Filter pressure drop (fluids.filters)

fluids.filters.round_edge_screen(alpha, Re, angle=0)[source]

Returns the loss coefficient for a round edged wire screen or bar screen, as shown in [R377381]. Angle of inclination may be specified as well.

Parameters:

alpha : float

Fraction of screen open to flow [-]

Re : float

Reynolds number of flow through screen with D = space between rods, []

angle : float, optional

Angle of inclination, with 0 being straight and 90 being parallel to flow [degrees]

Returns:

K : float

Loss coefficient [-]

Notes

Linear interpolation between a table of values. Re table extends from 20 to 400, with constant values outside of the table. This behavior should be adequate. alpha should be between 0.05 and 0.8. If angle is over 85 degrees, the value at 85 degrees is used.

References

[R377381](1, 2) Blevins, Robert D. Applied Fluid Dynamics Handbook. New York, N.Y.: Van Nostrand Reinhold Co., 1984.

Examples

>>> round_edge_screen(0.5, 100)
2.0999999999999996
>>> round_edge_screen(0.5, 100, 45)
1.05
fluids.filters.round_edge_open_mesh(alpha, subtype='diamond pattern wire', angle=0)[source]

Returns the loss coefficient for a round edged open net/screen made of one of the following patterns, according to [R378382]:

‘round bar screen’:

\[K = 0.95(1-\alpha) + 0.2(1-\alpha)^2\]

‘diamond pattern wire’:

\[K = 0.67(1-\alpha) + 1.3(1-\alpha)^2\]

‘knotted net’:

\[K = 0.70(1-\alpha) + 4.9(1-\alpha)^2\]

‘knotless net’:

\[K = 0.72(1-\alpha) + 2.1(1-\alpha)^2\]
Parameters:

alpha : float

Fraction of net/screen open to flow [-]

subtype : str

One of ‘round bar screen’, ‘diamond pattern wire’, ‘knotted net’ or ‘knotless net’.

angle : float, optional

Angle of inclination, with 0 being straight and 90 being parallel to flow [degrees]

Returns:

K : float

Loss coefficient [-]

Notes

alpha should be between 0.85 and 1 for these correlations. Flow should be turbulent, with Re > 500.

References

[R378382](1, 2) Blevins, Robert D. Applied Fluid Dynamics Handbook. New York, N.Y.: Van Nostrand Reinhold Co., 1984.

Examples

>>> round_edge_open_mesh(0.96, angle=33.)
0.02031327712601458
fluids.filters.square_edge_screen(alpha)[source]

Returns the loss coefficient for a square wire screen or square bar screen or perforated plate with squared edges, as shown in [R379383].

Parameters:

alpha : float

Fraction of screen open to flow [-]

Returns:

K : float

Loss coefficient [-]

Notes

Linear interpolation between a table of values.

References

[R379383](1, 2) Blevins, Robert D. Applied Fluid Dynamics Handbook. New York, N.Y.: Van Nostrand Reinhold Co., 1984.

Examples

>>> square_edge_screen(0.99)
0.008000000000000009
fluids.filters.square_edge_grill(alpha, l=None, Dh=None, fd=None)[source]

Returns the loss coefficient for a square grill or square bar screen or perforated plate with squared edges of thickness l, as shown in [R380384].

for Dh < l < 50D

\[K = \frac{0.5(1-\alpha) + (1-\alpha^2)}{\alpha^2}\]

else:

\[K = \frac{0.5(1-\alpha) + (1-\alpha^2) + f{l}/D}{\alpha^2}\]
Parameters:

alpha : float

Fraction of grill open to flow [-]

l : float, optional

Thickness of the grill or plate [m]

Dh : float, optional

Hydraulic diameter of gap in grill, [m]

fd : float, optional

Darcy friction factor [-]

Returns:

K : float

Loss coefficient [-]

Notes

If l, Dh, or fd is not provided, the first expression is used instead. The alteration of the expression to include friction factor is there if the grill is long enough to have considerable friction along the surface of the grill.

References

[R380384](1, 2) Blevins, Robert D. Applied Fluid Dynamics Handbook. New York, N.Y.: Van Nostrand Reinhold Co., 1984.

Examples

>>> square_edge_grill(.45)
5.296296296296296
>>> square_edge_grill(.45, l=.15, Dh=.002, fd=.0185)
12.148148148148147
fluids.filters.round_edge_grill(alpha, l=None, Dh=None, fd=None)[source]

Returns the loss coefficient for a rounded square grill or square bar screen or perforated plate with rounded edges of thickness l, as shown in [R381385].

for Dh < l < 50D

\[K = lookup(alpha)\]

else:

\[K = lookup(alpha) + \frac{fl}{\alpha^2D}\]
Parameters:

alpha : float

Fraction of grill open to flow [-]

l : float, optional

Thickness of the grill or plate [m]

Dh : float, optional

Hydraulic diameter of gap in grill, [m]

fd : float, optional

Darcy friction factor [-]

Returns:

K : float

Loss coefficient [-]

Notes

If l, Dh, or fd is not provided, the first expression is used instead. The alteration of the expression to include friction factor is there if the grill is long enough to have considerable friction along the surface of the grill. alpha must be between 0.3 and 0.7.

References

[R381385](1, 2) Blevins, Robert D. Applied Fluid Dynamics Handbook. New York, N.Y.: Van Nostrand Reinhold Co., 1984.

Examples

>>> round_edge_grill(.4)
1.0
>>> round_edge_grill(.4, l=.15, Dh=.002, fd=.0185)
2.3874999999999997