Hydrodynamics of three-phase fluidization of homogeneous ternary mixture in a conical conduit-Experimental and statistical analysis

Hydrodynamics of conical fluidized bed differ from that of columnar beds by the fact that a velocity gradient exists along the axial direction of the bed.The gas–liquid–solid fluidized bed has emerged in recent years as one of the most promising devices for three-phase operations.Such a device is of considerable industrial importance as evident from its wide applications in chemical,refining,petrochemical,biochemical processing,pharmaceutical and food industries.To explore this,a series of experiments have been carried out for homogeneous well-mixed ternary mixtures of dolomite of varying compositions in a three-phase conical fluidized bed.The hydrodynamic characteristics determined included the bed pressure drop,bed fluctuation and bed expansion ratios.The single and combined effects of operating parameters such as superficial gas velocity,superficial liquid velocity,initial static bed height,average particle size and cone angle on the responses have been analyzed using response surface methodology(RSM).A 25 full factorial central composite experimental design has been employed.Analysis of variance(ANOVA) showed a high coefficient of determination value and satisfactory prediction second-order regression models have been derived.Experimental values of bed pressure drop,bed fluctuation and bed expansion ratios have been found to agree well with the developed correlations.

Experimental study on dynamic behavior of mechanically pumped two-phase loop with a novel accumulator in simulated space environment

Mechanically pumped two-phase loop(MPTL)which is a prominent two-phase heat transfer technology presents a promising prospect in thermal control for space payload.However,transient behavior of MPTL caused by phase-change and heat sources load-on/off in simulated space environment is rarely reported.In the present study,one MPTL setup was designed and constructed,and experimentally studied.Particularly,a novel two-phase thermally-controlled accumulator integrated with passive cooling measure and three capillary structures was designed as the temperature-control device.Dynamic behavior of the start-up,temperature control,and temperature adjustment were monitored;meanwhile,thermodynamic behavior within the proposed accumulator,the operating behavior as well as the heat and mass transfer behavior between the main loop and the accumulator were revealed.The results show that the fluid management function of the capillary structures for the novel accumulator is verified.The working point of the MPTL system can be adjusted by changing the temperature control point of the accumulator and it is little influenced by external heat flux and heat sources on/off.Pressure-drop oscillations which are manifested as fluctuations of temperature and pressure can be observed after phase changing due to the compressible volume within the accumulator and the negative-slope portion of the internal pressure.

Flow-regime transitions in fluidized beds of non-spherical particles

Fluidized beds frequently involve non-spherical particles, especially if biomass is present. For spheri- cal particles, numerous experimental investigations have been reported in the literature. In contrast, complex-shaped particles have received much less attention. There is a lack of understanding of how par- ticle shape influences flow-regime transitions. In this study, differently shaped Geldart group D particles are experimentally examined. Bed height, pressure drop, and their respective fluctuations are analyzed. With increasing deviation of particle shape from spheres, differences in flow-regime transitions occur with a tendency for the bed to form channels instead of undergoing smooth fluidization. The correlations available in the literature for spherical particles are limited in their applicability when used to predict regime changes for complex-shaped particles. Hence, based on existing correlations, improvements are derived.