A single stage dry/wet dephlegmator: development, performance evaluation and application in a hybrid ACC at CSP or NGCC Scale.
| dc.contributor.advisor | Owen, Michael | en_ZA |
| dc.contributor.author | Du Plessis, J. J. P. | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering. | en_ZA |
| dc.date.accessioned | 2021-11-30T20:22:47Z | |
| dc.date.accessioned | 2021-12-22T14:25:50Z | |
| dc.date.available | 2021-11-30T20:22:47Z | |
| dc.date.available | 2021-12-22T14:25:50Z | |
| dc.date.issued | 2021-12 | |
| dc.description | Thesis (PhD)--Stellenbosch University, 2021. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: This thesis builds on previous research on the hybrid (dry/wet) dephlegmator (HDWD) undertaken at Stellenbosch University. The aim of this study was to advance the technological readiness and corroborate the advantages of the hybrid ACC. This was accomplished by proposing and validating correlations, developing and validating a discretised single-stage HDWD model, applying it in a hybrid ACC model for detailed performance analysis and examining the techno- economic feasibility of the hybrid ACC coupled to a ~238 MW steam turbine. This thesis consists of five published and unpublished papers, each presented as a chapter (Chapters 2 to 6) with a common link to accomplish the study’s aim. In Chapter 2 the air-side pressure drop through a bare tube bundle was experimentally investigated. The investigation was conducted to develop a new empirical correlation, that is more accurate for the given context. The new correlations have an absolute average error of 3.2% (dry) and 4.5% (deluge) between the measured and predicted values. Chapter 3 investigated the steam pressure drop inside a horizontal partial condenser to identify the most suitable steam-side pressure drop correlation for the HDWD model. An experimental apparatus was designed and built to measure the steam pressure drop under varying operating conditions. The results were compared to a selection of five correlations from literature to assess the applicability of the correlations. The most fitting correlation had a mean error of ±15.6% compared to the experimental results. n Chapter 4, a discretised modelling method for an evaporative cooler/condenser was developed and validated. The novel experimental apparatus consisted of a 20 row, evaporative cooler with intermediate thermocouples to measure the process fluid temperature throughout the height of the bundle (representative of control volumes). The predicted and measured temperatures correlated well, with an average error of 0.62% for the bulk process fluid outlet and 1.87% for the intermediate process fluid. In Chapter 5, a discretised HDWD model was developed to analyse the performance of a hybrid ACC against a conventional ACC. The increased cooling capacity of the deluged HDWD units resulted in a smaller overall ACC size (4 × 6 units) for the same heat load compared to a conventional ACC (6 × 6 units). The hybrid ACC required a lower ejector pressure, it was able to operate in dry mode for 75% (0.19 kL/MWh) and was able to mitigate negative wind effects. Chapter 6 examined the techno-economic feasibility of the hybrid ACC at six locations to address the system's cost-competitiveness relative to a conventional ACC. For the six sites, the annual specific water consumption ranged from 0.31 kL/MWh to 0.69 kL/MWh. The hybrid ACC was more capital-intensive per street, but required fewer streets and it was best suited for drier to moderate humidity locations; however, the feasibility depends on the HDWD-unit costs and water prices. The hybrid ACC can also be oversized at drier locations to reduce water consumption and still have an annualised cost lower than a conventional ACC. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Hierdie tesis bou voort op vorige navorsing oor ‘n hibriede (droë/nat) deflegmator (HDND) wat aan die Universiteit Stellenbosch onderneem is. Die doel van hierdie studie was om die tegnologiese-gereedheid te bevorder en die voordele van die hibriede lugverkoelde-stoomkondensor (LVK) te bevestig. Dit is bereik deur die gepaste korrelasies te ontwikkel en te bekragtig, 'n gediskretiseerde enkel-fase HDND model te ontwikkel en bekragtig, dit toe te pas in 'n hibriede LVK model vir gedetailleerde analise en die tegno-ekonomiese uitvoerbaarheid van die hibriede-LVK te ondersoek wat gekoppel is aan 'n ~238 MW stoomturbine. Hierdie tesis bestaan uit vyf gepubliseerde en ongepubliseerde artikels, elk aangebied as 'n aparte hoofstuk (Hoofstukke 2 tot 6). In Hoofstuk 2 is die HDND bundel se lug-kant drukval eksperimenteel ondersoek om 'n leemte in die bestaande literatuur te vul. Die eksperimentele werk is uitgevoer om 'n nuwe korrelasie te ontwikkel, wat meer akkuraat is vir die gegewe konteks. Die nuwe empiriese korrelasies het 'n absolute gemiddelde fout van 3.2% (droog) en 4.5% (nat) tussen die gemete en voorspelde waardes. In hoofstuk 3, is die HDND se stoom-kant drukval ondersoek met ‘n horisontale kondensor, om die mees geskikte stoom drukval korrelasie vir die HDND -model te identifiseer. 'n Eksperimentele apparaat was ontwerp en gebou om die stoom drukval te meet en vergelyk met 'n seleksie van vyf korrelasies uit literatuur om die mees gepaste korrelasies te identifiseer. Die mees gepaste korrelasie het 'n gemiddelde fout van ± 15.6% getoon in vergelyking met die eksperimentele resultate. n hoofstuk 4 is 'n gediskretiseerde modellerings metode vir 'n verdampings verkoeler/kondensor ontwikkel en bekragtig. Die unieke eksperimentele apparaat het bestaan uit 'n 20 ry verdampings verkoeler met intermediêre termokoppels om die temperatuur van die proses vloeistof te meet deur die hoogte van die bundel (verteenwoordigend van kontrole volumes). Die voorspelde en gemete temperatuur het goed gekorreleer, met 'n gemiddelde fout van 0.62% vir die proses vloeistof uitlaat en 1.87% vir die intermediêre temperatuur metings. In hoofstuk 5 is 'n gediskretiseerde HDND-model ontwikkel om die verrigting van 'n hibriede LVK teen 'n konvensionele LVK te vergelyk. Die verhoogde verkoelings kapasiteit van die HDND-eenhede het gelei tot 'n kleiner algehele LVK grootte (4 × 6 eenhede) vir dieselfde hittelas in vergelyking met die konvensionele LVK (6 × 6 eenhede). Die hibriede LVK het ‘n laer uitlaatdruk vereis, kon 75% van die jaar droog werk (0.19 kL/MWu) en ook negatiewe wind- effekte versag. Hoofstuk 6 het die tegno-ekonomiese haalbaarheid ondersoek van die hibriede LVK by ses verskeie terreine om die stelsel se vermoë en koste-mededingendheid te bepaal. Vir die ses terreine, het die jaarlikse spesifieke waterverbruik gewissel. van 0.31 kL/MWu tot 0.69 kL/MWu. Dit is vasgestel dat die hibriede LVK die beste geskik is vir areas met ʼn droë tot matige humiditeit maar die haalbaarheid hang egter af van die HDND-eenheidskoste en water pryse. Vir ‘n droër klimaat kan die hibriede LVK met addisionele kapasiteit ontwerp word om waterverbruik tot 50% te verminder en steeds laer jaarlikse koste toon as ‘n konvensionele LVK. | af_ZA |
| dc.description.version | Doctoral | en_ZA |
| dc.format.extent | 148 pages | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/123864 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Hybrid -- Cooling | en_ZA |
| dc.subject | Electric power production | en_ZA |
| dc.subject | Air cooled condenser | en_ZA |
| dc.subject | Evaporative cooling | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | A single stage dry/wet dephlegmator: development, performance evaluation and application in a hybrid ACC at CSP or NGCC Scale. | en_ZA |
| dc.type | Thesis | en_ZA |