Two-Dimensional Heat Conduction in Metal, Fluid Composites.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Because the size and weight of main propulsion and auxiliary systems are inversely proportional to the ease in which heat or energy is exchanged, a major thrust of the research and development program of the U.S. Navy is toward the design and development of equipment that perform at higher efficiency with a reduction in size and weight. In particular, one area of great interest is the reduction in size and weight of steam condensers. The heat-transfer effectiveness is governed by the amount of surface and the overall resistance to the flow of heat. Filmwise condensation of steam on externally-finned tubes is a very complex process. Recent experiments have shown that enhancement ratios ratio of steam-side heat-transfer coefficient to that of a smooth tube having the same diameter exceeded the area enhancement produced by the fins. Moreover, the enhancement ratios for fully flooded tubes exceed the values predicted by a simple, one-dimensional conduction model by a factor of 2 to 4. A new two-dimensional conduction model was developed, which showed that the one-dimensional model overpredicted the two-dimensional results for high conductivity tube-metals such as copper by as much as 13. The two-dimensional model also showed that variations in fin thickness or spacing can result in an overprediction by the one-dimensional model of the two-dimensional results by as much as twenty-two percent.
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