Corrective processes and heat-transfer coefficients within the tips of cryosurgical probes
Corrective processes and heat-transfer coefficients within the tips of cryosurgical probes
The subject of this dissertation is an experimental study of the heat transfer processes taking place in the confined space inside the tips of cryosurgical probes. As the transfer of heat between the walls of the cavity of the tip, and the coolant within it, is intimately linked to the flow characteristics of the coolant, a visualisation probe, using a jet of water, was constructed in order to simulate the flow of the coolant in the cavity. Photographic records of these flow patterns, taken on three different probes, are presented.The heat-transfer coefficients within the cavity of three different cryoprobes were calculated by using a transient method. The heat-flux through the heat-transfer surface and the temperature difference between the surface and the coolant were calculated from the numerical solution of the one-dimensional heat conduction equation and measurements of the changing temperature profiles in the heat probe, as it was cooled from room temperature to liquid nitrogen temperature. Forced-convection unstable film boiling and nucleate boiling of liquid nitrogen were investigated. The heat-transfer data for these two boiling regimes was correlated in terms of dimensionless groups: Nusselt, Reynolds and Prandtl numbers, temperature difference and geometrical parameters. Graphs of heat-transfer coefficient versus temperature difference, for each of the probes used, are plotted for different jet Reynolds numbers. These graphs show that large heat-transfer coefficients can be obtained with impinging jets of liquid nitrogen. Based on the correlation equations, as well as on the photographic records of the flow patterns, the way in which the heat-transfer coefficient is affected by the dynamics of the flow within the probe-tip and by the geometry of the tip is discussed. The better understanding ofthe convective processes within the probe-tip can be useful for designing more efficient cryoprobes, and for enabling surgeons to predict more accurately the size of frozen tissue by these probes.
University of Southampton
1979
Abreu, Omar
(1979)
Corrective processes and heat-transfer coefficients within the tips of cryosurgical probes.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The subject of this dissertation is an experimental study of the heat transfer processes taking place in the confined space inside the tips of cryosurgical probes. As the transfer of heat between the walls of the cavity of the tip, and the coolant within it, is intimately linked to the flow characteristics of the coolant, a visualisation probe, using a jet of water, was constructed in order to simulate the flow of the coolant in the cavity. Photographic records of these flow patterns, taken on three different probes, are presented.The heat-transfer coefficients within the cavity of three different cryoprobes were calculated by using a transient method. The heat-flux through the heat-transfer surface and the temperature difference between the surface and the coolant were calculated from the numerical solution of the one-dimensional heat conduction equation and measurements of the changing temperature profiles in the heat probe, as it was cooled from room temperature to liquid nitrogen temperature. Forced-convection unstable film boiling and nucleate boiling of liquid nitrogen were investigated. The heat-transfer data for these two boiling regimes was correlated in terms of dimensionless groups: Nusselt, Reynolds and Prandtl numbers, temperature difference and geometrical parameters. Graphs of heat-transfer coefficient versus temperature difference, for each of the probes used, are plotted for different jet Reynolds numbers. These graphs show that large heat-transfer coefficients can be obtained with impinging jets of liquid nitrogen. Based on the correlation equations, as well as on the photographic records of the flow patterns, the way in which the heat-transfer coefficient is affected by the dynamics of the flow within the probe-tip and by the geometry of the tip is discussed. The better understanding ofthe convective processes within the probe-tip can be useful for designing more efficient cryoprobes, and for enabling surgeons to predict more accurately the size of frozen tissue by these probes.
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Published date: 1979
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Local EPrints ID: 463799
URI: http://eprints.soton.ac.uk/id/eprint/463799
PURE UUID: ae2d46da-e96f-409e-92e0-cf5a59a44921
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Date deposited: 04 Jul 2022 20:57
Last modified: 04 Jul 2022 20:57
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Author:
Omar Abreu
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