Q&A forum: Pipe Flow Calculator
(gas and liquid)

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This is a very simple example about which I have a few queries:

A nylon pipe (spigot) internal dia 7mm, 8cm long - 2.820 KPa static pressure - venting to ambient.
The output flow is calculated as 3.95m/s, which is very low in contrast to measurements.
Also the volume emitted is 3.95 * 0.0000385=0.000152 m3/s, which is also very low.
The input data is below and attached.
Could you please have a quick look to see whether I have made any errors in the input parameters?

ϵ: surface roughness nylon spigot =0.0015mm=0.0000015m length 8 cm
1. ρ,1.22 -density- makes no difference to output velocity whatever value ?
2. RAM, of air 28.9644 g/mole - shouldn't this be Kg/mole ?
3. Actual flow is roughly 5-10 times as much as the calculator shows.
4. Why is there not a simple m/s flow rate in the output figures?

1. Density isn't used in the Gas calculation. It calculates the inlet density and the outlet density. This is a coding error - it shouldn't be asking for density for the gas calculation because it doesn't use it.

2. Yes it should

3. If you enter the RAM value of 0.0289644, the maximum outlet flow velocity will be about 122. Any other differences in the output velocity will be due to the input values used. RAM, viscosity, pressures, etc.

4. There is. It is the maximum outlet velocity (v̌₂), but only if your input data is in metres [/s]

In other words, PipeFlow's calculations are correct if you do the following:
A) Ignore the input data value for density in the 'Gas' calculation option
and
B) Enter RAM in kg/mol when using metric units with Newtons and kg

The calculator has since been modified to remove the requirement for density in the gas calculation

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