Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: High temperature heat sources are becoming an ever-increasing imperative in the
process industry for the production of plastics, ammonia and fertilisers, hydrogen, coal-toliquid
fuel and process heat. Currently, high temperature reactor (HTR) technology is
capable of producing helium temperatures in excess of 950°C; however, at these
temperatures, tritium, which is a radioactive contaminant found in the helium coolant
stream, is able to diffuse though the steel retaining wall of the helium-to-steam heat
exchanger. To circumvent this radioactivity problem, regulations require an intermediate
heat exchange loop between the helium and the process heat streams. In this paper, the
use of a uniquely designed sodium-charged heat pipe heat exchanger is considered, and
has the distinct advantage of having almost zero exergy loss as it eliminates the
intermediate heat exchange circuit.
In order to investigate this novel heat pipe heat exchanger concept, a special
intermediate-temperature (± 240°C) experimental heat pipe heat exchanger (HPHE) was
designed. This experimental HPHE uses Dowtherm A as working fluid and has two glass
windows to enable visual observation of the boiling and condensation two-phase flow
processes. A high temperature air-burner supply simulates the high temperature stream,
and the cold stream is provided by water from a constant-heat supply tank. This
experimental apparatus can be used to evaluate the validity of steady-state and start-up
transient theoretical models that have been developed.
This paper will highlight the special design aspects of this HPHE, the theoretical model
and the solution algorithm described. Experimental results will be compared with the
theoretically calculated results. The theoretical model will then be used to predict the
performance of a high temperature (sodium working fluid at 850°C) HPHE will be
undertaken and conclusions and recommendation made. / AFRIKAANSE OPSOMMING: Hoë temperatuur hitte bronne is besig om ‘n toenemende noodsaaklikheid te raak in die
proses industrie vir die vervaardiging van plastieke, ammoniak, kunsmis, waterstof,
steenkool-tot-vloeibare brandstof en proses hitte. Huidige hoë temperatuur reaktor
tegnologie is in staat om helium te verhit tot temperature hoër as 950°C, maar by sulke
hoë temperature is die vorming van tritium, wat ‘n radioaktiewe produk is, in die helium
verkoeling stroom wat deur die reaktor vloei, ‘n probleem. Die tritium is in staat om deur
die staal wand van ‘n enkel fase warmte uitruiler te diffundeer. Om hierdie radioaktiewe
probleem te uitoorlê, stel huidige regulasies voor dat ‘n oorgangs hitte uitruil lus gebruik
raak tussen die helium en proses strome van die reaktor stelsel. In hierdie tesis word ‘n
unieke natrium gevulde hitte pyp warmte uitruiler nagevors, hierdie ontwerp het die
voordeel dat dit geen “exergy” verlies het omdat dit nie ‘n oorgangs hitte uitruil lus
benodig nie.
Hierdie unieke konsep was nagevors deur ‘n spesiale oorgangs temperatuur (± 230°C)
eksperimentiële hitte pyp warmte uitruiler te ontwerp. Hierdie eksperimentiële hitte pyp
warmte uitruiler gebruik Dowtherm A as oordrags medium tussen die warm en koue
strome en het twee glas venters waardeur die kook en kondensasie van die oorgangs
medium dop gehou kan word. ‘n Hoë temperatuur verbrander simuleer die warm stroom
deur die reaktor en die koue stroom word gesimuleer deur koue water. Die
eksperimentiële opstelling sal gebruik word om die tyd afhangklike en tyd onafhangklike
teoretiese wiskundige modele te valideer.
Hierdie tesis sal die spesiale ontwerp aspekte van die hitte pyp warmte uitruiler,
teoretiese modelle en oplos algoritme te bespreek. Eksperimentiele resultate sal met die
teoretiese resultate vergelyk word en dan sal die teoretiese modelle gebruik word om ‘n
natrium gevulde warmte uitruiler te simuleer. Gevolgtrekkings en aanbevelings sal in die
lig van die resultate verskaf word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/80096 |
| Date | 03 1900 |
| Creators | Laubscher, Ryno |
| Contributors | Dobson, R. T., 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 | xvii, 120 p. : ill. |
| Rights | Stellenbosch University |
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