Concept explainers
Determine the internal energy change Δu of hydrogen, in kJ/kg, as it is heated from 200 to 800 K, using (a) the empirical specific heat equation as a function of temperature (Table A–2c), (b) the cv value at the average temperature (Table A–2b), and (c) the cv value at room temperature (Table A–2a)
(a)
The empirical specific heat equation as a function of temperature.
Answer to Problem 55P
The empirical specific heat equation as a function of temperature is
Explanation of Solution
From Appendix Table A-2c “Ideal-gas specific heats of various common gases”.
Write the expression for the empirical relation between
Here, the universal gas constant is
Write the expression for the change in internal energy.
Substitute
Write the expression for internal energy of empirical specific heat equation.
Here, the molar mass is
Conclusion:
Substitute
Substitute
Thus, the empirical specific heat equation as a function of temperature is
(b)
The
Answer to Problem 55P
The
Explanation of Solution
Write the expression for internal energy of
Determine the average temperature for the
From Table A-2b, write the value of ideal gas specific heat of various gases at various temperatures at 500 K average temperature.
Conclusion:
Substitute
Thus, the
(c)
The
Answer to Problem 55P
The
Explanation of Solution
Write the expression for internal energy of
Determine the room temperature for the
From Table A-2b, write the value of ideal gas specific heat of various gases at various temperatures at 300 K room temperature.
Conclusion:
Substitute
Thus, the
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Chapter 4 Solutions
THERMODYNAMICS: AN ENGINEERING APPROACH
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