Non Engineer Question about calculating vessel pressure with displaced fluid volumes 1

[Keegan4123]

Hi Everyone,

I am working on building a task list and work steps for a job regarding a vessel and tank loading. We don't have an engineer on staff because this stuff rarely comes up but I am hoping someone can point me in the direction of a correct formula. I am thinking the ideal gas law principles apply but I could be way off base.

I am trying to determine the end volume of a vessel after the having atmospheric air compressed by a volume of liquid.

We will have a vessel full of atmospheric air, and need to fill the vessel with a volume of fluid compressing the air to a max of 20-25psi. We need to figure out the estimated volume of fluid it would take to bring it up to that 20-25psi.

Known Variables:
Vessel volume is 21m3
Fluid Temp is 80 deg C
Maximum vessel pressure is 20-25psi
Ambient outside temp is -20deg c
Vessel walls 316 stainless however (no value for metal stretch or deformation to be used)

Unknown Variables
Fluid volume

Any help or a dummies' lesson in how to calculate this would be greatly appreciated.

Keegan

 

[goutam_freelance]

According to my calculation the fluid volume is 10.67 m^3. Calculation below:

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[HTURKAK]

Hello Keegan4123 (Petroleum),

I have cold region experience...
and as far as i understand, there is a 316 stainless steel vessel having 21m3.
The ambient temperature is-20deg c . So the temperature of the tank.
And you want to compress the air inside tank to 20-25psi with hot water having temperature +80 c degr.

I do not want to remind the calculation proposed by goutam_freelance (Mechanical) is based on the assumption of no heat transfer.. But just to remind the risk of thermal shock which the tank will be exposed to..

I write vessel thermal shock and check the web.. One of the possible outcome for the risk,

This vessel hydrotested and exposed to thermal shock..

I am not sure for the reason for compressing the air in the vessel but i think that it is not a good idea that , the use of 80 degr c hot water for -20degr tank. The temperature difference 100 degr. is substantial amount and may initiate the cracks . I will recommend the use of air or ask the services of expert to assess the risks for thermal shock.

 

[MortenA]

Keegan,

You will appreciate the helpfullness of people here - but what will you respond if they made a mistake or you misunderstood their advice? Just my friendly advice: If this is of any importance you should get professional help (a consultant). And yes, thats not free but are your or anybodys safety on the line i would say its mandatory and if your ass is on the line if anything goes wrong i will leave it up to you.

Best regards, Morten

 

[LittleInch]

I would agree with that.

Also if this is a horizontal vessel, then you can get large bending forces on the vessel as one side is still at -20 whilst the other is suddenly at 80C. This can bend or break vessels quite easily or fracture or break connections as the vessel expands in a non uniform manner.

The 100C difference of the air temp is very big and as noted the calculation assumes no heat transfer from the fluid to ambient and that fluid to air heat transfer is negligible.

However if this operation takes place over a long period then air temp will be lower than 80C and hence take more fluid (what is the "fluid" by the way?) than the calculation to reach your required pressure.

So min amount is 10.6m3

Max amount assuming the air cools to roughly zero C is about 13m3 to reach your desired pressure.

Also this assumes that the fluid doesn't gas off or boil.

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