University of Mindanao

Mechanical Engineering
Correlation Courses (ME 500)
Air Conditioning

Lecture:
1. A classroom that normally input required for this air- maintained at 27 oC DB and 20 oC
contains 40 people is to be air- conditioning system. WB. If the sensible heat ratio is
conditioned with window air- a. 10.06 hp 0.71, what is the latent heat load of
conditioning units of 5 KW b. 1.36 hp the theater?
cooling capacity. A person at rest c. 1.41 hp* a. 45.21 kW*
may be assumed to dissipate heat d. 7.94 hp b. 54.21 kW
at a rate of about 360 KJ/hr. There 5. An auditorium seating 1500 c. 110.682 kW
are 10 light bulbs in the room, people is to be maintained at 80 d. 42.51 Kw
each with a rating of 100 watts. ℉ dry bulb and 85℉ wet bulb 12. Re-circulated air of 10 kg/s with
The rate of heat transfer to the 53 KJ/kg dry air enthalpy and
classroom through the walls and temperature when outdoor air is at outside air of 4 kg/s with 90KJ/kg
the windows is estimated to be 91℉ dry bulb and 75℉ wet dry air enthalpy enters the
15,00 KJ/hr. If the room air is to bulb. Solar heat load is 110,000 conditioning unit. Determine the
be maintained at a constant Btu/hr and supply air at 60℉ , air conditioning capacity of air
temperature of 21oC, determine conditioning apparatus if the
determine the amount of supply
the number of window air- supply enthalpy to conditioned
air.
conditioning units required. space is 42 kJ/kg dry air.
a. 93,229.17 lb/hr*
a. 1 unit a. 154 KW
b. 83,229.17 lb/hr
b. 2 units * b. 302 KW*
c. 73,229.17 lb/hr
c. 3 units c. 204 KW
d. 63,229.17 lb/hr
d. 4 units d. 4.484 KW
6. A room contains air at 20C and 96
2. A 4m x 5m x 6m room is to be 13. 30 kg of dry air enters an adiabatic
kPA at a relative humidity of 75%.
heated by a baseboard resistance drying chamber at 88 degC and
Determine the enthalpy of moist
heater. It is desired that the with humidity ratio of 0.16 kg/kg
air.
resistance heater be able to raise d.a. the exhaust air leaves the
a. 45.919 KJ/kgda
the air temperature in the room drying chamber at 40 degC. What
b. 45.515 KJ/kgda
from 7 to 23oC within 15 minutes. is the rate of water removal in the
c. 49.515 KJ/kgda*
Assuming no heat losses from the drying chamber?
d. 41.815 KJ/kgda
room and an atmospheric pressure At 40C psat = 7.375 kpa; at 88, hg
7. Determine the mass of water
of 100 kpa, determine the required = 2656.9 Kj/kg
vapour contained in a 150m3 room
power of the resistance heater. a. 0.24 kg/s
at 100 kPa, 23C and 40% relative
Assume constant specific heats at b. 0.46 kg/s
humidity. From steam tables: Psat
room temperature. c. 0.38 kg/s
@ 23C=2.810 kPA.
a. 2.34 KW d. 0.58 kg/s*
a. 1.6342 kg
b. 1.91 KW* 14. Compute the humidity ration of air
b. 1.9342 kg
c. 4.56 KW condensing the density at 27 degC
c. 1.2342 kg*
d. 6.34 KW and 98 kPa is 1.32 kg/m3
d. 2.2342 kg
3. A student in a 4m x 6m x 6m a. 0.34 kgvapor/kgair
8. A 5 m x 4 m x 4 m room has an air
dormitory room turns on her 150 b. 0.43 kgvapor/kgair
temperature of 32 oC (psat = 4.559
watts fan before she leaves the c. 0.35 kgvapor/kgair*
kPaa, hg = 2559.9 kJ/kg) and the
room on a summer day, hoping d. 0.53 kgvapor/kgair
pressure is 101 kPaa. The mass of
that the room will be cooler when 15. Compute the humidity ratio of air
water vapor in air is 2.5 kg with R v
she comes back in the evening. @ 70% relative humidity and 25˚C
= 0.45 kJ/kg-oK. What is the
Assuming all the doors and when the barometric pressure is
relative humidity of the air?
windows are tightly closed and 101.325 kPa from steam tables.
a. 94.08 %*
disregarding any heat transfer Psat at 34˚C = 3.169 kPa
b. 74.08 %
through the walls and the a. 0.014 kg water vapor / kg dry
c. 84.08 %
windows, determine the air*
d. 64.08 %
temperature in the room when she b. 0.14 kg water vapor / kg dry air
9. An air-vapor mixture has a dry
comes back 10 hours later. Use c. 1.4 kg water vapor / kg dry air
bulb temperature of 30 oC and a
specific heat values at room d. 0.0014 kg water vapor / kg dry
humidity ratio of 0.015 kg/kg d.a.,
temperature, and assume the room air
calculate the enthalpy of the moist
to be at 100 kpa and 15oC in the 16. Wet material containing 220%
air.
morning when she leaves moisture (dry basis) is to be dried
a. 68.527 kJ/kg d.a*
a. 28.13oC at the rate of 1.5 kg / s in a
b. 86.527 kJ/kg d.a.
b. 38.13oC continuous dryer to give a product
c. 65.827 kJ/kg d.a.
c. 48.13oC containing 10%(dry basis). Find
d. 67.528 kJ/kg d.a
d. 58.13oC* the moisture removed in kg / hr.
10. The approach and efficiency of
4. An air-conditioning system is used a. 3543.75 kg / hr*
cooling tower are 10 oC and 65 %,
to maintain a house at 75OF when b. 3513.75 kg / hr
respectively. If the temperature of
the temperature outside is 95OF. c. 3563.75 kg / hr
water leaving the tower is 27 oC,
The house is gaining heat through d. 3563.75 kg / hr
determine the temperature of water
the walls and windows at a rate of 17. Copra enters a dryer containing
entering the tower.
1250 Btu/min, and the heat 70% moisture and leaves at 7%
a. 54.57 oC
generation rate within the house moisture. Find the moisture
b. 55.47 oC
from people, lights and appliances removed on each pound of solid in
c. 45.57 oC*
amounts to 350 Btu/min. the final product.
d. 54.75 oC
Determine the minimum power a. 6.258 lb
11. A 10 kg/s of air enters the theatre
b. 1.258 lb
at 16 oC. The theater is to be

Prepared by: Engr. Edgar Kenneth Luna

ME 500 Coordinator
 University of Mindanao
Mechanical Engineering
Correlation Courses (ME 500)
Air Conditioning
c. 4.258 lb d. 3140.25 kW
d. 2.258 lb*
18. Fifty kilogram of cooling tower
per second enter the condenser
15˚C and leaves at 50˚C. Find the
heat carried away by water.
a. 5234.45 kW
b. 5233.45 kW*
c. 2340.52 kW

Assignment:
1. A 10 m3 vessel contains 5 m3 of at a constant pressure of 200 kPa. requirement to vaporize all of the
liquid water and 5 m3 of saturated Calculate the work done by the liquid.
water vapor at 100kpa. Calculate system. a. 100,000 kJ*
the internal energy of the system a. 8 kJ* b. 2,000,000 kJ
using the steam tables. b. 10 kJ c. 300,000 kJ
a. 5 x 105 kJ c. 12 kJ d. 400,000 kJ
b. 8 x 105 kJ d. 14 kJ 13. A copper can of negligible heat
c. 1 x 106 kJ 8. Assume the total heat of capacity contains 1 kg of water
d. 2 x 106 kJ* vaporization (per gram) of water just above the freezing point. A
2. 3.0 lbm of air are contained at 25 can be used to supply the energy similar can contains 1 kg of water
psia and 100 °F. Given that Rair = needed to tear 1 g of water just below the boiling point. Two
53.35 ft-lbf / lbm-°F, what is the molecules apart from each other. cans are brought to into thermal
volume of the container? How much energy is needed per contact. Find the change in entropy
a. 10.7 ft3 molecule for this purpose? of the system?
b. 14.7 ft3 a. 6.74 x 10-20 J* a. 100 J*
c. 15 ft3 b. 1.74 x 10-20 J b. 200 J
d. 24.9 ft3 * c. 3.74 x 10-20 J c. 300 J
3. Twenty grams of oxygen (O2) are d. 2.74 x 10-20 J d. 400 J
compressed at a constant 9. An isobaric steam generating 14. The atomic weight of hydrogen is
temperature of 30°C to 5 % of process starts with saturated liquid 1gram per gram-atom. What is the
their original volume. What work at 20 psia. The change in entropy mass of hydrogen atom?
is done on the system? is equal to the initial entropy. a. 1.66 x 10-24 g/atom*
a. 824 cal What is the change in enthalpy b. 6.02 x 10-10 g/atom
b. 924 cal during the process? (Hint: Not all c. 1.0 x 10-23 g/atom
c. 944 cal liquid is vaporized.) d. 1 g/atom
d. 1124 cal * a. -230.4 BTU/lbm 15. In a gaseous mixture of 20 deg. C
4. A vessel with a volume of 1 cubic b. 230.4 BTU/lbm* the partial pressures of the
meter contains liquid water and c. 0 BTU/lbm components are as follows:
water vapor equilibrium at 600 d. 196.2 BTU.lbm Hydrogen, 200 mmHg; Carbon
kPa. The liquid water has a mass 10. A steam generator produces Dioxide, 150 mmHg; Methane,
of 1 kg. Using the steam tables, saturated steam at 100 psia from 320 mmHg; Ethylene, 105 mmHg.
calculate the mass of the vapor. saturated liquid at 14.7 psia. If the What is the total pressure of the
a. 0.99 kg heat source is a bath at 340F that mixture?
b. 1.57 kg produces 800 BTU/lbm, which of a. 755 mmHg*
c. 3.16 kg* the following is true? b. 255 mmHg
d. 2.54 kg a. The device cannot work because c. 345 mmHg
5. A cylinder and a piston the pressure gradient is greater d. 800 mmHg
arrangement contains saturated than zero. 16. Air undergoes an isentropic
water vapor at 110 °C. The vapor b. The device can work, but is compression from 14.7 psia to
is compressed in a reversible inefficient. 180.6 psia. If the initial
adiabatic process until the pressure c. The device violates the 1st law of temperature is 68 °F and the final
is 1.6 MPa. Determine the work thermodynamics.* temperature is 621.5 °F, calculate
done by the system per kilogram d. The device violates the 2nd law of the work done by the gas.
of water. thermodynamics. a. -136.2 BTU/lbm
a. -637 kJ/kg 11. If air is at a pressure, ρ , of 3200 b. -94.8 BTU/lbm*
b. -509 kJ/kg lbf/ft2, and at a temperature, T , of c. 0 BTU/lbm
c. -432 kJ/kg* 800°R, what is the specific d. 94.8 BTU/lbm
d. -330 kJ/kg volume, v? (R = 53.3 ft-lbf/lbm- 17. Gas is enclosed in a cylinder with
6. Ideal Oxygen is throttled at °R, and air can modeled as an ideal a weighted piston as the top
140degF from 10 atm to 5 atm. gas) boundary. The gas is heated and
What is the temperature change? a. 9.8 ft3/lbm expands from a volume 0.04 m3 to
a. 0* b. 11.2 ft3/lbm 0.1 m3. The pressure varies such
b. Negative c. 13.3 ft3/lbm* that PV = C, and the initial
c. Infinity d. 14.2 ft3/lbm pressure is 200 kPa. Calculate the
d. 1 12. A 5m3 vessel initially contains 50 work done by the system.
7. Gas is enclosed in a cylinder with kg of lquid water and saturated a. 6.8 kJ
a weighted piston as the top water vapor at total internal energy b. 7.33 kJ*
boundary. The gas is heated and of 27,3000 kJ. Calculate the heat c. 9.59 kJ
expands from a volume of 0.04 m3 d. 12.0 kJ

Prepared by: Engr. Edgar Kenneth Luna

ME 500 Coordinator
 University of Mindanao
Mechanical Engineering
Correlation Courses (ME 500)
Air Conditioning
18. From the steam tables, determine c. 3.31 kW 60degF; the density of air is
the average constant pressure d. 5.14 kW 0.0763 lbm/ft3; P1 = 14.7 psia
specific heat (Cp) of steam at 10 26. Water (specific heat cv = 4.2 kJ/kg- a. 8.342 psia*
kPa and 45.8°C. K) is being heated by a 1500W b. 5.34 psia
a. 1.79 kJ/kg.°C* heater. What is the rate of change c. 6.72 psia
b. 10.28 kJ/kg.°C in temperature of 1 kg of the d. 9.32 psia
c. 30.57 kJ/kg.°C water? 34. A cold tire contains 1000 in.3 of
d. 100.1 kJ/kg.°C a. 0.043 K/s air at 24 psia and 32degF. What
19. For an ideal gas, what is the b. 0.719 K/s pressure in the tire is needed if the
specific molar entropy change c. 0.357 K/s* temperature and volume are
during an isothermal process in d. 1.50 K/s increased to 35degF and 1020 in.3
w/c the pressure changes from 200 27. Calculate the change in enthalpy respectively?
kPa to 150 kPa? as 1 kg of nitrogen is heated from a. 23.57 psia*
a. 2.00 J/moleK 1000 K to 1500 K, assuming the b. 32.45 psia
b. 2.39 J/moleK* nitrogen is an ideal gas at a c. 43.54 psia
c. 2.79 J/moleK constant pressure. The d. 34.57 psia
d. 3.12 J/moleK temperature-dependent specific 35. Determine the specific gravity of
20. What is the value of the work done heat of nitrogen is: carbon dioxide gas (molecular
for a closed, reversible, isometric cp = 39.06 - 512.79T-1.5 + 1072.7T-2 weight = 44) at 150degF (66degC)
system? - 820.4T-3 and 20 psia (138 kPa).
a. Zero* cp is in kJ/Kmole-K and T is in K. a. 1.67*
b. Positive a. 600 kJ b. 1.45
c. Negative b. 700 kJ* c. 1.87
d. Positive or negative c. 800 kJ d. 1.30
21. If 1 lbm of steam at 14.7 psia, 63 d. 900 kJ 36. An empty polyethylene telemetry
% quality is heated isentropically, 28. Helium is compressed balloon and payload have a mass
at what pressure will it reach the isothermally from 14.7 psia and 60 of 500 lbm. The balloon is charged
saturated vapor state? °F. The compression ratio is 4. with helium when the atmospheric
a. 56 psia Calculate the change in entropy of conditions are 60degF and 14.8
b. 313 psia the gas given that RHe = 0.4961 psia. The specific gas constant of
c. 1852 psia BTU/lbm-°R. helium is 386.3 ft-lbf/lbm-R. What
d. 2585 psia* a. -2.76 BTU/lbm-°R is the volume of helium is
22. 200g of water are heated from 5C b. -0.689 BTU/lbm-°R* required?
to 100C and vaporized at a c. 0 BTU/lbm-°R a. 7544 ft3 *
constant pressure. The heat of d. 0.689 BTU/lbm-°R b. 6754 ft3
vaporization of water at 100C is 29. One kilogram of water (cv = 4.2 c. 7455 ft3
539.2 cal/g. The heat capacity at kJ/kg-K) is heated by 300 BTU of d. 6456 ft3
constant pressure, Cp is 1.0 energy. What is the change in 37. What is the change in entropy of 2
cal/gK. Determine the total change temperature, in K? kg water molecules when
in entropy. a. 17.9 K transformed at constant pressure of
a. 248.2 cal/K b. 71.4 K 1 atmosphere from water at
b. 298.2 cal/K c. 73.8 K 100degC to steam at the same
c. 348.0 cal/K* d. 75.4 K* temperature?
d. 398.2 cal/K 30. In an isentropic compression, p1 = a. 12.12 kJ/K*
23. What is true about the polytropic 200 psia, p2 = 300 psia, V1 = 10 b. 10.43 kJ/K
exponent, n , for a perfect gas in3, and k= 1.4. Find V2. c. 9.45 kJ/K
undergoing an isobaric process? a. 3.509 in3 d. 10.45 kJ/K
a. n>0 b. 4.500 in3 38. In a gaseous mixture of 20 deg. C
b. n<0 c. 5.000 in3 the partial pressures of the
c. n → infinity d. 6.095 in3* components are as follows:
d. n = 0* 31. 200 mL of oxygen are collected Hydrogen, 200 mmHg; Carbon
24. On a hot day, the temperature rises over water at 23C and a pressure Dioxide, 150 mmHg; Methane,
from 50F early in the morning to of 1 atmosphere. What volume 320 mmHg; Ethylene, 105 mmHg.
99F in the afternoon. What is the would the oxygen occupy dry at What is the mass fraction of
ratio of the concentration (in 273K and 1 atmosphere? Hydrogen ( m(H2) = 2, m(CO2) =
moles/ft3 of helium in a spherical a. 179.3 ml* 44, m(meth) = 16 and m(eth) = 30
balloon in the afternoon to the b. 184.4 ml kg/mol) ?
concentration of helium in the c. 190.0 ml a. 0.026 *
balloon in the morning? d. 194.5 ml b. 0.056
a. 0.51 32. A gas has a density of 0.094 lb/ft3 c. 0.076
b. 0.69 at 100degF and 2 atm. What d. 0.016
c. 0.91* pressure is needed to change the 39. Assume the total heat of
d. 1.10 density to 0.270 lb/ft3 at 250degF? vaporization (per gram) of water
25. Cool water at 9 deg. C enters hot- a. 7.28 atm* can be used to supply the energy
water from which warm water at a b. 6.32 atm needed to tear 1 g of water
temperature of 80 deg. C is drawn c. 3.45 atm molecules apart from each other.
at an average rate of 300 g/min. d. 5.25 atm What is the ratio of energy needed
How much average electric power 33. If atmospheric air 14.7 psia and per molecule to kT where k = 1.38
does the heater consume in order 60degF at sea level, what is the x 10-23 J/K?
to provide hot water at this rate? pressure at 12000 ft altitude if air a. 11.2
a. 4.18 kW* is incompressible. Note: @ b. 12.5
b. 2.35 kW c. 13.1 *

Prepared by: Engr. Edgar Kenneth Luna

ME 500 Coordinator
 University of Mindanao
Mechanical Engineering
Correlation Courses (ME 500)
Air Conditioning
d. 12.3 a. 1768 ft-lbf a. I
b. 1890 ft-lbf b. II
2
40. Steam at 1000 lbf/ft pressure and c. 2387 ft-lbf c. III
300°R has a specific volume of 6.5 d. 3768 ft-lbf* d. I and II *
ft3/lbm and a specific enthalpy of 49. How does an adiabatic process 55. A bicycle tire has a volume of 600
9800 lbf-ft/lbm. Find the internal compare to an isentropic process? cm3. It is inflated with CO2 to a
energy per pound mass of steam. a. Adiabatic: heat transfer = 0; pressure of 80 psi at 20C. How
a. 2500 lbf-ft/lbm Isentropic: heat transfer ≠ 0. many grams of CO2 are contained
b. 3300 lbf-ft/lbm* b. Adiabatic: heat transfer ≠ 0; in the tire?
c. 5400 lbf-ft/lbm Isentropic: heat transfer = 0. a. 3.03 g
d. 6900 lbf-ft/lbm c. Adiabatic: reversible; Isentropic: b. 4.83 g
41. Calculate the entropy of steam at not reversible. c. 5.98 g *
60 psia with a quality of 0.6. d. Both: heat transfer = 0; Isentropic: d. 6.43 g
a. 0.4274 BTU/lbm-°R reversible.* 56. When 0.5 g of a liquid is
b. 0.7303 BTU/lbm-°R 50. In an adiabatic, isentropic process, completely evaporated and
c. 1.1577 BTU/lbm-°R* p1 = 200 psia, p2 = 300 psia, and T1 collected in a 1 liter manometer,
d. 1.2172 BTU/lbm-°R = 700 °R. Find T2, using γ= 1.4. the pressure is 0.25 atmospheres
42. Find the change in internal energy a. 576 °R and the temperature is 27C.
of 5 lbm of oxygen gas when the b. 590 °R Assuming ideal behaviour,
temperature changes from 100°F c. 680 °R determine the molecular weight.
to 120°F. cv = 0.157 BTU/lbm-°R. d. 786 °R* The gas constant is R=0.0821
a. 14.7 BTU 51. Nitrogen is expanded atm/moleK.
b. 15.7 BTU* isentropically. Its temperature a. 2g
c. 16.8 BTU changes from 620 °F to 60 °F. b. 2.2 g
d. 147 BTU Find the pressure Ratio (p1/p2). c. 12.3 g
43. Determine the change in enthalpy a. 0.08 d. 49.2 g*
per lbm on nitrogen gas as its b. 12.9* 57. A 0.064 kg octane vapor (MW =
temperature changes from 500°F c. 23.2 114) is mixed 0.91 kg of air (MW
to 200°F. cp = 0.2483 BTU/lbm- d. 3547 = 29.0) in the manifold is 86.1
°R. 52. Nitrogen is expanded kPa, and the temperature is 290 K.
a. -74.49 BTU/lbm * isentropically. Its temperature Assume octane behaves ideally,
b. -72.66 BTU/lbm changes from 620 °F to 60 °F. The what is the total volume of this
c. -68.47 BTU/lbm volumetric ratio is V2/V1 = 6.22 mixture?
d. 63.78 BTU/lbm and the value of R for nitrogen is a. 0.895 cu. m. *
44. What is the resulting pressure 0.0787 BTU/lbm-°R. What is the b. 0.987 cu. m.
when one pound of air at 15 psia work done by the gas? c. 0.565 cu. m.
and 200°F is heated at constant a. -1112.7 BTU/lbm d. 0.654 cu. m.
volume to 800°F? b. -99.22 BTU/lbm 58. Determine the sp.heat weight of air
a. 15 psia c. 1112.7 BTU/lbm at 760 mmHg absolute and 22C?
b. 28.6 psia* d. 99.22 BTU/lbm* a. A.1.014 kg/m3
c. 36.4 psia 53. A device that is meant to extract b. B. 1.316 kg/m3
d. 52.1 psia power from waste process steam c. C. 1.197 kg/m3 *
45. What horsepower is required to starts w/ steam of 75% quality at d. D. 1.266 kg/m3
isothermally compress 800 ft3 of 100 psia. The exit conditions of 59. How long could a 2000 hp motor
air per minute from 14.7 psia to the steam are 70% quality at 14.7 be operated on the heat energy
120 psia? psia. Which of the following liberated by 1 mi.3 of ocean of
a. 28 Hp statements are true? water when the temperature of the
b. 108 Hp* I. The device violates the 1st law water is lowered by 1degC and if
c. 256 Hp of thermodynamics. all these heat were converted to
d. 13,900 Hp II. The device violates the 2nd law mechanical energy?
46. Calculate the work done by a of thermodynamics. a. 371.56 *
system in which 1 kg mole of III. The device generates positive b. 243.55
water completely evaporates at net power c. 384.76 yrs
100°C and 1 atmosphere pressure. IV. The device generates no net d. 376.57 yrs
a. 1000 kJ power. 60. Given that molar Cp of CO2 is 8.92
b. 2130 kJ a. I BTU (lb.moleR) and molar Cp of
c. 2490 kJ b. II N2 is 6.95 BTU/(lbmoleR), the
d. 3050 kJ* c. III* calculated Cp per pound of mixture
47. What is the equation for a work d. IV containing 25% vol. CO2 and 75%
done by a constant temperature 54. An engineer devices a scheme for vol. N2 is:
system? extracting some power from waste a. 0.23 BTU/lbR *
a. W = mRTln(V2 – V1) process steam. The steam enters a b. 2.23 BTU/lbR
b. W = mR(T2 – T1)ln V2/V1 device at 100 psi and quality 75% c. 5.21 BTU/lbR
c. W = mRTln V2/V1 * and exits at 14.7 psia and 65% d. 7.44 BTU/lbR
d. W = RTln V2/V1 quality. Which of the following 61. A mixture at 14.7 psia and 68F
48. A piston-cylinder system contains statements are true? that is 30% weight CO2 (m wt=44)
a gas which expands under a I. The produces 155 BTU/lbm of and 7% wt. N2 (m wt=28) has a
constant pressure of 1200 lbf/ft2. If work. partial pressure of CO2 in psia that
the piston is displaced during the II. The device violates 2nd law of is nearest to:
process, and the piston diameter is thermodynamics. a. 2.14
24”, what is the work done by the III. The device violates the 1st law b. 3.15 *
gas on the piston? of thermodynamics. c. 6.83

Prepared by: Engr. Edgar Kenneth Luna

ME 500 Coordinator
 University of Mindanao
Mechanical Engineering
Correlation Courses (ME 500)
Air Conditioning
d. 7.86 b. 0.20 ft3 80. Air is compressed adiabatically
62. Normal boiling point of liquid c. 0.32 ft3 * from 30degC to 100degC. If mass
oxygen is 90K. What is its temp in d. 0.40 ft3 of air being compressed is 5kg,
R? 70. Find the work possess for a helium Find the change of entropy?
a. -330R gas at 20C. a. 1.039 kj/kg
b. -183R a. 609kj/kg * b. 0.746 kj/kg
c. 162R* b. 168kj/kg c. 0*
d. 168R c. 229kj/kg d. 1.245 kj/kg
63. Shaft work of -15 BTU/lb and heat d. 339kj/kg 81. Two kilogram of air in a rigid tank
transfer of -10 BTU/lb change 71. Two kilogram of gas is confined in changes its temperature from
enthalpy of a system by: a 1m^3 tank 200kpa and 88degC. 32degC to 150degC. Find the work
a. -25 BTU/lb What type of gas is in the tank? done during the process.
b. -15 BTU/lb a. Helium a. 236
c. -10 BTU/lb b. Ethane * b. 170
d. +5 BTU/lb* c. Methane c. 195
64. A non-flow (closed) closed system d. Ethane d. 0*
contains 1lb of an ideal gas (Cp = 72. Find the enthalpy of the helium if 82. An ideal gas at 0.80 atmosphere
0.24, Cv = 0.17). The gas its internal energy is 200KJ/Kg. and 87degC occupies 0.450 liter.
temperature is increased by 10F a. 144 kj/kg How many moles are there is the
while 5 BTU of work are done by b. 223.42 KJ/kg sample? (R=0.0821 liter-
the gas. What is heat transfer in c. 333.42 KJ/kg * atm/mole-K)
BTU? d. 168 KJ/kg a. 0.0002 mole
a. -3.3 73. Compute the mass of a 2m^3 b. 0.0378 mole
b. -2.6 propane at 280 kpa and 40degC c. 0.0122 mole*
c. +6.7 * a. A.6.47 d. 0.0091 mole
d. +7.4 b. B. 5.1 83. A certain gas at 101.325 Kpa and
65. 55,000 gallons of water passes c. C. 10.20 10 degC whose volume is 2.83
through a heat exchanger and d. D. 9.47* m^3 are compressed into a storage
absorbs 28,000,000 BTU’s. The 74. Find the mass of 10 quartz of vessel of 0.31m^3 capacity. Before
exit temperature is 110F. The water admission, the storage vessel
entrance water temperature in F is a. 10.46kg contained the gas at a pressure and
nearest to: b. 9.46kg * temperature of 137.8 Kpa and 26
a. 49* c. 11.6kg degC; after admission the pressure
b. 56 d. 8.46kg has increased to 1171.8 Kpa. What
c. 68 75. Find the mass of carbon dioxide should be the final temperature of
d. 73 having a pressure of 20 psia at the gas in the vessel in kelvin?.
66. Work of polytropic (n=1.21) 200F with 10ft^3 volume. a. 298.0
compression of air ( Cp/Cv = 1.40) a. 1.04 lbs b. 319.0
in a system moving boundary from b. 1.14 lbs c. 180.0
P1 = 15 psia V1 = 1.0 ft3 to P2 = c. 1.24 lbs * d. 314.2*
150 psia V2 = 0.15 ft3. d. 1.34 lbs 84. A perfect gas has a value of R=
a. 35.5 ft.lb 76. Find the heat needed to raise the 58.8 ft-lb/lb-R and K= 1.26. if 20
b. 324 ft.lb temperature of water from 80^C to Btu are added to 10 lbs of his gas
c. 1080 ft.lb 100^C with 60% quality. Consider at constant volume when initial
d. 5150 ft.lb * an atmospheric pressure of temperature is 90 degF find the
67. A cylinder fitted with a weightless, 101.325 kpa. Use the approximate final temperature.
frictionless piston contains m enthalpy formula of liquid. a. 97 degF *
pounds of air at temperature T1 a. 293.09kj/kg b. 104 degF
volume V1, and ambient pressure b. 1,772.90 kj/kg c. 154 degF
Pa. Heat is added until the air in the c. 1,547.90 kj/kg d. 185degF
cylinder has a temperature T2, a d. 1,647.29 kj/kg * 85. Ammonia weighing 22 kgs is
volume V2, and ambient pressure 77. Find the enthalpy of water 212F confirmed inside a cylinder
Pa. The specific heat of air at and 14.7 psi dryness for factor is equipped with a piston has an
constant volume is Cp, the specific 30% use the approximate enthalpy initial pressure of 413 Kpa at 35
heat of air at constant volume is formula of liquid. degC if 3200 KJ of heat is added
Cv. The heat transferred during the a. 461 Btu/lb to the ammonia until its final
process is: b. 471 Btu/lb * pressure and temperature are 413
a. mCp (T2 - T1) c. 481 Btu/lb Kpa and 100 DegC respectively,
b. mCv (T2 - T1) – Pa(V2 - V1) d. 491 btu/lb what is the amount of work done
c. mCp (T2 - T1) + Pa(V2 - V1) 78. What is the approximate value of by the gas.
d. mCv (T2 - T1) + Pa(V2 - V1)* temperature if water having a. 667*
68. A high velocity flow gas at 800 enthalpy of 208 Btu/lb? b. 304
ft/sec possesses kinetic energy a. 138.87 deg C c. 420
nearest to which of the following? b. 115.55 deg C * d. 502
a. 1.03 BTU/lb c. 258.67 deg C 86. A tank contains 90 ft^3 of air at a
b. 4.10 BTU/lb d. 68.67deg C pressure of 350 Psig; of the air is
c. 9.95 BTU/lb 79. Convert 750R to K cooled until its pressure and
d. 12.8 BTU/lb * a. 390.33K temperature decreases to 200 Psig
69. Isentropic compression of 1 ft3 of b. 395K and 70 DegF respectively, what is
air (Cp/Cv = 1.40), at 20 psia to 100 c. 410.33K the decrease in internal energy?
psia gives a final volume of: d. 416.33K* a. 6232.09 Btu
a. 0.16 ft3 b. -5552 Btu

Prepared by: Engr. Edgar Kenneth Luna

ME 500 Coordinator
 University of Mindanao
Mechanical Engineering
Correlation Courses (ME 500)
Air Conditioning
c. 5552 Btu d. 435.29 KJ/kg b. -30 deg. C
d. -6232.09 Btu* 92. A rigid tank contains 2 kmol of N2 c. 40 deg. C
87. A large mining company was and 6 kmol of CO2 gases at 300 d. 53 deg. C
provided with a 3 m^3 of deg. K and 115 Mpa. Find the tank 97. The pressure of an automobile tire
compressed air tank. Air pressure volume using ideal gas equation. is measured to be 200 Kpa (gage)
in the tank drops from 700 kpa to a. 7.33 m^3 before the trip and 220 kpa (gage)
160 kpa while the temperature b. 5.33 m^3 after the trip at a location where
remains constants at 28 degC, c. 3.33 m^3 the atmospheric pressure is 90 kpa.
what percentage has the mass of d. 1.33 m^3* If the temperature of the air in the
air in the tank been reduced? 93. A spherical balloon with a tire before the trip is 25 deg. C, the
a. 74.00 diameter of 6 m is filled with air temperature after the trip is:
b. 72.45 helium at 20 deg. C and 200 Kpa. a. 45.6 deg. C*
c. 76.56 Determine the mole number. b. 54.8 deg C.
d. 78.57* a. 9.28 Kmol* c. 27.5 deg. C
88. steam at 2Mpa and 250deg C in a b. 10.28 Kmol d. 26.7 deg. C
rigid cylinder is cooled until the c. 11.28 Kmol 98. Water boils at 1 atm pressure in a
quality is 30%. Find the heat d. 13.28 Kmol stainless steel pan on an electric
rejected from the cylinder. 94. The air in an automobile tire with range. It is observed that 2 kg of
a. -432.23 a volume of 0.53 ft^3 is at 90 deg. liquid water evaporates in 30 min.
b. -926.26 F and 20 psig. Determine the the rate of heat transfer to the
c. -1265.02* amount of air that must be added water is
d. 1082.34 to raise the pressure to the a. 2.97 KW
89. At 1.8 Mpa, mixture steam and recommended value of 30 psig. b. 0.47 KW
water has an entropy of 3 KJ/kg Assume the atmospheric pressure c. 2.51 KW*
Deg K. find the enthalphy of the to be 14.6 psia and the temperature d. 3.12 KW
mixture. and the volume to remain constant. 99. Water is boiling in a pan on a
a. 1,627.11KJ/kg a. 0.026 lb* stove at sea level. During 10
b. 1,533.33 KJ/kg b. 0.046 lb minutes of boiling, it is observed
c. 1,234.45 KJ/kg c. 0.066 lb that 200 grams of water has
d. 1,162.40 KJ/kg* d. 0.086 lb evaporated. Then the rate of heat
90. Mixture with 70% quality at 95. A rigid tank contains 20 lbm of air transfer to the water is:
500kpa is heated isothermally until at 20 psia and 70 deg. F. more air a. 0.84 KJ/min
its pressure is 300kpa. Find the is adde to the tank until the b. 45.1 KJ/min*
heat added during the process. pressure and temperature rise to 35 c. 41.8 KJ/min
a. 745.92KJ/kg* psia and 90 deg. F, respectively. d. 53.5 KJ/min
b. 535.16 KJ/kg Determine the amount of air added 100. A one cubic meter container
c. 983.44 KJ/kg to the tank. contains a mixture of gases
d. 765.34 KJ/kg a. 11.73 lb composed of 0.02 kg/mol of
91. A tank contains exactly one b. 13.73 lb* oxygen and 0.04 kg-mol helium at
kilogram of water consisting of c. 15.73 lb a pressure of 220 Kpa. What is the
liquid and vapor in equilibrium at d. 17.73 lb temperature of this ideal gas
Mpa. If the liquid contains one- 96. A rigid tank contains 5 kg of an mixture in degrees kelvin?
third and the remaining is vapor of ideal gas at 4 atm and 40 deg. C. a. 441*
the volume of the tank, what is the Now a valve is opened, and half of b. 350
enthalpy of the contents of the mass of the gas is allowed to c. 400
tank? escape. If the final pressure in the d. 450
a. 644.40 KJ/kg tank is 1.5 atm. The final
b. 774.40 KJ/kg temperature in the tanks is:
c. 785.92 KJ/kg* a. -38 deg. C*

Prepared by: Engr. Edgar Kenneth Luna

ME 500 Coordinator