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INSTRUCTION: Solve or familiarize the answers 7. A refrigerator system consumed 28,800kw-hr
of the following very probable problems. per month of energy. These are 20% of
energy is lost due to cooling system of
1. The refrigerant volume flow rate at the compressor and motor efficiency is 90%. If
entrance of compressor were obtained from a COP of the system is 6, find the tons of
test on a twin cylinder, single acting 15 refrigeration of the system?
cm x 20 cm, 320 rpm compressor ammonia
refrigerating a plant to be 33 L/s. A. 43.15 TR
Determine the volumetric efficiency of the
compressor? B. 46.15 TR

A. 77.65% C. 49.15 TR

B. 87.6% D. 41.15 TR

C. 97.6% 8. A 23 tons refrigerator system has a heat

rejected of 100 kW. Find the energy
D. 65.65% efficiency ratio of the system?

2. Compute the humidity ratio of air at 70% A. 13.42

relative humidity and 25 ℃ when the
B. 14.42
barometric pressure is 101.325 kPa from
steam tables. Psat @34C=3.169 KPa? C. 15.42
A. 0.014 kg water vapor/kg dry air D. 6.83
B. 0.14 kg water vapor/kg dry air 9. If the energy efficiency ratio of the
refrigeration system is 12.6, what is the
C. 1.4 kg water vapor/kg dry air
COP of the system?
D. 0.0014 kg water vapor/kg dry air
A. 3.69
3. Compute the air flow in 𝑓𝑡 3 /𝑚𝑖𝑛 of
B. 4.23
mechanical ventilation required to exhaust
an accumulation of refrigerant due to leaks C. 5.92
of the system capable of revolving air from
the machinery room for a mass of 4 kg D. 6.83
refrigerant?
10. A refrigerator plant is rated at 15 tons
A. 200 capacity. How many pounds of air per hour
will it cool from 70 to 90℉ at constant
B. 210 pressure?
C. 220 A. 50,000 lb/hr
D. 230 B. 37,500 lb/hr
4. Compute the free-aperture cross-section in C. 52,000 lb/hr
𝑚2 for the ventilation of a machinery room
if the mass of refrigerant is 9 kg. D. 45,000 lb/hr

A. 0.3214 11. A basic refrigeration cycle requires 25 kW

when operating at a condenser temperature
B. 0.414 of 70 ℃ and a COP of 3.50. Determine the
sink temperature?
C. 0.5144

D. 0.614 A. -8.22 ℃

5. Wet material containing 220% moisture (dry B. -12.22 ℃

basis) is to be dried at the rate of
C. -10.22 ℃
1.5kg/s in a continuous dryer to give a
product containing 10% (dry basis). Find D. -6.22 ℃
the moisture removed, kg/hr.
12. An ice plant produces 15cm x 5cm x 100cm
A. 3543.75 kg/hr
ice block using brine at -12 ℃. What is
B. 3513.75 kg/hr the approximate freezing time per block?

C. 3563.75 kg/hr A. 11.5hrs

D. 3563.75 kg/hr B. 15.5hrs

6. Copra enters a dryer containing 70% C. 13.3hrs

moisture and leaves at 7% moisture. Find
D. 17.5hrs
the moisture removed on each pound of solid
in final product? 13. A cold storage plant has an average wall
gain load of 11 KW and air change head of 5
A. 6.258 lb
KW. The plant is used to cool 18.6 MT of
B. 1.258 lb product (c = 3.85 KJ/kg ℃) from 30 ℃ to
40 ℃ in 24 hrs. If the plant operates18hrs
C. 4.258 lb per day, what is the ref. capacity?
D. 2.258 lb A. 10.1 TR
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B. 12.6 TR B. 15.67%

C. 11.5 TR C. 21.48%

D. 13.5 TR D. 10.28%

14. Re-circulated air of 10kg/s with 53 KJ/kg 20. A refrigerant compressor has a theoretical
dry air enthalpy and outside air of 4 kg/s piston displacement of 8.04 𝑚3 /s. The
with 90 KKJ/kg dry air enthalpy enters the refrigerant enters the compressor with a
conditioning unit. Determine the air density of 16kg/ 𝑚3 . The enthalpy of the
conditioning capacity of air conditioning refrigerant increases by 101 KJ/kg across
apparatus if supply enthalpy to conditioned the evaporator. What is the refrigerating
space is 42 dry air? capacity of the system?
A. 154 KW A. 10 TR
B. 302 KW B. 20 TR
C. 214 KW C. 15 TR
D. 4.484 KW D. 25 TR
15. 30 kg/s of dry air enters an adiabatic 21. An ice plant produces 20 tons of ice per
drying chamber at 88℃ and with a humidity day at -16℃ from water at 25 ℃. If
ratio of 0.16 kg/kg d.a. the exhaust air miscellaneous losses are 12% of the
leaves the drying chamber at 40℃. What is freezing and chilling load. Calculate the
the rate of water removal in the drying refrigerating capacity of the plant in TR?
chamber?
A. 21.35 TR
At 40 ℃, Psat. = 7.357 kPa; at 88℃, hg =
26565.9 KJ/kg. B. 31.5 TR

A. 0.24 kg/s C. 43.12 TR

B. 0.46 kg/s D. 36.3 TR

C. 0.38 kg/s 22. A Carnot refrigeration system operates at

𝑇𝑚𝑎𝑥 / 𝑇𝑚𝑖𝑛 = 1: 5. Find the KW per ton of
D. 0.58 kg/s refrigeration?

16. Compute the specific volume of an air- A. 1.91

vapor mixture in cubic meters per kilogram
of dry air when the following conditions B. 2.15
prevail: t = 40℃, w = 0.015 kg/kg, and
C. 1.76
𝑃𝑡 = 100𝑘𝑃𝑎?
D. 1.55
A. 0.99𝑚3 /kg
23. A water cooler uses 50 lb/hr of melting
B. 0.89 𝑚3 /kg ice to cool running water from 80℉ to 42℉.
Based on the inside coil area, 𝑈1 =
C. 0.79 𝑚3 /kg
110 𝐵𝑡𝑢 /hr- 𝑓𝑡 2 -F. Find the gpm of water
D. 0.69 𝑚3 /kg cooled.

17. Compute the humidity ratio of air A. 0.10 GPM

considering the density at 27℃ and 98 kPa
B. 0.21 GPM
IS 1.32kg/𝑚3 ?
C. 0.38 GPM
A. 0.34 𝑘𝑔𝑣𝑎𝑝𝑜𝑟 / 𝑘𝑔𝑎𝑖𝑟
D. 0.45 GPM
B. 0.43 𝑘𝑔𝑣𝑎𝑝𝑜𝑟 / 𝑘𝑔𝑎𝑖𝑟
24. An auditorium seating 1500 people is to be
C. 0.35 𝑘𝑔𝑣𝑎𝑝𝑜𝑟 / 𝑘𝑔𝑎𝑖𝑟 maintained at 80℉ dry bulb and 65℉ wet
bulb temperature when outdoor air is 91℉
D. 0.53 𝑘𝑔𝑣𝑎𝑝𝑜𝑟 / 𝑘𝑔𝑎𝑖𝑟
dry bulb and 75℉ wet bulb. Solar heat
18. If the actual COP is 5.0, the indicated loads is 110,000 Btu/hr and supply air is
hp/ton of refrigeration is? at 60℉, determine the amount of supply air?

A. 4.71 HP/TR A. 93,229.17*

B. 24.26 HP/TR B. 83,229.17

C. 0.889 HP/TR C. 73,229.17

D. 0.94 HP/TR D. 63,229.17

19. An evaporator has a temperature of 3℃ with 25. At 35% solution leaves the absorber and 30%
the entrance enthalpy of 352.75 KJ/kg. At solution enters the absorber. The heat
3 ℃ hf = 319.56 KJ/kg and hg = 642.45 removed from the absorber by cooling water
KJ/kg. Find the equality after the is 547.6 Btu and ammonia is superheated by
expansion? 10°. Find the pound per pound of ammonia
gas from the evaporating coils?
A. 16.27%
A. 11
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B. 14 B. 50.4 KJ

C. 13 C. 15,156 KJ

D. 12 D. 1,863 KJ

26. Consider a refrigeration whose 40 watts 31. A classroom that normally contains 40
light bulb remains on continuously as a people is to be air-conditioned with window
result of a malfunction of the switch. If air-conditioning units of 5 KW cooling
the refrigerator has a COP of 1.3 and the capacity. A person at rest may be assumed
cost of electricity is 8 cents per kw-hr, to dissipate heat at a rate of about 360
determine the increase in the energy KJ/hr. These are 10 light bulbs in the room,
consumption of the refrigerator and its each with a rating of 100 watts. The rate
cost per year if the switch is not fixed? of heat transfer to the classroom through
the temperature of 21°C.
A. P49.59
A. 1 unit
B. P47.59
B. 2 units
C. P45.59
C. 3 units
D. P43.59
D. 4 units
27. A 75 hp motor that has an efficiency of 91%
is worn out and is replaced by a high- 32. In order to cool 1 ton (1000 kg) of water
efficiency motor that has an efficiency of at 20°C in an insulated tank, a person
95.4%. Determine the reduction in heat gain pours 80 kg of ice at -5°C into the water.
of the room due to higher efficiency under Determine the final equilibrium temperature
full-load conditions? in the tank. The melting temperature and
the heat of fusion of ice at atmospheric
A. 2.24 KW pressure are 0°C and 333.7 KJ/kg,
B. 2.44 KW respectively?

C. 2.64 KW A. 12.43 deg C

D. 2.84 KW B. 14.43 deg C

28. A household refrigerator that has a power C. 16.43 deg C

input of 450 watts and a COP of 2.5 is to D. 18.43 deg C
cool five large watermelons, 10 kg each, to
8 deg C. if the watermelons are initially 33. A thermoelectric refrigerator that
at 20 deg C, determine how long will it resembles a small ice chest is powered by a
take for the refrigerator to cool them. The car battery, and has a COP of 0.10. If the
watermelons can be treated as water whose refrigerator cools a 0.350 L canned drink
specific heat is 4.2 KJ/kg- °K? from 20 deg C to 40 deg C I 30 min,
determine the average electric power
A. A.2220 seconds consumed by the thermoelectric refrigerator?
B. B. 2230 seconds A. 130 W
C. C. 2240 seconds B. 110 W
D. D. 2250 seconds C. 120 W
29. When a man returns to his wall-sealed D. 140 W
house on a summer day, he finds that the
house is at 32°C. He returns on the air 34. A Carnot refrigerator operates in a room
conditioner which cools the entire house at in which the temperature is 25°C and
20°C in 15 minutes. If COP is 2.5, consumes 2 KW of power when operating. If
determine the power drawn by the air the food compartment of the refrigerator is
conditioner. Assume the entire mass within to be maintained at 3°C, determine the rate
the house is 800kg of air for which 𝑐𝑣 = 0.72 of heat removal from the food compartment?
KJ/kg-𝑘1 𝐶𝑝 = 1.0KJ/kg-K?
A. 1504.8 KJ/min
A. 1.072 KW
B. 1625 KJ/min
B. 2.072 KW
C. 12.86 KJ/min
C. 3.072 KW
D. 9.57 KJ/min
D. 4.072 KW
35. A household refrigerator with EER 8.0
30. A supply of 50kg chicken at 6°C contained removes heat from the refrigerated space at
in a box is to be frozen to -18°C in a a rate of 90 KJ/min. determine the rate of
freezer. Determine the amount of heat that heat transfer to the kitchen air?
needs to be removed. The latent heat of the
A. 101.25 KJ/min
chicken is 247 KJ/kg, and its specific heat
is 3.32 KJ/kg-C above freezing and 1.77 B. 128.46 KJ/min
KJ/kg-C below freezing. The container box
is 1.5 kg, and the specific heat of the box C. 63.05 KJ/min
material is 1.4 KJ/kg-C. Also the freezing
D. 80 KJ/min
temperature of chicken is -2.8°C?

A. 15,206.4 KJ
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36. An air-conditioning system is used to B. 15.5 hp
maintain a house 75℉ when the temperature
C. 18.61 hp
outside is when 95℉. The house is gaining
heat through the walls and windows at a D. 21.9 hp
rate of 1250 Btu/min, and the heat
generation rate within the house from 41. A Freon 22 air conditioning under standard
people, lights and appliances amounts to operating conditions of 35℃ condensing and
350 Btu/min. Determine the minimum power 5℃ evaporating temperatures. The volume
input required for this air-conditioning flow rate entering the compressor is 23.72
system? L/s. Determine the refrigerating effect is
164.kJ/kg. From the table for R22 the
A. 10.06 hp specific volume at the compressor entrance
B. 1.41 hp is 40.36 L/kg.

C. 1.36 hp A. 393.3 TR

D. 7.94 hp B. 96.4 TR

37. A refrigeration system is to cool bread C. 79.3 TR

loaves with an average mass of 450 g from D. 27.4 TR
22℃ to -10 ℃ at a rate of 500 loaves per
hour by refrigerated air. Taking the 42. The refrigerant volume flow rate at the
average specific and latent heats of bread entrance of compressor were obtained from a
to be 2.93 kJ/kg. ℃ and 109.3 kJ/kg, test on a twin cylinder, single acting 15cm
respectively, determine the product load? x 20cm, 320 rpm compressor ammonia
refrigerating plant to be 33 L/s. Determine
A. 541.7 kJ/min the volumetric efficiency of the compressor?
B. 761.5 kJ/min A. 77.65%
C. 351.6 kJ/min B. 97.6%
D. 409.9 kJ/min C. 87.6%
38. A house that was heated by electric D. 65.65%
resistance heaters consumed 1200kWh of
electric energy in a water month. If this 43. A vapor compression refrigeration system
house were heated instead by a heat pump is designed to have a 80 tons refrigerating
that has an average performance factor, PF nof refrigeration. Its actual COP is 4 and
of 2.4, determine how much money the 30 percent of the power supplied to the
homeowner would be saved that month. Assume compressor is lost in the form of friction
a price of 0.085$/kWh for electricity? and cylinder losses. Determine condenser
cooling water required for a temperature
A. $42.5 rise of 10℃?
B. $102 A. 5.63 kg/s
C. $59.50 B. 4.47 kg/s
D. $97.75 C. 7.82 kg/s
39. An ammonia simple saturation cycle D. 9.0 kg/s
operates with a suction pressure of 291.6
kPa and a condenser pressure of 1204 kPa 44. A twin cylinder ammonia compressor with
develops 15 tons of refrigeration. volume displacement of 14,726 𝑐𝑚3 operates
Determine the theoretical horsepower of the at 300 rpm. Condenser and evaporator
compressor. The following enthalpies have pressure are 1200 kPa and 227 kPa
been found: condenser entrance = 1653 respectively. Specific volume of
kJ/kg, exit = 346.6 kJ/kg; compressor refrigerant at the entrance of compressor
entrance = 1450.2 kJ/kg, exit = 1653 kJ/kg? is 528.6 L/kg. Compression process is
polytropic with n = 1.20 and clearance
A. 7.23 hp factor of compressor is 2 percent.
B. 15 hp Determine horsepower required?

C. 13 hp A. 60 hp

D. 8.23 hp B. 80 hp

40. An ammonia ice plant operates between a C. 70 hp

condenser temperature of 35°C and D. 90 hp
evaporator of -15°C. It produces 10 metric
tons of ice per day from water at 30°C to 45. A reversed Carnot cycle has a
ice at -5°C. Assuming simple saturation refrigerating COP of 2.5. Determine the
cycle, determine the horsepower of the ratio 𝑇𝐻 /𝑇𝐿 ?
motor if the adiabatic efficiency of the
compressor 𝑛𝑐 = 0.85 and mechanical A. 1.4
efficiency 𝑛𝑚 = 0.95. The specific heat of B. 1.25
ice is 2.094 kJ/kg.°C and the latent heat
is 335 kJ/kg? C. 1.5

A. 17.68 hp D. 1.2
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46. Three thousand cubic feet per minute of requires 10.12kWc compressor power and low-
air cooled condenser. If the load on the loop 15.93 kW, determine the COP of the
condenser is 64,800 Btu/hr, compute the system?
temperature rise of the air passing over
the condenser. Specific volume of standard A. 2.027 TR
air (13.34 𝑓𝑡 3 /lb)? B. 3.314 TR
A. 10℉ C. 5.22 TR

B. 20℉ D. 9.1 TR

C. 15℉ 51. When a man returns to his well-seated

house on a summer day, he finds that the
D. 25℉ house is at 32°C. he turns on the air
conditioner, which cools the entire house
47. Saturated vapor ammonia at -16°C(ℎ1 =1442.60
to 20°C in 5 min. if COP of the air-
kJ/kg) leaves the evaporator and enters the
conditioner system is 2.5, determine the
compressor at -6°C ( ℎ1 = 1465 kJ/kg). The power drawn by the air conditioners. Assume
refrigerant leaves the condenser as the entire mass within the house is
saturated liquid at 40°C (ℎ4 = 390.6kJ/kg)and equivalent to 800 kg of air for which c =
enter the expansion valve at 35°C ( ℎ5 = 0.72 kJ/kg.°C?
366.1kJ/kg) . Heat rejected from the
condenser amount to 50kW. The work to A. 7.68 kW
compressor is 208 kJ/kg , while the heat B. 19.2 Kw
loss from the compressor is 33 kJ/kg. if 95
kJ/kg of heat are lost in the piping C. 3.07 kW
between the compressor discharge and
D. 12.03 kW
condenser inlet, determine the
refrigerating capacity of the system? 52. It is desired to double the COP of a
reversed carnot engine for cooling from 5.0
A. 49.5 TR
by raising the temperature of heat addition
B. 12.88 TR while keeping the temperature of heat
rejection constant. By what percentage must
C. 46.61 TR the temperature of heat addition be raised?

D. 13.24 TR A. 10.1%

48. In an actual refrigeration cycle using R12 B. 8.1 %

as working fluid, the refrigerant flow rate
is 0.05kg/s. vapor enters the expansion C. 9.1 %
valve at 1.15 Mpa, 40°C(h=238.5 kJ/kg) and
D. 7.1 %
leaves the evaporator at 175 kPa, -15°C (h
= 345 kJ/kg). The electric input to motor 53. A single acting compressor has a
driving the compressor is measured and volumetric efficiency of 87%, operates at
found 3.0 kW. Motor efficiency at this load 500rpm. It takes in ammonia at 227 kPa and
is 92 percent and mechanical efficiency 82%. discharges it at 1204 kPa. The ammonia
Determine the actual coefficient of handled is 4.13 𝑚3 /min measured at the
performance for this cycle? discharge condition. If the compression is
polytropic with n = 1.20, determine the
A. 1.58
piston displacement per stroke.
B. 1.78
A. 0.0095 𝑚3
C. 2.36
B. 16.59 𝑚3
D. 1.34
C. 19.7 𝑚3
49. In an ammonia refrigeration system the
temperature in the evaporator is -12°C and D. 0.03814 𝑚3
the ammonia at the evaporator entry is
0.1511 dry while at exit is 0.95 dry. If 54. An ammonia water-cooled compressor
the rate of ammonia circulation is 5.64 receives the refrigerant at specific volume
kg/min, determine the refrigerating 62 L/kg. It has a piston displacement rate
capacity of the system. Enthalpy of of 5 𝑚3 /min. If a squirrel cage motor
saturated liquid and vapor at -12°C is running at 1200 rpm drives the compressor
144.929 kJ/kg and 1447.74 Kj/kg and average piston speed is 490 m/min,
respectively? calculate size of cylinder bore?

A. 17.82 TR A. 20.4 cm

B. 27.82 TR B. 16.13 cm

C. 34.82 TR C. 26.0 cm

D. 4.82 TR D. 13.6 cm

50. A two stage cascade vapor compression 55. A room contains air at 20° Celsius and 96
refrigeration system uses ammonia in the kPa at a relative humidity of 75%.
low-temperature loop and R-12 in the high- Determine the enthalpy of moist air where:
temperature loop. The ammonia provides 15 (Psat@ 20° Celsius = 2.339 kPa)(hg @ 20°
tons cooling. If the high-loop temperature Celsius = 2538.1 KJ/kgda)?
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A. 45.919 KJ/kgda economy, what would you recommend to this
manufacturer?
B. 45.515 KJ/kgda
A. Fix the temperature of condenser and
C. 49.515 KJ/kgda increase the temperature of the
D. 41.815 KJ/kgda evaporator by 25 K.

56. Determine the mass of water vapor B. Fix the temperature of condenser and
decrease the temperature of the
contained in a 150 𝑚3 room at 100 kPa, 23℃
evaporator by 25 K.
40 % relative humidity. From steam tables:
Psat @ 23 ℃ = 2.810 kPa? C. Fix the temperature of evaporator and
increase the temperature of the
A. 1.6342 kg
evaporator by 25 K.
B. 1.2342 kg
D. Fix the temperature of evaporator and
C. 1.9342 kg decrease the temperature of the
evaporator by 25 K.
D. 2.2342 kg
62. A creamer must cool 40,000 liters of milk
57. Specific volume is the number of cubic received each day from initial temperature
meters of mixture per kilogram of dry air. of 20°C to final temperature of 2°C in 10
If dry air has these following properties: hours. If refrigeration losses amount to 30%
Ra = 287 J/kg K, T = 303 K, Pa = 99.604 kPa. of the cooling load, what must be the
Solve for specific volume? capacity of the refrigerating machine if
the specific heat of milk is 0.93 Btu/lb-R
A. 0.873 𝑚3 /kg and SG = 1.15?
B. 0.953 𝑚3 /kg A. 33 TR

C. 0.853 𝑚3 /kg B. 43 TR

D. 0.783 𝑚3 /kg C. 38 TR

58. Compute the humidity ratio of air at 70% D. 48 TR

relative humidity and 25℃ when the
63. A refrigeration system produces 250 Btu/lb
barometric pressure is 101.325 kPa. From
of cooling. In order to have a rating of
steam tables: Psat at 34 ℃ = 3.169 kPa.
one ton of refrigeration, what mass of
A. 0.014 kg water vapor/kg dry air refrigerant shall be used in the
refrigeration system?
B. 0.14 kg water vapor/kg dry air
A. 1152 lb/day
C. 1.4 kg water vapor/kg dry air
B. 180 lb/hr
D. 0.0014 kg water vapor/kg dry air
C. 1920 lb/day
59. An inventor claims to have developed a
refrigeration unit which maintains the D. 360 lb/hr
refrigerated space at 20℉. He claims a 64. Express ten tons of refrigeration in
coefficient of performance of at least 7.50. CHU/hr?
How do you evaluate his claim?
A. 840
A. No data available to evaluate the claim
B. 2257
B. Possible
C. 970.3
C. Impossible
D. 66,666.67
D. More observation are required
65. A standard vapor compression refrigeration
60. A 200 mm x 300 mm ammonia water cooled system requires a compressor work of 5kW.
compressor at 1200 rpm receives refrigerant The condenser releases 15 kJ/s of heat.
at 200 kPa, -10℃, h = 1442 kJ/kg, 619.9 Determine the amount of air to be
L/kg specific volume and is compressed to a conditioned if the decrease in enthalpy at
final pressure and h = 1759 kJ/kg, k of the air conditioning unit is 50 kJ/kg?
ammonia. Calculate the work of the
compressor in horsepower? A. 0.40

A. 317 B. 0.60

B. 713 C. 0.20

C. 425 D. 0.80

D. 524 66. The refrigerant load of vapor compression

refrigeration system is 50 kJ/kg. The COP
61. A manufacturer of canot refrigerators has is 6. The enthalpy of the refrigerant
the choice of varying either the evaporator leaving the compressor is 85 kJ/kg.
temperature, 𝑇1 = 250 K or the condenser Determine the enthalpy entering the
temperature 𝑇2 = 500 K by plus or minus 25 K; compressor?
no restrictions are placed on the operating
A. 72 kJ/kg
temperatures. In the best interest of
B. 83 kJ/kg
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C. 77 kJ/kg B. 90 KJ/min

D. 88 kJ/kg C. 50 KJ/min

67. A 3-hp refrigerator of heat pump operates D. 140 KJ/min

between 0 ℉ and 100 ℉. The maximum
73. The rate of heat transfer to the
theoretical heat that can be transferred
surroundings from a person at rest is about
from the hot reservoir is nearest to?
400 KJ/hr. suppose that the ventilation
A. 76,000 Btu/hr system fails in an auditorium containing
120 people and assuming that the energy
B. 23,000 Btu/hr goes into the air of volume 1500 𝑚3
C. 13,000 Btu/hr initially at 300 deg K and 101 kPa,
calculate the rate in deg C/min of air
D. 43,000 Btu/hr temperature change?

68. What is the enthalpy of a refrigerant A. 0.81

entering the compressor in kJ/kg if the COP
of the refrigeration system is 4.80 and the B. 0.53
compressor work is 207.30 kJ/kg? The C. 0.63
enthalpy at the entrance of the evaporator
is 58.20 kJ/kg? D. 1.0

A. 1035.24 kJ/kg 74. What is the clearance volumetric

efficiency of an ammonia compressor
B. 1520.42 kJ/kg designed with 4% clearance and operating
C. 1043.25 kJ/kg between condenser temperature of 30℃ (Psat
= 1.1672 Mpaa) and evaporator temperature
D. 1053.24 kJ/kg of 4℃ (Psat = 497.48 kPaa)?
69. A refrigeration system operates on an A. 93.61%
ideal vapor compression using R-12 with a
saturated temperature -1.1℃ B. 96.31%
( ℎ𝑔 = 351.003kJ/kg ) and a liquid R-12 C. 93.68%
temperature at 30℃ ( ℎ𝑓 = 288.54kJ/kg ). What
is the mass flow rate of the refrigerant if D. 93.83 %
the refrigerating capacity is 1.776 TR in
75. A 10 kg/s of air enters the theater at
kg/s?
16 °C. The theater is to be maintained at
A. 0.40 kg/s 27 °C DB and 20 °C WB. If the sensible heat
ratio is 0.71, what is the latent heat load
B. 0.20 kg/s of the theater?
C. 0.30 kg/s A. 45.21 kW
D. 0.10 kg/s B. 110.682 kW
70. Ten gallons per minute of cooling water C. 54.21 kW
undergo an 8 °C temperature rise during
passage through a shell and tube condenser. D. 42.51 kW
If the refrigerant flow rate is 3kg/min and
76. The approach and efficiency of cooling
the tons of refrigeration is 5.15, what is
tower are 10 °C and 65%, respectively. If
the work of isentropic compression kJ/kg?
the temperature of water leaving the tower
A. 40 is 27 °C, determine the temperature of
water entering the tower?
B. 70
A. 54.57 °C
C. 60
B. 45.57 °C
D. 80
C. 55.47 °C
71. A businessman after feasibility study
found out that the ice consumption of his D. 54.75 °C
locality to be 48,000 kg of ice per day. He
77. An air-vapor mixture has a dry bulb
wants to manufacture at -10 °C from water
temperature of 30 °C and a humidity ratio
available at 25 °C. The estimated COP of
of 0.015 kg/kg d.a., calculte the enthalpy
the refrigeration system is 3.20. Determine
of the moist air?
the capacity of the compressor in hp?
A. 68.527 kg/kg d.a
A. 207
B. 65.827 kg/kg d.a
B. 107
C. 86.527 kg/kg d.a
C. 80
D. 67.528 kg/kg d.a
D. 190
78. A carnot refrigerator is to remove heat
72. A household with a COP of 1.8 remove heat
from a cooled space at a rate of 18 00
from a refrigerant space at rate of 0.90
kJ/hr to maintain the temperature at -8 °C.
KJ/min. determine the rate of heat transfer
If the air surrounding the refrigerator
to the kitchen air?
25 °C, determine the minimum power required
A. 40 KJ/min for the refrigerator?
 VIP - 4 REF/AIRCON
__________________________________________________________________________________________________
A. A. 0.723 kW

B. B. 0.623 kW

C. C. 0.523 kW

D. D. 0.423 kW

79. A 5m x 4m x 4m room has an air

temperature of 32 °C (Psat = 4.559 kPaa,
ℎ𝑔 = 2559.9 𝑘𝐽/𝑘𝑔)and the pressure is 101 kPaa.
The mass of water vapor in air is 2.5 kg
with 𝑅𝑣 = 0.45kJ/kg- °K. What is the relative
humidity of the air?

A. 94.08%

B. 84.08%

C. 74.08%

D. 64.08%

80. Fish weighing 11 000 kg with a

temperature of 20 °C is brought to a cold
storage and which shall be coolled to -
10 °C in 11 hours. Find the required plant
refrigerating capacity in Trif the
specifi9c heat of fish is 0.7 kCal/kg-°C
above freezing and 0.30 kCal/kg-°C below
freezing point that is -3 °C. The latent
heat of freezing is 55.5 kCal/kg?

A. 25.26

B. 15.26

C. 14.38

D. 24.38

81. A refrigeration system operates on the

reversed carnot cycle. The minimum
temperature are -25C and 72 C, respectively.
If the heat rejected at the condenser is
6000 kJ/min, find the tons of refrigeration
required?

A. 20.44 TR

B. 42.20 TR

C. 24.40 TR

D. 44.20 TR

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