Nitrogen expansion after pressure reducer valve
Nitrogen expansion after pressure reducer valve
(OP)
Good morning,
I have a installation which needs Nitrogen. I am using Nitrogen gas cylinders. The issue is that I have simulated the expansion proccess in a very simple way:
- Inlet line with fixed flow and pressure (around 200 bar)
- Pressure reducer valve
- Outlet line. Same flow (mass) and pressure (around 2,3 bar)
The problem is that depending on the thermodinamic model, temperature after the pressure reduction is very low or not so low. Any recommendation of which model I have to use?
Apart from that, Some years ago I used these cylinders to feed Nitrogen to a vessel for blanketing and I cannot remember any issue with temperature, so I am doubting if I am simulating it properly.
I have a installation which needs Nitrogen. I am using Nitrogen gas cylinders. The issue is that I have simulated the expansion proccess in a very simple way:
- Inlet line with fixed flow and pressure (around 200 bar)
- Pressure reducer valve
- Outlet line. Same flow (mass) and pressure (around 2,3 bar)
The problem is that depending on the thermodinamic model, temperature after the pressure reduction is very low or not so low. Any recommendation of which model I have to use?
Apart from that, Some years ago I used these cylinders to feed Nitrogen to a vessel for blanketing and I cannot remember any issue with temperature, so I am doubting if I am simulating it properly.
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RE: Nitrogen expansion after pressure reducer valve
In practice nothing is ideal so the actual temperature you get at delivery point is often higher as heat enters the system and also unless you're only using gas from the cylinder it mixes with other gases and heats up.
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RE: Nitrogen expansion after pressure reducer valve
Rules of thumb for Joule-Thompson temperature drop based on pressure cut exist, but the 'exact' answer depends a little bit on inlet temperature, e.g. using NIST REFPROP:
at 20°C and 200 barg inlet, h=270 kJ/kg
at 270 kJ/kg and 2.3 barg, T_out = -12.0°C
at 0°C and 200 barg inlet, h=243.1 kJ/kg
at 243.1 kJ/kg and 2.3 barg, T_out = -37.7°C
RE: Nitrogen expansion after pressure reducer valve
RE: Nitrogen expansion after pressure reducer valve
https://en.wikipedia.org/wiki/Joule%E2%80%93Thomso...
Pierre