A new experimental apparatus based on conductivity measurements has been developed to measure liquid and solid phase volume fractions in fluidised suspensions. The device provides a measurement of the instantaneous values of volume fractions: this characteristic has been used here to estimate the velocity at which voidage discontinuities travel in a solidliquid slugging fluidised suspension. The proposed method is based on the analysis of the rate of change of the electrical signal collected from various sensors placed along the fluidising column. The present work has verified the applicability of the new algorithm; measured voidage discontinuity velocities (i.e. the velocity of the interface separating dense and lean regions in the slugging suspensions) are reported and discussed in the light of existing fluid dynamic theories on the behaviour of such suspensions.
