Dust-Measurement - Paul Gothe GmbH

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Table C.2 — Values of Ki as a percentage - Tangential method for circular ducts
Ki
nd = 2 nd = 4 nd = 6 nd = 8
1 14,6 6,7 4,4 3,3
2 85,4 25,0 14,6 10,5
3 75,0 29,6 19,4
4 93,3 70,4 32,3
5 85,4 67,7
6 95,6 80,6
7 89,5
8 96,7
Method for rectangular ducts
In the method applicable to rectangular ducts, the sampling plane is divided into equal areas by lines parallel to the sides
of the duct, and a sampling point is located at the centre of each area (see Figure C.3).
In general, both sides of the rectangular duct are divided into an equal number of parts, giving areas which have the same
shape as the duct. The number of partial areas is thus the square of 1, 2, 3, etc. (see Figure C.3 a).
L1 and L2 being the dimensions of a section, where L1/L2 is greater than 2, side L1 shall be divided by a higher number
than L2 so that for each of the partial sections, the ratio l1/l2 (partial section) is less than 2.
If the lengths of the sides of the duct l1 and l2 are divided into n1 and n2 parts respectively, the number of sampling points
is n1 times n2 and the smallest distance from a wall of the duct will be l1/2n1 and l2/2n2.
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