Grain-crops are justly considered to be the staple food in Russia as well as all over the world. The specific feature is that postharvest processing of the grain and, above all, drying is an essential stage of providing products of high quality in the sufficient amount. The changes of the technological parameters of the drying process which take place over time, have a significant practical value in terms of monitoring the process and defining the modes providing the quality of the product as well as calculating energy demands necessary to carry out this process. Hereof, the quality of the product received is defined by minimum crack formation of rice grain after the process. The aim of the work is to get a mathematical model of hygrothermal mechanics of rice drying. On the basis of A.V. Lykov’s system of differential equations which describe the changes in moisture content, temperature and pressure, transition to the system of ordinary differential equations was offered which is based on drawing up balance of mass and heat during the process of drying. This approach does not consider the properties of moisture content and temperature within the material but takes into account their mean value. Using a simplified model of hygrothermal mechanics of rice drying that we have got enabled us to reproduce the process of drying in the conditions of minimum crack formation within the studied range (the temperature of the drying agent from 50 to 70 °C, speed from 2.3 to 2.8 м/sеk). The dependences we have got enable us to predict the quality of rice grain during drying.

hygrothermal mechanics, modelling, rice drying, differential equations, kinetic dependences, crack formation

1. Dhall A., Datta A.K. Transport in deformable food materials: A poromechanics approach. Chemical Engineering Science, 2011, no. 66 (24), pp. 6482-6497.

2. Lykov A.V. Teplomasoobmen [Heat and Mass Transfer (Reference Book)]. Мoscow, Energiya, 1971. 560 pp. (In Russ.).

3. Konovalov V.I., Kudra Т., Gatapova N.Ts. Modern issues of transfer theory in drying. Vestnik TGTU. [Bulletin of TSTU], 2008, vol. 14, no. 3, pp. 538-559. (In Russ.).

4. Podgornyi S.A., Koshevoi E.P., Kosachev V.S. Matematicheskoe modelirovanie protsessov sushki i konditsionirivaniya zerna [Mathematical modelling of the processes of drying and conditioning grain. Mass transfer potentials]. LAMBERT Academic Publishing, 2012. (In Russ.).

5. Kowalski S.J., Mierzwa D. Numerical analysis of drying kinetics for shrinkable products such as fruits and vegetables. Journal of Food Engineering, 2013, no. 114, pp. 522-529.

6. Mayor L., Sereno A.M. Modelling shrinkage during convective drying of food materials: a review. Journal of Food Engineering, 2004, no. 61, pp. 373-386. (In Russ.).

7. Khanali M., Rafiee Sh., Jafari A., Hashemabadi S.H. et al. Mathematical modeling of fluidized bed drying of rough rice (Oryza sativa L.) grain. Journal of Agricultural Technology, 2012, vol. 8(3), pp. 795-810.

8. Chiachung C., Po-Ching W. Thin-layer drying model for rough rice with high moisture content. J. agric. Engng Res., 2001, no. 80(1), pp. 45-52.