AVERAGING VOLUME SIZE DETERMINATION OF ELECTROCONDUCTIVE POROSITY PROBES

Electroconductivity probes, used to measure local porosity in a packed bed or filter cake, have a localized averaging volume over which the measurement is made. The extent of this averaging volume is detected by the effect of the proximity of a multiphase boundary, such as the cake-slurry boundary in filtration, on a probe's measurement. A computer simulation and experimental verification show that the extent of the averaging volume is primarily dependent on the characteristic length between the electrodes. Probes can be designed by sizing the characteristic length to obtain averaging volumes which satisfy the REV criteria in volume-averaging theory. The extent of the averaging volume also determines how close a probe may be to a multiphase boundary without the boundary affecting the measurement. © 1990.