GAS-TO-PARTICLE AND PARTICLE-TO-PARTICLE HEAT-TRANSFER IN FLUIDIZED-BEDS OF LARGE PARTICLES

Gas-to-particle and interparticle transfer rates were measured, at room temperature, for three different materials, in the range 1 less than equivalent to U/U//m//f less than equivalent to 3. 5 and 0. 900 less than equivalent to d//p less than equivalent to 2. 250 mm by means of batch runs in which wet capillary-porous particles were dried in fluidized beds of similar dry ones. It was observed that gas-to-particle convective transfer coefficients vary only slightly with the air velocity. A 'slow-bubble model' convenient for large particle fluidization, was developed to explain this finding and provided interesting data concerning the gas flow distribution in beds of large particles. The particle-to-particle heat transfer coefficients, nearly independent on the particle thermal properties, were correlated by the following equation: h//p//p equals 206d//p** minus **1**. **2**2(U/U//m//f)** minus **0**. **5**6.