Reference no: EM13866884
1. Four (4.0) lbm of CO2 are contained in a piston-cylinder system. The CO2 is initially at a temperature T1=500°R and pressure p1=20 psia. The CO2 undergoes the following two processes:
Process 1-2: adiabatic compression from state 1 to state 2 with T2=800°R and pressure p2=400 psia
Process 2-3: an internally reversible isothermal expansion from state 2 to state 3 with pressure p3=50 psia
(a) Calculate the change in entropy (in Btu/°R) for the CO2 for each process. Comment on whether or not process 1-2 is possible for an adiabatic system.
(b) Calculate the work and heat transfer (Btu) for each process.
2. Two insulated tanks both contain air and are connected by a line with a closed valve. The volume of tank A is 2.0 m3 and the volume of tank B is 5.0 m3. Initially, tank A contains air at 500 K and 600 kPa and tank B contains air at 900 K and 200 kPa. The valve is opened and the gases in each tank mix and eventually the system reaches equilibrium at temperature T2 and pressure p2. Assume that the volume of the connecting line is negligible compared to the volume in the tanks, and that the connecting line is well-insulated also.
(a) Determine the final temperature T2 (K) and pressure p2 (kPa).
(b) Calculate the entropy generation (in kJ/K) for the tank mixing process.
3. Steam enters one side of a mixing chamber at a pressure of 60 psia and a temperature of 350oF (State 1). Water with a mass rate of flow of 22 lbm/s enters the other side of the mixing chamber at a pressure of 60 psia and a temperature of 290oF (State 2). Water leaves the mixing chamber as a saturated liquid at a pressure of 60 psia (State 3). The mixing chamber loses heat at a rate of 9.35 Btu/s from its surfaces to the surroundings. The average surface temperature of the mixing chamber is 130oF .
(a) Complete the table below.
(b) Find the mass flow rate of the steam at state 1, in lbm/s.
(c) Find the entropy generation for the mixing chamber, in Btu/(s-oR).
(d) Show states 1, 2, and 3 on a T-s diagram.
|
State
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p psia
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T oF
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x or region
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h Btu/lbm
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s Btu/(lbm-°R)
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1
|
60
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350
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|
|
|
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2
|
60
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290
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|
|
|
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3
|
60
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|
0
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