This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ... are desirable, whenever they can be applied, because of the convenience in obtaining changes of speed and because the motors may easily be direct-connected to the fan. Alternating current motors are used but they usually run at higher speeds, requiring reduction drives and are not so satisfactory in regulation. Speed ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ... are desirable, whenever they can be applied, because of the convenience in obtaining changes of speed and because the motors may easily be direct-connected to the fan. Alternating current motors are used but they usually run at higher speeds, requiring reduction drives and are not so satisfactory in regulation. Speed reductions of 40 per cent, may be had with alternating current machines where required. 131. Speed of the Pan: --A blower fan, exhausting into the open air, will deliver air with a linear velocity slightly below the peripheral velocity of the fan blades, but if this same fan be connected to a system of ducts and heater coils, the linear velocity of the air becomes much less because of the increased resistance and the lag or slip that takes place between the fan blades and the moving air. In the average heating system this slip may be as great as 40 to 50 per cent. See Art. 127. It is customary, therefore, in applying blowers to heating systems, to consider the linear velocity of the air as it leaves the fan to be onehalf that of the periphery of the fan blades. Since the velocity of the air upon delivery from the fan should not exceed 1800 to 2500 feet per minute, the outer point on the fan blades should not be expected to move faster than 3600 to 5000 feet per minute. Knowing this peripheral velocity, the revolutions per minute may be selected and the diameter obtained. In all direct-connected fans the revolutions per minute must agree with that of the engine or motor. In belted fans, however, this restriction need not apply. It is found that ordinary blower fans running at high speeds are very noisy and so practice has determined largely the number of revolutions to use. Speeds used by the American Blower Company in the latest type of Sirocco..
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PLEASE NOTE, WE DO NOT SHIP TO DENMARK. New Book. Shipped from UK in 4 to 14 days. Established seller since 2000. Please note we cannot offer an expedited shipping service from the UK.
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PLEASE NOTE, WE DO NOT SHIP TO DENMARK. New Book. Shipped from UK in 4 to 14 days. Established seller since 2000. Please note we cannot offer an expedited shipping service from the UK.
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Seller's Description:
PLEASE NOTE, WE DO NOT SHIP TO DENMARK. New Book. Shipped from UK in 4 to 14 days. Established seller since 2000. Please note we cannot offer an expedited shipping service from the UK.
