Hydrodynamic study of the granular flow in the solar dryer

There are a great many drying processes and types of equipment, such as dryers with immersed channels; the main advantage of this type of dryer, and the reason why it is chosen by manufacturers, is the homogeneous distribution of the drying air, made possible by dihedrons. In our work, we have investigated a flow model with a random double dispersion and have finally shown that the dispersion coefficients are not constant but vary depending on the position of the granular material in the column of dihedrons.

A model for the flow of granular material in a column of dihedrons is proposed which takes into consideration the two dispersion coefficients [8]. Other models in the literature, often neglect the longitudinal direction compared to the dispersive flux in the transversal direction [9]. where u (CC ′′ ) = 3.2.3. Measurement of the dispersion coefficients (D constant) As direct measurement of the dispersion coefficients, Dx and Dy, is not possible, their determination was carried out by fitting the results of the velocity field obtained experimentally with those predicted by the mathematical modelling. For the mathematical resolution of the model, we adopted the method developed in the previous paragraph, which consists of carrying out the calculation, step by step, starting with a module situated at the bottom of the column and going up by successive iteration to higher modules. In this way, it can be seen that, in the first zone, the number of equations of the system is less than the number of unknowns (C5, C6, Dx and Dy). To deal with this problem, we proposed an additional hypothesis by supposing that, in the first zone, there is only plug flow of the granular material so that Dx = 0. The numerical resolution of the system of equation gives a coefficient value of Dy =1.75 × 10−5 m2/s, which minimises the difference between the experimental and the modelled velocity profiles. Assuming that, due to the low velocity of the grains during the flow, the transversal dispersion coefficient can maintain the same value along the column, we determined the longitudinal dispersion coefficient Dx in the following zone using the same approach. The value found is Dx = 10−6 m2/s.