A study of boiling heat transfer in liquid nitrogen
A study of boiling heat transfer in liquid nitrogen
In an air separation plant, there is a need to reduce power consumption of the main compressor by improving the heat transfer coefficient in the condensor-reboiler unit. This work investigates the boiling of liquid nitrogen from aluminium surfaces with a view to improving the heat transfer coefficient. Experiments on smooth surfaces, rough surfaces, surfaces of different sizes ranging from 3.2 cm to 60 cm in open channel, closed channel and plate-fin configurations were conducted. Among the mechanisms shown to have improved the heat transfer coefficient are the use of artificially roughened surfaces and the generation of turbulence in liquid nitrogen by bubbles generated by an external source and from the heat transfer surface. Use of loaded epoxy insulation with thermal contraction matching that of Aluminium facilitates the design of rigs of various dimensions. Other results include: (i) a temperature gradient exists in liquid nitrogen during natural convection closed channel flow, the temperature being higher at the top. During nucleate boiling region, the temperature is slightly lower at the top. (ii) Void fraction and vapour quality increases with increasing heat flux in the static case but not in the dynamic case. (iii) the point of inception of turbulence is at x/L^! O.3 to 0.4 and at a Modified Raleigh number of 5.0 to 90 x 1012. The correlation for open channel flow isNu = 0.47 [ 9a(M) ] 0.26
University of Southampton
1983
Mirza, Saadat
(1983)
A study of boiling heat transfer in liquid nitrogen.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In an air separation plant, there is a need to reduce power consumption of the main compressor by improving the heat transfer coefficient in the condensor-reboiler unit. This work investigates the boiling of liquid nitrogen from aluminium surfaces with a view to improving the heat transfer coefficient. Experiments on smooth surfaces, rough surfaces, surfaces of different sizes ranging from 3.2 cm to 60 cm in open channel, closed channel and plate-fin configurations were conducted. Among the mechanisms shown to have improved the heat transfer coefficient are the use of artificially roughened surfaces and the generation of turbulence in liquid nitrogen by bubbles generated by an external source and from the heat transfer surface. Use of loaded epoxy insulation with thermal contraction matching that of Aluminium facilitates the design of rigs of various dimensions. Other results include: (i) a temperature gradient exists in liquid nitrogen during natural convection closed channel flow, the temperature being higher at the top. During nucleate boiling region, the temperature is slightly lower at the top. (ii) Void fraction and vapour quality increases with increasing heat flux in the static case but not in the dynamic case. (iii) the point of inception of turbulence is at x/L^! O.3 to 0.4 and at a Modified Raleigh number of 5.0 to 90 x 1012. The correlation for open channel flow isNu = 0.47 [ 9a(M) ] 0.26
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Published date: 1983
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Local EPrints ID: 459728
URI: http://eprints.soton.ac.uk/id/eprint/459728
PURE UUID: 347aa050-a1dd-4ba7-8c31-2a74976c5d7c
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Date deposited: 04 Jul 2022 17:17
Last modified: 04 Jul 2022 17:17
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Author:
Saadat Mirza
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