Co-current hot-air dryers
Industrial drying: principles and calculation of equipment

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 A₀, before being reheated to become the air A₁ entering the dryer, under the effect of the power ${\stackrel{\cdot }{Q}}_1$...