Pressure Increase in Liquid Full Pipework
Pressure Increase in Liquid Full Pipework
(OP)
I have been asked to calculate the increase in pressure when adding a certain mass of LPG to an already liquid full LPG line. The pipework volume is fixed, there is no increase in temperature, only increase in LPG mass, so the pressure increase will be almost instantaneous due to the very low compressibility, no doubt raising above the flange rating, but now sure how I calculate the final pressure to confirm this.





RE: Pressure Increase in Liquid Full Pipework
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. ùGalileo Galilei, Italian Physicist
RE: Pressure Increase in Liquid Full Pipework
RE: Pressure Increase in Liquid Full Pipework
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. ùGalileo Galilei, Italian Physicist
RE: Pressure Increase in Liquid Full Pipework
Bulk Modulus = -V dp/dv
If changing volume by 1%, dv = 0.01V
Therefore, dp = - Bulk Modulus x 0.01V/V
= 0.01 x Bulk Modulus
RE: Pressure Increase in Liquid Full Pipework
RE: Pressure Increase in Liquid Full Pipework
I took "liquid full" to mean that it was full of liquid (i.e. the pressure and temperature put the fluid in the "sub-cooled liquid" region). I'm not sure why you think it is two phase, the OP never mentioned the actual pressure or temperature of the line.
Green999
I think you are confusing the constant of integration in that equation with what has become known as Bulk Modulus. So:
dp = - Constant x 0.01V/V
Bulk Modulus = Constant * 0.01 so
dP = -Bulk Modulus
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. ùGalileo Galilei, Italian Physicist
RE: Pressure Increase in Liquid Full Pipework
I have looked at several examples on sites now including manufacturers and they all seem to agree with what I wrote above.
RE: Pressure Increase in Liquid Full Pipework
Using Δ instead of the derivative function:
A 0.01 mass addition is, in fact, a 0.01 increase in density.
Therefore, E ≅ Δp/0.01 and Δp ≅ 0.01 E.
Errors and omissions accepted.
RE: Pressure Increase in Liquid Full Pipework