Size a Flash Vessel 2

[sjdonovan1]

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!

 

[ione]

For sizing flash steam recovery vessel

http://www.spiraxsarco.com/resources/steam-engineering-tutorials/condensate-recovery/flash-steam.asp

 

[sjdonovan1]

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.

 

[ione]

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%.

 

[sjdonovan1]

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

 

[ione]

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.

 

[Shmulik]

thread124-125547

http://www.pennseparator.com/pbs6.htm