Thesis
Steady state heat transfer characterization of a liquid metal thermal switch
Washington State University
Master of Science (MS), Washington State University
2005
Handle:
https://hdl.handle.net/2376/362
Abstract
Steady state heat transfer characteristics have been quantified for a liquid metal thermal switch. The application motivating this research is the P3 micro heat engine which converts heat energy into electrical power using the charge generating property of PZT. Stacks of engines are necessary to produce a useable charge and cyclic heating must be realized to make these stacks efficient. The thermal switch consists of a silicon substrate with mercury micro-droplets deposited in a 1600 droplet array. Droplets are deposited using a vapor deposition process where mercury vapor preferentially condenses on 30 [mu]m2 gold pads sputtered on the silicon substrate. When the droplet arrays make contact with a second silicon substrate heat is transferred and the switch is "on". When the droplet arrays do not make contact, heat transfer across the resulting gas gap is sharply reduced and the switch is "off". Three gas gaps are compared for the thermal switch. The reference condition is a gap filled with air at ambient pressure. The second condition is Xenon at ambient pressure. The third condition is air at a pressure of 0.5 torr. The vacuum and xenon conditions reduce the transfer of heat in comparison with air when the switch is "off". By reducing the heat transfer greater thermal isolation can be obtained at smaller gap distances. The ideal switch would have minimal heat transfer in the ìoffî position and maximum heat transfer in the ìonî position. A non-dimensional parameter the ratio of thermal resistance, "off" to "on", is used to gauge the effectiveness of thermal switches. Xenon at ambient pressure has the best ratio of 143, when switching from 1 N load to 88 [mu]m distance. This is followed by air at ambient pressure, 123, and air at 0.5 torr, 74. When switching from 1N to 22 [mu]m distance the best ratio is obtained for air at 0.5 torr which is 60. This value followed by xenon at 50 and air at ambient pressure, 43.
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Details
- Title
- Steady state heat transfer characterization of a liquid metal thermal switch
- Creators
- Travis Sloan Wiser
- Contributors
- Robert Foster Richards (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525106401842
- Language
- English
- Resource Type
- Thesis