Chapt06

The moody loss due to the axial length of the bend

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Unformatted text preview: en the expansion section and the end of the separation zone gives a theoretical loss KSE 1 d2 D2 2 hm V /(2g) 2 (6.101) | v v Note that K is based on the velocity head in the small pipe. Equation (6.101) is in excellent agreement with experiment. For the sudden contraction, however, flow separation in the downstream pipe causes the main stream to contract through a minimum diameter dmin, called the vena contracta, as sketched in Fig. 6.22. Because the theory of the vena contracta is not well developed, the loss coefficient in the figure for sudden contraction is experimental. It | e-Text Main Menu | Textbook Table of Contents | Study Guide 1.0 t =0 d t K V 0.02 l 0.5 (a) 0 0.1 0.2 l d 0.3 0.4 0.6 Sharp-edged L V d θ r 0.4 K θ= 10° 50° 0.2 30° Fig. 6.21 Entrance and exit loss coefficients: (a) reentrant inlets; (b) rounded and beveled inlets. Exit losses are K 1.0 for all shapes of exit (reentrant, sharp, beveled, or rounded). (From Ref. 37.) 0 (b) r d 0 0.10 0.15 0.20 r, L dd 1.0 Sudden expansion 0.8 d V D hm K= V 2/(2 g) 0.6 Eq. (6.101) Eq. (6.102) 0.4 Sudden contraction: Vena contracta V 0.2 v v | d D Fig. 6.22 Sudden expansion and contraction losses. Note that the los...
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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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