File:Handbook for heating and ventilating engineers (1913) (14595163099).jpg

Identifier: handbookforheati02hoff (find matches)
Title: Handbook for heating and ventilating engineers
Year: 1913 (1910s)
Authors: Hoffman, James David, 1868- (from old catalog) Raber, Benedict Frederick, 1882- (from old catalog) joint author
Subjects: Heating Ventilation
Publisher: New York (etc.) McGraw-Hill book company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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product of the coefficient of reduced velocityand the coefficient of reduced area. From tests by Weisbachthe following approximate values are quoted by the Sturte-vant Company in Mechanical Draft, page 152. Orifice in a thin plate, .56 •Short cylindrical pipe, .75 Rounded off conical mouth piece, .98 Conical pipe, angle of convergence about 6°, .92 125. Results of Tests to Determine the Relation be-tween Pressure and Velocity in Air Transmission:—In fan construction the number of blades, the shape of the blades,the sizes of the inlet and outlet openings, the shape andsize of the casement around the blades and the speed, allhave an effect upon the relation between the pressure andthe velocity of the air discharge. From recent tests con-ducted in the Mechanical Engineering Department, Univer-sity of Nebraska, the curves shown in Pig. 101, a, were ob- 12 5£ H si== ri ^ K^ H m H n T 9 bcr -A Si i?-^ ^^ ^ w^ n ^ ba .2 3 4 .5RATIO OF OPENING Fig. 101a. .6 9 190 HEATING AND VENTILATION
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2 .3 4 5RATD or OPENING Fig. 101b. tained. A Number 2 Sirocco blower was belted to an elec-tric motor and delivered air to a horizontal, circular pipewhose length was nine times the diameter. This pipe wasprovided with reducing nozzles which varied the area ofdischarge by -tenths from full opening to full closed. Theair tube was provided also with manometer tubes for static,dynamic and velocity pressures, arranged with an adjustablescale to read to either .01 or .002 inch of water. The grosspower was taken by wattmeter and the delivered powerfrom motor to fan was taken by dynamometer. In additionto this, the frictional horse-power of the fan and motorunit was obtained by removing the fan wheel from theshaft and taking readings with all other conditions remain-ing as nearly constant as possible. The friction power,when deducted from tlie grcss power recorded by the watt-meter, gave the readings for the net horse-power curve.A galvanized iron intake, enlarged from the size of thefan int

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