Energy Required to Vaporize Methanol

[jjackson927]

I apologize for the fact that I am a complete layman. It might be time for me to go and learn some thermodynamics.

I am working on the design for a production lab at my Community College, and while I'm sure we have engineers to do this for us, I was really curious about sizing a boiler. I will not be heating methanol alone, I think if I can understand the process, then I can do the rest.

I do believe there are 2 terms in the problem.

Q=C_P (kJ/kg) * m *\DeltaT + Latent heat of Vaporization (kJ/kG)*m

Am I missing anything here? My question is, how do I account for that fact that the C_P changes with the temperature of the medium? I have a background in Calculus and Diff Eq, with one semester of Physics (Calculus based mechanics), I'm just not sure what to do here.

 

[FredGarvin]

Here are a couple of links for methanol properties:

http://www.engineeringtoolbox.com/methanol-properties-d_1209.html

http://www.google.com/url?sa=t&source=web&ct=res&cd=1&url=http%3A%2F%2Fwww.methanex.com%2Fproducts%2Fdocuments%2FTISH_english.pdf&ei=BmaDSe6tCd-Btwe9xbHICQ&usg=AFQjCNE2IumqcN455h4Lte2Id0rfFRRIXQ&sig2=ClwRe8q3jLPB9j2aQp29rA

The easy way that works pretty well is to use a spreadsheet and calculate the energy required for small incremental temperature increase steps. Then you can use the referenced chart and adjust the Cp value as you increase temperature. To get the total you sum up the incremental changes.

Honestly, since the boiling point is only around 60°C, I'd seriously consider just using the max value and treat it as a constant. I guess it just depends on what kind of accuracy you are looking for. Also, don't forget, the Cp value is at a constant pressure.