HW8

For number 40 on the homework, can we assume that the system is isochoric because in the book it says that for a steady state process, the mass and entropy of the fluid in the control volume is constant. Are we allowed to use isochoric equations to solve for q of the process?

You could use the equations for an isochoric process only if the volume per mole of the fluid stays the same throughout the process, not the control volume. Thus, if the conditions indicated suggest a constant volume per mol of the flowing streams, you can use isochoric expressions. If not, you will need to use more general expressions.

MSS

Problem 43

Dear Class,

There is a typo in Problem 43.
Problem 43 should read:
"Superheated steam at 500 kPa and 300 deg. C ..."
The online version has been corrected.

-Nathan

AIChE membeship

Dear Class,

Several student had problems with AIChE's membership website when attempting to join AIChE for assignment 6. As a result you may attach proof of membership to Problem Set 8 or 9 to receive bonus points for the final if you have not done so already.

-Nathan

HW8, problem 39

I am doing problem 39 on the homework and I am not sure how to calculate T2.

Remember that you now have multiple thermodynamic laws that you can apply to any process. Think about solving problems systematically by applying all of these laws. If you are still confused, go back to HW6 where you have solved problems for T2 exactly like this before.

-MSS

Problem 33 on Problem Set 7

Dear Class,

There is a typo in the problem set. For Problem 33 parts (c) and (d) the efficiency (eta) is 70% of the Carnot efficiency as it was in parts (a) and (b).

-Nathan

Hints for Problem Set 6

Dear Class,

Here are some hints for Problem Set 6.

Problem 29
You should assume that air is at 1 atm. You should be able to model air as an ideal gas to acceptable accuracy.

Problem 30
Propane is usually stored as a saturated liquid.

The equations used in this assignment generally offer good agreement with tabulated data for the conditions of interest. If you find that your |%error| is large (ie more than 10%) you have probably made an error.

-Nathan

Extension for HW6

Dear class,

I received a request to extend the HW6 deadline. I am willing to do this, but mainly because I believe it is very important after the midterm for you catch up to material that you did not understand. As such, you may turn in HW6 this Friday at the beginning of class.

However, HW7 will still be given out tomorrow (Wed) and it will still be due a week later (the next Wed). There will be no other extensions for homework given, except of course in extenuating circumstances on an individual basis. I expect that you should be starting on your homework sets well-before the Monday or Tuesday before they are due, in order to time-manage this course's workload with your other courses.

Cheers,
MSS