Thesis (MScEng)--Stellenbosch University, 2007. / ENGLISH ABSTRACT: A natural draught wet-cooling tower (NDWCT) was modelled using the Merkel method with an
improved energy equation as recommended by Kloppers and Kroger (2005a) - referred to as the
Improved Merkel method. The improved energy equation is used for calculating the heat rejection rate of
the tower and includes the energy associated with water evaporation. The sensitivity indexes of a
NDWCT were calculated numerically with the Improved Merkel method model. It was found that the
perfonnance of a NDWCT is most sensitive to the fill Merkel number. The "Natklos" fill test facility at
Stellenbosch University was used to estimate typical uncertainties found in fill performance
characteristics. The zeroth order uncertainty for the Merkel number and loss coefficient was calculated to
be 0.2100 m-1 and 0.4248 m- 1
, respectively, while the first order uncertainty for the Merkel number and
loss coefficient was calculated to be 0.1933 m- 1 and 0.2008 m-1
, respectively. ASME requires that the
uncertainty in tower capability has to be less than 6 % for a NDWCT perfonnance test to be deemed
ASME approved. Propagating typical measurement uncertainties found in NDWCT test standards and
experimental data into the tower capability showed that the 6 % uncertainty limit imposed by ASME is
unrealistic and too stringent. Performance curve generator (PCG) is a software package developed that
generates NDWCT perfonnance curves. With these performance curves it is possible to easily and
effectively adjust the off-design test results in order to detennine whether the NDWCT has met its
guarantee or not. / AFRIKAANSE OPSOMMING: Die werksverrigting van 'n natuurlike trek nat koeltoring (NTNT) is gemodelleer deur gebruik te maak
van die Merkel metode met 'n verbeterde energie vergelyking, soos aanbeveel deur Kloppers en Kroger
(2005a) - Verbeterde Merkel metode. Die energie vergelyking word gebruik om die toring se tempo van
warmteoordrag te bereken en sluit die energieverlies as gevolg van verdamping in. Die Verbeterde
Merkel metode model was gebruik om die sensitiwiteits-indekse van 'n NTNT te bepaal. Die analise toon
dat die toring se werksverrigting die sensitiefste is vir die pakking se Merkel getal. Die Natklos pakkingstoetsfasiliteit
aan die Universiteit van Stellenbosch was gebruik om tipiese onsekerheid in die pakkingsprestasiekarakteristieke
te bepaal. Die zero-orde onsekerheid in die Merkel getal en verlieskoeffisient was
bereken as 0.2100 m· 1 en 0.4248 m· 1
, onderskeidelik, terwyl die eerste-orde onsekerhede bereken was as
0.1933 m·1 en 0.2008 m· 1
, onderskeidelik. Die toelaatbare onsekerheid in toringvennoe vir 'n NTNT
aanvaardingstoes volgens ASME is 6 %. Deur tipes meetonsekerhede, soos gegee deur NTNT
aanvaardings-toesstandaarde sowel as eksperimentele data, deur te propageer, word 'n onsekerheid veel
groter as die toelaatbare 6 % gegenereer. 'n Renekaarpakket, genaamd Performance Curve Generator
(PCG), is ontwikkel om werksverrigtinskurwes vir 'n NTNT te genereer. PCG se werksverrigtinskurwes
maak dit moonltik om maklik te bepaal of a NTNT sy ontwerpskriterea bereik het of nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50709 |
| Date | 03 1900 |
| Creators | Van Der Merwe, Daniel |
| Contributors | Reuter, H. C. R., Kroger, D. G., Stellenbosch University. Faculty of Engineering. Dept. of Mechanical & Mechatronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 1 v. (various foliations) : ill. |
| Rights | Stellenbosch University |
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