# Homework Help: Converging and diverging nozzles

1. Apr 29, 2015

### tsukuba

1. The problem statement, all variables and given/known data
air flows through a device such that the stagnation pressure is 0.6 MPa, the stagnation temperature is 400° C, and the velocy is 570 m/s.
Determine the static pressure and temperature of the air at this state.

2. Relevant equations
Tt=T + V2 / 2 Cp where Cp is 1.005 Kj/ Kg* ° K

3. The attempt at a solution
what I did was Isolate for T since that is what I am looking for.

2 Cp x Tt - v2 = T
somewhere in here I know I have to throw in 1000m2/s2/ Kj/kg °k
when I do that I get -323.5 ° K

the answer is 518.6 ° K

Someone please let me know where I have gone wrong. Thank you

2. Apr 29, 2015

### SteamKing

Staff Emeritus
Your algebra is a little dodgy in solving for T.

The correct equation is:
Tt = T + [V2 / (2 Cp)]

which means your equation for T is incorrect.

3. Apr 29, 2015

### tsukuba

brackets or no brakets, wouldn't T stay the same when isolating it?

4. Apr 29, 2015

### SteamKing

Staff Emeritus
Tt = T + [V2 / (2 Cp)]

T = Tt - [V2 / (2 Cp)]

2 Cp x Tt - V2 = T

which is not the same. Apparently, you multiplied only one side of the equation by (2 Cp).

5. Apr 29, 2015

### tsukuba

hmm, not sure how you get that equation but I'm still not getting the right answer. I will have to ask the professor tomorrow