What are the coefficients of thermal expansion for methanol in F^-1?

[Q_Goest]

Hi CS. Feel free to butt in all you want. I think Ron already bought REFPROP database though (per post 24).

Ron, I assume you bought REFPROP, is that right?

What I'm saying about using Cp is that you can't use it. You can't use Cp nor Cv because both of these are for specific cases (either constant pressure or constant volume). So I would recommend using the database.

I understand you have the initial state, volume, and mass. The only thing you know about the final state is temperature. You don't have volume either since we are assuming that will change depending on pressure. But pressure depends on heat input.

Here’s my suggestion. Calculate vessel volume from the simplified description of a cylinder with a piston and a spring holding back the piston. You can then equate your actual hardware to this model since even if it is a blocked in pipe, you have a linear spring rate dependent on the pipe's modulus of elasticity. So you should be able to create a graph of volume versus pressure for any given model, and that graph will vary depending on the spring rate you choose.

You should also be able to create a graph of pressure versus volume given your known temperature. These two graphs should cross at a single point which is the final volume and pressure for the system at your given final temperature.

Rather than actually graph it, I’d suggest making a spreadsheet using REFPROP and take a guess at the pressure. This will give you the final fluid density which you can then calculate the volume from. This volume however, has to exactly equal the volume of your simplified model with the piston and spring for the given pressure. When the methanol volume and the cylinder volume are equal, you'll have found the solution for the final state of the fluid, including the final pressure. Put a cell in your spreadsheet that takes the difference between the two volumes and make that equal zero by changing the guess at pressure.

Once you do this, you will have found the final state and you could also determine heat input if that’s important to you.

 

[rppearso]

Hi CS. Feel free to butt in all you want. I think Ron already bought REFPROP database though (per post 24).

Ron, I assume you bought REFPROP, is that right?

What I'm saying about using Cp is that you can't use it. You can't use Cp nor Cv because both of these are for specific cases (either constant pressure or constant volume). So I would recommend using the database.

I understand you have the initial state, volume, and mass. The only thing you know about the final state is temperature. You don't have volume either since we are assuming that will change depending on pressure. But pressure depends on heat input.

Here’s my suggestion. Calculate vessel volume from the simplified description of a cylinder with a piston and a spring holding back the piston. You can then equate your actual hardware to this model since even if it is a blocked in pipe, you have a linear spring rate dependent on the pipe's modulus of elasticity. So you should be able to create a graph of volume versus pressure for any given model, and that graph will vary depending on the spring rate you choose.

You should also be able to create a graph of pressure versus volume given your known temperature. These two graphs should cross at a single point which is the final volume and pressure for the system at your given final temperature.

Rather than actually graph it, I’d suggest making a spreadsheet using REFPROP and take a guess at the pressure. This will give you the final fluid density which you can then calculate the volume from. This volume however, has to exactly equal the volume of your simplified model with the piston and spring for the given pressure. When the methanol volume and the cylinder volume are equal, you'll have found the solution for the final state of the fluid, including the final pressure. Put a cell in your spreadsheet that takes the difference between the two volumes and make that equal zero by changing the guess at pressure.

Once you do this, you will have found the final state and you could also determine heat input if that’s important to you.

I have not bought REFPROP yet I have just been using the NIST data base

 

[rppearso]

check it out,

Here is what I did for the thermal expansion, see what you think, I still ended up with 9300 psig even including the modulus of elasticity and I would like a reality check on that number because I was expecting something like 2000-3000 psig but its in the ball park and I have been surprised before.

Thank you for the help this has been great working on this problem along with the Joule thompson problem.

My next endevor is to get into line integration to solve for the surface areas of weird surfaces for fire relief valves.

 

[rppearso]

Sorry the dT should be 80 not 540. This will give you a pressure of 1500 psig which exceeds the pressure of A spec piping. This is so sweet that I was finally able to get a reasonable answer.