Mean particle diameters

Abstract

Mean particle diameters are important for the science of particulate systems. This thesis deals with a definition system for these mean diameters, called Moment-Ratio (M-R) definition system, and provides a general statistical and physical basis. Also, the current DIN/ISO definition system is discussed. Many types of mean diameters defined according to the M-R system are not merely statistical parameters, but quantities of physical relevance because of causal relationships with, e.g., physical product and process properties. The nomenclature of these mean diameters clearly conveys their physical meanings. Methods were developed to derive theoretically or select empirically the proper type of mean diameter describing a product or process property. Examples from the areas of evaporation, heat transfer, and turbulent two-phase flow, illustrate the theoretical approach. The empirical approach is illustrated by examples, mainly, from the areas of high shear granulation in detergent processing and pharmaceutics. An example from the foods area is concerned with a visual ranking of photographs of bubble size distributions of chocolate mousse samples. The selected type of mean bubble diameter suggests that our visual system, i.e., eyes + brain, has a logarithmic response.