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is the area of the duct, is the velocity of the fluid. The practicalities of mine ventilation led Atkinson to group some of these variables into one all-encompassing term: Area and perimeter were incorporated because mine airways are of irregular shape, and both vary along the length of an airway.
Round duct is made using a continuous spiral forming machine which can make round duct in nearly any diameter when using the right forming die and to any length to suit, but the most common stock sizes range evenly from 4" to 24" (10-60 cm) with 6"-12" (15-30 cm) being most commonly used. Stock pipe is usually sold in 10' (300 cm) joints.
The amount of ventilation in an ETS area is equal to the amount of an ETS-free area plus the amount V, where: V = DSD × VA × A/60E V = recommended extra flow rate in CFM (L/s) DSD = design smoking density (estimated number of cigarettes smoked per hour per unit area) VA = volume of ventilation air per cigarette for the room being designed (ft ...
Bretschneider's formula generalizes Brahmagupta's formula for the area of a cyclic quadrilateral, which in turn generalizes Heron's formula for the area of a triangle.. The trigonometric adjustment in Bretschneider's formula for non-cyclicality of the quadrilateral can be rewritten non-trigonometrically in terms of the sides and the diagonals e and f to give [2] [3]
Chipping Sodbury Tunnel ventilation shaft Swan St. ventilation shaft on the Burnley Tunnel Ventilation shafts of the Velser tunnel, the Netherlands. In subterranean civil engineering, ventilation shafts, also known as airshafts or vent shafts, are vertical passages used in mines and tunnels to move fresh air underground, and to remove stale air.
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giving the basic form of Brahmagupta's formula. It follows from the latter equation that the area of a cyclic quadrilateral is the maximum possible area for any quadrilateral with the given side lengths. A related formula, which was proved by Coolidge, also gives the area of a general convex