Humidification and drying of granular matter - correlation of mass change and effective dielectrometry

Purpose: The purpose of this paper was to record and mutualy correlate mass changes of population of micro-granules of rye starch and effective dielectric permittivity of this system taking places during humidification and drying processes. Design/methodology/approach: Mass changes of biopolymeric mirco-granular sample occuring during its exposition on saturated water vapour at room temperature, was recorded in the time by means of precise torsional balance equipped with special chamber. The same was done in case of drying. Monitoring of effective dielectric permittivity was performed by means of interdigit comb capacitor and precise RLC meter equipped with PC program. Specially designed and constructed measuring chamber was applied to control temperature and relative humidity (RH %) of ambient sample atmosphere. Findings: Interdigit dielectric spectroscopy method turned out to be more sensitive technique to follow details of humidification as well as drying processes. Correlation of changes of effectife dielectric permittivity with simultaneously occurring mass increase or decrease can be a way to describe the humidification and drying processes of micro-granular biopolymeric sample. Practical implications: Effective dielectric permittivity monitoring of humidification and drying processes turned out to be much more selective than only gravitational measurement of mass change. For modeling purpose correlation of both is giving new possibilities of modelling approach. Originality/value: For the first time practically important humidification and drying processes were monitored in statu nascendi, without disturbing geometry of granules starch by means of ε' values evolution record. It was enabled by application of interdigit comb capacitor as sensing unit.