A Model for the Relative Velocity of a Particle in an Impingement Dryer: Application to Heat Transfer

Abstract

A simplified mathematical model for the relative gas-particle motion in a confined jet impingement dryer is developed. Model predictions based on an unsteady momentum balance are in good agreement with the observed cycling motion of a spherical particle. The model is applied to coriander seeds submerged in a flow field of superheated steam. It is found that relative motion occurs in unsteady turbulent regime, and that steady settling velocity of particles is never achieved. Model results are applied to correlate experimental heat transfer data of an impingement dryer. Experimental Nu numbers compare fairly well with correlations for fluidized systems.

Keywords:

• Impingement dryer
• Superheated steam
• Gas-particle relative velocity
• Heat transfer coefficients

Acknowledgments

This work was supported by Research Project Fondecyt 1020434 (Chile).