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http://10.1.7.192:80/jspui/handle/123456789/8964
Title: | Investigation of Heat Transfer in Pool Boiling of r-141b Over Roughened Surfaces |
Authors: | Parekh, Maulik |
Keywords: | Mechanical 2016 Project Report 2016 Mechanical Project Report Project Report 16MMET 16MMET12 Thermal Thermal 2016 |
Issue Date: | 1-Jun-2018 |
Publisher: | Institute of Technology |
Series/Report no.: | 16MMET12; |
Abstract: | Pool boiling is a highly preferred mechanism for efficiently dissipating large amount of heat from a surface. The boiling heat transfer phenomena has been applied to several engineering and industrial fields requiring the removal of high heat flux, such as power plants, electronic chip cooling and marine ship power generation. In the boiling state, the most effective heat transfer region is the nucleate boiling heat transfer region, where the bubble generation, and it's growth and detachment from a heating surface repeatedly occur, resulting in low surface temperature. As the nucleate boiling heat transfer and critical heat flux are the main factors governing the boiling heat transfer and influencing thermal and economic efficiency and safety, numerous studies to enhance them have been conducted so far. Many techniques such as active technique, passive technique, compound technique etc. have been used for the experimental work to enhance the heat flux. The objective of the present work is to study the heat transfer enhancement in nucleate pool boiling region by surface modification. An experimental setup to study pool boiling heat transfer was designed and fabricated. In order to maintain constant pressure during the boiling process, a separate refrigeration unit was used to supply chilled water to the condenser coil. Initial experiments on pool boiling of R-141b over plain cylindrical copper surface have been compared with values obtained from Rohsenow and Cooper equation. The surface roughness of the copper sleeve is measured and found to be 0.98μm for plain surface which has been modified to surface roughness of 3.2μm. Experiments to study the effect of varying pressure on a plain surface and effect of higher surface roughness were conducted. Results indicate that the heat transfer co-efficient increases with increasing heat flux for R-141b. With increasing pressure from 0 to 0.5 kg/cm2 gauge, the heat transfer co-efficient increases by about 9% and increasing pressure from 0.5 to 0.75 kg/cm2 gauge, the heat transfer co-efficient increases by about 5%. This clearly shows that with an increase in pressure, the heat transfer co-efficient increases. For surface roughness of 3.2μm over the boiling surface, the heat transfer co-efficient increased by 60% as compared to a surface roughness of 0.98μm. The variation of observed heat transfer co-efficient matches the trend predicted by Cooper correlation in the range within 3-18%. |
URI: | http://10.1.7.192:80/jspui/handle/123456789/8964 |
Appears in Collections: | Dissertation, ME (Thermal) |
Files in This Item:
File | Description | Size | Format | |
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16MMET12.pdf | 16MMET12 | 26.4 MB | Adobe PDF | ![]() View/Open |
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