Abstract
Tests were conducted to find the effects of moisture content, cutting length and date of cutting on the resistance to air-flow through orchard grass hay.
Hay samples were packed into the bin of 7.7cm in diameter to a depth of 30cm.
Pressure drop-air flow relationship was observed for various hay density (D. M 50-250kg/m3), moisture contents (wet basis 20-80%), cutting length (2-3cm, 10-20cm, no cutting) and date of cuttting (first and second).
The results were as follows:
1) The general equation for air flow through hay in a depth of 30cm is
P=KDmVn(=kdmVn)
Where p: Pressure drop, mmAq
K, k: constant for material and test condition.
D: dry matter density, kg/m3
d: apparent density, kg/m3
V: air velocity, m/s
m: density exponent.
n: velocity exponent.
2) Coefficients K, k, density exponent m and velocity exponent n were not affected very much cutting length.
3) Velocity exponent n reduced slightly as dry matter hay density increased, moisture content increased and second cutting hay was greater than first cutting hay.
The value of first cutting hay was 0.9-1.3, second cutting hay was 1.1-1.3
4) Coefficients K, k reduced as moisture content increased. Density exponent m increased slightly as moisture content increased. k, m of first and second cutting hay was respectively as follows:
m1=0.02512M+2.0197
Log k1=-0.07048M-1.9391
m2=0.02512M+2.5108
Log k2=-0.06118M-2.9636
5) Resistance to air flow decreased as moisture content decreased with the same dry matter density.
6) First cutting hay had a lower resistance to air flow than second cutting hay with the same dry matter density.
