Infrared thermal imaging to detect moisture uniformity during drying of valerian root (Valeriana officinalis L.).

Publikations-Art

Kongressbeitrag

Autoren

Argyropouls, D; Müller, J

Erscheinungsjahr

2013

Veröffentlicht in

Proceedings

Seite (von - bis)

1 - 5

Tagungsname

Euro Drying (EuroDrying’2013)

Tagungsort

Paris, France

Tagungsdatum

2 - 6 October 2013

Schlagworte

drying

A common problem occurring during drying of valerian is the uneven moisture distribution between the different parts of the rootstock. Consequently, the objective of this study was to detect non-uniform drying of a bulk by infrared thermography. The drying behaviour of each constituent was also determined separately. The experiments were carried out in a through-flow laboratory dryer at a temperature of 45 °C, at corresponding relative humidity and a constant air velocity of 0.4 m/s. An infrared camera was incorporated in the system in order to acquire the instantaneous surface temperature map of the sample in the drying chamber. Drying air temperature, product temperature and moisture content were also measured at regular intervals. Thermal images clearly showed that the rhizomes present in the bulk had a lower surface temperature in comparison to the thinner roots. This observation was confirmed by the different drying kinetics between the constituents of the herb. Although the roots and hairs followed a similar pattern the rhizomes indicated a comparably long drying behaviour. For instance, when the roots reached a moisture content of 10% the rhizomes still possessed a moisture content of 45% wet basis. Further drying in order to achieve moisture uniformity of the bulk resulted in over drying of the thinner particles. IR thermography seems to be a useful technique for the optimization of industrial processes preventing uneven moisture distribution and over drying.