Depressurization in HYSYS - Simulation Problem
Depressurization in HYSYS - Simulation Problem
(OP)
Dear All,
My question is regarding depressurizing in HYSYS.
I want to depressurize 24” (ID 547.72 mm, thk 30.94 mm) 52 m length pipe. Pipe volume is 12.3 m3.
Geometry:
2” line present on 24” line. On 2” line there is one RO (Restriction Orifice), upstream of RO there is globe valve and after 600 mm (minimum) there is ball valve after ball valve a spool piece and 24” line. Downstream of RO is routed to vent line open to atmosphere, having approximately 0.2 bar drop in line.
From ball valve to vent line material is LTCS having design temperature -50°C.
After running this model in HYSYS, I am getting final vapour temp as 0.18°C and minimum temp as -2.8°C. Upstream of ball valve line design temperature is 5°C. I want to restrict vapour minimum temp to 5.5°C
Input:
Operating Condition: 86 bara & 22°C.
Ambient Temp = 5°C
Natural Gas: 84.46mol % Methane
Regards,
My question is regarding depressurizing in HYSYS.
I want to depressurize 24” (ID 547.72 mm, thk 30.94 mm) 52 m length pipe. Pipe volume is 12.3 m3.
Geometry:
2” line present on 24” line. On 2” line there is one RO (Restriction Orifice), upstream of RO there is globe valve and after 600 mm (minimum) there is ball valve after ball valve a spool piece and 24” line. Downstream of RO is routed to vent line open to atmosphere, having approximately 0.2 bar drop in line.
From ball valve to vent line material is LTCS having design temperature -50°C.
After running this model in HYSYS, I am getting final vapour temp as 0.18°C and minimum temp as -2.8°C. Upstream of ball valve line design temperature is 5°C. I want to restrict vapour minimum temp to 5.5°C
Input:
Operating Condition: 86 bara & 22°C.
Ambient Temp = 5°C
Natural Gas: 84.46mol % Methane
Regards,





RE: Depressurization in HYSYS - Simulation Problem
Best regards
Morten
RE: Depressurization in HYSYS - Simulation Problem
RE: Depressurization in HYSYS - Simulation Problem
So maybe my question was a little useless - but i consider my answer correct
Since he havnt been back for 16 days then i assume hes found a solution
Best regards
Morten
RE: Depressurization in HYSYS - Simulation Problem
Now having said all this, whats the problem with just letting the system depressure to your calculated temperature of -2.8C. It is below the 5.5C minimum, but due to reduced stress from lower pressure, your material should be able to drop below your 5.5C minimum temperature.
If you cannot let the temperature drop below 5.5C because of something other than pipe materials, then get out your heat transfer books (simulate a heat exchanger in HYSYS).
RE: Depressurization in HYSYS - Simulation Problem
should have seen that myself. You are right.
Best regards
Morten
RE: Depressurization in HYSYS - Simulation Problem
What is your basis for constant enthalpy Delta H=0?
I believe the process p, T, will lie between that of an adiabatic or isothermal process.
Regards
RE: Depressurization in HYSYS - Simulation Problem
Best regadrs
Morten
RE: Depressurization in HYSYS - Simulation Problem
Regards
RE: Depressurization in HYSYS - Simulation Problem
If you really need to coorect for heat flux e.g. a fire case then you must do it step by step and is back at the HYSYS solution (you will of course use HYSYS to determine the adiabatic depres temp - but not the depres module).
Best regards
Morten
RE: Depressurization in HYSYS - Simulation Problem
pv^gamma= constant or p/mass^gamma=constant
Regards
RE: Depressurization in HYSYS - Simulation Problem
RE: Depressurization in HYSYS - Simulation Problem
Thanks MortenA for finishing up.
Basis for delta H=0?????
RE: Depressurization in HYSYS - Simulation Problem
What you are looking for is the JT coefficient or the change in temperature per change in pressure.