ABSTRACT
This chapter considers water the liquid to be removed by thermal means using air as the drying medium. Similar calculation procedures are also applicable to other liquids and gases, which are insoluble and non-reacting with these liquids. Most temperature-dependent sorption isotherm equations used for calculation of the heat of sorption give discontinuity at critical moisture content. In batch drying, conditions inside the dryer vary both in space and in time, which makes the calculations more complicated than in the case of continuous drying. The basic parameters that need to be calculated are material holdup in the dryer and material residence time necessary to complete the specified drying duty. Psychrometric charts, most commonly used to determine air humidity on the basis of wet and dry bulb temperatures, are prepared in orthogonal coordinates with temperature as the abscissa and humidity as the ordinate.
