Heat transfer in fluidized beds.

Abstract

The unsteady state heat transfer between gas and solid particles was studied in fluidized beds, 2 and 4 inches in diameter. Air velocities of 0.543 to 4.347 ft./sec. and bed-settled heights to diameter ratios from 0.2 to 8 were employed in transient heating and cooling of 0.004 to 0.2324 inch particles of glass beads, silica gel and alumina between 130 and 288°F. The effect of several variables, particle size (0.004 - 0.2324 inch), bed-settled heights (0.8 - 16 inch) particle densities (8.5 - 206 lbs./cu. ft), thermal conductivities (0.013 - 1.8 Btu/(hr.) (ft.2) (°F/ft.) and air velocities (0.543 - 4.347 ft./sec.) on the space-averaged heat transfer coefficient has been investigated. Using a new approach in interpreting heat transfer driving force, a correlation between the heat transfer coefficient and several parameters for two ranges of modified Reynolds numbers 10 to 60, and 60 to 2200 has been developed (a) for Reynolds number 10 to 60 UDP kf= 0.08CP fmfk f0.4 LsDt -1.3 DPDt 4.3 kskf -4rs rf 7.8DpVf rfmf -6.1; (b) for Reynolds number 60 to 2200 UDpkf =0.0011 CPfmf kf 0.4Ls Dt-1. 3DP Dt4.3 ksk f-4 rsr f7.8 DpVfrf mf -3.1.