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Hydrodynamic calculation butterfly valve double disc

Butterfly_valve_(double_disc)
Butterfly valve (double disc)
Double_disc
Double disc

Values for calculation

$D$ $\mathrm{mm}$
$L_D$ $\mathrm{mm}$
$c$ $\mathrm{mm}$
$D_s$ $\mathrm{mm}$
$Q_{max}$ $\mathrm{m^3/s}$
$H$ $\mathrm{m}$
$g$ $\mathrm{m/s^2}$
$T$ $\mathrm{°C}$
$ρ$ $\mathrm{kg/m^3}$
$P_T$ $\mathrm{Pa}$
$ΔP$ $\mathrm{m}$
$h$ $\mathrm{m}$
$ρ_{air}$ $\mathrm{kg/m^3}$
$p_{a}$ $\mathrm{Pa}$
$n$
$t$ $\mathrm{s}$
$L$ $\mathrm{m}$
$ζ$

Calculation

Velocity in valve

$$v_{max}=\cfrac{4\cdot 10^6\cdot Q_{max}}{π\cdot D^2}$$

Theoretical pressure in the valve at full opening

$$Δ_h=\cfrac{v_{max}^2}{2\cdot g}\cdot \left(ζ+1\right)$$

Pressure parameter

$$p=\cfrac{Δ_h}{H}$$

Effective closing time factor

$$c_{ef}=0$$

Under-pressure behind the valve

$$P_{u}=\max\left(-\cfrac{L\cdot v_{max}}{g\cdot t\cdot c_{ef}}, -10\right)$$

Requirements

$$0 < p \le 1$$