Calculating Flow Rate for CO2 Cylinders System

AI Thread Summary
The discussion revolves around calculating the flow rate for a CO2 cylinder system with two 1/2'' lines leading to identical pressure safety valves (PSVs) and then merging into a 1'' pipe. The user seeks to determine if the flow rate can be calculated using the provided valve specifications and whether the maximum mass flow of 8372.849 kg/hr is feasible through a 1/2'' opening. Concerns are raised about the potential for the flow path to freeze due to CO2's Joule-Thomson effect, especially under high pressure conditions. Additionally, there is a debate about the appropriateness of seeking design advice for a life-safety system on an online forum. The conversation highlights the importance of verifying backpressure and flow calculations in such critical applications.
cerny77
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Hello guys,
I need to calculate the flow rate for the following system. 2 lines of CO2 cyclinders at 60 bar. Each line (1/2'') goes to a 1/2'' PSV valve. Downstream the 2 PSV the line are collected together into 1'' pipe.
The two PSV are identical and as per datasheet they have the following characteristics:
- max volume flow (working condition): 24,669 m^3/h
- max volume flow (standard condition): 4265,116 m^3/h
- max mass flow: 8372,849 kg/hr
First question: Do you think it is possible to calculate the flow rate trhough the 1'' pipe with the datas above?
second question: don't you think that 8372,849 kh/hr are a huge quantity considering that all this mass with pass through 1/2'' hole?
Thank you very much!
 
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Is this a sustained flow? Carbon dioxide has a huge Joule-Thomson coefficient, and it's no trick at all for a flow path to freeze closed at even small constrictions. You say PSV: this is to relieve a system to prevent overfilling of bottles?
 
The flow will occur in case, during CO2 discharge for fire extinguish, pressure in the line will go for some reason above 170 Barg (PSV set point). Under this circumstances I will have flow through the system (CO2 nozzles) plus flow through the 2 PSV valves which will relieve the pressure. I need now to calculate the flow on the two (1/2'') lines downstream the PSV's having just data sheet of the valves and pressure upstream each valve (170 Barg).
 
cerny77 said:
Hello guys,
I need to calculate the flow rate for the following system. 2 lines of CO2 cyclinders at 60 bar. Each line (1/2'') goes to a 1/2'' PSV valve. Downstream the 2 PSV the line are collected together into 1'' pipe.
The two PSV are identical and as per datasheet they have the following characteristics:
- max volume flow (working condition): 24,669 m^3/h
- max volume flow (standard condition): 4265,116 m^3/h
- max mass flow: 8372,849 kg/hr
First question: Do you think it is possible to calculate the flow rate trhough the 1'' pipe with the datas above?
second question: don't you think that 8372,849 kh/hr are a huge quantity considering that all this mass with pass through 1/2'' hole?
Thank you very much!

cerny77 said:
The flow will occur in case, during CO2 discharge for fire extinguish, pressure in the line will go for some reason above 170 Barg (PSV set point). Under this circumstances I will have flow through the system (CO2 nozzles) plus flow through the 2 PSV valves which will relieve the pressure. I need now to calculate the flow on the two (1/2'') lines downstream the PSV's having just data sheet of the valves and pressure upstream each valve (170 Barg).

What are your professional education and certifications for being given the job of designing this fire extinguishing system? Why are you asking on an Internet forum how to design a system that has life-saving (or not) ramifications?
 
The system is already designed... i wanted just to double check backpressure downstream the PSV valves and i have just asked feedback on how to calculate flow rate of CO2 gas flow... not to design the system, but anyway... you're right...maybe i shouldn't ask such kind of info trhough a forum just thought it could be interesting also for others.
Thanks
 

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