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Is it possible to сalculate discharge / flow rate on the pipe diameter and the pressure (for constant pressure)?

For example:

enter image description here

Pressure_internal = 5 bar, Diameter_pipe = 36 mm, Density_water = 1000 kg/m^3

Bernoulli's Formula (online calculation):

$$\frac{\rho v^2}{2} + \rho g h + p = const$$

$$v \approx \sqrt{(p_i-p_a)\frac{2}{\rho_w}} = \sqrt{(5 \mathrm{bar}-1 \mathrm{bar})\frac{2}{1000 \frac{\mathrm{kg}}{\mathrm{m}^3} }}=28.284 \frac{\mathrm{m}}{\mathrm{s}}$$

Then the discharge should be (online calculation):

$$Q = Sv = (\pi r^2) v = \pi * (18\mathrm{mm})^2 *28.284\frac{\mathrm{m}}{\mathrm{s}} = 1717.81 \frac{\mathrm{l}}{\mathrm{min}}$$

Did I miss anything? How can I perform a calculation correct?

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    $\begingroup$ What reality are you seeing? This simple analysis appears to ignore factors like viscosity, friction in the pipe, turbulence and so on - however it can place a useful bound on the discharge rate. $\endgroup$
    – user_1818839
    Commented Feb 28, 2017 at 13:22
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    $\begingroup$ As @BrianDrummond points out, this formulation ignores the key variable that determine the flow. You need to account for the length of the pipe, the friction in the pipe, the physical properties of the liquid, whether the flow is laminar or turbulent, and entrance and exit losses. The place to start is here: en.wikipedia.org/wiki/Darcy-Weisbach_equation $\endgroup$
    – Mark
    Commented Feb 28, 2017 at 21:19
  • $\begingroup$ all muliplications are wrong please check $\endgroup$
    – OASIS POOLS
    Commented Mar 26, 2019 at 8:18
  • $\begingroup$ @OASISPOOLS I have added a link to an online calculator. Which of the calculations do you think is wrong? $\endgroup$
    – Artyom Ionash
    Commented Apr 10, 2020 at 10:56
  • $\begingroup$ Are you multiplying the area in mm^2 by velocity in m/s ? make sure your units agree. $\endgroup$
    – Solar Mike
    Commented Apr 10, 2020 at 11:13

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