3 replies to this topic

[Sunkara]

I am in a assignment where I have to calculate the following,

in a unit m3 volume of tank some paraxylene is existing at 2 bar (assume). Now I need to know how much volume is required to build the pressure to 3 bar?
I can not find the way to do this assignment, wether bulk modulus/ compressibility will play the role here. if so how?
Please help me

[MrShorty]

I don't want to do your homework for you (I'm not even sure you've given enough information to solve it anyway).

Perhaps a question to get you started. At it's core, the question is really asking you, "how can you relate pressure and volume." So the first question I will ask you is, "what equations do you know that show how pressure and volume are interrelated"?

[Sunkara]

@ Mr Shorty

"what equations do you know that show how pressure and volume are interrelated"?
my answer is Peng Robinson equation. But it is not easy to do manually. any other way to solve plz help. I am not asking you to do my home work, just asking you to help (suggest a way).

Thanks

[MrShorty]

correct, Peng Robinson (which is just one example of many equations of state of the Van der Waals form) is a commonly used equation of state. And, as you also noted, because these EOS's are almost always cubic in volume, there is a good deal of effort and tedium that goes into solving them. It sometimes seems that we spend a lof of effort extolling the virtues of the cubic EOS, then spend the same amount of effort trying to figure out how to avoid using them.

If there is another, simpler equation for solving this problem, it will still come back to the same question -- what (simpler) equations do you know of that relate pressure and volume? You specifically asked about bulk modulus (=1/isothermal compressibility), so I'll ask, what is the bulk modulus? Does it describe a relationship between pressure and volume?