Concept explainers
The rate of entropy generation for this process.
Answer to Problem 105P
The rate of entropy generation for this process is
Explanation of Solution
Express the mass flow rate of dry air at state 1.
Here, volume flow rate at state 1 is
Express the mass flow rate of dry air at state 2.
Here, volume flow rate at state 2 is
Express the mass flow rate of dry air at state 3 from the conservation of mass.
Express enthalpy at state 3.
Here, enthalpy at state 1 and 2 is
Express specific humidity at state 3.
Here, specific humidity at state 1 and 2 is
Determine the entropy balance on the mixing chamber for water.
Determine the partial pressure of water vapour at state 1 for air steam.
Determine the partial pressure of dry air at state 1 for air steam.
Here, the pressure at the state 1 is
Determine the partial pressure of water vapour at state 2 for air steam.
Determine the partial pressure of dry air at state 2 for air steam.
Here, the pressure at the state 2 is
Determine the partial pressure of water vapour at state 3 for air steam.
Determine the partial pressure of dry air at state 3 for air steam.
Here, the pressure at the state 3 is
Determine the entropy balance on the mixing chamber for the dry air.
Here, the coefficient of constant pressure is
Determine the rate of entropy generation.
Conclusion:
Refer Figure A-31E, “psychometric chart at
Here, initial enthalpy is
Refer Figure A-31E, “psychometric chart at
Here, enthalpy at state 2 is
Refer Table A-4E, “saturated water-temperature table”, and write the entropy at state 1 and 2 at temperature of
Substitute
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Refer Figure A-31E, “psychometric chart at
Refer Table A-4E, “saturated water-temperature table”, and write the entropy at state 3 at temperature of
Here, entropy of saturation liquid at temperature of
Write the formula of interpolation method of two variables.
Here, the variables denote by x and y is temperature and specific entropy at state 3 respectively.
Show the specific entropy at state 3 corresponding to temperature as in Table (1).
Temperature |
Specific entropy at state 3 |
85 | 2.0214 |
86.7 | |
90 | 2.0079 |
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Substitute 1 atm for
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Substitute 1 atm for
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Substitute 1 atm for
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Thus, the rate of entropy generation for this process is
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Chapter 14 Solutions
Thermodynamics: An Engineering Approach
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