CO2 temperature rise after pumps
CO2 temperature rise after pumps
(OP)
CO2 enters the first pump at 300psi 0C, exits at 850psi 30C, enters the second pump, exits at 1200psi 50C. What temperature would it exit the second pump at if the initial temp was 35C?
I've searched the forums, textbooks and after several attempts of calculating I don't think I have the right approach. Any suggestions would be very appreciated.
I've searched the forums, textbooks and after several attempts of calculating I don't think I have the right approach. Any suggestions would be very appreciated.





RE: CO2 temperature rise after pumps
If temperature_2 and temperature_3 are the result of the energy of compression of the pumps, (and are not being regulated or cooled somehow), and if the flow rate remains the same.
Then, why do you not think the greater inlet temperature would yield a greater outlet temperature, if the pump energy difference did not change?
RE: CO2 temperature rise after pumps
Well what is your approach?? Then we might be able to comment.
CO2 is strange stuff and you're close to the phase boundary changes with your quoted pressures and temperatures.
Do you keep constant entropy?
BTW at the pressures and temperatures you're quoting, CO2 is normally regarded as vapour / gas, not a liquid. hence you're looking at compressors, not pumps
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: CO2 temperature rise after pumps
RE: CO2 temperature rise after pumps
Approaching it as an enthalpy problem hasn't got me anywhere because none of the ∆H = ∆U + ∆(PV) variables are constant.
The temperature rise is from the energy added to the system by the compressors/pumps. For simplicity can I assume the temperature differences can be directly converted to Joules, so a 30 C rise is 56973 added to the system?
(1 Joule is equal to 0.000526565076466 Celsius heat unit.)
RE: CO2 temperature rise after pumps
RE: CO2 temperature rise after pumps
Also, how accurate do you need the number? If +/- 5C is good enough and you are staying away from the phase transition then just take the current temp rises and be done with it.
RE: CO2 temperature rise after pumps
When you say "staying away from the phase transition"; it does reach critical temperature and pressure in the second booster. What effect does this have on the system?
+/- 5 C is good enough, did you land on this range because of the finite energy added to the system?
Thanks
RE: CO2 temperature rise after pumps
35 C and higher and you're in vapour phase so it will start to behave a bit more like a standard gas especially if you stay below 1070 psig.
As you're heading into 1200, then you're in super critical when it gets all weird again.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: CO2 temperature rise after pumps
The phase transition comment goes along with what LittleInch is saying, behavior gets complicated.
RE: CO2 temperature rise after pumps
RE: CO2 temperature rise after pumps
RE: CO2 temperature rise after pumps
That's what I was trying to get him to do. I don't know CO2, since my history is with steam systems. But - if it were steam - you would HAVE TO get the enthalpy staes at each point (before and after each compressor), then explicity look at the steam tables (CO2 tables) and determine the points on CO2's equivilent of the Moiller diagram before and after each compressor. Change the inlet temperature, then determine if that change in inlet temperature going into the first compressor is going to change the state in between, then determine if the same nbr 2 compressor is going to act the same way at the higher inlet temperature during compression. (Probably will, but that's like assuming water will behave the same way at 30 degrees F as it did at 34 degrees F. )
RE: CO2 temperature rise after pumps
I used an inline gas heater with a PID loop, and there is a temperature sensor on the inlet of the pump system that verified I was indeed warming the gas up to 35 C
I'm still going to try to work it out on paper, thank you for all the help and comments.
RE: CO2 temperature rise after pumps
+0 deg C to +50 deg C, then +5 Deg C to +55 deg C (maybe) is "only" a 10% change in temperature, against a 4x times the pressure increase. Wouldn't take much heat loss in the pipes and flanges to "lose" 2-3 degrees of the potential increase at the outlet.