Simultaneous Momentum, Heat, and Mass Transfer with Color Change during Paddy Storage in Silo

Abstract:

A theoretical model has been developed to describe heat, mass, and momentum phenomena in cylinder-shaped silos where paddy is stored. Calculation based on the model predicts local temperature and moisture within the silo as a function of time and space. This information is then coupled with known kinetics of color change to predict yellowness or whiteness generated during storage. The model is evaluated using the published data. Natural air currents and the corresponding moisture migration are small for short storage periods and more extensive for long-term storage. The calculated result shows the similar trend to the published data in that moisture migrates from the central region, where the grains experience high temperature, to the outer regions, where the grains have lower temperatures. Paddy near the wall and on the top of the silo has relatively lower whiteness than at inner areas for storing it at 15% wet basis, this low luminosity is in part motivated by relative humidity, which is relatively high at such areas. At elevated initial moisture contents, paddy at the inner areas has lower whiteness due to large accumulation of heat from grain respiration, hence, it is a predominant effect on the color change, while the humidity plays a minor role.

Keywords:

• Mixed convection
• Paddy
• Storage
• Yellowness

ACKNOWLEDGEMENT

The authors thank the Thailand Research Fund for supporting this work.

Notes

*See Soponronnarit[16] and **Thorpe.[3]