Handbook for heating and ventilating engineers . V 2 X X X 12 or r = V /iio (8) where hu> = the difference in height in inches of the columnsof a water manometer, with both legs connected as described,and a temperature of 60 degrees. By a similar method theformula may be reduced for a mercury or other manometer,or for other temperatures than 60 degrees. (See Art. 1021,Trans. A. S. M. E. Vol. XXV.) In using the Pitot tube or the anemometer, the factshould not be lost sight of that the velocity varies froma minimum at the inner walls of the tube to the maximumat the center of
Handbook for heating and ventilating engineers . V 2 X X X 12 or r = V /iio (8) where hu> = the difference in height in inches of the columnsof a water manometer, with both legs connected as described,and a temperature of 60 degrees. By a similar method theformula may be reduced for a mercury or other manometer,or for other temperatures than 60 degrees. (See Art. 1021,Trans. A. S. M. E. Vol. XXV.) In using the Pitot tube or the anemometer, the factshould not be lost sight of that the velocity varies froma minimum at the inner walls of the tube to the maximumat the center of the tube. It seems that the friction at theInner walls throws the moving fluid into a number ofconcentric layers, those toward the center moving the fast-est, those toward the Inner wall of the pipe the a circular tube, the variation of velocities of thesedifferent layers may be approximately represented by theabscissae of a parabola, Fig. 11, with its axis on the axis ofthe circular pipe. Weisbach, on page 189 of his Mechanics of. Fig. 11. CHIMNEYS 35 Air Machinery, quotes tlie average speed at two-thirds of theradius from the center, this value being obtained by ex-periments. For conduits of other shapes the position ofmean velocity must be determined experimentally. Thisvariation of velocity from the center of the stream less-ening- tow^ard the walls may possibly account for the varia-tions shown by the anemometers. It is evident thatif such an instrument, with a given diameter of vanewheel, be placed at the center of a pipe of large radius itwould tend to register a higher velocity than the recording meters may be obtained for keep-ing permanent records of the flow of air and steam throughpipes and ducts. The record from the meter indicates direct-ly the cubic feet of free air or other fluid used during eachhour of the day. 16. Amount of Air Required to Burn Carbon:—The chiefproduct in the combustion of carbon with the oxygen of theair is C
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectventila, bookyear1913
