Related Resources: fluid flow

### Pressure Loss Across Louvers Equation and Calculator

Head or pressure loss coefficient and head (pressure) loss of a fluid in across angled louvers inside a pipe equation and calculator.

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The heat flow (q) from the plate is calculated as:

hL = kloss x (um2 / (2 x g) )

Where kloss is the head loss coefficient, um is the flow velocity in the pipe, and g is the gravitational acceleration. kloss is dependant on the Reynolds Number Re . If Re is smaller than or equal to 50, then (1 - 50 / Re) is taken to be zero:

Where kqu is a function of the angle and the number of  louvers based on a table of values (see table below), and Re is the Reynolds Number and is calculated as:

Re = um x Dh / v

Where:

N = Number of Louvers
A = Angle of louvers
a = Width (m)
g = 9.80665 m/s2
um = Flow Velocity in tube (m/s)
v = Kinematic Velocity (kg/m-s)
Dh = hydraulic diameter of the tube (m) - A square cross section has a hydraulic diameter equal to the width of the tube.
kqu = Angle vs Number of louver constant - see table below

kqu

 ↑ No. Louvers ↓ ← Angle → 0 10 20 30 40 50 60 70 80 2 0.07 0.4 1.10 2.20 5.50 11.5 30.0 80.0 300.0 3 0.14 0.25 0.80 2.00 4.50 10.0 20.0 40.0 140.0 4 0.12 0.22 0.73 1.70 4.00 8.00 14.0 30.0 110.0 5 0.15 0.20 0.65 1.50 3.00 7.00 13.0 35.0 70.0 6 0.20 0.35 1.00 2.30 4.80 8.50 16.0 35.0 150.0

References

Idel'chik, I E. and Fried, Erwin., Flow Resistance, a Design Guide for Engineers , Taylor & Francis, Washington D.C. 1989. p 306.