Tag Archives: forced drying

313-319 A. Aboltins, J. Tomsu and P. Kic
Red clover drying coefficient dependencies on air velocity at constant drying temperature
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Red clover drying coefficient dependencies on air velocity at constant drying temperature

A. Aboltins¹*, J. Tomsu² and P. Kic²

¹Latvia University of Agriculture, Institute of Agricultural Machinery, Cakstes blvd.5, LV–3001 Jelgava, Latvia
²Czech University of Life Sciences Prague, Faculty of Engineering, Kamycka 129, CZ16500 Prague 6, Czech Republic
*Correspondence: aivars.aboltins@inbox.lv

Abstract:

The clover is widely used as feed of animals and preservation of fodder is an important problem. This paper informs about the experimental and theoretical investigations of red clover (Trifolium pratense) drying by forced convection. This research is focused on verification of influence of different air velocities on the drying process of red clover in thin layer in mild temperatures (22 °C) and rather high relative humidity of air (70%). The initial moisture content of clover was determined by gravimetric method using the hot air drying in the electric oven. Special device for convection drying with air flow passing through material from the bottom through supporting trays with a sieve (dimensions of mesh 3 x 4 mm) by constant temperature was used for drying when the air velocity 0.7 m s-1, 1.0 m s-1, 1.2 m s-1 and 2.0 m s-1. These results was compared with drying by free convection. Changes of clover samples were determined from the measured values of weight using the gravimetric method. The function of drying coefficient K(t) is determined (using thin layer theory) and theoretical results are compared with experimental results. Using experimental results were determined relationships between air velocity and parameters included in function of drying coefficient. This allows theoretically to predict the drying process depending on the air velocity.

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737–744 P. Kic
Effect of different air velocities on convective thin-layer drying of alfalfa for livestock feeding
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Effect of different air velocities on convective thin-layer drying of alfalfa for livestock feeding

P. Kic

Czech University of Life Sciences Prague, Faculty of Engineering, Kamycka 129, CZ165 21 Prague 6, Czech Republic
Correspondence: kic@tf.czu.cz

Abstract:

Alfalfa (Medicago sativa) is widely used as forage which has very high feeding value. The aim of this paper is to inform about the experimental and theoretical investigations of alfalfa drying in thin layer. Special device for convection drying with air flow passing through material from bottom through supporting trays with sieve by constant temperature was used for drying when air velocity was 0.7 m s-1, 1 m s-1, 1.2 m s-1 and 2.0 m s-1. The results were compared with natural convection drying by the same temperature, but with the 0 m s-1 air velocity. The increased air velocity for convection influenced drying process positively. The results show that the differences between the drying with air velocities 1.2 m s-1 and 2 m s-1 are very small, therefore 1.2 m s-1 could be realised as an optimum. The evaluation of measurement results was focused on curves of drying rate, changes in water content and changes of moisture depending on the time and their mutual relations. Experimental data create the background for calculation of main parameters useful for description and modelling of the drying process, which can be helpful e.g. for decision of optimum drying time. Drying alfalfa for hay by forced convection shortened the drying time as compared with natural convection two and a half times. Drying alfalfa for haylage by forced convection shortened the drying time as compared with natural convection even four times.

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