Red clover drying coefficient dependencies on air velocity at constant drying temperature
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
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.