Industrial drying: principles and calculation of machines

The previous articles [J 2 451] and [J 2 452] presented "hot-air drying", its industrial applications and energy-saving techniques, for the common case where hot air provides the product with the energy to vaporize water, via convective air/product transfers. The following two articles [J 2 453] and [J 2 454] describe "other drying modes than hot air", where the air circulating around the product is generally colder than the product, and where it is not the air that provides the heat useful for vaporizing the water, but other heating modes, with specific advantages and disadvantages that will be described. In particular, it will be demonstrated that, in certain cases, energy consumption can be reduced by a factor of 2 to 15 compared with hot-air drying, by changing the drying mode, which is of the utmost industrial interest. Articles [J 2 453] and [J 2 454] are classified according to the type of heat input.

In [J 2 453] (this article):

• conduction drying: the product is brought into contact with a wall heated to the hot-source temperature ${\theta }_{sch}$ (°C) at the surface, and heat is transferred to the product by conduction through this wall, then by conduction into the product. Depending on the conditions, in particular the plate temperature in relation to the pressure p _...