Dependence of Heat-Transfer coefficient for immersed surfaces in a gas-fluidized bed on pressure

The correlations and theories developed for the prediction of heat-transfer coefficients for immersed surfaces in fluidized beds are examined for their applicability and appropriateness at different pressures. It is found that the pressure dependence of minimum fluidization velocity and heat-transfer coefficient for ‘small’ and ‘large’ particle systems can be reconciled with an adequate interpretation of available correlations and model expressions on the basis of a recently proposed particle classification scheme. The latter utilizes the concept of Archimedes number to provide a particle classification scheme which interprets particles into different categories, keeping both hydrodynamic and thermal behaviors of the bed consistent with each other at the same time. Good agreement of the available experimental data with appropriate theories is demonstrated.