Figure 1.17. Operating conditions for an in-bin wheat-drying system and a maize-drying system.
System Operating Condition.If the system curve and the fan curve of a grain-drying system are plotted on the same graph, the operating condition of the fan/drying system is located at the intersection of the two curves. This is illustrated in Fig. 1.17 for an in-bin system in which both maize and wheat are dried. The axial-fan output for maize is 283 m3/min, but for wheat it is only 170 m3/min because of the larger static pressure of wheat.
On large grain silos, two fans frequently are placed in parallel in order to increase the airflow rate. (Only identical fans should be chosen for parallel installation.) The performance of a parallel-airflow system is shown in Fig. 1.18; the airflow characteristics of the system are found by adding the flowrate of the fans at a particular static pressure.
Figure 1.18. Performance of identical fans in parallel.