HW10s - Spring 2006 Thermodynamics Homework #10 Solutions...

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Spring 2006 1 ME 201 Thermodynamics Homework #10 Solutions 1. Three of the process that occur in the piston cylinder device of an internal combustion engine are: Process 1: Constant pressure heat addition during which the volume doubles Process 2: Isentropic expansion during which the volume increases 9 times Process 3: Constant volume heat removal to a final pressure of 100 kPa At the start of process 1 the engine contains 0.035 liters of air at 950 K and 5.7 MPa. For each of the three processes the air undergoes find the work and heat transfer in kJ. What is the total work and heat transfer for all three processes together? Solution: We will work this problem process by process. System Type: Closed System Working Fluid: Air (ideal gas) Process: Isobaric State 1 State 2 T 1 = 950 K T 2 = 1900 K P 1 = 5700 kPa P 2 = 5700 kPa V 1 = 0.035 liters = 3.5 x 10 -5 m 3 V 2 = 7.0 x 10 -5 m 3 m 1 = 7.317 x 10 -4 kg m 2 = 7.317 x 10 -4 kg u 1 = 716.55 kJ/kg u 2 = 1582.6 kJ/kg v 1 = 4.783 x 10 -2 m 3 /kg v 2 = 9.566 x 10 -2 m 3 /kg Italicized values are from ideal gas relations or air tables. Bold values are calculated. Q = UNKNOWN W sh = 0 W bnd = P(V 2 -V 1 ) (isobaric) Initial State: Fixed Final State: UNKNOWN Conservation of Mass: m 1 = m 2 1st Law: U 2 - U 1 = Q-W bnd
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ME 201 Thermodynamics Spring 2006 2 Approach: To fix the final state we will use our process description along with the conservation of mass to determine the final specific volume. The boundary work is
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HW10s - Spring 2006 Thermodynamics Homework #10 Solutions...

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