The purpose of this investigation was to improve upon the overall design of a 15-plate fractionating assembly used in the separation of simple binary mixtures of isopropyl alcohol and water, to recalibrate all measuring devices used in the operation of the column, to develop an analytical method by which the composition of liquid samples from the column could be determined accurately and quickly, and, in general, to place the assembly in such condition that experimental runs can be made more easily with a higher degree of accuracy than has previously been possible. / Master of Science

Gas absorption may be defined as the transfer from a gas to a liquid of one or more components of a gaseous mixture by means of solution in a liquid. This is accomplished by bringing the two phases together, with a large amount of interfacial surface, in an economical manner for commercial use. Much is lacking in knowledge of the theory of gas absorption. This lack of knowledge and the wide variety of purposes and specifications have caused many types of absorption equipment to be designed, built and used. The objective in all causes has been to increase the surface of contact between the gas and the liquid at low installation cost and with low operating costs. The most common type of absorption equipment is the packed tower. It consists, essentially, of a vertical shell filled with an inert packing material. Absorption is accomplished by countercurrent operation, the solvent being allowed to trickle down over the packing material while the gas passes up through the wetted packing. The tower packing is the fundamental consideration in improving the efficiency of the equipment. A packing material should have a low resistance to gas flow so as to give low maintenance costs, a high absorption capacity and low costs of installation. In any case, the packing that most completely fills the requirements should be used. It is the purpose of this investigation to make a study of the characteristics of operation of copper knit-metal cloth, in comparison to Raschig rings, when used absorption tower packings. / Master of Science

A questioning of methods: If we are to accept existing American culture as an entity, should design not embody the spirit inherent in that culture? In Europe, architecture has been afforded the luxury of time. There, the concept of dwelling has encompassed the questions of man’s position as a rational being separated both from his surrounding environment and his divinity. A sense of alienation from such a universe forced him to search beyond his immediate environment. The role of architecture thus became a mediator, a departure point where man could dwell between heaven and earth. Sanctity, purity, proportion, centrality, and hierarchy all became building blocks for an architecture striving for a transcendental perfection. In the United States, however, architecture has been adjusted to accept its surrounding environment as a formal model. Space is defined either by the existing condition of the environment or by the will of man existing within his surroundings. Man, no longer alien or subservient, now does not need a mediator but instead a throne on which to share in the government within his surrounding environment. As a result, the American conception of space (i.e. the ‘tradition of the way we view our landscape’) has evolved into something different from that of our European counterparts. In a sense, America is the embodiment of the rational enlightenment in a new society. Its history lies not in the hearts and minds of its citizens, but on the other side of the ocean. Because of this unique occurrence where history loses its proximity, America has been able to develop into what Jean Beaudrillard describes as truly modern: a “utopia achieved”. It is a space where random meets rational and the limitless becomes a limit, a space which rejects European conceptions of centrality and hierarchy. If the foundations of Europe lie within the philosophy of Aristotle, than those of North America lie within the theories of Newton. Whereas Aristotle revealed the parameters of a perfect order, along with its ensuing hierarchy and centrality. In Dice Thrown, Benjamin Gianni investigates both early American farmsteads as well as the development of its cities (the rural and the urban) and compares them to European types. In the rural comparison, the European farm seems to be organized around a courtyard, creating an order of symmetry and proportion. The American farm structures, however, are arranged loosely in a cluster, their relationship being functional necessities and a common way of building (the doghouse is designed to look like the shed, which is designed to look like the main house). Moreover, Gianni draws similar contraindications in the urban comparison. In Europe, the city is autonomous, walled off from the outside and arranged in a hierarchy with the most important structures at the highest points in the center. Conversely, in American cities the countryside is brought into the city at its center in the form of parks to remind the people of their link with their natural origins. For traditional Europe then, purity and perfection lie in the symbolic harmony of formal relationships, where a center defines the elements around it and provides a place for man between nature and the heavens. For America, however, purity and perfection lie in the vast expanse of the natural surroundings. No longer a symbolic mediator between heaven and earth, architectural forms confront the world around it as it is. Without the guidance of formal relationships in culture, we have developed a conception of arrangement (or anAmerican type) which combines the classical adaptation of a rational imposition by a grid system with the limitless aspect of horizontal space. So important in the United States is the sanctity of individual freedoms. This suggests that the individual has the capacity through rational thought to intervene in nature and dictate his or her destiny. In early America, cities were built modeling the roman grid system. The urban plan was derived rationally as an egalitarian way of dividing space. Also inherent in theAmerican mind set, however, was the perception of boundless opportunity and individual freedom which promoted a dimensionless unregulated horizontal expansion of the built environment. The grid emerged as a way of organizing town centers. No sacred truths of the heavens and the earth were revealed, no ritual was carried out in a departure point for the transcendental; instead, a rational organization occurred as a means of confronting an environment as it existed in its own state, just as earlier settlements had developed a seemingly random order based on the boundless opportunities of providing landscape as a means of confronting nature in its own state. An interesting paradox emerged between two orders. One looked as if buildings and places were dropped from the sky, left to be dwelled within depending on how they tumbled and lied to rest on the landscape; a celestial game of jax played on an uneven surface. The other depended on a complete and unyielding imposition on the landscape where every thing, place or building was measured or monitored. As a result cities would emerge, each with their own rational imposition, with no relationship to each other. Today, a certain randomness permeates their rational existence. The result has been deformative. That is the realization of something completely different from original intention. It is a combination of an upward extrusion with the introduction of a diffusive horizontally which re-orders its existence. It is, in a sense, a changing of definition. Even New York, with its density and strictly imposed grid, has a kind of deformative diss-order which defines its place as a totally American (though unique in and of itself) phenomenon. Rem Koolhaas identifies the madness of piling up chaos on chaos in a rigid system which creates its “delirious effect” Even language, signs, and meaning have become deformative, setting in motion a wave of paradoxical relationships.Intention dissolves over time, history becomes representative or imitative, the immutable becomes alterable, and new definitions are formed to re-explain existence. The universal, the transcendental, they are the spiraling center which decomposes and recomposes, leaving sometimes only a shell from which to decipher meaning and existence. Umberto Eco, in his essay "Travels in Hyper-reality”, examines the relationship in American culture between the sign, the thing, and that which links them together, history. The sign is not a means for understanding the thing it symbolizes but rather is an object which "aims to be the thing, to abolish the distinction of the reference. This is the mechanism of replacement." In doing so, the sign becomes more real (or hyper-real) than the thing because it is identified by and more tangible to the existence of our culture. This explains our fascination with historical reenactments, dramatizations, wax museums, escalators, and Dysney main streets. All are hyper-realities which have taken over and become "more real” than the things they represent. They are “better” because they excite the senses and give material evidence of our place in history. In doing so the hyper-real in American culture has successfully performed an about face in the way we define things, creating the perfect irony: “the completely real becomes the completely fake”. If modernism lies within the tradition of the way we view ourselves and our landscape, if we live in Newton’s limitless universe of absolute space independent of perfect geometry, if we live devoid of origin with no primitive accumulation of time, if architectural space does not always necessitate the symbolic harmony of formal relationships but rather seeks to confront its natural surroundings, if the arrangement of space is deformative, lying somewhere in between rational intervention and the application of the limitless, and if irony is the result of our application of language and meaning, should these conditions not become tools for design in architecture? Does this not suggest that the modern conception of space has deformed itself into something completely different from that of our European counterparts? / Master of Architecture

Yes / Natural draft cooling towers are subjected to dynamic air temperature and humidity ratio of air throughout the day. Their performances based on steady state model is restricted to single air temperature and humidity ratio of air values and thus are not accurate. In this work, a dynamic model for a natural draft cooling tower is developed. Air temperature and relative humidity data for Johannesburg were acquired to develop dynamic correlations for these two parameters and are embedded in the process model together with the dynamic model of the collection basin of the tower. A simple algorithm is proposed to solve the resulting boundary value problem. Finally, the common perception that seawater/river water should be used instead of freshwater as cooling medium is tested via optimisation where the operating costs of the process for two cooling mediums is minimised. The freshwater has been found to be cost effective cooling medium.

Yes / Cooling towers are a relatively inexpensive and consistent method of ejecting heat from several industries such as thermal power plants, refineries, and food processing. In this research, an earlier model from literature was to be validated across three different case studies. Unlike previous models, this model considers the height of the fill as the discretised domain, which produces results that give it in a distribution form along the height of the tower. As there are limitations with the software used (gPROMS) where differential equations with respect to independent variables in the numerator and denominator cannot be solved, a derivative of the saturation vapour pressure with respect to the temperature of the air was presented. Results shown were in agreement with the literature and a parametric sensitivity analysis of the cooling tower design and operating parameters were undertaken. In this work the height of fill, mass flowrates of water and air were studied with respect to sensitivity analysis. Results had shown large variations in the outlet temperatures of the water and air if the mass flows of water and air were significantly reduced. However, upon high values of either variable had shown only small gains in the rejection of heat from the water stream. With respect to the height of the fill, at larger heights of the fill, the outlet water temperature had reduced significantly. From a cost perspective, it was found that a change in the water flowrate had incurred the largest cost penalty with a 1% increase in flowrate had increased the average operating cost by 1.2%. In comparison, a change in air flowrate where a 1% increase in flowrate had yielded an average of 0.4% increase in operating cost.

Master of Science

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.

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.

Orientador: José Pissolato Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-18T03:00:37Z (GMT). No. of bitstreams: 1 Pinto_AndreJinnoGomes_M.pdf: 60896723 bytes, checksum: 8ce23cc18a981b5042b135acfc03ec42 (MD5) Previous issue date: 2011 / Resumo: As redes de transmissão de energia elétrica estão entre as grandes contribuições que a engenharia ofereceu à civilização moderna. Se tornando aparentes, pelas expressivas linhas de transmissão de alta tensão apoiadas sobre elevadas torres de aço que cruzam o território nacional em todas as direções. No corrente trabalho tem-se por objetivo tratar das alternativas não-convencionais de transmissão de energia elétrica. Comparando o desempenho dessas novas estruturas com o comportamento das estruturas atualmente utilizadas no sistema de transmissão convencional. Para tal são descritos alguns dados da atual configuração do sistema de transmissão nacional. Ademais, breves descrições técnicas serão apresentadas sobre os principais componentes de linhas de transmissão convencionais, tais como: condutores múltiplos, isoladores e anéis anticorona. Tais definições serão introduzidas com o âmbito de proporcionar uma maior familiaridade com o tema em estudo. Uma análise minuciosa é traçada no cálculo dos parâmetros elétricos na frequência, seguido de um estudo dos transitórios eletromagnéticos no domínio do tempo. Causados por sinais de tensão aplicados a entrada das linhas de transmissão / Abstract: The transmission of electric energy is among the great contributions that engineering offered to modern civilization. Becoming apparent, by the expressive lines of high voltage transmission supported on large steel towers that crisscross the country in all directions. In the current work has been aimed at dealing with alternative non-conventional electric power transmission. Comparing the performance of these new structures with the behavior of the structures currently used in conventional transmission system. For such thing are described some of the current configuration of the national transmission system. In addition, brief technical descriptions are presented on the main components of conventional transmission lines, such as multiple conductors, insulators and anti-corona rings. Such definitions will be introduced to the scope of providing a greater familiarity with the subject under study. A detailed analysis is plotted on the calculation of electrical parameters on frequency, followed by a study of electromagnetic transient time domain. Caused by voltage signals applied to the input of the transmission lines / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

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