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- Title
- ANALYSIS AND OPTIMIZATION OF A SOLAR THERMAL COLLECTOR WITH INTEGRATED STORAGE.
- Creator
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Bonadies, Monica, Kapat, Jay, University of Central Florida
- Abstract / Description
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Solar energy, a topic popular in the United States during the oil embargo of the 1970ÂÂ's, has become a relevant topic once more with the current focus on reducing greenhouse emissions. Solar thermal energy in particular has become popular as it uses existing steam turbine technology to produce electricity, with the benefit of using solar energy to produce steam rather than coal or nuclear heat sources. Solar thermal can also be used at lower temperatures to heat water...
Show moreSolar energy, a topic popular in the United States during the oil embargo of the 1970ÂÂ's, has become a relevant topic once more with the current focus on reducing greenhouse emissions. Solar thermal energy in particular has become popular as it uses existing steam turbine technology to produce electricity, with the benefit of using solar energy to produce steam rather than coal or nuclear heat sources. Solar thermal can also be used at lower temperatures to heat water for pools or for residential use. While this energy source has its benefits, it has the problem of being opportunistic – the energy must be used as it is captured. With the integration of storage, a solar thermal system becomes more viable for use. In this work, a low temperature (50-70o C) thermal storage unit with a solar thermal collector is experimentally run then studied using both analytical and numerical methods. With these methods, suggestions for future developments of the storage unit are made. The prototype collector and storage combination tested worked best during the winter months, when there was low humidity. Furthermore, the heat exchanger design within the storage unit was found to work well for charging (heating) the unit, but not for discharging the storage to heat water. The best modeling method for the storage unit was the use of FLUENT, which would allow for the suggested changes to the prototype to be simulated before the next prototype was constructed.
Show less - Date Issued
- 2010
- Identifier
- CFE0003260, ucf:48548
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003260
- Title
- MEASUREMENTS IN AIR-WATER BUBBLY FLOW THROUGH A VERTICAL NARROW HIGH-ASPECT RATIO CHANNEL.
- Creator
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Patrick, Benjamin, Kumar, Ranganathan, University of Central Florida
- Abstract / Description
-
Two-Phase bubbly flows are encountered in a wide range of industrial applications, particularly where phase changes occur as seen in high performance heat exchangers and boiling reactors for power generation. These flows have been extensively studied in channels with circular geometries using air-water flows, though little data exists for flows through narrow rectangular channels. Measurements in thin geometries are particularly challenging since large bubbles bridge the gap, and it is...
Show moreTwo-Phase bubbly flows are encountered in a wide range of industrial applications, particularly where phase changes occur as seen in high performance heat exchangers and boiling reactors for power generation. These flows have been extensively studied in channels with circular geometries using air-water flows, though little data exists for flows through narrow rectangular channels. Measurements in thin geometries are particularly challenging since large bubbles bridge the gap, and it is difficult to compare point measurements with photographic techniques. The objective of this study is to explore the abilities of hot-film anemometry and high speed photography for taking measurements in a narrow vertical rectangular channel for a range of volume fractions, with particular attention on the narrow dimension. Hot-film anemometry (HFA) is a measurement technique originally developed for the measurement of fluid velocities, but has since been found to have applications for broader measurements in multiphase flow. With the sensor operating on the principle of heat loss, the method takes advantage of the differing abilities of the phases to transport heat, with each phase leaving its own signature in the signal response. The linchpin of this method lies in the ability to accurately distinguish between the two phases within the signal, and to execute this operation, various algorithms and techniques have been developed and used with some success for a wide range of flow conditions. This thesis is a study of the various methods of analysis such as amplitude threshold for triggering, and small slope threshold for finely tuning the edges of the bubble interactions, and demonstrates the capabilities of the hot-film sensor in a narrow rectangular vertical duct with a high aspect ratio. A vertical acrylic test section was fabricated for the purposes of this study, inset with a rectangular channel 38.1mm in width and 3.125mm in depth. Experiments were conducted for volume fractions ranging from 2% to 35%, which remained within the limits of the bubbly flow regime, but ranged from small uniform bubbles to larger bubbles coalescing into a transition regime. The hot-film signal was analyzed for void fraction, bubble speed, and bubble size. An in- depth study of the various methods of phase discrimination was performed and the effect of threshold selection was examined. High-speed video footage was taken in conjunction with the anemometer data for a detailed comparison between methods. The bubble speed was found to be in close agreement between the HFA and high-speed video, staying within 10% for volume fractions above 10%, but still remaining under a 30% difference for even as low as the 2% volume fraction, where measurements have been found to be historically difficult. The trends with volume fraction between the HFA and high-speed results were very similar. A correlation for narrow rectangular channels employing a simple drift flux model was found to compare with the void fraction data where appropriate. Good agreement was found between the methods using a hybrid phase discrimination technique for the HFA data for the void fraction and bubble speed results, with the high-speed video results showing a slight over-estimation in regards to the bubble size.
Show less - Date Issued
- 2011
- Identifier
- CFE0004006, ucf:49185
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004006
