Calculating Flow Rate for CO2 Cylinders System

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Discussion Overview

The discussion revolves around calculating the flow rate for a CO2 cylinder system involving pressure relief valves (PSVs) and the implications of flow through different pipe sizes. The context includes concerns about the system's design and operational parameters related to fire extinguishing applications.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant inquires whether it is feasible to calculate the flow rate through a 1'' pipe given the specifications of the PSVs and the upstream pressure of 170 Barg.
  • Another participant raises concerns about the potential for freezing in the flow path due to the Joule-Thomson effect, questioning the nature of the flow as sustained.
  • A participant clarifies that the flow will occur during CO2 discharge when the pressure exceeds the PSV set point, and seeks to calculate the flow in the 1/2'' lines downstream of the PSVs.
  • One participant questions the qualifications of the original poster in designing a fire extinguishing system, suggesting that seeking such information on a forum may not be appropriate given the safety implications.
  • The original poster responds that the system is already designed and they are looking for feedback on calculating CO2 gas flow rates rather than designing the system itself.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness of seeking design feedback on a public forum, with some questioning the qualifications of the original poster while others focus on the technical aspects of flow rate calculations. There is no consensus on the feasibility of the calculations or the implications of the flow characteristics.

Contextual Notes

Participants have not reached a consensus on the calculations or the safety considerations involved. There are unresolved questions regarding the assumptions made about flow conditions and the implications of the PSV characteristics.

Who May Find This Useful

Individuals interested in fluid dynamics, pressure relief systems, and safety considerations in engineering design may find this discussion relevant.

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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