Modelling intermittent drying of rough rice and control of the drying and tempering stages

K. Toyoda, H. Kojima, I. Farkas

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The effects of tempering and controlling air temperature on an intermittent(multipass) drying process were investigated to find a basic strategy for controlling a recirculation dryer. Discussion in this study was limited to thin layer drying(single-kernel drying). The drying periods in each pass of intermittent drying were estimated using a drying model, "two-tank model". Moreover, the length of the cumulative drying time when the grain is exposed to heated air, was defined as "effective drying time" to make a comparison between the average drying rates of continuous drying and intermittent drying. As a result, it was found that the length of the drying period in each pass should be limited within the period I where a husk is chiefly dried at a high drying rate so that the intermittent operation could reduce by 35 - 60% of the effective drying time compared to continuous drying at same air temperature. As a quality index, the authors adopted the germination ratio which grain moisture and temperature of grain influenced sensitively. The relation between a germination ratio and the drying conditions, temperature and initial moisture of rough rice, was formulated as a quality model and the critical temperature to maintain 95% germination was calculated based on the relation. Moreover, a desirable drying period in each pass was estimated based on the critical temperature by the drying model. Trough computer simulation, it was suggested that intermittent drying with a rise in air temperature in each pass could provide shorter effective drying time and desirable germination ratio of the grain compared to intermittent drying with a fixed temperature of the air. model, effective drying time.

Original languageEnglish
Pages (from-to)351-359
Number of pages9
JournalActa Horticulturae
Publication statusPublished - Dec 1 1996



  • Effective drying time
  • Germination
  • Recirculation dryer
  • Thin layer drying
  • Two-tank model

ASJC Scopus subject areas

  • Horticulture

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