Mechanical Engineering - Steam Nozzles and Turbines - Discussion

35. 

In a De-Laval nozzle expanding superheated steam from 10 bar to 0.1 bar, the pressure at the minimum cross-section (i. e. pressure at throat, p2) will be

[A]. 3.3 bar
[B]. 5.46 bar
[C]. 8.2 bar
[D]. 9.9 bar

Answer: Option B

Explanation:

No answer description available for this question.

Shantanu Pal said: (Jan 26, 2015)  
Cause p2/p1 = 0.546 as the steam is initially super heated and n = 1.3. Now, p1 = 10 bar. So the pressure at throat p2 will be 0.546*10 = 5.46 bar.

Felix said: (Sep 28, 2015)  
Pressure ratio (p2/p1 = 0.546), while p1 = 10 bar, p2 = 10x0.546, p2 = 5.46.

Daka Hitesh said: (Aug 24, 2016)  
Pressure Ratio:

For Gas : 0.462.
For Wet : 0.582.
For Saturated : 0.577.
For Super Heated :0.546.

Anil said: (Jul 8, 2017)  
You are Exactly Correct @Daka Hitesh.

Kunal said: (Jul 28, 2017)  
Critical pressure ratio.

Pc/P1 = (2/n+1)^(n/n-1),
P1 = 10,
n = 1.3 for supersaturated steam.

Navyaa said: (Jan 25, 2019)  
Thanks all for explaining it.

Siddu said: (Apr 11, 2019)  
P2/p1 = 0.546 for super saturated steam
And 0.578 for dry saturated steam,
And 0.582 for the wet st.eam,
In problem p1 is given as 10,
Then p2= 0.546 * 10 because super saturated steam p2 = 5.46.

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