Fluid_Flow_Rules_of_Thumb_for_Chemical

Fluid Flow

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2. McAllister, E. W., Pipe Line Rules of Thumb Handbook, 3rd Ed., Gulf Publishing Co., pp. 247-248, 1993. 3. Branan, C. R., The Process Engineer's Pocket Hand- book, Vol. 1, Gulf Publishing Co., p. 4, 1976.

LE - 5 + 0.1305 X 30 = 8.92 miles equivalent of single 12-in. ID line

References

1. Maxwell, J. B., Data Book on Hydrocarbons, Van Nostrand, 1965.

Sonic Velocity

To determine the critical pressure ratio for gas sonic velocity across a nozzle or orifice use

To determine sonic velocity, use

V~ - ~/KgRT

critical pressure ratio - [ 2 / ( K + 1)]k/(k-~)

where

If pressure drop is high enough to exceed the critical ratio, sonic velocity will be reached. When K - 1.4, ratio - 0.53.

Vs = Sonic velocity, ft/sec K = Cp/Cv the ratio of specific heats at constant pressure to constant volume. This ratio is 1.4 for most diatomic gases. g = 32.2ft/sec 2 R = 1,544/mol. wt. T = Absolute temperature in ~

Source

Branan, C. R., The. Process Engineer's Pocket Hand- book, Vol. 1, Gulf Publishing Co., 1976.

Metering

2g - 64.4 ft]sec 2 Ah - Orifice pressure drop, ft of fluid D - Diameter Co - Coefficient. (Use 0.60 for typical application where Do/Op is between 0.2 and 0.8 and Re at vena con- tracta is above 15,000.)

Orifice

1/2

Uo - Up2

- Co (2gAh) 1/2

Permanent head loss % of Ah Permanent Do/Dr Loss 0.2 95 0.4 82 0.6 63 0.8 40

Venturi

Same equation as for orifice:

Co - 0.98

One designer uses permanent loss - Ah (1 - Co)

Permanent head loss approximately 3-4% Ah.

where

Uo - Velocity through orifice, ft/sec Up - Velocity through pipe, ft/sec