Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The water utilized by passive air-conditioning systems in buildings is typically
required at higher elevations. The thermally driven natural circulation water pump
(TDNCWP) is a passively driven pumping system for delivering water from
ground level against gravity to a higher elevation. It consists of a humid air closed
duct loop to which a temperature difference is applied, resulting in a density
gradient driven flow. A hot water evaporation tray inside the loop at ground level
introduces water vapour to the loop air flow, and a cold condensation plate inside
the loop at the elevated level removes this water vapour for passive airconditioning
usage. In this thesis, a one-dimensional theoretical and numerical
simulation model is developed. Experiments were conducted on two experimental
TDNCWP set-ups of different cross sectional areas to evaluate the pump design
and the theoretical model.
It is shown in this thesis that the TDNCWP can provide water at varied elevations
using non-mechanical, passive means. A temperature difference of 9 to 12.5 °C
induced an average velocity of 0.4 to 0.6 m/s for a duct cross section of 100 mm2.
For a larger cross section of 400 mm2, a temperature difference of 2 to 5 °C
induced an average velocity of 0.25 to 0.3 m/s. An asymmetrical velocity profile
was observed which varied at different points in the loop. A water delivery rate of
1.2 to 7.5 L/day was experimentally determined which compares well to the
passive air-conditioning water requirements of a small building. The theoretical
model over-predicted the delivery rate at increased duct cross sectional areas but
fared well when compared to the smaller experimental model results.
Further refinement of the numerical model and the TDNCWP design is required,
and recommendations were made regarding this. It is clear however that the
TDNCWP provides an alternative to a conventional water pump for low-volume
water pumping requirements. / AFRIKAANSE OPSOMMING: Die water wat gebruik word deur passiewe lugversorgingstelsels in geboue word
tipies benodig op hoër vlakte. Die termies gedrewe natuurlike sirkulasie
waterpomp (TDNCWP) is ʼn passiewe gedrewe pomp stelsel vir die lewering van
water vanaf die grondvlak teen swaartekrag na ʼn hoër vlak. Dit bestaan uit 'n
vogtige geslote lug geut siklus waarop ʼn temperatuur verskil toegepas word, dit
lei tot vloei gedrewe deur ʼn digtheids gradiënt. ʼn Warm water verdampings-pan
binne die geut op grondvlak stel waterdamp aan die geut lugvloei toe, en ʼn koue
kondensasie plaat binne die geut op die verhoogde vlak verwyder hierdie
waterdamp vir passiewe lugversorgings gebruik. In hierdie tesis word ʼn eendimensionele
teoretiese en numeriese simulasie model ontwikkel. Eksperimente is
uitgevoer op twee eksperimentele TDNCWP stelsels van verskillende deursnee
grootes om die pomp ontwerp en die teoretiese model te evalueer.
Die tesis dui aan dat die TDNCWP water kan voorsien teen verskillende hoogtes
op ʼn nie-meganiese, passiewe wyse. ʼn Temperatuur verskil van 9 tot 12.5 °C
veroorsaak ʼn gemiddelde snelheid van 0.4 tot 0.6 m/s vir ʼn geut deursnit van 100
mm2.Vir ʼn groter deursnit van 400 mm2, het ʼn temperatuur verskil van 2 tot 5 °C
ʼn gemiddelde snelheid van 0.25 tot 0.3 m/s veroorsaak. ʼn Asimmetriese
snelheidsprofiel was waargeneem wat gewissel het op verskillende punte in die
siklus. ʼn Water voorsienings tempo van 1.2 tot 7.5 L / dag was eksperimenteel
waargeneem wat goed vergelyk met die passiewe water lugversorging vereistes
van 'n klein gebou. Die teoretiese model het ʼn groter voorsienings tempo voorspel
vir die groot deursneë, maar het goed gevaar in vergelyking met die kleiner
eksperimentele model.
Verdere verfyning van die numeriese model en die TDNCWP ontwerp word
vereis, en aanbevelings is gemaak ten opsigte van hiervan. Dit is egter duidelik
dat die TDNCWP ʼn alternatief is vir konvensionele lae-volume water pomp
applikasies. / National Research Foundation (NRF)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/97066 |
| Date | 03 1900 |
| Creators | Hobbs, Kyle |
| Contributors | Dobson, Robert Thomas, 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 | 114 pages : illustrations |
| Rights | Stellenbosch University |
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