Thesis (MEng) -- Stellenbosch University, 1991. / ENGLISH ABSTRACT: In the present study various mathematical models have been developed for the analysis of
spray cooled finnned-tube heat exchangers. These models range from simplified models
based on the work by Kreid et al. [78KR1], Nakayama et al. [88NA1] and Erens et al.
[90ER1] to a more comprehensive model based on the work by Poppe [84P01].
Computer programs were written to evaluate the performance prediction of these models
on spray cooled heat exchangers in the vertical air flow mode.
Experimental tests were conducted on a four-row finned-tube heat exchanger in a vertical
air /water mist flow to verify the mathematical models and it was found that the performance
of this heat exchanger could be predicted within 20 per cent using the accurate model.
Significant performance enhancement (up to 3.5 times the dry performance) was found by
spraying relatively small amounts of water onto the heat exchanger. The spray water
massflow rate was found to have a significant effect on the two phase pressure drop across
the heat exchanger.
The present study indicated certain important factors which have to be taken into
consideration when designing spray cooled heat exchanger units. These include the
geometry of the finned-tubes, the temperature difference between the process water and the
optimum air and the air /spray water ratio. / AFRIKAANSE OPSOMMING: In die tesis is 'n aantal wiskundige modelle ontwikkel wat gebruik kan word vir die analise
van sproei verkoelde vinbuis warmte uitruilers. Die wiskundige modelle wissel van
eenvoudige modelle wat gebaseer is op die werk van Kreid et al. [78KR1 ], Nakayama et al.
[88NA1] en Erens et al. [90ER1] tot 'n omvattende model wat gebaseer is op die werk van
Poppe [84 PO 1].
Rekenaar programme is geskryf om die die modelle se voorspellingsvermoe van die
kapasiteit van sproei verkoelde warmte uitruilers te evalueer.
'n Eksperimentele ondersoek is gedoen op 'n warmte uitruiler met vier vinbuis rye in 'n
toetsseksie met vertikale lugvloei. Die toets resultate is gebruik vir die evaluasie van die
wiskundige modelle en het getoon dat die akkurate model se voorspellings binne 20 per sent
van die gemete kapasitiet van die uitruiler val. Die eksperirnentele werk het verder
aangetoon dat deur klein hoeveelhede water op die uitruiler te sproei, 'n toename in
kapasiteit tot 3.5 keer die droe werkverrigting moontlik is. Die twee-fase drukval oor die
uitruiler is sterk bei:nvloed deur die sproei water massavloei.
Die analitiese navorsmg wat gedoen is met behulp van die rekenaar programme het
aangedui dat daar 'n paar belangrike faktore is wat in ag geneem moet word met die
ontwerp van sproei verkoelde warmte uitruilers. Die faktore sluit die vinbuis geometrie, die
temperatuur verskil tussen die proses water en lug en optimum lug/sproeiwater massavloei
verhouding in.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/69378 |
| Date | 01 1900 |
| Creators | Kriel, Dawid Eduard |
| Contributors | Erens, P. J., 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 | Unknown |
| Type | Thesis |
| Format | ca. 236 leaves : ill. |
| Rights | Stellenbosch University |
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