Excel Column Definitions for Data Collected at Indian Head 2007 to 2015 from Reliable System. This is for the record and is only useful to those having the data.
A. Date & time stamp of sensor readings on the hour Nov 03/15 17:27:23
B. lowest temperature sensor close to perforated tube, ⁰C
C. Tm, mid temperature sensor in the grain half way up, ⁰C
D. Tt, highest temperature sensor in the grain ⁰C
E. T, temperature of discharge air just inside roof opening, ⁰C
F. RH, relative humidity of the discharge air %
G. Pressure in inches of water or CFM, fans running if pres > 0.05
H. Temperature of outside air, ⁰C
I. RHair, relative humidity of outside air, %
J. Not usually used but in bigger bins pressure is sometimes here
K. Net H20 leaving the bin per cubic meter, grams per cubic meter
L. =IF(G1 > 0.05,750 * K1 * 60/35310,0) if the fan is running, multiply K by the number of cubic feet that are leaving the bin. In this case CFM is 750 and there are 35.31 cubic feet in a cubic meter
M. MC , moisture content of the grain,%. The initial moisture content is manually put in Row 1 and then we subtract from that using the amounts from L. We need to know the number of bushels and weight of the grain so that the ratio can be calculated.
N. RHthres % Knowing the MC and Temp of the grain, we can plug these into an EMC equation and get the relative humidity that this grain wants to be at.
O. EMChum , EMC absolute humidity, grams of water per cubic meter that the grain wants the air surrounding it to contain this much water, and we calculate this from the psychrometric equation or the saturation equation factored by RHthres, just calculated in column N.
P. This is the ratio that shows how much water was added to the air as it passed through the grain and how close it got to the EMC value: (Dchargehum – Airhum)/(EMChum – Airhum). The Dchargehum will be trying to get to the EMChum but will never get there, so this ratio will less than one.
Q. Ƭ, Time Constant for how long it takes the outside air to acquire moisture from the air and be 63% of the way to EMC We know how close it got from P. and we can calculate the time, t, that is was in contact with the grain by knowing the number of bushels and the CFM. The smaller bins hold 2200 bushels, and one bushel is 1.2446 ft3. So the bin is 2738 ft3. But the grain takes about half this space so there is 1369 ft3 of air. At 3000 CFM we would get an air exchange every 1369/3000 = 0.45 min. Or, the air is in contact the grain for 0.45 min. The time constant, Ƭ = -t / ln( P – 1) where t is 0.45 min and P is ratio calculated in column P. This time constant is important in understanding the amount of time that is needed to reach equilibrium.
R. Ratio of t/Ƭ. The bigger this number, the closer we are to equilibrium. It is a measure of the efficiency to which we are using the energy in the grain to dry. The bigger this number, the more energy we are using from the grain to dry.
S. Safe days. See Spoilage Index Report on how safe days and spoilage index is calculated.
T. Spoilage Index.