RADIOACTIVE PARTICLE TRACKING TECHNIQUE FOR INVESTIGATION OF PHASE RECIRCULATION AND TURBULENCE IN MULTIPHASE SYSTEMS

The development of a noninvasive PC-based computer automated radioactive particle tracking (CARPT) facility for investigation of phase recirculation and turbulence in multiphase systems such as fluidized beds and bubble columns is presented. In this facility, the motion of a single radioactive particle, which is dynamically similar to the recirculating phase, is monitored by an array of scintillation detectors which surround the test section. An on-line computer is used to map the flow field of the recirculating phase. The data acquisition is achieved by commercially available nuclear instrumentation via a modular, high-speed GPIB-CAMAC system through assembly language software. Using CARPT, solids' motion in gas-fluidized beds and liquid motion in bubble columns have been investigated. The capabilities and versatility of the CARPT facility is described by illustrating some typical results for mean recirculation in gas-fluidized beds with and without internals and in a gas-liquid bubble column. The results include the mean circulation profiles and turbulence parameters such as the Reynolds normal and shear stresses and the turbulent eddy dispersion coefficients. Potential applications of CARPT technique to other recirculating systems are also discussed.