Thursday, April 05, 2007

HW #3, P5 - Clapeyron & Clausius-Clapeyron Equations - 6 pts

Estimate the latent heat of vaporization, in Btu/lbm, of ammonia at -10oF using:

a.) The Clapeyron Equation
b.) The Clausius-Clapeyron Equation
c.) The ammonia tables

13 comments:

Anonymous said...

is the posted answer to this question (part a) correct?

Anonymous said...

nm, i got it

Anonymous said...

is this question be cancelled by Dr. B?

Anonymous said...

Delta V wiggle vaporization is just the two V values listed in the thermo table, the vapor minus the liquid value, changed into m^3 per mole?

Anonymous said...

i was zoning out in class when we talked about solving this one (a and b)....can anyone offer some help?? thank you

Anonymous said...

does anybody know how to change the unit from (J/mol) to (Btu/lbm)?

Anonymous said...

Again asking the same question that "questionguy" did, wasn't this problem got cut out of the hw as told by the professor in an e-mail that he sent to the whole class last Thursday.

Dr. B said...

QuestionGuy:
No, this problem has not been cancelled.

Dr. B said...

Questioning:
Yes.

Dr. B said...

Bill Clinton:
The key is P* = Psat and you can lookup Psat data in the ammonia tables in the appendix of your book.
For clapeyron, estimate dP*/dT as deltaP* / deltaT. For Clausius-Clapeyron, determine the slope as delta[Ln{P*}]/delta[1/T].
In both cases, use the slope to determine the latent heat of vaporization.

Dr. B said...

QuestionGuy:
Do the units one at a time using the unit conversions in the back of your book. You will also need the molecular weight to get from mass to moles or vice-versa.
1 J = 9.478e-4 Btu
1 gmole = 17 g/gmole
1 lbm = 453.593 g

Dr. B said...

Anonymous:
No, this problem was not cut out. You must have printed the HW AFTER I updated the assignment page.

Dr. B said...

JustWondering:
Yes, I think my answer is correct. Why do you ask ?