1. Determination of the diameter of economic mine ventilation duct
1.1 Mine ventilation duct purchase cost
As the diameter of the mine ventilation duct increases, the required materials also increase, so the purchase cost of the mining vent duct also increases. According to the statistical analysis of the price given by the mine ventilation duct manufacturer, the price of the mining ventilation duct and the diameter of the mining ventilation duct are basically linear as follows:
C1 = ( a + bd) L ( 1)
Where, C1 – purchase cost of mine ventilation duct, CNY; a – increased cost of mine ventilation duct per unit length, CNY/m; b – basic cost coefficient of unit length and a certain diameter of mine ventilation duct; d – diameter of mining ventilation duct, m; L – The length of the purchased mining ventilation duct, m.
1.2 Mining ventilation duct ventilation cost
1.2.1 Analysis of local ventilation parameters
The wind resistance of the mine ventilation duct includes the friction wind resistance Rfv of the mine ventilation duct and the local wind resistance Rev, where the local wind resistance Rev includes the joint wind resistance Rjo, the elbow wind resistance Rbe and the mining ventilation duct outlet wind resistance Rou (press-in type) or inlet wind resistance Rin (extraction type).
The total wind resistance of the press-in mine ventilation duct is:
(2)
The total wind resistance of the exhaust mine ventilation duct is:
(3)
Where:
Where:
L – the length of the mine ventilation duct, m.
d – the diameter of the mine ventilation duct, m.
s – the cross-sectional area of the mine ventilation duct, m2.
α – Coefficient of frictional resistance of mine ventilation duct, N·s2/m4. The roughness of the inner wall of the metal ventilation duct is roughly the same, so the α value is only related to the diameter. The frictional resistance coefficients of both flexible ventilation ducts and flexible ventilation ducts with rigid rings are related to wind pressure.
ξjo – the local resistance coefficient of the mine ventilation duct joint, dimensionless. When there are n joints in the whole length of the mine ventilation duct, the total local resistance coefficient of the joints is calculated according to nξjo.
n – the number of joints of the mine ventilation duct.
ξbs – local resistance coefficient at the turning of the mine ventilation duct.
ξou – local resistance coefficient at the outlet of the mine ventilation duct, take ξou = 1.
ξin – local resistance coefficient at the inlet of the mine ventilation duct, ξin = 0.1 when the inlet is completely rounded, and ξin = 0.5 – 0.6 when the inlet is not rounded at a right angle.
ρ – air density.
In local ventilation, the total wind resistance of the mine ventilation duct can be estimated based on the total friction wind resistance. It is generally believed that the sum of the local wind resistance of the joint of the mine ventilation duct, the local wind resistance of the turning, and the wind resistance of the outlet (press-in type) or inlet wind resistance (extraction type) of the mine ventilation duct are approximately 20% of the total frictional wind resistance of the mine ventilation duct. The total wind resistance of the mine ventilation is:
(4)
According to the literature, the value of the frictional resistance coefficient α of the fan duct can be regarded as a constant. The α value of the metal ventilation duct can be selected according to Table 1; The α value of JZK series FRP ventilation duct can be selected according to Table 2; The frictional resistance coefficient of the flexible ventilation duct and the flexible ventilation duct with a rigid skeleton is related to the wind pressure on the wall, the frictional resistance coefficient α value of the flexible ventilation duct can be selected according to Table 3.
Table 1 Frictional resistance coefficient of metal ventilation duct
| Ducting diameter(mm) | 200 | 300 | 400 | 500 | 600 | 800 |
| α × 104 /( N·s2·m-4 ) | 49 | 44.1 | 39.2 | 34.3 | 29.4 | 24.5 |
Table 2 Frictional resistance coefficient of JZK series FRP centilation duct
| Ducting type | JZK-800-42 | JZK-800-50 | JZK-700-36 |
| α × 104 /( N·s2·m-4 ) | 19.6-21.6 | 19.6-21.6 | 19.6-21.6 |
Table 3 The coefficient of frictional resistance of the flexible ventilation duct
| Ducting diameter(mm) | 300 | 400 | 500 | 600 | 700 | 800 | 900 | 1000 |
| α × 104 /N·s2·m-4 | 53 | 49 | 45 | 41 | 38 | 32 | 30 | 29 |
To be continued…
Post time: Jul-07-2022
