Shallow fluidised-bed heat transfer

Shallow fluidised-beds have great potential as heat exchangers, since the pressure drop incurred is low enough not to require the use of large fans. An investigation of shallow-bed heat transfer is reported here and the observations are compared with established deep-bed experience. Several peculiarities were found and are discussed and the heat transfer data are compared quantitatively with deep-bed correlations. The prediction of the fluidising velocity at which the heat transfer coefficient maximum is obtained is considered in some detail, since this is an important consideration in heat exchanger design. A simple hypothesis based upon the two-phase theory of fluidisation is proposed as an alternative to the present, inaccurate empirical approach.