Problem 13.22
[Difficulty: 3]
Given:
Data on three tanks
Find:
Mass flow rate; Pressure in second tank
Solution:
The given or available data is:
R
=
286.9
J/kg.K
k
=
1.4
A
t
=1
cm
2
We need to establish whether each nozzle is choked.
There is a large total pressure drop so this is likely.
However, BOTH cannot be choked and have the same flow rate.
This is because Eq. 13.9a, below
(13.9b)
indicates that the choked flow rate depends on stagnation temperature (which is constant) but also
stagnation pressure, which drops because of turbulent mixing in the middle chamber.
Hence BOTH nozzles
cannot be choked.
We assume the second one only is choked (why?) and verify later.
Temperature and pressure in tank 1:
T
01
=
308
K
p
01
=
650
kPa
We make a guess at the pressure at the first nozzle exit:
p
e1
=
527
kPa
NOTE: The value shown is the final answer!
It was obtained using
Solver
!
This will also be tank 2 stagnation pressure:
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 Fall '07
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