Intermediate state fluidization is represented by a fuzzy set. One parameter

heterogeneity

deduced from statistical characteristics of fluidization voidage spectrum and εmf

is defined as the membership function of the fuzzy set. Interpretation by fuzzy sets of gas- solid and liquid -solid fluidization experiments under various pressures

fluid viscosities and particle properties

illustrates that the configuration of two - phase structure in fluidized bed varies with operating parameters as well as material properties. By means of fuzzy sets

the heterogeneity

or the grade of aggregative

of a certain fluidization state can be referred to as a specific number ranging from 0 to 1.