. Steady state heat transfer tests are performed on these tubes fitted
in a double-pipe counter-flow heat exchanger, with heated water in the annulus and
coolingwater inside the tube. The experimentally determined thermal conductivities
of the coatings range from 0.5 to 2.3 W/m·K. The effective coated-tube conductivity
and the coating factor depend on the tube material and size, as well as the coating
thickness. A one-dimensional condenser model is used to parametrically investigate
the relative overall effect on condenser performance. From these results, coating
guidelines for Admiralty brass tubes are proposed in terms of the minimum and
maximum coating conductivity and thickness. The effect of the coating on the thermal
performance is equivalent to a Heat Exchange Institute (HEI) cleanliness factor
of at least 0.85, when adhering to these guidelines. APCs provide a layer of protection
against corrosion, erosion and fouling and can preferentially fill tube-wall pits.
They can therefore be used to extend the condenser life-span effectively, but, to ensure
minimal impact on the overall condenser performance, the coating thickness
and conductivity must be carefully controlled and verified experimentally. / AFRIKAANSE OPSOMMING: Die termiese geleidingsvermoë, die effektiewe termiese geleidingsvermoë van bedekte
buise en die bedekkingsfaktor van drie kunsmatige beskermingsbedekkingslae
wat op kondensorbuise aangewend word, word eksperimenteel geëvalueer. Hierdie
evaluering verbreed die beperkte beskikbare kennis oor sodanige bedekkingslae, wat
nodig is vir effektiewe kondensor herinrigting en bedryf. Die lae word teen diktes van
44, 46, 50 en 130 μm in 25.4 mm geelkoperbuise aangewend. Warmteoordragstoetse
by gestadigde toestande word gedoen op hierdie buise in ’n dubbelpyp-teenvloeiwarmteoordraer,
met verhitte water in die annulus en verkoelingswater binne-in die
buis. Die eksperimenteel bepaalde termiese geleidingkoëffisiënte wissel tussen 0.5
tot 2.3 W/m·K. Die effektiewe geleidingsvermoë en bedekkingsfaktor hang af van sowel
die buis se materiaal en grootte sowel as die dikte van die bedekkings. ’n Eendimensionele
kondensormodel word gebruik om die algehele effek van hierdie beskermingsbedekkingslae
op kondensorwerkverrigting parametries te ondersoek. Riglyne
ten opsigte van aanwending van beskermingslae vir buise van “Admiralty” geelkoper
word verskaf in terme van die minimum en maksimum geleidingsvermoë en dikte
van bedekkingslae. Met behulp van hierdie riglyne word ’n “Heat Exchange Institue”
(HEI) ekwivalente skoonheidsfaktor van minstens 0.85 op ’n nuwe buis behaal.
Hierdie kunsmatige bedekkingslaeslae bied beskerming teen korrosie, erosie en bevuiling
en kan klein kuile in die buiswand vul. Hulle kan dus gebruik word om die lewensduur
van die kondensator te verleng, maar hul dikte en geleidingsvermoë moet
noukeurig beheer word en moet eksperimenteel geverifieer word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/85698 |
| Date | 12 1900 |
| Creators | Goodenough, John L. |
| 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 | xv, 121 p. : ill. |
| Rights | Stellenbosch University |
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