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Feasibility of different enhanced cooling media for more economic power generationWoest, Maria Susanna 07 August 2014 (has links)
M.Tech. (Metallurgical Engineering) / Please refer to full text to view abstract
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Performance optimization of engineering systems with particular reference to dry-cooled power plants /Conradie, Antonie Eduard. January 1995 (has links)
Dissertation (PhD)--University of Stellenbosch, 1995. / Bibliography. Also available via the Internet.
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Perimeter fan performance in forced draught air-cooled steam condensersVan der Spuy, Sybrand Johannes 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Axial flow fan arrays form part of air-cooled steam condensers in direct drycooled
power plants. This dissertation investigates the performance of axial flow
fans when located at the perimeter of a fan array. The perimeter (or edge) fans
may experience a reduction in air flow through the fan due to the prevalence of
distorted inlet conditions upstream of the fan. The reduction in air flow leads to a
reduction in the heat transfer capability of the steam condenser and a consequent
reduction in the electricity output of the power plant.
Due to the physical size of an air-cooled condenser, full-scale experiments are
often impractical and computational fluid dynamics (CFD) is used to model its
performance under various conditions. To limit the size of the CFD model the
axial flow fans in the CFD analysis are represented by means of simplified
methods. Three different simplified methods are presented and applied to a CFD
model of a single axial flow fan, namely the pressure jump method (PJM),
actuator disc method (ADM) and extended actuator disc method (EADM). The
results are compared to experimental values. The comparison highlights the
limitations of the models: The ADM fails to model fan performance correctly at
low flow rates, while the PJM ignores the variation in fan blade properties at
different locations within the fan rotor. The EADM is presented as an
improvement on both the other two models.
A multiple fan test facility is constructed, consisting of three 630 mm diameter
fans extracting air from a common inlet chamber. The inlet chamber is
constructed in such a way that one of the three fans act as the perimeter (edge)
fan. The floor of the inlet chamber can be adjusted to increase or reduce the inlet
flow distortion experienced by the edge fan. Six different fan configurations are
tested in the position of the edge fan and an empirical method is derived by which
the volumetric effectiveness of an edge fan can be predicted. The experimental
results are compared to CFD results for the same facility using the three different
simplified simulation methods investigated previously. Particle image velocimetry
(PIV) measurements are also performed upstream of the edge fan and the velocity
profiles at the inlet of the fan are compared to the profiles obtained numerically.
The comparisons show that the EADM predicts the performance of the edge fan
more accurately than the ADM en PJM.
The effect of adding a walkway and removing the bell mouth upstream of the
edge fan was investigated using the EADM. The results are used to show the
location of the loss mechanisms upstream of the edge fan. The addition of a
walkway moves the location of the pressure loss away from the edge fan bell
mouth towards the edge of the walkway. Consequently the distortion directly
upstream of the edge fan is reduced and its volumetric effectiveness increased.
The effect of removing the edge fan’s bell mouth is similar to the effect of adding
a walkway upstream of the edge fan. / AFRIKAANSE OPSOMMING: Aksiaalwaaiermatrikse vorm deel van lugverkoelde kondensors in direk droëverkoelde
kragstasies. Hierdie verhandeling ondersoek die werkverrigting van
aksiaalwaaiers wat geleë is op die rand van ‘n groot waaiermatriks. Die
randwaaiers kan ’n vermindering in deurvloei ondervind as gevolg van versteurde
inlaattoestande stroom-op vanaf die waaier. Die vermindering in lugvloei lei tot ’n
vermindering in die warmetoordagvermoë van die stoomkondensor en ’n
gepaardgaande afname in die elektrisiteitslewering van die kragstasie.
As gevolg van die fisiese grootte van die lugverkoelde kondensor is volskaalse
eksperimente gewoonlik onprakties en word berekeningsvloeimeganika (BVM)
gebruik om die werking van die aanleg onder verskeie toestande te modelleer. Ten
einde die grootte van die BVM model te beperk, word die aksiaalwaaiers in so ‘n
BVM analiese voorgestel met behulp van vereenvoudigde metodes. Drie
verskillende vereenvoudigde metodes word aangebied en toegepas op ‘n BVM
model van ‘n enkelwaaier, naamlik die druksprongmetode, die aksieskyfmetode
en die verlengde aksieskyfmetode. Die resultate word vergelyk met
eksperimentele waardes. Die vergelyking benadruk die beperkings van die
modelle: Die aksieskyfmetode kan nie die werking van die waaier akkuraat
voorspel by lae vloeie nie en die druksprongmetode ignoreer die variasie in
lemeienskappe op verskillende liggings binne-in die waaierrotor. Die verlengde
aksieskyfmetode word voorgestel as ‘n verbetering op die ander twee metodes.
‘n Veelvuldige waaiertoetsfasiliteit is saamgestel, bestaande uit drie 630 mm
deursnee waaiers wat lug uit ’n gemeenskaplike inlaatkamer suig. Die inlaatkamer
is so saamgestel dat een van die waaiers in die fasiliteit ‘n randwaaier
verteenwoordig. Die vloerhoogte van die inlaatkamer kan aangepas word om die
inlaatversteuring wat deur die raandwaaier ondervind word te vermeerder of te
verminder. Ses verskillende waaierkonfigurasies is getoets in die
randwaaierposisie. ‘n Empiriese metode waarmee die volumetriese effektiwiteit
van ‘n randwaaier voorspel kan word is afgelei. Die eksperimentele resultate word
vergelyk met ooreenstemmende BVM resultate vir dieselfde fasiliteit deur gebruik
te maak van die drie verskillende vereenvoudigde metodes wat vroeër ondersoek
is. Partikelbeeld snelheidsmetings word ook stroom-op vanaf die randwaaier
uitgevoer en die snelheidsprofiele by die inlaat van die waaier word vergelyk met
profiele wat numeries bereken word. Die vergelykings wys dat die verlengde
aksieskyfmetode die werkverrigting van ’n aksiaalwaaier meer akkuraat voorspel
as die aksieskyf- of druksprongmetodes.
Die effek van die installering van ‘n loopvlak en die verwydering van die
randwaaier se inlaatmondstuk word ondersoek met behulp van BVM deur gebruik
te maak van die verlengde aksieskyfmetode. Die resultate word spesifiek gebruik
om die ligging van die verliesmeganismes stroom-op vanaf die randwaaier aan te
dui. Die resultate wys dat die installering van ‘n loopvlak die ligging van die
drukverlies wegneem vanaf die rand van die waaierinlaat na die rand van die
loopvlak. Dit verminder die inlaatversteuring stroom-op vanaf die randwaaier en die volumetriese effektiwiteit word verhoog. Die verwydering van die randwaaier
se inlaatmondstuk het ‘n soortgelyke effek as die installering van ‘n loopvlak
stroom-op vanaf die randwaaier.
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Air-cooled heat exchangers and cooling towers : thermal-flow performance evaluation and designKroger, Detlev G. 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: During the last 30 years I have been involved in the theory and practice of thermal engineering and
in particular, in the areas of air-cooled heat exchangers and cooling towers for the power,
refrigeration, process and petrochemical industries in South Africa and internationally. During this
period, I have authored and co-authored more than 120 papers that were published in technical
journals or presented at conferences nationally or internationally. Most of these papers are included
in a manuscript entitled "Air-cooled Heat Exchangers and Cooling Towers", in which Ipresent a
systematic approach to the thermal performance evaluation and design of industrial air-cooled heat
exchangers and cooling towers. This original publication also includes the relevant practice
applicable to the design of cooling systems, based on my experience as a consultant to industry.
Design offices throughout the world presently follow our design methods, or at least employ many
of our research results. Our work has furthermore contributed to the development of improved
cooling system designs (e.g. new dephlegmator header designs), components (e.g. single-row
flattened finned tubes) and product improvement and quality control (e.g. performance testing and
measurement of thermal contact resistance between fin and tube during production). Many of our
research findings have found application in the modification of existing cooling systems. The
manuscript has also been used as reference work during the presentation of short courses to
practising engineers and consultants in industry and to engineering graduates at the University of
Stellenbosch.
A two-volume edition of this manuscript was published by PennWell Corp., Tulsa, Oklahoma, USA
in 2004. / AFRIKAANSE OPSOMMING: Gedurende die laaste 30 jaar was ek betrokke by die teorie en praktyk van lugverkoelde warmteoordraers
en koeltorings vir die kragopwekkings-, verkoelings-, proses- en petro-chemiesenywerhede
in Suid-Afrika sowel as in die buiteland. Gedurende hierdie periode was ek outeur en
mede-outeur van meer as 120 publikasies wat in tegniese tydskrifte, of by plaaslike of oorsese
konferensies aangebied is. Die meeste van hierdie publikasies vorm deel van 'n manuskrip getiteld
"Air-cooled Heat Exchangers and Cooling Towers" waarin ek 'n sistematiese benadering tot die
bepaling van die termiese vermoë en ontwerp van industriële lugverkoelde warmteoordraers en
koeltorings aanbied. Hierdie oorspronklike publikasie bevat ook die relevante praktyk wat van
toepassing is op verkoelingsaanlegte. Ontwerpkantore wêreldwyd volg tans hierdie
ontwerpsmetodes, of gebruik ten minste baie van ons navorsingsresultate. Ons werk het verder
bygedra tot die ontwikkeling van verbeterde verkoelingsaanlegte (bv. nuwe deflegmatore),
komponente (bv. enkelbuisry platvinbuise ) en verbeterde produkte en kwaliteitskontrole
(bv. toetsing van verkoelingsvermoë oftermiese kontakweerstand tussen vin en buis gedurende
produksie). Baie van ons bevindinge het toepassing gevind in die modifikasie van
verkoelingsaanlegte. Die manuskrip is ook as verwysing gebruik gedurende die aanbieding van
kort kursusse aan ingenieurs in die praktyk en aan nagraadse studente aan die Universiteit van
Stellenbosch.
'n Twee-volume uitgawe van die manuskrip is deur PennWell Corp., Tulsa, Oklahome, VSA in
2004 gepubliseer.
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Performance optimization of engineering systems with particular reference to dry-cooled power plantsConradie, Antonie Eduard 03 1900 (has links)
Thesis (PhD (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 1995. / Computer simulation programs were developed for the analysis of dry-cooling systems for power
plant applications. Both forced draft direct condensing air"cooled condensers and hyperbolic natural
draft indirect dry-cooling towers are considered.
The results of a considerable amount of theoretical and experimental work are taken into account to
model all the physical phenomena ofthese systems, to formu1ate the problems in formal mathematical
terms and to design and apply suitable computational algorithms to solve these problems effectively
and reliably.
The dry-cooling systems are characterized by equation-based models. These equations are
simultaneously solved by a specially designed constrained nonlinear least squares algorithm to
determine the performance characteristics of the dry-cooling systems under fixed prescnoed
operating conditions, or under varying operating conditions when coupled to a turbo-generator set.
The solution procedure is very fast and effective.
A capital and operating cost estimation procedure, based on information obtained from dry-cooling
system component manufacturers and the literature, is proposed. Analytical functions express the
annual cost in terms ofthe various geometrical and operating parameters ofthe dry-cooling systems.
The simu1ation and the cost estimation procedures were coupled to a constrained nonlinear
programming code which enable the design of minimum cost dry-cooling systems at fixed prescribed
operating conditions, or dry-cooling systems which minimize the ratio of total annual cost to the
annual net power output of the corresponding turbo-generator set. Since prevailing atmospheric
conditions, especially the ambient temperature, influence the performance of dry-cooling systems,
wide fluctuations in turbine back pressure occur. Therefore, in the latter case the optimal design is
based on the annual mean hourly frequency ofambient temperatures, rather than a fixed value.
The equation-based models and the optimization problems are simultaneously solved along an
infeasible path (infeasible path integrated approach). The optimization model takes into
consideration all the parameters that may affect the capital and operating cost of the dry-cooling
systems and does not prescribe any limits, other than those absolutely essential due to practical
limitations and to simulate the systems effectively. The influence that changes ofthe constraint limits
and some problem parameters have on the optinmm solution, are evaluated (sensitivity analysis). The Sequential Quadratic Programming (SQP) method is used as the basis in implementing nonlinear
optimization techniques to solve the cost minimirnti~n problems. A stable dual active set algorithm
for convex quadratic programming (QP) problems is implemented that makes use of the special
features ofthe QP subproblems associated with the SQP methods. TIrls QP algorithm is also used as
part of the algorithm that solves the constrained nonlinear least squares problem This particular
implementation of the SQP method proved to be very reliable and efficient when applied to the
optimization problems based on the infeasible path integrated approach.
However, as the nonlinear optimization problems become large, storage requirements for the Hessian
matrix and computational expense of solving large quadratic programming (QP) subproblems
become prohibitive. To overcome these difficulties, a reduced Hessian SQP decomposition strategy
with coordinate bases was implemented. This method exploits the low dimensionality of the
subspace of independent decision variables. The performance of this SQP decomposition is further
improved by exploiting the mathematical structure of the engineering model, for example the block
diagonal structure ofthe Jacobian matrix. Reductions ofbetween 50-90% in the total CPU time are
obtained compared to conventional SQP optimization methods. However, more function and
gradient evaluations are used by this decomposition strategy.
The computer programs were extensively tested on various optimization problems and provide fast
and effective means to determine practical trends in the manufacturing and construction of costoptimal
dry-cooling systems, as well as their optimal performance and operating conditions in power
plant applications.
The dissertation shows that, through the proper application of powerful optimization strategies and
careful tailoring of the well constructed optimization model, direct optimization of complex models
does not need to be time consuming and difficult.
Reconnnendations for further research are made. / Imported from http://etd.sun.ac.za April 2010.
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Comparative Chemistry of Thermally Stressed North Lake and Its Water Source, Elm Fork Trinity RiverSams, Barry L. 12 1900 (has links)
To better understand abiotic dynamics in Southern reservoirs receiving heated effluents, water was analyzed before and after impoundment in 330 ha North Lake. Macronutrients, metals, and chlorinated hydrocarbons were measured. Concentrations of nutrients and metals in sediments were quantified in this 2 yr study. River water prior to impoundment contained 16 times more total phosphorus, and supported 23 times more Selenastrum capricornutum cells in an algal assay than reservoir water. The reservoir has essentially no drainage and since evaporation is high, the concentrations of many dissolved solids have increased since the reservoir was filled in 1958. North Lake is now phosphorus limited. Apparently altered chemical equilibria have caused precipitation or adsorption of phosphorus with calcium and iron.
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Computer optimization of dry and wet/dry cooling tower systems for large fossil and nuclear power plants.Choi, Michael Kam-wah. January 1978 (has links)
Thesis: M.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1978 / Includes bibliographical references. / M.S. / M.S. Massachusetts Institute of Technology, Department of Mechanical Engineering
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