Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Natural draught wet-cooling tower rain zone performance can be significantly enhanced by reducing the mean drop size in the rain zone with the installation of specially designed grids below the cooling tower fill. Drops enter the rain zone in the form of a polydisperse drop distribution, dripping from below the cooling tower fill, comprising relatively large drops. In order to design and optimize a grid for breaking up these drops, the mechanisms of drop break-up after impingement on the grid surface, referred to as splashing, straddling and dripping, need to be clearly understood. Two of these mechanisms, splashing and straddling, are therefore investigated experimentally using high speed video cameras to measure initial drop sizes, mass fractions and drop size distributions after impingement on different horizontal slats covered with a thin layer of water. The following parameters are varied independently for these experiments: drop fall distance, initial drop size, slat width and the water film thickness on the slats. Dripping from below the grid, is investigated theoretically. The effect of drop interaction on the drop size distribution in the rain zone is also investigated experimentally by measuring the drop distributions at the top and bottom of rain zones with a height of approximately 7.05 m to 7.65 m for different inlet distributions. The experimental drop break-up data, numerically obtained splash drop trajectory data and drop interaction data found in literature are used to develop a theoretical model of a purely counter flow cooling tower rain zone with and without installed grids. The model is compared to experimental data and theoretical data from literature and the predicted thermal and dynamic behaviour of the rain zone are generally found to be in good agreement with these results. Ultimately, this model is used for the optimization of the grid layout in terms of variables such as distance between the grid and the fill, slat width, slat spacing and slat height. It is found that the best drop break-up is achieved for grids comprising narrower slats with lower grid porosities as opposed to grids comprising wider slats. For the determined optimal grid layout it is found that a significant improvement in cooling tower performance can be achieved. / AFRIKAANSE OPSOMMING: Nat-koeltoringreënsonevermoë kan aansienlik verhoog word deur die druppelgrootte in hierdie gebied te verklein deur roosters, wat spesifiek vir hierdie doel ontwerp is, onder die pakkingsmateriaal te installeer. Die inlaatdruppelverdeling aan die bokant van die reënsone bestaan uit ‘n verdeling van relatief groot druppels wat drip van die onderkant van die pakkingsmateriaal. Ten einde ‘n rooster te ontwerp en te optimeer wat hierdie druppels kan opbreek moet die meganismes van druppelopbreking, bekend as spatting, vurking en drip goed verstaan word. Spatting en vurking is om hierdie rede eksperimenteel ondersoek, met behulp van hoëspoed videokameras. Die volgende veranderlikes is onafhanklik verander tydens hierdie eksperimente: valafstand van die druppel, aanvanklike druppelgrootte, latwydte en die dikte van die lagie water bo-op die lat. Die dripmeganisme aan die onderkant van die rooster is slegs teoreties ondersoek. Die effek wat druppelinteraksie in die reënsone het op die druppelgrootte is ondersoek deur die druppelgroottes aan die bo- en onderkant van ‘n 7.05 m tot 7.65 m reënsone te meet vir verskillende druppelinlaatverdelings. Die eksperimentele druppeldata, sowel as numeries berekende data wat die snelheid en trajek van spatdruppels beskryf, tesame met data vir druppelinteraksies wat uit die literatuur verkry is word gebruik om ‘n teoretiese model te ontwikkel vir ‘n suiwer teenvloei koeltoringreënsone met en sonder roosters. Hierdie model word vergelyk met eksperimentele data en data wat uit die literatuur verkry is en daar is gevind dat daar oor die algemeen ‘n goeie ooreenstemming is tussen die voorspelde en gemete termiese en dinamiese gedrag van die reënsone. Uiteindelik word die model gebruik vir die optimering van die rooster in terme van die volgende veranderlikes: afstand tussen rooster en pakkingsmateriaal, latwydte, latspasiëring en lathoogte. Daar word gevind dat beter druppelopbreking verkry word deur gebruik te maak van smaller latte en ‘n laer roosterporeusiteit. Daar is gevind dat die bepaalde optimale roosteruitleg in die reënsone van ‘n koeltoring ‘n wesenlike verbetering in koeltoringvermoë tot gevolg kan hê.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Dissertation (PhD)--University of Stellenbosch, 1995. / Bibliography. Also available via the Internet.

No description available.

Thesis (M.Tech.:Biotechnology)-Dept. of Biotechnology, Durban University of Technology, 2007 xvi, 185 leaves / Spirulina is a blue-green, multicellular, filamentous cyanobacterium that can grow to sizes of 0.5 millimetres in length. It is an obligate photoautotroph and has a pH growth range from 8.3 to 11.0.The large-scale production of Spirulina biomass depends on many factors, the most important of which are nutrient availability, temperature and light. These factors can influence the growth of Spirulina and the composition of the biomass produced by changes in metabolism. Brine effluent from cooling towers of electricity generating plants may provide an ideal growth medium for Spirulina based on its growth requirements, i.e. high alkalinity and salinity. The aim of this research was to optimise brine effluent from cooling towers by supplementing it with salts, in order to use this optimised effluent in a small open laboratory raceway pond in an attempt to increase the biomass production of Spirulina.

Thesis (M.Eng. (Chemical Engineering)) -- Universiteit van Pretoria, 2007. / Includes bibliographical references.

Thesis (Master)--İzmir Institute Of Technology, İzmir, 2005. / Keywords: Artificial neural networks, fuzzy logic, modeling, cooling load, prediction. Includes bibliographical references (leaves. 44-45).

Thesis (M.Eng.)(Chemical Engineering)--University of Pretoria, 2006. / Accompanied by a CD-ROM: Appendix B. Cooling tower model results. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (M.Tech.:Biotechnology)-Dept. of Biotechnology, Durban University of Technology, 2007 xvi, 185 leaves / Spirulina is a blue-green, multicellular, filamentous cyanobacterium that can grow to sizes of 0.5 millimetres in length. It is an obligate photoautotroph and has a pH growth range from 8.3 to 11.0.The large-scale production of Spirulina biomass depends on many factors, the most important of which are nutrient availability, temperature and light. These factors can influence the growth of Spirulina and the composition of the biomass produced by changes in metabolism. Brine effluent from cooling towers of electricity generating plants may provide an ideal growth medium for Spirulina based on its growth requirements, i.e. high alkalinity and salinity. The aim of this research was to optimise brine effluent from cooling towers by supplementing it with salts, in order to use this optimised effluent in a small open laboratory raceway pond in an attempt to increase the biomass production of Spirulina.

After the notorious outbreak and discovery of Legionella bacteria in 1976, the waterborne pathogen was added to the list of disease-causing agents associated with the built environment. Legionella pneumophila was discovered when it was identified as the agent that caused 34 deaths and an outbreak of pneumonia-like symptoms in several attendees of the 1976 American Legion Convention held in Philadelphia (OSHA, 2017). Recently published data from the year 2015 reported more than 6,000 Legionnaires’ cases identified in the United States (CDC, 2016). This is a concerning number given that one in every ten infected persons will die of the disease. It is believed that case numbers are likely under-reported, given that Legionnaires’ disease is very difficult to diagnose. Legionella species live naturally in bodies of water, including lakes and rivers. Legionnaires’ disease has been associated with the introduction of Legionella into manmade water systems. The presence of Legionella has been reported in cooling towers, domestic hot-water systems, humidifiers, decorative fountains, grocery spray misters, spas, whirlpools, and dental water lines, among other systems housing stagnant water (CDC, OSHA, 2017). From an occupational exposure standpoint, cooling towers are considered the most concerning source of Legionella pneumophila exposures, based on data from previous cases (Principe et al., 2017). The purpose of this research was to measure the effectiveness of biocide substitution and maintenance management in evaporative condensers. Such condensers were previously identified as having high counts of Legionella pneumophila in the water and/or on surfaces. The study sites were in the states of Florida and Georgia. Initial water testing for Legionella was carried out between July and August of 2016. Results from 2016 showed high counts of colony forming units (CFU) per millimeter (mL) at baseline assessment. An intervention of biocide substitution and enhanced management planning was recommended to lower or eliminate L. pneumophila from the water basins of the evaporative condensers. Follow-up results of water sampling conducted between July and August 2017 showed reduction of CFU counts after the intervention plan had been implemented for an entire year.