Quantification of conductive heat transfer between immersed surfaces and the adjacent layer of particles in gas-fluidized beds

NÉSTOR JAVIER MARIANI; GERMÁN DÉLFOR MAZZA; GUILLERMO FERNANDO BARRETO

Bilbao, España

Congreso; II European Congress on Fluidization.; 1997

Universidad del País Vasco

The evaluation of the heat transfer coefficient hwp between a heat exchanging surface immersed in a fluidized bed and the adjacent layer of particles is analysed in this work. Gas convective and radiant effects are not included here. The inclusion of hwp, or an equivalent formulation, in mechanistic models describing heat transfer has been necessary because the sudden voidage variation close to the immersed wall restrains significantly the heat transfer rate. However, there is not at present a widely accepted expression to evaluate hwp. A precise formulation for hwp  accounting for transient conduction inside spherical particles, the Smoluchowski effect, the concentration of particles in the adjacent layer (Np) and an effective separation gap (l0) is developed here.