anyone wanna work with me on this homework tomorrow night?
I've got all but 4 I think

8/30/2005 1:03:01 AM

you have the 5th edition book? i had the 4th and was totally working on wrong homework.

8/30/2005 7:21:40 AM

yea i do but i can't get a few of them

8/30/2005 10:12:48 AM

i wont get back from class till around 4 but i can help you out
i haven't looked at the assignment yet, but i've probably done it before (was making an a in this class last semester before i had to withdraw for mono)

8/30/2005 1:20:54 PM

If I hadn't already gone home and lived an hour away...

8/30/2005 1:48:46 PM

oh great! i'm free now. just pm me back. we can probably meet in the library, which is convient for me so i can photocopy the homework problems.

8/30/2005 1:53:33 PM

Is anyone having any luck with 3-54? I figured I would start from the table and checked the pressure at the temperature. But I can't figure out the rest. Any ideas?

Question:
A 0.5 m^3 vessel contains 10 kg of ref. 134-a at -20 degrees C. Find: Pressure, total int. energy and, the volume occupied by the liquid phase.

9/5/2005 2:55:49 PM

you know the container volume and the quanity

so from that you get the specific volume

@ -20 degrees C the specific volume ranges from 0.0007361 for a sat. liquid and 0.1464 for a sat vapor

find the quality and then use that to find the other properties at that state

9/5/2005 3:24:05 PM

ya I got ideas from the example on pg 131-132 in the 5th ed.
Thanks for your help.

9/5/2005 5:58:13 PM

it's that time again...I've worked on em and for 54 my answers are different than the book so

Anyone want to work on them conmigo?

I can't make the TA's offic hours bc I'll be in class

[Edited on September 6, 2005 at 9:54 AM. Reason : asdf]

9/6/2005 9:54:02 AM

I'll work with ya if you want...I'll pay ya back and you know I need the problems.

9/6/2005 11:57:16 AM

I'll help if you let me be godfather.

9/6/2005 12:12:27 PM

Just pick out a time & place and I'll be there

(Won't be posting for a while, but will periodically check teh web)

9/6/2005 1:14:59 PM

anyone still having problems? i'll be happy to help if you got questions

9/6/2005 8:13:18 PM

is the quality .338 or am i completely off?

9/6/2005 8:28:25 PM

I got .338 for quality

9/6/2005 8:38:15 PM

who wants to post homework problems?

9/6/2005 8:44:43 PM

.338 is what i got

[Edited on September 6, 2005 at 9:09 PM. Reason : .]

9/6/2005 8:58:20 PM

these tables are giving me major problems. im still not even sure im filling them in right for the first 3 problems

9/6/2005 9:03:45 PM

do you have a problem with one of them specificially? i can walk you through it

9/6/2005 9:07:34 PM

well for the first one, 3-26, for example.

ok the first line wants P and the phase description. so....we're supposed to look up 50 degrees in table A-4...then draw a T-v diagram, find vf and vg...determine where the given v is located and that should give us the phase description. from there you know since its in the liquid-vapor region that the P is whats given in either table a-4 or a-5. is that right?

beyond that, im not really sure how to find v and the phase description when T and P are given.

9/6/2005 9:18:13 PM

let me start by saying this book has some excellent examples and some deal with this exact stuff

for 3.26...

H20

T        P      v       phase
50            4.16
        200             sat vap
250   400
110   600

9/6/2005 9:27:02 PM

alright, so i guess i knew what was going on for the first two lines.

ok, getting the phase from P and T i think i got figured out.

thanks

[Edited on September 6, 2005 at 9:35 PM. Reason : .]

9/6/2005 9:30:38 PM

you should be able to get the other problems from that

really though this is like the best book i have used as far as explaining stuff and showing examples. if you get tripped up be sure to flip through and look at examples in the section. also right before the problems is a review of equations from the chapter

[Edited on September 6, 2005 at 9:37 PM. Reason : .]

9/6/2005 9:36:19 PM

appreciate it

9/6/2005 9:37:20 PM

anyone else? i learn best by explain stuff to people

9/6/2005 9:55:34 PM

any help with 59?

9/7/2005 12:44:39 AM

approximate v from the tables, get the volume in m^3, then you can solve for the mass
the temp you read right off the tables because they give you a presssure and a phase
approximate h1 and look up h2 at your pressure and phase and then solve for your entropy change

9/7/2005 6:30:34 AM

anybody think they can help me out? i need to photocopy the homework problems and tables from the fifth edition. it looks like the bookstore won't have the book in time for me before exam 1. it won't take much of your time, and doing it before the weekend would help out a lot.

9/8/2005 10:09:25 AM

this is our second assignment
why didnt you buy the book already

there were plenty in there when i bought mine last week

9/8/2005 5:02:34 PM

i have the wrong edition. i put in a special order for an exchange tuesday of last week and they still don't have it. and i've also been checking everyday since then. so are you going to help me?

[Edited on September 8, 2005 at 5:31 PM. Reason : .]

9/8/2005 5:29:24 PM

they gave me a new package with the old tables...

9/8/2005 5:33:41 PM

whats different with the tables?

9/8/2005 5:44:49 PM

it's updated.

9/8/2005 5:46:43 PM

whats updated?
cause my pack came with the old tables too

shit a lot of the values are different, now i got to flip back and forth


[Edited on September 8, 2005 at 5:52 PM. Reason : .]

9/8/2005 5:50:56 PM

bttt

Need to photocopy someones book. If I have it done by Saturday, I can bring help to yall when you can't figure out a homework problem (I know this stuff very well)

I'll be on campus till near midnight, so homebody hook me up plz.

Oh yeah, $2 to buy some sodas for yourself too as extra motivation.

9/9/2005 5:14:47 PM

how do you do 75?

9/13/2005 5:53:32 PM

anyone know how to do 3.75?

I get the general idea but I get stuck and don't know what to do with what he said in class.

9/13/2005 8:05:35 PM

anybody think the van der Waals, Beattie-Bridgeman and Benedict-Webb-Rubin equations will be on the test? It's not hard, I just don't want to have to worry about the memorizing the huge equation.

9/13/2005 8:27:13 PM

i doubt it

ok i keep getting 3.51 wrong, any help

9/13/2005 8:44:44 PM

nevermind i got it

9/13/2005 9:23:54 PM

I got 236 kPa for the first part of 3.75. What are you getting?

9/13/2005 9:38:02 PM

is anything from chapter 4 supposed to be on the test?

9/13/2005 9:48:34 PM

hmm
i got 227.7 kPa

ok so i made a mistake somewhere

[Edited on September 13, 2005 at 10:30 PM. Reason : .]

9/13/2005 10:09:42 PM

^^ Just chapters 1, 2, and 3

The test won't be that difficult, so quit stressing about it.

Some tips.. (I had him last semester, and I know the first few chapters like the back of my hand...BTW this is probably stuff he's already told you since it's very self explanitory)

Know your quality equations

Know how to draw a P-T or P-V diagram or whatnot and be able to UNDERSTAND what it means when you move from point A to point B.

Know your equations of state and how to use it to solve problems.

Know the equations for efficiency (efficiency used to not be in Chapter 2...but since it is now, it won't hurt to know how to use the equations)



The equations that are usually given are obscure and really don't help at all, unless you're good with integrals and derivations.

9/13/2005 10:55:24 PM

hey guys for 3.51 i've found the pressure at state one to be 38.58kPa and the quality to be .04012. however, i'm not sure how to determine what the temperature would be when you get to being a saturated vapor. i'm just totally drawing a blank.

and for 3.60 i'm not sure how to tie in the critical values for H20. i know where to find the critical values (temperature 300-whatever Celcius, etc.) but i'm not sure what to do with them.


i think i'm missing something fundamental that is similar in both these problems....

9/13/2005 11:20:52 PM

If it's a saturated vapor, then the temperature is equal to the saturation temperature...geez.

Can't think of the other one off the top of my head.

9/13/2005 11:43:44 PM

yeh i understand that... we start at 75 celcius then we add heat... so i look up the temp. tables at 75 celcius and check the Psat=38.58 kPa, then go to the pressure tables and look up the Tsat for ~38 kPa but that is ~75 celcius, not 187 celcius as the book says...


are those the right steps or am i as dumb as you make me out to be?

9/14/2005 12:15:03 AM

For the test tonight, what do we get to use as far as formulas?

9/14/2005 2:49:54 PM

"I have neither given nor recieved unauthorized aid on this exam"

9/14/2005 3:22:20 PM