Because batch dryers are relatively cheap to build and inexpensive to maintain, they are widely used to dry agricultural products. A major drawback of these dryers is the continuously changing temperature and humidity of the drying air due to heat and mass transfer inside the dryers so that saturation level of the air is often reached before it leaves the dryer. This problem can be avoided by determining the suitable loaning capacity for the dryer in relation to the inlet air condition. The maximum load can be determined either by limiting the number of trays, or by fixing tray lending with the above constrained condition of saturation. In either case, productivity, which is the maximum load divided by the corresponding drying time, is obtained and the optimum condition for each flow rate can then be determined It was found for both drying conditions that there is a maximum value of productivity that determines the optimum dimensions and performance of the dryer at every flow rate.