Soal soal dibawah ini merupakan merupakan contoh penerapan dari konsep yang teah dijelaskan dalam
pertemuan ke 4 dan 5, baik substansi materi yang tertuang dalam e learning termo maupun saat
perkuliahan tatap muka di ruang kelas
EXAMPLE E3-1 At the exit of a nozzle (see accompanying
figure) a gas has the following properties: V1 = 95 m/s,
mdot2 = 0.5 kg/min, Jdot2 = 0.0635 kW. If the nozzle exit
diameter is 1 cm, determine (a) two thermodynamic
properties at the exit, and (b) the flow rate of enthalpy.
Neglect potential energy. [ Manual Solution] [TEST Solution]
Answers: (a) 0.895 m3/kg, 3.11 kJ/kg, (b) 0.02 kW
EXAMPLE E3-2 The specific volume of a gas in m3/kg is
experimentally related to the independent properties
temperature and pressure through the following functional
relationship: = 4.157 T/p, where T and p are expressed in K
and kPa respectively. Determine the change in , (a) exactly
and (b) approximately using Taylor's theorem for the
following change of state. State-1: p = 101 kPa, T = 1000 K;
State-2: p=100 kPa, T = 1005 K. [Manual Solution]
Answers: (a) 0.619m3/kg, (b) 0.615m3/kg
EXAMPLE E3-3 A piston-cylinder device contains steam at a
pressure of 1 MPa and a temperature of 300oC. Evaluate (a)
the difference between the left and right hand sides of the
first T-ds equation if the system comes to a new equilibrium
with its pressure decreasing by 1 kPa and temperature
increasing by 1oC. Use PC (Phase-Change) system state
daemon. (b) What-if-scenario: How would the answer
change if steam had velocities of 10 m/s and 100 m/s in the
two states? [Manual Solution] [TEST Solution]
Answers: (a) 5.3%, (b) 5.3%
EXAMPLE E3-4 A block of aluminum of mass 5 kg, initially at
equilibrium with the surroundings at 30oC and 100 kPa, is
placed in a pressurized chamber kept at a pressure of 10 MPa
and a temperature of 200oC. Determine the change in (a) the
internal energy, (b) enthalpy, (c) entropy of the block after it
comes to equilibrium with the chamber pressure and
temperature What-if-scenario: How would the answer in
part (a) and (c) change if the block were made of (e) copper,
(f) gold? [Manual Solution] [TEST Solution]
Answers: (a) 765 kJ, (b) 783.3 kJ, (c) 2.0 kJ/K, (d) 157.7 kJ, (e) 328.1 kJ, (f)
109.7 kJ
EXAMPLE E3-5 A pumping system delivers liquid water at a
higher pressure in an isentropic (constant entropy) manner.
At the inlet p1=100 KPa , V1 =10 m/s and z1 =0 and at the
exit p2 = 1000 KPa, V2 = 15 m/s and z2 = 5 m. Determine
the change in (a) specific internal energy, (b) specific stored
energy, (c) specific enthalpy, and (d) specific flow energy
between the inlet and exit. [Manual Solution] [TEST Solution]
Answers: (a) 0 kJ/kg, (b) 0.11 kJ/kg, (c) 0.90 kJ/kg, (d) 1.01 kJ/kg
EXAMPLE E3-6 Calculate the saturation temperature of (a)
water, (b) ammonia, (c) R-134a, and (d) nitrogen at 100
kPa. What-if-Scenario: How would the answers change if
the pressure were increased to 1 MPa? [Manual Solution] [TEST
Solution]
Answers:(a) 99.61oC, (b) -33.63oC, (c) -26.58oC, (d) -195oC, (e) 24.89oC
EXAMPLE E3-7 A pipe carrying refrigerant R-12 at 25oC as a
saturated liquid develops a small leak. Assuming the
atmospheric conditions to be 100 kPa and 25oC, determine
(a) the direction of flow at the leak, and (b) the temperature
of the refrigerant when exposed to the atmosphere. [Manual
Solution] [TEST Solution]
EXAMPLE E3-8 A tank contains superheated steam at 120
kPa. If the specific enthalpy is 2700 kJ/kg, determine the
temperature of the steam. [Manual Solution] [TEST Solution]
Answers: 112.86oC
EXAMPLE E3-9 A rigid tank with a volume of 0.02 m3 contains
0.5 kg of refrigerant ammonia (NH3) at 25oC. Determine the
phase composition. [Manual Solution] [TEST Solution]
Answers: Saturated Mixture
EXAMPLE E3-10 In the previous problem determine (a) x, (b)
u, and (c) the volume fraction y occupied by the liquid phase.
[Manual Solution] [TEST Solution]
Answers:(a) 35.12%, (b) 678.6 kJ/kg, (c) 540mL
EXAMPLE E3-11 The tank in the last example is heated until
all the liquid completely vaporizes. Determine (a) the
pressure, and (b) temperature in the tank. (c) What-if-
Scenario: How would the answers change if the tank were
heated until the liquid volume reduced to 200 mL? [Manual
Solution] [TEST Solution]
Answers: (a) 3148 kPa, (b) 67.8oC, (c) 2517 kPa
EXAMPLE E3-12 Saturated vapor of refrigerant R-134a flows
into an isentropic (constant entropy) compressor at a
pressure of 100 kPa. If the exit pressure is 1 MPa, determine
(a) the exit temperature. (b) Can you explain why entropy
remains constant despite an increase in temperature at the
exxit? [Manual Solution] [TEST Solution]
Answers:(a) 48.91oC, (b) 1.02 MPa
EXAMPLE E3-13 Water at 5 MPa and 140oC is pressurized at
constant entropy to a pressure of 10 MPa. Determine (a) the
change in temperature, and (b) enthalpy. Use the CL sub-
model for liquid water. (c) What-if-Scenario: How would
the results change if (c) the compressed liquid table or (d)
the solid/liquid model were used to model liquid water
instead? [Manual Solution] [TEST Solution]
Answers: (a) 0oC, (b) 5.79 kJ/kg, (c) 5.86 kJ/kg, 5.01 kJ/kg
EXAMPLE E3-14 A piston cylinder device having a volume of
2 L contains argon at a pressure of 1 atm and a temperature
of 550oR. The gas is heated to a temperature of 800oR in a
constant volume process. Determine (a) the mass of the gas,
and (b) the change in pressure, (c) entropy during the
process. Assume the atmospheric conditions to be 100 kPa
and 25oC. (e) What-if-Scenario: How would the answer in
part (c) change if the heating were carried out at a constant
pressure? [Manual Solution] [TEST Solution]
Answers:(a) 0.003 kg, (b) 46.1 kPa, (c) 0.0003 kJ/K, (d) 0.027 kJ, (e) 0.044 kJ
EXAMPLE E3-15 Superheated steam at a pressure of 10 kPa
and temperature 200oC undergoes a process to a final
pressure and temperature of 50 kPa and 300oC respectively.
Determine (a) Δv, (b ) Δu, (c) Δh, and (d) Δs, assuming
superheated steam to behave like a perfect gas. (e) What-
if-Scenario: How would these results change if the phase-
change model were used? [Manual Solution] [TEST Solution]
Answers:(a) -16.56m3/kg, (b) 141 kJ/kg, (c) 187.2 kJ/kg, (d) -0.38 kJ/kg.K,
(e) -16.54m3/kg
EXAMPLE E3-16 A tank of volume 10 m3 contains air at a
pressure of 100 kPa and a temperature of 300 K. The air is
heated to a temperature of 2000 K. Treating air as an ideal
gas, determine (a) the final pressure, and the change in the
total internal energy of air. (c) What-if-Scenario: How
would the answers change if the perfect gas model were
used? [Manual Solution] [TEST Solution]
Answers: (a) 667 kPa, (b) 17004 kJ, (c) 667 kPa
EXAMPLE E3-17 A tank of volume 10 m3 contains nitrogen at
a pressure of 3 MPa and a temperature of 125 K. Determine
the mass of nitrogen in the tank using the (a) ideal gas, (b)
real gas (Lee Kestler), and (c) real gas (Nelson-Obert)
models. What-if-Scenario: (c) How would the answers
change if the phase-change model were used? [Manual Solution]
[TEST Solution]
Answers: (a) 806 kg, (b) 1754 kg, (c) 1833 kg
EXAMPLE E3-18 (a) Predict the pressure of oxygen gas
having a temperature of 200 K and a specific volume of
0.001726 m3/kg using the real gas model. What-if-
Scenario: How would the answer change if we used (b) the
ideal gas equation of state, (c) the van der Waals equation,
(d) the BWR equation, or (e) the phase-change model is
used.? [Manual Solution] [TEST Solution]
Answers: (a) 21.33 MPa, (b) 29.55 MPa, (c) 24.57 MPa, (d) 19.5 MPa
EXAMPLE E3-19 Superheated steam at a pressure of 500 kPa
and temperature of 450oC undergoes an isothermal process
to a final pressure of 20 MPa. Determine the change in (a)
specific volume, and (b) enthalpy employing the real gas
model. What-if-Scenario: How would the answers change if
(c) the phase-change, (d) ideal gas, and (e) the perfect gas
model were used? [Manual Solution] [TEST Solution]
Answers: (a,c,d,e) -0.65 m3/kg, (b) -274.5 kJ/kg