Chapt06

The constants will change if other diameter units are

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Unformatted text preview: and contractions. The original, or classical, venturi was invented by a U.S. engineer, Clemens Herschel, in 1898. It consisted of a 21° conical contraction, a straight throat of diameter d and length d, then a 7 to 15° conical expansion. The discharge coefficient is near unity, and the nonrecoverable loss is very small. Herschel venturis are seldom used now. The modern venturi nozzle, Fig. 6.39c, consists of an ISA 1932 nozzle entrance and a conical expansion of half-angle no greater than 15°. It is intended to be operated in a narrow Reynolds-number range of 1.5 105 to 2 106. Its discharge coefficient, shown in Fig. 6.42, is given by the ISO correlation formula Cd 0.9858 0.196 4.5 (6.136) It is independent of ReD within the given range. The Herschel venturi discharge varies with ReD but not with , as shown in Fig. 6.41. Both have very low net losses. The choice of meter depends upon the loss and the cost and can be illustrated by the following table: Type of meter Net head loss Cost Orifice Nozzle Venturi Lar...
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This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.

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