(a)
The velocity V2 and change in entropy (s2− s1) at the exit of the duct for air.
Answer to Problem 9.1P
At the exit of the duct for air.
The velocity
Explanation of Solution
Given information:
At section 1,
Pressure p1 = 140 kPa
Temperature T1 = 260° C
Velocity V1 = 75 m/s
Downstream, at section 2, the values are
Pressure p2 = 30 kPa
Temperature T2 = 207° C
Gas constant for air R = 287 J/kg-K
The specific heat at constant pressure cp = 1005 J/kg-K
Calculation:
For calculating the downstream velocity, the adiabatic steady-flow energy equation can be used
Now, for calculating the entropy change
Conclusion:
Thus, at the exit of the duct for air, the velocity
(b)
The velocity V2 and change in entropy (s2− s1) at the exit of the duct for argon.
Answer to Problem 9.1P
At the exit of the duct for argon, the velocity V2 = 246.034 m/s and change in entropy is
Explanation of Solution
Given information:
At section 1,
Pressure p1 = 140 kPa
Temperature T1 = 260° C
Velocity V1 = 75 m/s
Downstream, at section 2, the values are
Pressure p2 = 30 kPa
Temperature T2 = 207° C
Gas constant for air R = 208 J/kg-K
The specific heat at constant pressure cp = 518 J/kg-K
Calculation:
For calculating the downstream velocity, the adiabatic steady-flow energy equation can be used
For Argon,
let us take
k = 1.67
The gas constant for Argon R = 208 J/kg.K
Specific heat at constant pressure cp = 518 J/kg.K
Now, for calculating the entropy change:
Conclusion:
Thus, At the exit of the duct for argon, the velocity V2 = 246.034 m/s and change in entropy is
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Chapter 9 Solutions
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