Help needed !!!

[vadik]

Hello! I am a new member on this forum..
I need help with Thermodynamics...
I have few problmes that for some reason i don't see how to solve..

Problem 1
 A closed constant volume container of air initially at 150 psia. and 200 F cools down to 60 F. Using the ideal gas model what is the final pressure?

Problem 2
An open feedwater heater takes in 1000 lb/hr of water at 250 psia and 80 F and uses mixing wit saturated steam at 250 psia to provide saturated liquid at 250 psia. What flow rate lb/hr of steam is needed. Assume no hear is lost to the invirement. Look up property values in the back of the text.


Could someone help me solving these two problems?
Thank you very much!
Vadim

[Fu-Kwun Hwang]

Problem 1 can be solved by ideal gas law: PV=nRT
n should be the same, R is a constant, You can find out P1, T1 and T2 from the question (with proper unit)

Problem2: Need more information from your textbook. You need to find out by yourself.

[vadik]

In first problem V (Volume) is not given and i don't know how to find V

[Fu-Kwun Hwang]

Because the Volume V is the same. (n,R are also the same)
P₁ V = nR T₁
P₂ V = nR T₂

You should be able to find out P₂ from the above equations.

[vadik]

Yes, i was able to find P2

Thank you for your help!

[HUMSHAPHY]

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