The website says the homework is problems 8.3, 8.22, 8.28, 8.31. I have the old edition of the book, does anybody know if the problems are the same?

1/25/2006 6:17:31 PM

he copied the questions to pdf format for those of us with the old edition

Also, make sure you are in the right website, I had his old site bookmarked for the first week, and had no idea what he was talking about

http://www.mae.ncsu.edu/homepages/echekki//MAE302_Spring06/main.htm
just go to assignments and go to the problems that are PDF'd under it

1/25/2006 7:24:16 PM

oh yeah, I had the wrong website. thanks

1/25/2006 7:31:21 PM

any help on 9.59?

I don't know wtf to do with the rpm value or the fact that it is 6 cylinders. Does the 4.5 L mean that vmax will be .0045 m³ ??

1/25/2006 10:07:45 PM

help on 9.37??

[Edited on January 25, 2006 at 10:56 PM. Reason : n/m got it]

1/25/2006 10:42:48 PM

i havent gotten to those yet, but look in the discussion board on his website for hints on 9.59

1/25/2006 11:12:34 PM

You only use the rpm value in part d.

W_net (with a dot on top) = n (with a dot on top, the rpm value given) * W_net / 2

1/26/2006 12:01:53 AM

.59 anyone??

1/26/2006 1:02:11 AM

where is the problem session room for tonight??

2/1/2006 11:00:40 AM

What is the formula for work of an ericsson cycle? I can't find it anywhere in my notes or online

2/1/2006 8:20:47 PM

just like the work for other heat engines

qin - qout

2/1/2006 9:59:20 PM

thx

2/1/2006 10:49:19 PM

so how do you do 9.93?

2/1/2006 11:25:05 PM

you use wnetout = wT - wC

where wT = h3 - h4 and wC = h2 - h1

to find enthalpy, you have to find the P for state 2 and 4 and look up the corresponding h on the air table

2/1/2006 11:31:56 PM

alright i actually got that one shorty after i asked. but what about 9.97? any luck on that one? help?

2/2/2006 12:10:43 AM

actually, do you know how to find thermal efficiency for 9.93?

I'm working on 9.97 right now, I'll get back on that one

2/2/2006 12:20:56 AM

i just used nth = wnet/qin

2/2/2006 12:31:10 AM

yeah but how do you find qin? I was using h3-h2 but that didn't work

2/2/2006 12:36:30 AM

should be h3-h5

and you can look up h3 in the tables knowing T3 = 1200 K

you also have to look up Pr3.

then you use: Pr4 = (P4/P3)*Pr3. you know (P4/P3) = (1/10) since r = 10

once you have Pr4 you find h4.

AND, since effectivness = (h5-h2)/(h4-h2) = 100% you know that h4 = h5

so then you can say qin = h3 - h5(h4)

that may be hard to follow i know so just ask away if you dont understand it

2/2/2006 12:44:15 AM

okay, I got it

for 9.97, you have to use the pressure ratio to find T2 and T4

to find Wnet you have to find thermal efficiency, because Wdot = (nth)(Qdot in)

and for part a, assuming const specific heat, nth = 1- (T6-T1)/(T3-T5)

it's like 9.93, you have to use T5 and T6 because it is an ideal Brayton cycle. I still don't know about part b though

2/2/2006 1:04:04 AM

pressure ratio? we aren't give that.

so Wdot = nth*Qdot in

and nth = 1-(T6-T1)/(T3-T5)

so T6 = T2 and T5 = T4, right?

how do you get T2 and T4 from T1 and T3 and no pressure ratio?



n/m P2 = P3 right, im retarded

[Edited on February 2, 2006 at 1:26 AM. Reason : .]

2/2/2006 1:23:37 AM

fuck this test

2/6/2006 3:54:49 PM

I hope he doesn't give anything with variable specific heat

2/6/2006 10:53:58 PM

which is exactly what he did!

2/9/2006 7:23:40 PM

doh!

2/9/2006 8:30:06 PM

for 10.34, it says that the turbine efficiency is 80%

does that mean that both turbines are 80%, the low and high pressure?

2/15/2006 8:07:01 PM

no just use it for the second turbine to find like h4actual. You can assume that the first turbine is operating at superheated steam and just use the steam tables. Hope that helps.

[Edited on February 15, 2006 at 9:06 PM. Reason : ]

2/15/2006 9:05:55 PM

anyone having any luck with 10-47??

3/1/2006 11:46:39 AM

anyone? anyone?

10-47. anyone?

3/1/2006 4:40:38 PM

anyone want to meet up and study today?

I'll be in broughton study lounge at 4 until whenever

4/10/2006 3:17:35 PM

do you know how to do 15-21?

maybe its supposed to be easy, but im not gettin it

4/10/2006 5:42:07 PM