An experimental and computational study of wall to bed heat transfer in a bubbling gas–solid fluidized bed

The Eulerian–Eulerian approach is used to predict wall to bed heat transfer coefficient in a gas–solid fluidized bed with a jet by a heated wall. The constant viscosity model (CVM) and kinetic theory of granular flows (KTGF) are used to describe the solid phase rheology. A solid phase molecular thermal conductivity model specifically developed for the near wall region is used in the present work since wall to bed heat transfer occurs through the particle layer in contact with the wall. A comparison of the predicted and measured heat transfer coefficient is presented for different jet velocities, particle sizes and particle types and good agreement is observed between the predicted and measured values. It is observed that the predicted heat transfer coefficient is not affected significantly by the drag model or solid phase rheology model (CVM or KTGF) provided all other model parameters and operating conditions are same. Additionally for KTGF, over-prediction of heat transfer coefficient is observed in the case where solid phase thermal conductivity is expressed in terms of granular temperature rather than molecular conduction. Inclusion of particle rotation in the KTGF model reduces this over-prediction by around 17%.