Unformatted text preview: y Guide 370 Chapter 6 Viscous Flow in Ducts 20.00
Gate 16.00 Disk
0.25 Fig. 6.18b Average-loss coefficients
for partially open valves (see
sketches in Fig. 6.17). 0.30 0.40 0.50 0.60 0.70 0.75 0.80 0.90 1.00 Fractional opening h
D 1000.00 100.00 K 10.00 80
20 30 40 0.10 50 60 70 90 Valve opening angle, degrees
(b) The butterfly valve of Fig. 6.19a is a stem-mounted disk which, when closed, seats
against an O-ring or compliant seal near the pipe surface. A single 90° turn opens the
valve completely, hence the design is ideal for controllable quick-opening and quickclosing situations such as occur in fire protection and the electric power industry. However, considerable dynamic torque is needed to close these valves, and losses are high
when the valves are nearly closed.
Figure 6.19b shows butterfly-valve loss coefficients as a function of the opening angle for turbulent-flow conditions (
0 is closed). The losses are huge when the
opening is small, and K drops off nearly exponentially with the opening angle. Th...
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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.
- Spring '08