×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Size a Flash Vessel
2

Size a Flash Vessel

Size a Flash Vessel

(OP)
Hello,
I am trying to size a flash vessel.
It will be used to receive content from a few relief valves and bursting disks.

The worst case scenario will deliver a tortal of 4 litres of water at 180 degC and at a pressure of 30 bar to atmosphere.
I need to size the vessel and the pipesize that will deliver the contents to the vessel.

Thanks in advance for any help!


 

RE: Size a Flash Vessel

(OP)
But this requires a known flowrate. I do not know what flow i will have. I need to calculate this first but i am unsure of how.

RE: Size a Flash Vessel

You have indicated the worst scenario as  4 litres of sub cooled water, but in which time? Flow rate is mandatory.
When you have established this you can proceed as it follows.

With the conditions you've described, P = 30 barg at T = 180 °C, you are dealing with sub-saturated water.
1.    Specific enthalpy of sub cooled water: 764 kJ/kg.
2.    Surplus of heat available when at 0 barg is equal to (764 -419) = 345 kJ/kg.
3.    Specific enthalpy of saturated steam at 0 barg :  2257 kJ/kg
4.    Percentage of flash steam from sub saturated water: 345/2257 *100 = 15.28%.
 

RE: Size a Flash Vessel

(OP)
Thanks alot ione for your help with this.

So lets say i had a flow of 0.002m3/sec

From this you are saying i shall be getting
0.1528*0.002 = 0.3*(10^-3) m3/sec of steam produced?

Also when you mention sub cooled, do you mean sub saturated??

Where can i read more on the information you have given??

As well as this method, i have also looked at the Souders-Brown equation. Dont know what your thoughts are on that method..

Cheers

:)

RE: Size a Flash Vessel

The terminology "sub saturated" is undoubtedly more correct.

As specific enthalpy is referred to the unit of mass I consider it is better to convert volume flow rate to mass flow rate.

At 30 bar(g) and 180 °C the water density is approx 888.5 kg/m^3.

So your mass flow is:

888.5 * 0.002 = 1.777 kg/s

As the sizing chart requires hourly steam flow, you will get:

1.777 *0.1528* 3600 = 977.5 kg/h

Reputable members of this community have already touched the theme involving the Souders-Brown equation. If you've already looked at this FAQ
http://www.eng-tips.com/faqs.cfm?fid=1153

IMO there's nothing to add.
 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources