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Title: Joule heating in magnetohydrodynamic duct flows
Author: Mao, Jie
ISNI:       0000 0001 3618 6001
Awarding Body: Coventry University
Current Institution: Coventry University
Date of Award: 2006
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Joule heating effect in liquid metal magnetohydrodynamic (MHD) flows has been investigated numerically with reference to self-cooled liquid metal blankets for tokamaks. To investigate main effects associated with the Joule heating, pressure-driven Hartmann flow, fully developed MHD flow in a rectangular duct and developing MHD duct flow in a rectangular duct are studied in detail. An external, strong magnetic field is applied in the direction transverse to the flow. The walls are both electrically and thermally conducting, while the outside surface of the walls is thermally insulating. At the entrance into the duct the temperature is a constant. As the fluid progresses through the duct, the electric currents are induced as a result of MHD interaction. These currents . result in volumetric heating of both the fluid and the walls, and the temperature rises along the flow. As the outside boundaries are thermally insulating, the temperature accumulates within the domain. .. The electric currents are induced in the core, and return via the side layers, Hartmann layers at the walls, and in the walls themselves. If the walls are electrically insulating, the magnitude of the electric currents i~ insufficient to heat up the fluid by more than a few degrees. If the walls are electrically conducting, much stronger currents circulate within the flow. It is shown that in the Hartmann flow and fully developed flow model in rectangular duct with electrically conducting walls, the temperature along the flow at the fluidHartmann wall interface may rise by over 100°C over a distance of about 180 values of the characteristic length, which is roughly the total length of the blanket. This is a sufficiently high value to be taken into account in blanket design. The Joule heating effect in the Hartmann flow, in the fully developed rectangular duct MHD flow and in the three-dimensional rectangular duct MHD flow is compared. It is shown that the Joule heating effect is strongly dependent on the wall conductance ratio, the Hartmann number and the average velocity of the fluid. A detailed investigation of the effect of these parameters on the resulting rise of temperature has been performed. The investigation shows that the Joule heating effect may be a significant factor for the development of the fusion blanket not employing insulating coatings. Finally, the effects to be expected for the electrical conductivity dependent a temperature in duct flows are outlined.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available