DWYER INSTRUMENTS, INC.
Phone: 219/879-8000 www.dwyer-inst.com
P.O. BOX 373 • MICHIGAN CITY, INDIANA 46361, U.S.A.
Fax: 219/872-9057
e-mail: [email protected]
©Copyright 2004 Dwyer Instruments, Inc. Printed in U.S.A.
7
/04 FR# 72-440451-01 Rev. 2
FLOW EQUATIONS
1. Any Liquid
Q (GPM) = 5.668 x K x D
2
x
∆
P/Sf
2. Steam or Any Gas
Q (lb/Hr) = 359.1 x K x D
2
x
p x
∆
P
3. Any Gas
Q (SCFM) = 128.8 x K x D
2
x P x
∆
P
(T + 460) X S
S
DIFFERENTIAL PRESSURE EQUATIONS
1. Any Liquid
∆
P (in. WC) = Q
2
x Sf
K
2
x D
4
x 32.14
2. Steam or Any Gas
∆
P (in. WC) = Q
2
K
2
x D
4
x p x 128,900
3. Any Gas
∆
P (in. WC) = Q
2
x S
S
x (T + 460)
K
2
x D
4
x P x 16,590
Technical Notations
The following notations apply:
∆
P = Differential pressure expressed in inches of water column
Q = Flow expressed in GPM, SCFM, or PPH as shown in equation
K = Flow coefficient— See values tabulated on Pg. 3.
D = Inside diameter of line size expressed in inches.
For square or rectangular ducts, use:
D =
4
x
Height
x
Width
π
P = Static Line pressure (psia)
T = Temperature in degrees Fahrenheit (plus 460 = °Rankine)
p = Density of medium in pounds per square foot
S
f
= Sp Gr at flowing conditions
S
S
= Sp Gr at 60°F (15.6°C)
SCFM = ACFM X
(
14.7 + PSIG
)
(
520*
)
14.7
460 + °F
ACFM = SCFM X
(
14.7
)
(
460 + °F
)
14.7+ PSIG
520
POUNDS PER STD. = POUNDS PER ACT. X
(
14.7
)
(
460 + °F
)
CUBIC FOOT
CUBIC FOOT
14.7 + PSIG
520*
POUNDS PER ACT. = POUNDS PER STD. X
(
14.7 + PSIG
)
(
520*
)
CUBIC FOOT
CUBIC FOOT
14.7
460 + °F
1 Cubic foot of air = 0.076 pounds per cubic foot at 60° F (15.6°C) and 14.7 psia.
* (520°= 460 + 60°) Std. Temp. Rankine
SCFM TO ACFM EQUATION
REVISEDBulletin F-50 7/8/04 8:04 AM Page 4
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