
(a)
The critical temperature of air.
The critical pressure of air.
The critical density of air.
(a)

Answer to Problem 38P
The critical temperature of air is
The critical pressure of air is
The critical density of air is
Explanation of Solution
Write the formula to calculate the stagnation temperature of ideal gas.
Here, the static temperature of ideal gas is
Write the formula to calculate the stagnation pressure of ideal gas.
Here, the static pressure of ideal gas is
Write the formula to calculate the density of the ideal gas.
Here, the pressure of the ideal gas is
Write the formula to calculate the critical temperature at the throat of nozzle.
Here, the stagnation temperature of ideal gas is
Write the formula to calculate the critical pressure at the throat of nozzle.
Here, the stagnation pressure of ideal gas is
Write the formula to calculate the critical density at the throat of nozzle.
Here, the stagnation density of ideal gas is
Conclusion:
Refer Table A-2, “Ideal-gas specific heats of various common gases” to obtain value of universal gas constant, specific heat of pressure, and the specific heat ratio of air at
Substitute
Substitute 200 kPa for
Substitute
Substitute
Thus, the critical temperature of air is
Substitute
Thus, the critical pressure of air is
Substitute
Thus, the critical density of air is
(b)
The critical temperature of helium.
The critical pressure of helium.
The critical density of helium.
(b)

Answer to Problem 38P
The critical temperature of helium is
The critical pressure of helium is
The critical density of helium is
Explanation of Solution
Conclusion:
From the Table A-2, “Ideal-gas specific heats of various common gases” to obtain value of universal gas constant, specific heat of pressure, and the specific heat ratio of helium at
Substitute
Substitute 200 kPa for
Substitute 214.2 kPa for
Substitute
Thus, the critical temperature of helium is
Substitute
Thus, the critical pressure of helium is
Substitute
Thus, the critical density of helium is
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Chapter 17 Solutions
Thermodynamics: An Engineering Approach
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