This document contains 39 multiple choice questions related to thermodynamics concepts such as power, heat transfer, enthalpy, entropy, ideal gases, and thermodynamic processes. The questions assess understanding of key equations, properties of substances, and calculations involving changes in temperature, pressure, volume, and other thermodynamic variables.

1. Activity No. 3
ME 413 (Refrigeration Engineering)
October 29, 2021
1. What is then power of a steam jet 15 mm in diameter moving at 750 m/s? Steam
condition, 1.4 kg/cm², dry saturated ( v= 1.256 m³/kg).
a. 29.67 kW c. 19.67kW
b. 39.67 kW d. 49.67kW
2. How much power is there in kinetic energy of the atmosphere ( density = 1.217 kg/m³)
at 56 kph wind velocity? Consider the section that passes through a 3 m diameter circular
area normal to the velocity.
a. 10.21 kW c. 16.21 kW
b. 15.21 kW d. 17.21 kW
3. An electric heater is to heat 11 kg of oil per min. from 4.5 ᵒC to 65.5ᵒC. Specific heat of the
oil is 2.1 J/gm-ᵒC. How many watts should this heater consume?
a. 20 448 W c. 20 400 W
b. 33 448 W d. 23 442 W
4. Find the enthalpy of 1 kg of wet saturated steam at a pressure of 0.20 bar and dryness
fraction of 0.85 At 0.20 bar, hf = 251 kJ/kg, hfg = 2358 kJ/kg
a. 2200 kJ/kg c. 2255.30 kJ/kg
b. 2525.30 kJ/kg d. 2000 kJ/kg
5. If the specific enthalphy of wet saturated steam ata pressure of 11 bar of 2681 kJ/kg, find
its
a. 0.75 c. 0.95
b. 0.85 d. 0.65
6. Find the heat transfer required to convert 5 kg of water at a pressure of 20 bar and
temperature of 21ᵒC into steam of dryness fraction 0.90 at the same pressure.
Properties of Steam: P =20bar; hf = 909 kJ/kg; hfg = 1890 kJ/kg
Note: for water at 21ᵒC, h = 88 kJ/kg
a. 10 610 kJ c. 12 610 kJ
b. 11 610 kJ d. 15 610 kJ
7. A closed vessel contains air at a pressure of 140 Kpag and temperature of 20ᵒC. Find the
final gauge pressure if the air is heated at constant volume to 40ᵒC. Take the atmospheric
pressure as 759 mm Hg.
a. 156.46 c. 136.46
b. 146.46 d. 126. 46
8. Water substance at 70 bar and 65ᵒC enters a boiler tube of constant inside diameter of
25 mm. the water leaves the boiler tube at 50 bar and 700 k at velocity of 100m/s.
Calculate the inlet volume flow in li./sec, At 70 bar & 65ᵒc, v1 = 0.001017 m³/kg, at 50 bar
& 700 K, v2 = 0.06081 m³/kg
a. 0.75 c. 0.82
b. 0.64 d. 0.96
9. A group of 50 persons attend a secret meeting in room which is 12 m wide by 10 m long
and a ceiling height of 3m. The room is completely sealed off and insulated. Each persons
gives off 150 kCal per hour of heat and occupies a volume of 0.20 m³. The room has an

2. initial pressure of 101.3 kPa and temperature of 16ᵒC. Calculate the room temperature
after 10 minutes. Use R = 0.287 kJ/kg-K; Cv = 0.171 kCal / kg-K.
a.33.1ᵒC c. 38.7ᵒC
b. 37.7ᵒC d. 31.7ᵒC
10. Steam at 1000 lbf/ft² pressure and 300ᵒR has specific volume of 6.5 ft³/lbm and a
specific enthalpy of 9800 ft-lbf/lbm. Find the internal energy per pound mass of steam.
a. 2500 ft-lbf/lbm c. 5400 ft-lbf/lbm
b. 3300 ft-lbf/lbm d. 6900 ft-lbf/lbm
11. Three pounds mass of air are contained at 25 psia and 100ᵒF. Given that Rair = 53.35 ft-
lbf/lbm. What is the volume of the container?
a. 10.7 ft³ c. 20.6 ft³
b. 15 ft³ d. 24.9 ft³
12. Determine the average constant pressure specific heat of steam at 10 kPa and 45.8ᵒC.
Note: From steam table, at 47.7ᵒC, h= 2588.1 kJ/ and at 43.8ᵒC, h= 2581.1kJ/kg.
a. 1.79 kJ/kgᵒC c. 30.57 kJ/kgᵒc
b. 10.28 kJ/kgᵒC d. 100.1 kJ/kgᵒC
13. A 10 m³ vessel initially contains 5 m³ of liquid water and 5 m³ of saturated vapour at
100 kPa. Calculate the internal energy of the system.
Properties of liquid water and saturated vapour: At 100kPa. Vf= 0.001043 m³/kg; Vg =
1.6940 m³/kg; Uf= 417.3 kJ/kg; Ug = 2506.1kJ/kg
a. 2.0 x 10⁶ k c. 3.0 x 10⁶ kJ
b. 1.0 x 10⁶ kJ d. 5.0 x 10⁶ kJ
14. A vessel with a volume of 1 m³ contains liquid water and water vapor in equilibrium at
600 kPa. The liquid water has a mass of 1 kg. Calculate the mass of the water vapour.
Prpoerties of liquid water and water vapor at 600 kPa; Vf = 0.001 101 m³/kg; Vg = 0.3157
m³/kg
a. 1.57 kg c. 2.54 kg
b. 1.89 kg d. 3.16 kg
15. If 6 liters of a gas at a pressure of 100 kPaa are compressed reversibly according to PV²
= C, unitl the volume becomes 2 liters. Find the final pressure.
a. 600 kPaa c. 900 kPaa
b. 800 kPaa d. 1000 kPaa
16. The flow energy of 124 liters per minute of a fluid passing a boundary to system is
108.5 kJ/ min. Determine the pressure at this point.
a. 875 kPa c. 975 kPa
b. 675 kPa d. 575 kPa
17. Work done by a substance in reversible nonflow manner in accordance with V = 100/P
ft³, where P is in psia. Evaluate the work done on or by the substance as the pressure
increases from 10 psia to 100 psia.
a. 33 157.22 ft-lb c, 43 157.22 ft-lb
b. -33 157.22 ft-lb d. -43 157.22 ft-lb

3. 18. A closed gaseous system undergoes a reversible process during which 25 Btu are
rejected, the volume changing from 5 ft³ to 2 ft³, and the pressure remains constant at 50
psia. Find the change of internal energy.
a. -52.76 Btu c. 2.76 Btu
b. -2.76 Btu d. 52.76 Btu
19. Assume 8 lb of a substance receive 240 Btu of heat at constant volume and undergo a
temperature change of 150ᵒF. Determine the average specific heat of the substance during
the process.
a. 0.5 Btu/lbᵒF c. 0.40 Btu/lbᵒF
c. 0.3 Btu/lbᵒF d. 0.20 Btu/lbᵒF
20. the following expressions relate to a particular gaseous mass: PV = 95T, h = 120 + 0.60T
where this units obtain on psf, V in ft³/lb, T in ᵒR and h in Btu/lb. If the specific heats are
temperature dependent only, find Cp and Cv.
a. 0.6 Btu/lbᵒR, 0.48 btu/lbᵒR c. 0.60 Btu/lbᵒR, 0.7 Btu/lbᵒR
b. 0.3 btu/lbᵒF, 0.50 Btu/lbᵒR d. 0.50 Btu/lbᵒR, 0.48 Btu/lbᵒR
21. Calculate the entropy of steam at 60 psia with a quality of 0.60. Properties of steam at
60 psia: Sr = 0.4274 Btu/lbᵒR & Sfg = 1.2172 Btu/lbᵒR.
a. 0.4247 btu/lbᵒR c. 0.7303 Btu/lbᵒR
b. 1.1577 btu/lbᵒR d. 0.896 Btu/lbᵒR
22. Find the change in internal energy of 5 lbm of oxygen when the temperature changes
from 100ᵒC to 120ᵒF, Cv = 0.157Btu/lbm-ᵒR.
a. 14.70 Btu c. 16.80 Btu
b. 15.70 Btu d. 147 Btu
23. Water ( Specific heat, Cv = 4.2 kJ/kg-K) is being heated by 1500 – W heater. What is the
rate of change in temperature of 1kg of water.
a. 0.043 Kelvin/s c. 0.357 Kelvin/s
b. 0.179 Kelvin/s d. 1.50 Kelvin/s
24. One kilogram of water ( Cv = 4.2 kJ/kg-K) is heated by 300 BTU of energy. What is the
change in temperature in K?
a. 75.36 K c. 73.80 K
b. 125.20 K D. 17.96 K
25. Determine the change in enthalpy per lb mass of nitrogen gas as its temperature
changes from 500ᵒF to 200ᵒF. (Cp = 0.2483 BTU/lbmᵒR)
a. -74.49 Btu/lbm c. -68.47 Btu/lbm
b. -72.68 Btu/lbm d. -63.78 btu/lbm
26. Calculate the change in enthalpy as 1 kg of nitrogenis heated from 1000 K to 1500 K,
assuming the nitrogen is an ideal gas at a constant pressure. the temperature dependent
specific heat of nitrogen is Cp = 39.06 – 512.79 T ¹·⁵ + 1072.7 T ² - 820.4 T ⁻³where Cp is in
kJ/kg-mol, and T is in K.
a.600kJ c.800kJ
b. 697.27 kJ d. 897.27 kJ
27. What is the resulting pressure when one pound of air at 15 psia and 200ᵒF is heated at
constant volume to 800ᵒF?

4. a. 15 psia c. 36.4 psia
b. 28.6 psia d. 52.1 psia
28. The temperature of an ideal gas remains constant while the absolute pressure changes
from 103.4 kPaa to 827.2 kPaa. if the initial volume is 80 liters, what is the final volume?
a. 5 li c. 15 li
b. 10 li d. 20 li
29. For a certain ideal gas, R = 0.277 kJ/kg-K and k= 1.384. What are the values of Cp and
Cv?
a. 0.9884 kJ/kg-K, 0.7213 kJ/kg-K c. 0.7124 kJ/kg-K, 0.8124 kJ/kg-K
b. 1 kJ/ kg-K, 0.8124 kJ/kg-K d. 0.9984 kJ/kg-K, 0.6124 kJ/kg-K
30. A mixture is formed at 689.48 kPaa, 37.8 ᵒC by bringing together these gases each
volume before mixing measured at 689.48 kPaa, 37.8ᵒC; 3 mol CO₂ after mixing.
a. 217.73 kPaa c. 326.60 kPaa
b. 145.15 kPaa d. 445.15 kPaa
31. An air with mass of 0.454 kg and an unknown mass of CO₂ occupy an 85 liters tank at
2068.44 kPaa. If the partial pressure of the CO₂ is 344.74 kPaa, determine its mass.
a. 0.138 kg c. 0.183 kg
b. 0.238 kg d. 0.283 kg
32. After series of state changes, the pressure and volume of 2.286 kg of Nitrogen are each
doubled. What is ΔS?
a. 2.807 kJ/ kg-K c. 2.987 kJ/ kg-K
b. 2.268 kJ/ kg-K d. 3.40 kJ/ kg-K
33. The temperature of 4.82 lb of Oxygen occupying 8 ft³ is changed from 110ᵒF to 200ᵒF
while pressure remains constant at 115 psia. Determine the final volume.
a. 7.26 ft³ c. 9.26 ft³
b. 8.26 ft³ d. 10.26 ft³
34. Twenty grams of oxygen gas (O₂) are compressed at a constant temperature of 30 ᵒC at
5% of their original volume. What work is done on the system? Use R of air, 0.0619 Cal/gm-
K.
a. 824 Cal c. 944 Cal
b. 924 Cal d. 1124 Cal
35. Helium ( R = 0.4968 Btu/lbmᵒR) is compressed isothermally from 14.7 psia and 68ᵒF.
the compression ratio is 4. Calculate the work done by the gas.
a. -364 Btu/lbm c. -187 Btu/lbm
b. -145 Btu/lbm d. -46.7 Btu/lbm
36. Gas is enclosed in a cylinder with a weighted piston as the top boundary. The gas is
heated and expands from a volume of 0.04 m³ to 0.10 m³ at a constant pressure of 200 kPa.
Calculate the work done by the system.
a. 8 kJ c. 12 kJ
b. 10 kJ d. 14 kJ

5. 37. A piston cylinder system contains a gas which expands under a constant pressure of
1200 lb/ft². If the piston is displaced 1 ft during the process, and the piston diameter is 2ft.
What is the work done by the gas on the piston?
a. 1768 ft-lb c. 3768 ft-lb
b. 2387 ft-lb d. 4000 ft-lb
38. Gas is enclosed in a cylinder with a weighted piston as the top boundary. The gas is
heated and expands from a volume of 0.04 m³. The pressure varies such that PV =
constant and the initial pressure is 200 kPa. Calculate the work done by the system.
a. 6.80 kJ c. 9.59 kJ
b. 7.33 kJ d. 12kJ
39. In an isentropic process, P1 = 200 psi, P2 = 300 psi and T1 = 700ᵒR, Find T2 using k = 1.4
a. 576ᵒR c. 786ᵒR
b. 680ᵒR d. 590ᵒR
40. Nitrogen (k = 1.4) is expanded isentropically. Its temperature changes from 620ᵒF. Find
the pressure ratio (P1/P2).
a. 0.08 c. 26.2
b. 12.91 d. 35.47
41. Nitrogen is expanded isentropically. Its temperature changes from 620ᵒF to 60ᵒF. The
volumetric ratio is (V1/V2) = 6.22 and the value of R for nitrogen is 0.0787 Btu/lbmᵒR. What
is the work done by the gas?
a. -100.18Btu/lbm c. 110.18Btu/lbm
b. 120.27 Btu/lbm d. -120.27 Btu/lbm
42. If the ᵒF scale is twice the ᵒC scale, what is the reading in the Fahrenheit scale?
a. 160ᵒ c. 140ᵒ
b. 320ᵒ d. 280ᵒ
43. Water enters the condenser at 30ᵒC and leaves at 60ᵒC. What is the temperature
Difference in ᵒF?
a. 16.67 c. 54
b. 48.67 d. 22
44. A cylinder and piston arrangement contains saturated water vapour at 110ᵒC. the
vapour is compressed in a reversible adiabatic process until the pressure is 1.6 Mpa.
Determine the work done by the system per kg of water. At 110ᵒC, S1 = 7.2387kJ/kg-K, U1
= 2518.1 kJ/kg and at 1.6 Mpa, S2 = 7.2374 kJ/kg-K,U2 = 2950.1 kJ/kg, T2 = 400ᵒC
a. -500 kJ/kg c. -632 kJ/kg
b. -432 kJ/kg -700 kJ/kg
45. Helium is compressed isothermally from 14.7 psia and 68ᵒF. The compression ratio is 4.
Calculate the change in entropy of the gas given that RHELIUM = 0.4961 Btu/lbmᵒR.
a.-0.688 Btu/lbmᵒR c. 0.658 Btu/lbmᵒR
b. -2.76 Btu/lbmᵒR d. 2.76 Btu/lbmᵒR
46. Steam at a pressure of 9 bar (hf = 743 kJ/kg, hfg = 2031 kJ/kg) is generated in an
exhaust gas boiler from feedwater at 80ᵒC (h = 334.9 kJ/kg). If the dryness fraction of the
steam is o.96, determine the heat transfer per kilogram of steam.

6. a.2357.86 c.1357.86
b. 3357.86 d. 5357.86
47. If wet saturated steam at 8 bar (hfg = 2048 kJ/kg) requires 82 kJ of heat per kg of steam
to completely dry it, what is the dryness fraction of the steam?
a. 0.76 c. 0.96
b. 0.86 d. 0.66
48. Wet saturated steam at 17 bar (hf = 872 kJ/kg, hfg = 1293 kJ/kg) dryness 0.97 is
produced from feedwater at 85ᵒC ( h= 335.9 kJ/kg). Find the heat energy supplied per kg.
a. 4381.41 kJ/kg c. 2381.41 kJ/kg
b. 1381.41 kJ/kg d. 3381.41 kg
49. A turbo generator is supplied with superheated steam at a pressure of 30 bar and
temperature 350ᵒC ( h= 3117 kJ/kg). The pressure of the exhaust steam from the turbine is
0.06 bar ( hf = 152 kJ/kg, hfg = 2415 kJ/kg) with a dryness fraction of 0.88. If the turbine
uses 0.25 kg per second, calculate the power equivalent of the total enthalpy drop.
a. 109.95 kW c. 309.95 kW
b. 209.95 kW d. 409.95 kW
50. Steam enters the super heaters of a boiler at a pressure of 20 bar ( hf = 909 kJ/kg, hfg =
1890 kJ.kg, vg = 0.09957 m³/kg) and dryness 0.98 and leaves at the same pressure at a
temperature of 350ᵒC ( h= 3138 kJ/kg, v = 0.1386 m³/kg). Find the percentage increase in
volume due to drying and superheating.
a. 12.04 c. 32.04
b. 22.04 d. 42.04
51. Steam at the rate of 500 kg/hr is produced by a steady flow system boiler from
feedwater entering at 40ᵒC. Find the rate at which heat is transformed in kCal/hr if the
enthalpy of steam is 600 kCal/kg and of steam 50 kCal/kg.
a. 275,000 kCal/hr c. 375,000 kCal/hr
b. 175,000 kCal/hr d. 475,000 kCal/hr
52. Steam leaves an industrial boiler at 827.4 kPa and 171.6ᵒC ( hf = 727.25 kJ/kg, hfg =
2043.2 kJ/kg). A portion of the steam is passed through a throttling calorimeter and is
exhausted to the atmosphere when the calorimeter pressure is 101.4 kPa and a
temperature of 115.6ᵒC ( h = 2707.6 kJ/kg ). How much moisture does the steam leaving
the boiler contain?
a. 2.08% c. 4.08%
b. 3.08% d. 5.08%
53. During the polytropic process of an ideal gas, the state changes from 138 kPa and 5ᵒC to
kPa and 171ᵒC. Find the value of n.
a. 1.354 c. 1.345
b. 1.253 d. 1.234
54. For an ideal gas, what is the specific molar entropy change during an isothermal
process in which the pressure changes from 200 kPa to 150 kPa?
a. 2.39 J/mol – K c. 3.39 J/mol – K
b. 1.39 J/mol – K d. 4.39 J/mol – K
55. Water enters the heater at 25ᵒC and leaves at 80ᵒC. What is the temperature change in
Fᵒ?

7. a. 55 c. 11
b. 99 d. 65
56. The suction pressure of a pump reads 600 mm Hg vacuum. what is the absolute
pressure in Kpa?
a. 11.33 c. 21.33
b. 31.33 d. 41.33
57. One kilogram of wet steam at a pressure of 8 bar ( Vg = 0.2404 m³/kg, Vf = 0.0011148
m³/kg, Vf = 0.0010836 m³/kg) and dryness 0.94 is expanded until the pressure is 4 bar (Vg
= 0.4625 m³/kg, Vf = 0.0010836 m³/kg. If expansion follows the law PNⁿ = C, where n =
1.12, find the dryness fraction of the steam at the lower pressure.
a. 0.9072 c. 0.2260
b. 0.4197 d. 0.2404
58. 2.5 liters of superheated steam at 25 bar and 400ᵒC ( v= 0.1252 m³/kg) is expanded in
an engine to a pressure of 0.1 bar ( vg = 14.674 m³/kg, vf = 0.0010102 m³/kg ) when its
dryness fraction is 0.9. Find the volume of the steam.
a. 163.74 liters c. 363.74 liters
b. 263.74 liters d. 463.74 liters
59. A. 1.5 kg of wet steam at a pressure of 5 bar ( hf = 640 kJ.kg, hfg = 2109 kJ/kg) dryness
0.95 is blown into 70 liters of water of 12ᵒC ( h= 50.4 kJ/kg). Find the final enthalpy of the
mixture.
a. 74.80 kJ/kg c. 94.80 kJ/kg
b. 84.80 kJ/kg d. 104.80 kJ/kg
60. Wet saturated steam at 16 bar ( hf = 859 kJ/kg, hfg = 1935 kJ.kg, x = 0.98) reducing
valve and is throttled to a pressure of 8 bar ( hf = 721 kJ/kg, hfg = 2048 kJ/kg). Find the
dryness fraction of the reduced pressure steam.
a. 0.8833 c. 0.9933
b. 0.7733 d. 0.6633
61. A vessel of volume 8.7 m³ contains air and dry saturated steam at a total pressure of
0.06 bar and temperature 29ᵒC ( Psat = 0.04 bar, v = 34.80 m³/kg). Taking the R for air as
287 J/kg – K, calculate the mass of steam and the mass of air in the vessel.
a. 0.25 kg, 0.204 kg c. 0.25 kg/ 350 kg
b. 0.35 kg, 0.204 kg d. 0.35 kg, 0.45 kg