Abstract:
Convective dryers are widely used in various fields, such as for drying pasta, fruit, vegetables, agricultural plant seeds etc. Several variants of dryers have been designed so far, such as: dryers with intermediate heating of the drying agent, dryers with partial recirculation of the drying agent, closed circuit dryers and those ones with combined technical solutions. None of the above solves the problem regarding the drying agent flow uniformity. In the case of existing world-wide tower dryers, drying is more intense towards the end of the drying agent mixing chamber. To overcome this shortcoming, an innovative cylindrical tower dryer was conceived, which evens the drying agent parameters. The dryer contains a conical device mounted inside the perforated cylinder above the burner. This device is based on the Coandă effect according to which, a fluid jet has the tendency to stay attached to a convex surface.
The device has been designed after Computational Fluid Dynamics simulations (CFD), after which optimum setting
adjustments have been made to achieve uniformity of the speed and temperature profiles across the entire interior
surface of the perforated cylinder, regardless the porosity of the seed layer. Experiments were conducted using barley
seeds with three initial moisture contents, five air temperatures (40oC to 80oC) and four fan speeds (1 m/s to 2.5 m/s).
The obtained results showed a reduction of protein loss of up to 1.77%, a reduction of germination capacity loss of up to
9.87%, a decrease of the energy consumption of up to 10-15% and a decrease of the drying time of up to 20%,
compared to the results obtained with a conventional tower dryer. The advantages of using the new developed dryer are:
drying process uniformity, energy consumption and drying time reduction, seed quality improvement, construction cost
reduction and material economy.
