1. Co-current hot-air dryers

Useful variables are defined in figure 1 : water contents are here average values in the thickness of the product or layer (unless specified in the text, as X _Ps product surface content), in the form X _P (kg water/kg dry matter) on a dry basis for product P, and Y (kg water/kg dry air) for air. By convention, throughout this article, what enters the dryer (air or product) is indexed 1, and what leaves is indexed 2. Index 3 describes the product cooler outlet after drying, if any. We'll call the ambient air A ₀ , before being reheated to become the air A ₁ entering the dryer, under the effect...