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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Condition-based monitoring of natural draught wet-cooling tower performance-related parameters

Ehlers, Frederik Coenrad 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The meteorological conditions at Eskom’s Majuba Power Station are measured, evaluated and trended in this dissertation. The results are used to evaluate the current natural draught wet-cooling tower (NDWCT) design- and performance test specifications and to compare these to the original design- and performance test specifications. The evaluation reveals that the design parameters for the NDWCTs at Majuba Power Station, a cooling system that was originally designed optimally, could have been determined differently and arguably more accurately by using the wet-bulb temperature (Tawb) as the main design variable instead of the dry-bulb temperature (Ta). A new technique to determine optimal NDWCT design and performance test conditions is consequently proposed. In order to satisfy the atmospheric conditions required for a successful NDWCT performance test, it is also proposed that the tests be undertaken between 12:00 and 14:00 during Summer. It is found that the NDWCT inlet Tawb, measured at specific heights, does not compare well to the far-field Tawb measured at the same heights when a Tawb accuracy of 0.1 K is required. It is proposed that a more representative far-field Tawb measuring height of 10 m should be used in future NDWCT designs as the NDWCT design temperature reference height. The industry-standard reference height should, however, still be used during temperature profile calculations. A parametric study of the water-steam cycle and wet-cooling system at Majuba indicates that during full load conditions, the generated output (Pst) is primarily dependent on the condenser saturation pressure (pc). The latter is reliant on Tawb, the temperature lapse rate (LRT) that is represented by the temperature profile exponent (bT), the main cooling water flow rate (mcw), atmospheric pressure (pa), and wind speed (VW). Using historical plant data relatively simple methods, enabling the quick and effective determination of these relationships, are proposed. The plant-specific and atmospheric parameters required for these analyses are also tabulated. Two NDWCT effectiveness models, one mathematical (Kröger, 1998) and one statistical artificial neural network (ANN) model are presented and evaluated. ANNs, which are not often used to evaluate NDWCT effectiveness, provide accurate NDWCT temperature approach results within 0.5 K of measured values for varying dependent variables. This motivates that an ANN, if set up and used correctly, can be an effective condition-monitoring tool and can be used to improve the accuracy of more empirical NDWCT performance models. The one-dimensional mathematical effectiveness model provides accurate results under NDWCT design conditions. The dependency of Majuba’s NDWCT to the rain zone mean drop diameter (dd) is evaluated by means of the one-dimensional mathematical model. A reduction in dd from 0.0052 m to 0.0029 m can reduce the NDWCT re-cooled water temperature (Tcwo) so that the rated pc is reduced by 0.15 kPa, which relates to a combined financial saving during peak and off-peak periods of R1.576M in 2013 and R1.851M in 2016. Similar improvements can result in higher savings at other wet-cooled stations in the Eskom fleet due to less optimally-designed wet-cooling systems. The proposed techniques should be considered in future economic evaluations of wet-cooling system improvements at different power stations. / AFRIKAANSE OPSOMMING: Die meteorologiese toestande by Eskom se Majuba-kragstasie is deur die navorser gemeet en -evalueer. Die resultate word gebruik om die Natuurlike-trek, Nat koeltoring (NTNKT) se ontwerp- en werkverrigting toetsspesifikasies te evalueer en vergelyk met die oorspronklike toetsspesifikasies. Die resultate dui daarop dat die ontwerpsparameters vir die NTNKTs by Majuba-kragstasie, ‘n verkoelings-sisteem wat aanvanklik optimaal ontwerp is, op ‘n ander, selfs meer akkurate manier bepaal kon word deur die natbol-temperatuur (Tawb) te gebruik as die hoof-ontwerpsparameter inplaas van die droëbol temperatuur (Ta).’n Nuwe tegniek wat gebruik kan word om akkurate NTNKT ontwerp- en werkverrigting toetsspesifikasies te bepaal word voorgestel. Die tydperk vir die mees optimale atmosferiese toestande, wanneer NTNKT-toetse uitgevoer moet word, word vasgestel as tussen 12:00 en 14:00 tydens Somermaande. Dit word bewys, vir ’n Tawb akkuraatheid van 0.1 K, dat die NTNKT inlaat-Tawb, gemeet by verskillende hoogtes, nie vergelykbaar is met Tawb wat ver van die NTNKT af op dieselfde hoogtes gemeet word nie. ’n Meer aanvaarbare hoogte van 10 m word voorgestel as die NTNKT ontwerpstemperatuur verwysingshoogte vir toekomstige NTNKT ontwerpe wanneer die Tawb ver van die NTNKT af meet word. Die industrie-standaard temperatuur verwysingshoogte moet wel steeds gebruik word tydens temperatuur-profielberekeninge. ’n Parametriese studie van die turbine se water-stoom siklus en die nat-verkoelingstelsel by Majuba dui daarop dat die generator se uitset (Pst) hoofsaaklik afhanklik is van die kondensator se druk (pc) gedurende vol-vrag toestande. Druk (pc) is weer afhanklik van Tawb, die temperatuur vervaltempo (LRT) wat voorgestel word deur die temperatuur profiel eksponent (bT), die verkoelingswater-vloeitempo (mcw), atmosferiese druk (pa) en windspoed (VW). Deur die gebruik van historiese data word redelike eenvoudige metodes voorgestel om dié verhoudings doeltreffend te bepaal. Die atmosferiese- en stasie-spesifieke parameters wat benodig word vir dié ontleding is ook getabuleer. Twee modelle vir NTNKT-effektiweit, ’n wiskundige (gebaseer op Kröger, 1998) en statistiese kunsmatige neurale-netwerk (KNN) model, word aangebied en geëvalueer. KNNe, wat nie gereeld gebruik word om NTNKTe se effektiwiteit te evalueer nie, lewer akkurate NTNKT temperatuur-benadering resultate binne 0.5 K van die gemete resultate vir wisselende afhanklike parameters. Dié resultate motiveer dat ’n KNN wat korrek opgestel is doeltreffend gebruik kan word om die toestand van NTNKTs te bepaal en om die akkuraatheid van ander NTNKT-modelle te verbeter. Die eendimensionele, wiskundige model lewer akkurate resultate onder NTNKT ontwerpspesifikasies. ’n Wiskundige NTNKT-model word gebruik om die afhanklikheid van Majubakragstasie se NTNKTe tot die reënsone druppelgrootte (dd) te bereken. 'n Vermindering in dd van 0,0052 tot 0,0029 m kan die NTNKT se afgekoelde watertemperatuur (Tcwo), van só 'n aard verlaag dat pc verminder met 0,15 kPa. Só kan ’n gesamentlike vol- en gedeeltelike vrag finansiële besparing van R1.576M in 2013 en R1.851M in 2016 behaal word. Soortgelyke verbeterings aan verkoelingstelsels sal lei tot meer en hoër besparings by ander Eskom nat-verkoelde stasies. Dié tegnieke moet in ag geneem word tydens toekomstige ekonomiese evaluasies van verbeterings tot nat-verkoelingstelsels by ander kragstasies.
2

Experimental and numerical evaluation of anisotropic fill performance characteristics in cross- and counterflow

Grobbelaar, Pieter Jacobus 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The confidence level of modeling cooling towers, where oblique air flow within anisotropic fills takes place, is higher when the change in fill‟s performance cha-racteristics, dependent on the way that air flows through the fill, is better unders-tood. A trickle fill‟s performance characteristics in crossflow are compared to its per-formance characteristics in counterflow by doing crossflow fill tests that are per-formance comparable to counterflow tests with the same fill. In order to do these tests, an existing crossflow fill test facility is critically evaluated and improved. The difference between crossflow and counterflow trickle fill performance charac-teristics is found to depend on air mass velocity (Ga) and water mass velocity (Gw) and to be between 0 and 35% for the Merkel number (Me) and up to almost 200% for the loss coefficient. Additionally, the validity of a recently developed 2-dimensional evaporative cool-ing model is investigated by comparing its predictions to experimental results. The following conclusions are made: - For trickle fill and rain zone tests, the model, with the present assumptions, predicts the average temperature of the outlet air to within approximately 0.4 °C. - Currently, temperature profiles that are experimentally measured at the air and water outlets are subject to significant edge effects, which prevent a fair com-parison to model predictions. - The model predictions can be improved if local variations in Me and the redi-stribution of water by the fill are taken into account. / AFRIKAANSE OPSOMMING: Die betroubaarheid van die modellering van koeltorings, waar lug skuins deur anisitropiese pakking (of “fill” in Engels) vloei, is hoër indien die verandering in die pakking se verrigtingseienskappe, wat afhang van die manier waarop die lug deur die pakking vloei, beter verstaan word. „n Drup pakking (of “trickle fill” in Engels) se verrigtingseienskappe in kruisvloei word vergelyk met dié in teenvloei deur kruisvloei pakking toetse, wat direk vergelykbaar is met teenvloei toetse vir dieselfde pakking, te doen. Ten einde hieredie toetse te doen, word ʼn bestaande kruisvloei toets fasiliteit krities ondersoek en verbeter. Dit word bevind dat die verskil tussen die drup pakking se kruisvloei en teenvloei verrigtingseienskappe afhang van lug massa snelheid (Ga) en water massa snelheid (Gw) en 0 tot 35% is vir die Merkel getal (Me) en so groot as 200% is vir die verlies koëffisiënt. Verder word die geldigheid van ʼn 2-dimensionele nat-verkoelingsmodel wat onlangs ontwikkel is ondersoek deur die model se voorspellings te vergelyk met eksperimentele resultate. Die volgende gevolgtrekkings word gemaak: - Die model, met huidige aannames, voorspel die gemiddelde uitlaat lug temperatuur met ʼn afwyking van ongeveer 0.4°C. - Die temperatuur profiele wat eksperimenteel gemeet word by die lug en water uitlate is onderworpe aan noemenswaardige rand effekte, wat ʼn behoorlike vergelyk met model voorspellings verhoed. - Die model se voorspelling van die profiele kan verbeter word indien die lokale variasies in Me en die herverdeling van die water deur die pakking in ag geneem kan word.
3

Performance characteristics of an air-cooled steam condenser incorporating a hybrid (dry/wet) dephlegmator

Heyns, Johan Adam 12 1900 (has links)
Thesis (MScEng (Mechanical and Mechatronic Engineering))--Stellenbosch University, 2008. / This study evaluates the performance characteristics of a power plant incorporating a steam turbine and a direct air-cooled dry/wet condenser operating at different ambient temperatures. The proposed cooling system uses existing A-frame air-cooled condenser (ACC) technology and through the introduction of a hybrid (dry/wet) dephiegmator achieves measurable enhancement in cooling performance when temperatures are high. In order to determine the thermal-flow performance characteristics of the wet section of the dephlegmator, tests are conducted on an evaporative cooler. From the experimental results, correlations for the water film heat transfer coefficient, air-water mass transfer coefficient and the air-side pressure drop over a deluged tube bundle are developed. During periods of high ambient temperatures the hybrid (dry/wet) condenser operating in a wet mode can achieve the same increased turbine performance as an oversized air-cooled condenser or an air-cooled condenser rith adiabatic cooling (spray cooling) of the inlet air at a considerably lower cost. For the same turbine power output the water consumed by an air-cooled condenser incorporating a hybrid (dry/wet) dephlegmator is at least 20% less than an air- cooled condenser with adiabatic cooling of the inlet air. / Sponsored by the Centre for Renewable and Sustainable Energy Studies, Stellenbosch University
4

Performance evaluation of natural draught cooling towers with anisotropic fills

Reuter, Hanno Carl Rudolf 12 1900 (has links)
Thesis (PhD) -- University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In the design of a modern natural draught wet-cooling tower (NDWCT), structural and performance characteristics must be considered. Air flow distortions and resistances must be minimised to achieve optimal cooling which requires that the cooling towers must be modelled two-dimensionally and ultimately threedimensionally to be optimised. CFD models in literature are found to be limited to counterflow cooling towers packed with film fill, which is porous in one direction only and generally has a high pressure drop, as well as purely crossflow cooling towers packed with splash fill. This simplifies the analysis considerably as the effects of flow separation at the air inlet are minimised and fill performance is determined using the method of analysis originally employed to determine the fill performance characteristics from test data. Many counterflow cooling towers are, however, packed with trickle and splash fills which have anisotropic flow resistances, which means the fills are porous in all flow directions and thus air flow can be oblique through the fill, particularly near the cooling tower air inlet. This provides a challenge since available fill test facilities and subsequently fill performance characteristics are limited to purely counter- and crossflow configuration. In this thesis, a CFD model is developed to predict the performance of NDWCTs with any type of spray, fill and rain zone configuration, using the commercial code FLUENT®. This model can be used to investigate the effects of different: atmospheric temperature and humidity profiles, air inlet and outlet geometries, air inlet heights, rain zone drop size distributions, spray zone performance characteristics, variations in radial water loading and fill depth, and fill configurations or combinations on cooling tower performance, for optimisation purposes. Furthermore the effects of damage or removal of fill in annular sections and boiler flue gas discharge in the centre of the tower can be investigated. The CFD modelling of NDWCTs presents various options and challenges, which needed to be understood and evaluated systematically prior to the development of a CFD model for a complete cooling tower. The main areas that were investigated are: spray and rain zone performance modelling by means of an Euler-Lagrangian model; modelling of air flow patterns and flow losses; modelling of fill performance for oblique air flow; modelling of air pressure and temperature profiles outside and inside the cooling tower. The final CFD results for the NDWCT are validated by means of corresponding one-dimensional computational model data and it is found that the performance of typical NDWCTs can be enhanced significantly by including protruding platforms or roundings at the air inlet, reducing the mean drop size in the rain zone, radially varying the fill depth and reducing the air inlet height. / AFRIKAANSE OPSOMMING: By die ontwerp van ‘n moderne natuurlike trek nat koeltoring (NTNK), moet strukturele en werkverrigtings eienskappe in ag geneem word. Wanverdeelde lugvloei en vloeiweerstande moet geminimaliseer word om optimale verkoeling te bewerkstellig, wat vereis dat die koeltorings twee-dimensioneel en uiteindelik driedimensioneel gemodelleer moet word om hulle te kan optimeer. Dit is gevind dat berekeningsvloeidinamika (BVD of “CFD” in engels) modelle in die literatuur, beperk is tot teenvloei koeltorings gepak met film tipe pakking, wat net in een vloeirigting poreus is en boonop gewoonlik ook ‘n hoë drukval het, sowel as suiwer dwarsvloei koeltorings met spatpakking. Hierdie vergemaklik die analise aansienlik omdat die effekte van vloeiwegbreking by die luginlaat verklein word en die pakking se werkverrigtingsvermoë bereken kan word met die analise metode wat oorspronklik gebruik is om die pakkingseienskappe vanaf toets data te bepaal. Baie teenvloei koeltorings het egter drup- (“trickle”) of spatpakkings met anisotropiese vloeiweerstand, wat beteken dat die pakking poreus is in alle vloeirigtings en dat die lug dus skuins deur die pakking kan vloei, veral naby die koeltoring se lug inlaat. Hierdie verskaf ‘n uitdaging aangesien beskikbare pakking toetsfasiliteite, en dus ook pakking karakteristieke, beperk is tot suiwer teenvloei en dwarsvloei konfigurasie. ‘n BVD model word in hierdie tesis ontwikkel wat die werkverrigtingsvermoë van NTNK’s kan voorspel vir enige sproei, pakking en reënsone konfigurasie deur van die kommersiële sagteware FLUENT® gebruik te maak. Hierdie model kan gebruik word om die effekte van verskillende: atmosferiese temperatuur- en humiditeitsprofiele, lug inlaat en uitlaat geometrië, lug inlaat hoogtes, reënsone druppelgrootteverdelings, sproeisone werkverrigtingskarakteristieke, variasie in radiale waterbelading en pakking hoogte, en pakking konfigurasies of kombinasies op koeltoringvermoë te ondersoek vir optimerings doeleindes. Verder kan die effekte van beskadiging of verwydering van pakking in annulêre segmente, en insluiting van ‘n stoomketel skoorsteen in die middel van die toring ondersoek word. Die BVD modellering van NTNK bied verskeie moontlikhede en uitdagings, wat eers verstaan en sistematies ondersoek moes word, voordat ‘n BVD model van ‘n algehele NTNK ontwikkel kon word. Die hoof areas wat ondersoek is, is: sproeien reënsone modellering mbv ‘n Euler-Lagrange model; modellering van lugvloeipatrone en vloeiverliese; modellering van pakking verrigting vir skuins lugvloeie; modellering van lugdruk- en temperatuurprofiele buite en binne in die koeltoring. Die BVD resultate word mbv van data van ‘n ooreenstemmende eendimensionele berekeningsmodel bevestig en dit is bevind dat die werkverrigting van ‘n tipiese NTNK beduidend verbeter kan word deur: platforms wat uitstaan of rondings by die luginlaat te installeer, die duppelgrootte in die reënsone te verklein, die pakkingshoogte radiaal te verander, en die luginlaathoogte te verlaag.
5

Optimisation criteria of a Rankine steam cycle powered by thorium HTR / Steven Cronier van Niekerk

Van Niekerk, Steven Cronier January 2014 (has links)
HOLCIM has various cement production plants across India. These plants struggle to produce the projected amount of cement due to electricity shortages. Although coal is abundant in India, the production thereof is in short supply. It is proposed that a thorium HTR (100 MWt) combined with a PCU (Rankine cycle) be constructed to supply a cement production plant with the required energy. The Portland cement production process is investigated and it is found that process heat integration is not feasible. The problem is that for the feasibility of this IPP to be assessed, a Rankine cycle needs to be adapted and optimised to suit the limitations and requirements of a 100 MWt thorium HTR. Advantages of the small thorium HTR (100 MWt) include: on-site construction; a naturally safe design and low energy production costs. The reactor delivers high temperature helium (750°C) at a mass flow of 38.55 kg/s. Helium re-en ters the reactor core at 250°C. Since the location of the cement production plant is unknown, both wet and dry cooling tower options are investigated. An overall average ambient temperature of India is used as input for the cooling tower calculations. EES software is used to construct a simulation model with the capability of optimising the Rankine cycle for maximum efficiency while accommodating various out of the norm input parameters. Various limitations are enforced by the simulation model. Various cycle configurations are optimised (EES) and weighed against each other. The accuracy of the EES simulation model is verified using FlowNex while the optimised cycle results are verified using Excel’s X-Steam macro. It is recommended that a wet cooling tower is implemented if possible. The 85% effective heat exchanger delivers the techno-economically optimum Rankine cycle configuration. For this combination of cooling tower and heat exchanger, it is recommended that the cycle configuration consists of one de-aerator and two closed feed heaters (one specified). After the Rankine cycle (PCU) has been designed and optimised, it is evident that the small thorium HTR (100 MWt) can supply the HOLCIM plant with the required energy. The optimum cycle configuration, as recommended, operates with a cycle efficiency of 42.4% while producing 39.867 MWe. A minimum of 10 MWe can be sold to the Indian distribution network at all times, thus generating revenue. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014
6

Optimisation criteria of a Rankine steam cycle powered by thorium HTR / Steven Cronier van Niekerk

Van Niekerk, Steven Cronier January 2014 (has links)
HOLCIM has various cement production plants across India. These plants struggle to produce the projected amount of cement due to electricity shortages. Although coal is abundant in India, the production thereof is in short supply. It is proposed that a thorium HTR (100 MWt) combined with a PCU (Rankine cycle) be constructed to supply a cement production plant with the required energy. The Portland cement production process is investigated and it is found that process heat integration is not feasible. The problem is that for the feasibility of this IPP to be assessed, a Rankine cycle needs to be adapted and optimised to suit the limitations and requirements of a 100 MWt thorium HTR. Advantages of the small thorium HTR (100 MWt) include: on-site construction; a naturally safe design and low energy production costs. The reactor delivers high temperature helium (750°C) at a mass flow of 38.55 kg/s. Helium re-en ters the reactor core at 250°C. Since the location of the cement production plant is unknown, both wet and dry cooling tower options are investigated. An overall average ambient temperature of India is used as input for the cooling tower calculations. EES software is used to construct a simulation model with the capability of optimising the Rankine cycle for maximum efficiency while accommodating various out of the norm input parameters. Various limitations are enforced by the simulation model. Various cycle configurations are optimised (EES) and weighed against each other. The accuracy of the EES simulation model is verified using FlowNex while the optimised cycle results are verified using Excel’s X-Steam macro. It is recommended that a wet cooling tower is implemented if possible. The 85% effective heat exchanger delivers the techno-economically optimum Rankine cycle configuration. For this combination of cooling tower and heat exchanger, it is recommended that the cycle configuration consists of one de-aerator and two closed feed heaters (one specified). After the Rankine cycle (PCU) has been designed and optimised, it is evident that the small thorium HTR (100 MWt) can supply the HOLCIM plant with the required energy. The optimum cycle configuration, as recommended, operates with a cycle efficiency of 42.4% while producing 39.867 MWe. A minimum of 10 MWe can be sold to the Indian distribution network at all times, thus generating revenue. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014
7

Performance evaluation of wet-cooling tower fills with computational fluid dynamics

Gudmundsson, Yngvi 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A wet-cooling tower fill performance evaluation model developed by Reuter is derived in Cartesian coordinates for a rectangular cooling tower and compared to cross- and counterflow Merkel, e-NTU and Poppe models. The models are compared by applying them to a range of experimental data measured in the cross- and counterflow wet-cooling tower test facility at Stellenbosch University. The Reuter model is found to effectively give the same results as the Poppe method for cross- and counterflow fill configuration as well as the Merkel and e-NTU method if the assumptions as made by Merkel are implemented. A second order upwind discretization method is applied to the Reuter model for increased accuracy and compared to solution methods generally used to solve cross- and counterflow Merkel and Poppe models. First order methods used to solve the Reuter model and crossflow Merkel and Poppe models are found to need cell sizes four times smaller than the second order method to obtain the same results. The Reuter model is successfully implemented in two- and three-dimensional ANSYS-Fluent® CFD models for under- and supersaturated air. Heat and mass transfer in the fill area is simulated with a user defined function that employs a second order upwind method. The two dimensional ANSYS-Fluent® model is verified by means of a programmed numerical model for crossflow, counterflow and cross-counterflow. / AFRIKAANSE OPSOMMING: ‘n Natkoeltoring model vir die evaluering van pakkings werkverrigting, wat deur Reuter ontwikkel is, word in Kartesiese koördinate afgelei vir ‘n reghoekige koeltoring en word vergelyk met kruis- en teenvloei Merkel, e-NTU en Poppe modelle. Die verskillende modelle word vergelyk deur hulle op ‘n reeks eksperimentele data toe te pas wat in die kruis- en teenvloei natkoeltoring toetsfasiliteit by die Universiteit van Stellenbosch gemeet is. Dit is bevind dat die Reuter model effektief dieselfde resultate gee as die Poppe model vir kruis- en teenvloei pakkingskonfigurasies sowel as die Merkel en e-NTU metode, indien dieselfde aannames wat deur Merkel gemaak is geїmplementeer word. ‘n Tweede orde “upwind” metode word op die Reuter model toegepas vir hoër akkuraatheid en word vergelyk met oplossingsmetodes wat gewoonlik gebruik word om kruis- en teenvloei Merkel en Poppe modelle op te los. Eerste orde metodes wat gebruik is om die Reuter model en kruisvloei Merkel en Poppe modelle op te los benodig rooster selle wat vier keer kleiner is as vir tweede orde metodes om dieselfde resultaat te verkry. Die Reuter model is suksesvol in twee- en driedimensionele ANSYS-Fluent® BVD (“CFD”) modelle geїmplementeer vir on- en oorversadigde lug. Warmte- en massaoordrag in die pakkingsgebied word gesimuleer mbv ‘n gebruiker gedefinieerde funksie (“user defined function”) wat van ‘n tweede orde numeriese metode gebruik maak. Die tweedimensionele ANSYS-Fluent® model word m.b.v. ‘n geprogrameerde numeriese model bevestig vir kruis-, teen- en kruis-teenvloei.
8

A critical evaluation and refinement of the performance prediction of wet-cooling towers

Kloppers, Johannes Christiaan 12 1900 (has links)
Thesis (PhD (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2003. / The thermal performance prediction of wet-cooling towers is critically analyzed and refined. Natural draft counterflow towers and mechanical draft counterflow and crossflow towers are considered. The Merkel, Poppe and e-NTU heat and mass transfer methods of analysis are derived from first principles, as these methods form the cornerstone of wet-cooling tower performance evaluation. The critical differences between these methods, when applied to fill performance analyses and cooling tower performance evaluations, are highlighted. The reasons for these differences are discussed with the aid of psychrometric charts. A new extended empirical relation for the loss coefficient of fills is proposed where the viscous and form drag effects are accounted for as well as the buoyancy, momentum and fill height effects. The empirical equation for the transfer characteristic of fills is extended to include the effects of fill height and the inlet water temperature. Empirical equations to predict the temperature inversion profile, height of the temperature inversion and the height from which air is drawn into the cooling tower are developed. The influence of temperature and humidity inversions on the performance of wet-cooling towers is subsequently investigated. A comprehensive analytical computer program is developed to predict and optimize the performance of wet-cooling towers. Computer programs are also developed to generate cooling tower performance curves, analyze fill performance test data and plot psychrometric charts.
9

Návrh chladícího okruhu pro odvod tepla z kondenzátoru parní turbíny / Design of a cooling circuit for heat removal from a steam turbine condenser

Susna, David January 2018 (has links)
This thesis deals with the problems of wounding of low potential transferred from steam turbine condenser. First, in the theoretical part variations of steam condenser design are described. Then there is a description of variations of cooling cycles and possibilities of their operation range. In second part of the thesis there are two common cooler options chosen. Those are wet cooling tower with natural draft and dry chiller with forced draft. Two types of cooling liquid are chosen to be used for dry cooling. These are water and the other one is 50 % mixture of water and propylene glycol. Based on the calculation results of both cooling cycle variations appropriate pumps are chosen, fan for forced convection respectively. Parts of the thesis are also projection drawings for both calculated variations.

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