Instructions for use: compute "k" based on previous drying runs. Enter the three moistures, the drying volume, n and the feedrate from that run, then press the "Compute k" button. The "drying volume" is the volume of the heated portion of the drying system. To find the feedrate for new initial or final moisture conditions, change the first two fields and press the "Compute feedrate" button.

Picking a grain fills in k, n and the equilibrium moisture with values fitted to 44 logged runs of one dryer: n = 1.0, equilibrium moisture 6%, and k of 0.337 for barley, 0.200 for wheat, 0.256 for canola. Use them as a starting point and recompute k from your own dryer once you have a run to fit. Because the three are fitted together, changing one of them invalidates the other two; pick "Other" if you are supplying your own set.

The 6% equilibrium moisture is a fitted constant, not a measured equilibrium moisture content. The real value for hot dryer air is nearer 2%; the higher number absorbs part of the model error and removes a bias against initial moisture. n cannot be fitted from ordinary records, because it trades off against the equilibrium moisture, so it is pinned at 1.0.

Expect roughly 25% error on the predicted feedrate, and more than that when the initial and final moisture are close. Removing less than about two points of moisture predicts a feedrate faster than the dryer can run; read that as "as fast as it will go" rather than as a number.

Calculations are based on Page's equation for thin layer drying. See the background page for more details on the model. Comments to the webmaster.