Fluidization

A bench-scale fluidized bed has been designed and constructed for the investigation of pressure fluctuations within a large particle gas fluidized bed in the presence of horizontal tube banks. The pressure fluctuations inside the fluidized bed are investigated under different operating conditions, including a range of fluidization velocities, two particle sizes and two configurations of the tube banks. Different flow parameters like the standard deviation of the pressure fluctuations, 90% fluctuation ranges, power spectral density functions, dominant fluctuation frequencies, autocorrelation and crosscorrelation coefficients, and Hurst exponents by fractal analysis are determined. From the experimental data, quantitative information on the fluctuations are generated for use in evaluating the dynamic behavior of the fluidized bed. These parameters are found to strongly depend on fluidization velocity, configurations of tube banks and position in the bed. The flow regime characteristics with different flow parameters are discussed according to these results.

A Computer Automated Radioactive Particle Tracking (CARPT) facility was designed and implemented for the investigation of hydrodynamics in two phase flows. This facility was complemented by a versatile fluidized bed facility capable of handling high air flow rates. Solids mean dynamic behavior and heat transfer to internals in a 29.21 cm diameter fluidized bed were investigated for different operating conditions. Different flow parameters like the solids ensemble-averaged velocity, stagnancy and the phase density in the presence of horizontal tubes were determined using the CARPT facility. Local circumferential variations of heat transfer coefficients at the surface of horizontal tubes were measured at different locations in a large particle fluidized bed using a miniature heat transfer probe assembly. The influence of solids hydrodynamics on the heat transfer coefficient in gas-fluidized beds was investigated. The data obtained in the present study was compared to current heat transfer models for large particle gas-fluidized beds.