Round-Edged Grid

                        Circular Cross-Section

                              (IDELCHIK)

Model description:

This model of component calculates the minor head loss (pressure drop) generated by the flow in a round-edged grid (perforated plate) installed in a straight pipe.

The head loss by friction in the inlet and outlet piping is not taken into account in this component.

Model formulation:

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Hydraulic diameter (m):

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Pipe cross-section area (m²):

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Cross-section area of one hole (m²):

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Clear cross-sectional area of the grid (m²):

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Mean velocity in pipe (m/s):

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Mean velocity in holes (m/s):

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Mass flow rate (kg/s):

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Reynolds number in pipe:

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Reynolds number in holes:

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Local resistance coefficient:

n Re₀ ³ 10⁵

    ([1] diagram 8-4)

            with :

            Coefficient of effect of the round:

    ([1] diagram 8-4)

n Re₀ £ 10⁵

        Quadratic local resistance coefficient:

    ([1] diagram 8-4)

Velocity factor:

    ([1] diagram 8-5)

Contraction factor:

    ([1] diagram 8-5)

         Coefficient of local resistance:

l  30 < Re₀ < 10⁵

    ([1] diagram 8-5)

l  10 < Re₀ £ 30

([1] diagram 8-5)

l  Re₀ £ 10

    ([1] diagram 8-5)

    ([1] diagram 8-5 with r/Dh = 0.2)

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Pressure loss coefficient (based on the mean pipe velocity):

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Total pressure loss (Pa):

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Total head loss of fluid (m):

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Hydraulic power loss (W):

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Symbols, Definitions, SI Units:

D_h          Hydraulic diameter (m)

D₁          Pipe internal diameter (m)

F₁          Pipe cross-sectional area (m²)

N           Holes number ()

D₀         Holes diameter (m)

F₀          Clear cross-sectional area of the grid (m²)

f₀          Cross-section area of one hole (m²)

Q          Volume flow rate (m³/s)

w₁          Mean velocity in pipe (m/s)

w₀          Mean velocity in holes (m/s)

G           Mass flow rate (kg/s)

r            Radius of the round (m)

Re₁        Reynolds number in pipe ()

Re₀        Reynolds number in holes ()

z_1quad     Quadratic pressure loss coefficient determined as Re = 10⁵ ()

z_j          Velocity factor ()

`e_0Re        Contraction factor ()

z₁          Coefficient of local resistance ()

z            Pressure loss coefficient (based on the mean pipe velocity) ()

DP          Total pressure loss (Pa)

DH         Total head loss of fluid (m)

Wh        Hydraulic power loss (W)

r           Fluid density (kg/m³)

n           Fluid kinematic viscosity (m²/s)

g           Gravitational acceleration (m/s²)

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Validity range:

· any flow regime: laminar and turbulent

· stabilized flow upstream of the grid

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Example of application:

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References:

[1] Handbook of Hydraulic Resistance, 3rd Edition, I.E. Idelchik

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HydrauCalc                                                                                    Edition: May 2020

© François Corre 2019-2020