Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: This report describes the Experimental and Numerical Investigations conducted, during
the determination of the structural mechanics of elliptical tubes, viz. the F- and the Atubes.
This report is requested in an endeavour to assist Sasol, who is currently busy
developing and updating specifications on Air Cooled Heat Exchangers.
The objectives of this report therefore are to : (1) determine the strength and the
effectiveness of the tube-to-tube-sheet joints. (2) determine the allowable pressure
limits on the tubes and (3) investigate the effects of thermal load and vibration on the
tube bundle. A series of experiments were conducted to meet these objectives. From a
Shear Load experiment it was found that the maximum allowable axial load on the Fand
the A-tube is 14.55 kN and 20. 86 kN respectively. Fin Plates were found to have
little effect on the bending strength of the tube, w~ilst they have significant effect on the
resistance to volumetric expansion of the tube. In fact the more fins per unit length the
greater the resistance to volumetric expansion of the tube. These conclusions were
drawn from Bending and Pressure Load experiments respectively and supported by
FEM analysis of the tube using NASTRAN.
When the design pressure limit given by the manufacturer (GEA Air Cooled Systems),
were tested using FEM analysis, it was found that they cause no significant deformation
and failure of the tubes. Thermal stresses on the tube bundle greatly affect the first tube
in the first row (row closest to the flanges) of the tube bundle and it is recommended
that provision for thermal expansion be made to reduce these stresses. To reduce
vibrations induced by the fan, it is recommended that the natural frequency of the tube
bundle must not equal the number of blades (N) times the angular frequency (co) of the
fan, or multiples thereof, of each mode of vibration. / AFRIKAANSE OPSOMMING: Hierdie tesis beskrywe die Numeriese en Eksperimentele ondersoeke na die sterkte van
elliptiese verkoelingsbuise, naamlik die F- en A- tipes. Hierdie werk sal Sasol, wat huidiglik
besig is met die opgradering, van spesifikasies vir lugverkoelde hitteuitruilers van nut
wees.
Die doelwitte van hierdie tesis is om: (1) die sterkte en effektiwiteit van die buis laste was
die buis and die buisplaat verdind, te ondersoek, (2) die toelaatbare druklimiete, sowel as
(3) die effek wat hitte en vibrasie op 'n buisbundel het, te ondersoek. 'n Reeks
eksperimente is uitgevoer om hierdie doelwitte te bevredig. 'n Skuifbelastingseksperiment
het aangedui dat die toelaatbare krag wat op 'n F- en A-buis respektiewelik aangewend
kan word 14.55 kN en 20.86 kN is. Die ondersoek het aangetoon dat vinne geen
noemenswaardige effek op die buigsterkte van die buise gehad het nie, maar dat dit 'n
aansienlike verstywingseffek teen volumetriese verandering as gevolg van interne druk,
gehad het. Hierdie gevolgtrekkings is bereik deur die Druk- en Buigtoetse wat numeries
bevestig is met die NASTRAN eindige element analise (EEA) pakket.
EEA het aangetoon dat die druklimiete voorgeskryf deur die buisvervaardiger (GEA Air
Cooled Systems) nie noemenswaardige vervorming van die buise tot gevolg gehad het
nie. Termiese belastings het 'n groot invloed op die eerste buise (die rye naaste aan die
flense) van 'n buisbundel. Die invoeging van uitsettingslaste word aanbeveel om die
spannings hier te verminder. Om vibrasie van die buisbundel te verhoed word aanbeveel
dat die resonansfrekwensie van die buisbundel nie gelyk is aan die aantal lemme (N)
vermenigvuldig met die rotasie frekwensie (co)van die waaier vir elke vibrasiemode.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51748 |
| Date | 04 1900 |
| Creators | Sizani, Xolile L. |
| Contributors | Terblanche, E., 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 | 1 v. (various pagings) : ill. |
| Rights | Stellenbosch University |
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