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The effect of ionization of spray on the wetting characteristics of an adiabatically cooled heat exchanger

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dc.contributor.advisor Kr"oger DG, Prof en
dc.contributor.author Esterhuyse B de W en
dc.date.accessioned 2016-09-22T08:35:32Z
dc.date.available 2016-09-22T08:35:32Z
dc.date.submitted 2004 en
dc.identifier.uri http://hdl.handle.net/20.500.11892/32360
dc.description.abstract An investigation was made into the use of pre-cooling of air with evaporative cooling as a means of improving the performance of air-cooled heat exchangers (finned tube) under conditions of ambient temperatures above maximum design values and during times of increased load. A review of previous research on this subject indicated that the concept is theoretically sound, but that practical application thereof is still limited. It was found that one of the major areas of concern is the wetting of the heat exchanger finned surface and subsequent corrosion.<br><br> Mathematical models were derived for the behavior of liquid droplets in free air stream conditions and droplets that have penetrated a laminar hydrodynamic boundary layer formed on a flat plate. These two models were combined to determine the behavior of a liquid droplet for its entire lifetime. It was found that evaporation of droplets in a boundary layer resulted in major improvements in heat transfer. In an attempt to prevent droplets from impacting and wetting the finned tube heat exchanger, the use of electrostatically charged water spray was investigated. Experiments were performed to determine the charging performance of a capacitive electrostatic nozzle. It was found that this type of nozzle successfully charged droplets in a spray. Experiments were then performed whereby electrostatic spray was sprayed on to a heat exchanger with a similar electric charge as the droplets. It was found that droplet deposition decreased significantly as the charge on the droplets was increased. However, total prevention of deposition could not be achieved, since the equipment used could not produce high enough voltages. This concept shows some promise, and it is recommended that further research be performed on it. At this stage, no reliable method of evaporative precooling of air has yet been found. The only viable option for cooling capacity shortages at present is the construction of large air-cooled heat exchangers or the addition of wet cooling towers. en
dc.language English en
dc.title The effect of ionization of spray on the wetting characteristics of an adiabatically cooled heat exchanger en
dc.type Masters degree en
dc.description.degree MEng en

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