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Pressure Loss Across Louvers Equation and Calculator
Fluids Flow Design and Engineering
Hydraulic Pneumatic Design Engineering
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:
h_{L} = k_{loss} x (u_{m}^{2} / (2 x g) )
Where k_{loss} is the head loss coefficient, u_{m} is the flow velocity in the pipe, and g is the gravitational acceleration. k_{loss} 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 k_{qu} 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 = u_{m} x D_{h} / v
Where:
N = Number of Louvers
A = Angle of louvers
a = Width (m)
g = 9.80665 m/s^{2}
u_{m} = Flow Velocity in tube (m/s)
v = Kinematic Velocity (kg/ms)
D_{h} = hydraulic diameter of the tube (m)  A square cross section has a hydraulic diameter equal to the width of the tube.
k_{qu} = Angle vs Number of louver constant  see table below
k_{qu}
↑
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.
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