dsfsd34532423
Badges: 2
Rep:
?
#1
Report Thread starter 1 year ago
#1
question:
In a CHP power plant superheated steam in a back-pressure steam turbine is expanded adiabatically from 100 bar and 500°C to saturated vapour at 10 bar. Neglecting the kinetic and potential energy
terms, if the turbine power is 𝑊dot = 6 MW, what is the mass flow rate of the steam?
(Ans. 10.08 kg/s)

so the equation i have is -Wdot = Mdot* change in enthalpy, since kinetic energy potential energy is neglected and process is adiabetic so no Qdot
-Wdot = 6 * 10^6
and i got the first enthalpy as 3373 * 10^3, and 2nd enthalpy as 763*10^3. both units in J/kg
so i end up with (-6*10^6)/(10^3(763-3373)) = 2.3298
i dont know where im going wrong
i write 'dot' to show the variable account for mass flow rate
0
reply
assassinjeev22
Badges: 14
Rep:
?
#2
Report 1 year ago
#2
Alright, so everything is fine until the 2nd enthalpy value. First enthalpy value is correct! To get the 2nd enthalpy value use the saturated water and steam tables and find the row where P = 10 bar (for the 2nd state). Now since it is saturated vapour it lies on the VLE curve of saturated steam and hence has a dryness fraction (x value) of 1. Now, for the steam tables the formula for specific enthalpy is: h = hf + x (hg - hf). Now since x is 1, specific enthalpy for state 2 is just hg value from the table. Put that in instead of 763 and you should get 10.08. Hope that helps!
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

How do you prefer to get careers advice?

I like to speak to my friends and family (18)
8.74%
I like to do my own research online using careers specific websites (125)
60.68%
I like speaking to the careers advisors at school, college or uni (30)
14.56%
I prefer to listen watch videos or listen to podcasts of people in my chosen career (29)
14.08%
Something else (let us know in the thread) (4)
1.94%

Watched Threads

View All
Latest
My Feed