Welcome to the Thermodynamics course at Green River Community College in Auburn, WA, USA.
Feel free to post any general questions about the course as comments on this blog entry.
I have created a blog entry for each chapter we will cover in this course. If you think your question applies to a specific chapter, then please post your question as a comment on the appropriate blog entry.
I have created a blog entry for each of the 7 HW assignments in the course. If you have a question about a problem in the HW, please post it as a comment on the appropriate blog entry. Be sure to state which problem number your question refers to !
You can post your questions using your Google ID or a crazy fake name or your real name or you can post anonymously. Whatever makes you happy. Just don't hesitate to ASK !
Remember...
"It's not a miracle, mother, it's thermodynamics !"
- Harrison Ford in Mosquito Coast
2 comments:
Hi I am an undergrad and was wondering if you could give any hints how to start off this question:
A rigid vessel contains 5 kg of a mixture of air and water. The relative humidity of the mixture is 0.9 at 20 C. The energy required to raise the temp of the mixture from 20 C to 40 C is 73 kJ. Treat the air and water vapor as perfect gases. Find for a temp of 40 C
1 - mass of air
2 - volume of mixture
3 - pressure of mixture
4 - dew point temp
5 - relative and specific humidities...
I can get the pressure of the vapor at 20 C and have tried writing and energy balance for the overall change in U. Help would be greatly appreciated!!
Anon 5:23pm
Step 1: check out my lesson about humidity on my website:
http://localhost/tcd-web-07/T1-tutorial/ch02/lesson-D/pg06.php
Step 2 - Look up Cv for air and Cv for water vapor. Remember that in terms of molar heat capacity, Cp = Cv + R.
Step 4 - From an energy balance and the given value of Q you can now determine the mole mole fractions of air and water in the gas. Q = Cp,avg * DT and Cp,avg = ya*Cpa+yw*Cpw
Step 2 - use the mole fraction of water in the tank and the initial relative humidity and the info you find on my website to determine P1.
Step 3 - Calculate the avg molecular wt, the total moles in the tank, the moles of air in the tank, and then the mass of air in the tank.
Step 4 - Apply the IG EOS to determine the volume of the tank.
Hopefully you can take it from here. Best of luck.
Post a Comment