Experimental Study of a Novel Thermosyphonic MHD Electric Generator 1999-01-2509

A direct energy conversion from thermal to electrical is experimentally verified in using a thermosyphonic hydro-magnetic 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 generator in this work differs in using thermosyphon driven motion in a bottom-heated closed loop, thus eliminating the use of a pump while permitting operation at high temperatures. A workable model of the generator is designed and built using salt and water solution as the working fluid. The design calculations of the MHD generator and the range of parameters involved are based on the analytical results obtained from previous work, which allowed prediction of the optimal range of the magnetic field strength as related to the driving temperature difference.

The loop is constructed from glass, with platinum-coated electrodes placed vertically opposite to each other on each side of the loop walls. A transverse magnetic field is imposed through a careful design of a set of electromagnets with minimum circuit reluctance. The lower part of the loop is heated using a hot water bath with thermostat control, while the upper part of the loop is cooled using a cold water jacket through which water is recirculated from a water chill unit. The electromagnet provided a magnetic field strength from 0.01-0.2 T, where as the driving temperature difference between the hot and cold portion of the loop ranged from 20-80 °C.

The induced electric voltage from the proposed MHD generator was measured in the laminar flow range. Preliminary results show that the induced voltage increases with increased temperature difference between the hot and cold parts of the loop and also increases with increased electrical conductivity of the salt and water solution.