An experimental study of heat transfer to cryogenic nitrogen gas in a rotating, annular duct
An experimental study of heat transfer to cryogenic nitrogen gas in a rotating, annular duct
The thermal convection in the annular neck of a rotating,liquid nitrogen cryostat is investigeted the relevance of this work to the vapour cooling problem of large superconducting alternators is expounded. The presentation of a sarvey of-the heat transfer literatureis followed by a theoretical analysis of the fluid dynamics of the rotating,stratified vapour column in the cryostat neck.The rotationally-induced heat flux into the cryostat interior is explained in terms of Ekman layer suction,and a dependence of the boil-off rate on the square root of the angular velocity is predicted; measurements taken with the rotating cryostat are in good agreement with this theory.The construction and design of the cryostat and heat transfer apparatus ore described. Average heat transfer coefficients to the nitrogen gas from both the inner and outer neck walls have been measured ; the rotational speed of the cryostat was varied between 0-314 rad/s,producing a,maximum centrifugal acceleration in the annular gap equivalent to 240g.The effects of forced convection and heat flux on the buoyancy-driven flow were also studied. It is found that rotation enhanced heat transfer from the outer wall by up to a factor of three,while the Nusselt number at the inner wall was diminished considerably at high angular speeds. Established correlations are inadequate to predict heat transfer in the rotating cryostat neck,and this is shown to be caused by secondary flow,driven by the Coriolis acceleration.
University of Southampton
1978
Booth, D.A
(1978)
An experimental study of heat transfer to cryogenic nitrogen gas in a rotating, annular duct.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The thermal convection in the annular neck of a rotating,liquid nitrogen cryostat is investigeted the relevance of this work to the vapour cooling problem of large superconducting alternators is expounded. The presentation of a sarvey of-the heat transfer literatureis followed by a theoretical analysis of the fluid dynamics of the rotating,stratified vapour column in the cryostat neck.The rotationally-induced heat flux into the cryostat interior is explained in terms of Ekman layer suction,and a dependence of the boil-off rate on the square root of the angular velocity is predicted; measurements taken with the rotating cryostat are in good agreement with this theory.The construction and design of the cryostat and heat transfer apparatus ore described. Average heat transfer coefficients to the nitrogen gas from both the inner and outer neck walls have been measured ; the rotational speed of the cryostat was varied between 0-314 rad/s,producing a,maximum centrifugal acceleration in the annular gap equivalent to 240g.The effects of forced convection and heat flux on the buoyancy-driven flow were also studied. It is found that rotation enhanced heat transfer from the outer wall by up to a factor of three,while the Nusselt number at the inner wall was diminished considerably at high angular speeds. Established correlations are inadequate to predict heat transfer in the rotating cryostat neck,and this is shown to be caused by secondary flow,driven by the Coriolis acceleration.
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Published date: 1978
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Local EPrints ID: 467253
URI: http://eprints.soton.ac.uk/id/eprint/467253
PURE UUID: 361fa715-0ddf-42f0-beb1-5f6905087217
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Date deposited: 05 Jul 2022 08:17
Last modified: 05 Jul 2022 08:17
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Author:
D.A Booth
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