Could provide an example of converting Nl/min to l/min.

Guest

Hi,

Nl/min means "normal liters per minute". It is the amount of air that flows through a pipe, but calculated back to 'normal' conditions.

Normal conditions being:
0 degrees Celsius
1 atmosphere (1.01325 bar)

The quick and dirty method:

Divide the Normal liters per minute (Nl/min) by the pressure plus 1 to get the l/min through the pipe.

50 Nl/min at 7 bar = 50/8 = 6.25 l/min compressed air flow through the pipe.

The exact method, using the 'ideal gas law':

PV=nRT

Since the amount of molecules stay the same, we can say:

V1 = (P2/P1*T1/T2)*V2.

V1 = normal liters per minute
V2 = liters per minute

P1 = pressure at normal conditions
P2 = actual pressure

T1 = temperature at normal conditions
T2 = actual temperature of air

The P1/P2 part compensates for the difference in pressure.
The T1/T2 part compensates for the difference in temperature.

In the calculation to normal conditions, we need to use absolute pressure (not relative) and absolute temperature (Degrees Kelvin: 0 degrees Celsius is 273.15 degrees Kelvin).

Example 1: 50 l/min at 7 bar, 25 degrees Celsius, to Nl/min

50 Lpm x (810 kPa/101.325 kPa) x 273.15 / (273.15 + 25) = 367 NL/min

Example 2: 500 Nl/min to actual compressed air flow at 7 bar and 20 degrees Celsius.

(7 bar relative = 8 bar absolute = 8 * 101.325 = 810 kPa)

500 Nl/min = (810 kPa/101.325 kPa) x 273.15/(273.15 + 20) * V2

We can calculate that V2 = 67.2 l/min

Answer: there flows 67.2 liters of compressed air thruogh the pipe, at 7 bar and 20 degrees Celsius.

Remember:
liters/min is what you will measure using a flow meter. There are flow meters that can also show Nl/min (it wil need a built-in pressure and temp sensor also for this).

Nl/min is what is usually indicated on compressors and also on pneumatic devices.

I hope all of this made sense, it can become quite messy when typing math in plain text.

Why do you want to convert nl/min to l/min?

1) If you want know the correct pipe size for your compressed air system, be sure to check out my compressed air pipe sizing page.

2) If you want to buy a compressor en want to know the capacity? Go to the air compressor buying guide.

Please let me know if you have more questions.

Cas
Owner of air-compressor-guide.com

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