QUANTITATIVE CAPACITIVE MEASUREMENTS OF VOIDAGE IN GAS-SOLID FLOWS

Abstract
New capacitance probes were developed for quantitative, time-dependent measurements of voidage in gas-solid flows. Based on a unique guard circuit which nearly eliminates all stray and cable capacitances, these probes are fast (2 kHz) and they do not require in situ calibration. Two configurations were studied: small parallel plates for recording voidage profiles, and a non-intrusive design for local voidage measurements near a wall Static tests were performed using a fixed bed of known voidage and dielectric constant. The probes were also demonstrated in a two-dimensional fluidized bed of glass beads.