Problem 3.2 Given: A gas contained in a piston-cylinder assembly undergoes a the
ID: 1860978 • Letter: P
Question
Problem 3.2
Given: A gas contained in a piston-cylinder assembly undergoes a thermodynamic cycle consisting of three processes in series.
Process 1-2: P1 = 1 bar, V1 = 1.5 m3, compression with PV = constant, 1W2 = -104 kJ, U1 = 512 kJ, U2 = 690 kJ
Process 2-3: 2W3 = 0, 2Q3 = -150 kJ
Process 3-1: 3W1 = 50 kJ
Changes in kinetic and potential energy may be neglected.
Find: a)1Q2, 3Q1, and U3 (kJ) and b) state whether this is a power cycle?
Assume:
Analysis:
Problem 3.3
Given: For a power cycle the heat transfers are Qin = 55 kJ and Qout = 35 kJ.
Find: a) Make a schematic of the power cycle as shown in Figure 2.17 and write the correct heat transfer values into the diagram. b) Calculate the net work and c) thermal efficiency.
Problem 3.4
Given: A refrigeration cycle operates with a coefficient of performance of 1.5. For the cycle Qout = 500 kJ.
Find: a) Make a schematic of the refrigeration cycle as shown in Figure 2.17 and write the correct heat transfer value into the diagram. b) Calculate the Qin and c) Wcycle.
Analysis:
Problem 3.5
Given: Water at the following states
a) P = 5 bar, T = 151.9oC
b) P = 5 bar, T = 200oC
c) T = 200oC, P = 2.5 MPa
d) T = 160oC, P = 4.8 bar
e) T = -12oC, P = 1 bar
Find: a) For each of the states, determine whether the water is compressed liquid, saturated liquid, mixed liquid/vapor, saturated vapor, or superheated vapor. b) Draw P-v and T-v diagrams and show the location of each state. See Example problem 3.1 to see an example of sketching P-v and T-v diagrams.
Analysis:
Problem 3.6
Given: The table below contains property data for water vapor.
P = 1.0 MPa
P = 1.5 MPa
T(oC)
v (m3/kg)
T(oC)
v (m3/kg)
200
0.2060
200
0.1325
240
0.2275
240
0.1483
280
0.2480
280
0.1627
Find: Use linear interpolation to find a) specific volume at T = 240oC and P = 1.3 MPa, b) the temperature at P = 1.5 MPa and v = 0.1555 m3/kg, and c) specific volume at T = 220oC and P = 1.4 MPa.
Analysis:
P = 1.0 MPa
P = 1.5 MPa
T(oC)
v (m3/kg)
T(oC)
v (m3/kg)
200
0.2060
200
0.1325
240
0.2275
240
0.1483
280
0.2480
280
0.1627
Explanation / Answer
1Q2=690-512+104=282kJ;
U3-U2=0-150=>U3=U2-150=540kJ;
3Q1+1Q2+2Q3= -104+50 =>3Q1 = -54-150+282=78kJ;
yes this is a power cycle as work is done
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