Thin-layer drying characteristics and modelling of fresh and field-dried buckwheat hay

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Date
2020-04
Authors
Patil, Mehul
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Abstract
Thin-layer drying characteristics of fresh and partially field-dried buckwheat hay were studied at 30 to 180 °C drying temperatures, 12.5 to 60% relative humidities and 0.2 m s-1 constant airflow. The hay was harvested three different times with a 10 to 12 days interval between the harvesting times. Three-fourth of the harvested hay was sun-dried on the field for 4 days (referred to as partially field-dried hay). The drying behaviour of different parts of the hay (flowers, leaves and stems) was tested separately. During drying, the hay samples’ mass was measured at intervals of 60 to 900 s. These measurements were used to characterize the drying behaviour of fresh or partially field-dried hay, which include: mass ratios, drying constants, effective water diffusivities and activation energies. Non-linear regression analysis was conducted using semi-theoretical or empirical models. A constant-rate period of drying for different parts of both fresh and partial field-dried hay was not observed. These distinctive parts required varying drying times to reach their EMC. The order of the drying time from fastest to slowest, is: flowers, leaves, then stems. Partially field-dried and/or later harvested hay needed less drying time. Because of its highest R2 and the lowest MSE, the logarithmic model was the best fit model for all of the tested drying and harvest conditions. Optimum harvesting time was about 70 days after sowing. The hay’s effective moisture diffusivity ranged between 10-12 to 10-9 m2 s-1; the activation energy of the hay ranged between 19.63 to 37.42 kJ mol-1. The determined drying characteristics of fresh and field-dried hay would be useful in designing of commercial drying system for buckwheat hay.
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Keywords
Thin-layer drying, Modelling, Buckwheat, Hay, Field-dried hay
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