A novel MHD electrical generator using turbulent hydromagnetic flow in a side-heated thermosyphonic loop

Conference · Wed Jul 01 04:00:00 EDT 1998

OSTI ID:20000303

Ghaddar, N

A direct energy conversion from thermal to electrical is envisioned in using a thermosyphonic hydromagnetic closed loop flow as an electrical generator. Magnetohydrodynamic (MHD) generators are typically based on pressure driven electrically conducting liquid flow in a channel passing between poles of a magnet. The suggested generator in this work differs in using thermosyphon driven turbulent motion in a side-heated closed loop, thus combining in a single unit the functions of a turbine and generator and eliminating the use of a pump while permitting operation at very high temperatures. An analytical one-dimensional model is developed to predict the hydrodynamic characteristics of the suggested MHD generator where a steady turbulent thermosyphonic side-heated loop containing an electrically conducting fluid is placed in a transverse magnetic field. The analytical model, which is based on the use of the Branover turbulent hydromagnetic flow solution for estimation of the wall shear stress, correlates the induced flow velocity and induced electrical current by buoyant action in terms of the relevant flow and geometric parameters. The study covers ranges of the Grashof number, Gr, from 10{sup 8} to 10{sup 16}, the Hartmann number, Ha, from 0 to 200, and the Prandtl number, Pr, from 0.02 to 7. It is found that the induced electric current increases sharply with increased Hartmann number at low values and then as Ha is increased further, the induced current either decreases or increases at a much lower rate depending on the Grashof number and the Prandtl number. The results are used to find an optimal Hartmann number, i.e. the smallest Hartmann number that gives the maximum induced electric current. The optimal Hartmann number increases with increased Grashof number. The existence of an optimal Hartmann number is significant in optimizing the MHD loop efficiency of conversion from thermal/mechanical to electrical energy.

• Research Organization: American Univ. of Beirut, New York, NY (US)
• OSTI ID: 20000303
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
DESIGN
GRASHOF NUMBER
HARTMANN NUMBER
MAGNETOHYDRODYNAMICS
MATHEMATICAL MODELS
MHD GENERATORS
ONE-DIMENSIONAL CALCULATIONS
PRANDTL NUMBER
THERMOSYPHON EFFECT
TURBULENT FLOW