Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 6th Sem New 2161908 Refrigeration And Air Conditioning Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VI(NEW) ? EXAMINATION ? SUMMER 2019
Subject Code:2161908 Date:29/05/2019
Subject Name:Refrigeration and Air Conditioning
Time:10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of Refrigeration Air-Conditioning charts and Steam tables is permitted
Q.1 (a) What is the difference between Refrigeration & Heat pump How
is the effectiveness of refrigeration system is measured.
03
(b) Explain the method of designation of refrigerant with example. 04
(c)
Explain in brief simple air ?refrigeration system. Show processes on T-s
diagram and derive equation of COP in terms of temperatures.
07
Q.2 (a) Why air craft cooling is required? Explain. 03
(b) What is the effect of sub-cooling on the performance of vapour
compression refrigeration system ?
04
(c) Explain the effect of suction pressure & delivery pressure on
performance of vapour compression refrigeration using P-H & T-s
diagram
07
OR
(c) A refrigeration machine is required to produce ice at 0 ?C from
water at 20 ?C. The machine has a condenser temperature of 25 ?C
while evaporator temperature is -5 ?C. The relative efficiency of
the machine is 50% and 6 kg of Freon-12 is circulated through the
system per minute. The refrigerant enters in the compressor with
dryness fraction of 0.6. Calculate the amount of ice produced in 24
hrs. Take latent heat of ice 335 kJ/kg
Temperature
(?C )
Liquid Heat
(KJ/Kg)
Latent Heat
(KJ/Kg)
Entropy of
Liquid
(KJ/Kg K)
25 59.7 138 0.2232
-5 31.4 154 0.1251
07
Q.3 (a) Explain two physical & two thermodynamic properties of
Refrigerant.
03
(b)
State Various evaporator in use. Compare flooded and DX(dry
expansion)type evaporator
04
(c)
A single compressor using R-12 as refrigerant has three evaporators of
capacity 30TR, 20TR and10TR.The temperature in the three evaporators
is to be maintained at -10
o
C , 5
o
C and 10
o
C respectively. The condenser
pressure is 9.609 bar. The liquid refrigerant leaving the condenser is sub-
cooled to 30
o
C. The vapour leaving the evaporators is dry and saturated.
Assuming isentropic compression, calculate (a) the mass of refrigerant
flowing through each evaporator; (b) the power required to drive the
compressor; and (c) C.O.P. of the system.
07
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Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VI(NEW) ? EXAMINATION ? SUMMER 2019
Subject Code:2161908 Date:29/05/2019
Subject Name:Refrigeration and Air Conditioning
Time:10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of Refrigeration Air-Conditioning charts and Steam tables is permitted
Q.1 (a) What is the difference between Refrigeration & Heat pump How
is the effectiveness of refrigeration system is measured.
03
(b) Explain the method of designation of refrigerant with example. 04
(c)
Explain in brief simple air ?refrigeration system. Show processes on T-s
diagram and derive equation of COP in terms of temperatures.
07
Q.2 (a) Why air craft cooling is required? Explain. 03
(b) What is the effect of sub-cooling on the performance of vapour
compression refrigeration system ?
04
(c) Explain the effect of suction pressure & delivery pressure on
performance of vapour compression refrigeration using P-H & T-s
diagram
07
OR
(c) A refrigeration machine is required to produce ice at 0 ?C from
water at 20 ?C. The machine has a condenser temperature of 25 ?C
while evaporator temperature is -5 ?C. The relative efficiency of
the machine is 50% and 6 kg of Freon-12 is circulated through the
system per minute. The refrigerant enters in the compressor with
dryness fraction of 0.6. Calculate the amount of ice produced in 24
hrs. Take latent heat of ice 335 kJ/kg
Temperature
(?C )
Liquid Heat
(KJ/Kg)
Latent Heat
(KJ/Kg)
Entropy of
Liquid
(KJ/Kg K)
25 59.7 138 0.2232
-5 31.4 154 0.1251
07
Q.3 (a) Explain two physical & two thermodynamic properties of
Refrigerant.
03
(b)
State Various evaporator in use. Compare flooded and DX(dry
expansion)type evaporator
04
(c)
A single compressor using R-12 as refrigerant has three evaporators of
capacity 30TR, 20TR and10TR.The temperature in the three evaporators
is to be maintained at -10
o
C , 5
o
C and 10
o
C respectively. The condenser
pressure is 9.609 bar. The liquid refrigerant leaving the condenser is sub-
cooled to 30
o
C. The vapour leaving the evaporators is dry and saturated.
Assuming isentropic compression, calculate (a) the mass of refrigerant
flowing through each evaporator; (b) the power required to drive the
compressor; and (c) C.O.P. of the system.
07
2
OR
Q.3 (a) Explain hermetically sealed compressor. 03
(b)
Explain construction and working of Thermostatic Expansion valve with
neat sketch
04
(c) With a diagram explain Li-BR Vapor absorption refrigeration
system and write its application.
07
OR
Q.4 (a) What is relative humidity ? Derive its equation in terms of degree
of saturation.
03
(b)
Define following term related to psychrometry
1. Wet bulb temperature
2. Dry bulb temperature
3. Dew point temperature
4. Specific humidity
04
(c) Explain (i)Heating & humidification
(ii)Cooling & Dehumidification
07
OR
Q.4 (a) What is the difference between Vapour compression refrigeration
& Vapour absortion refrigeration system.
03
(b) Explain adiabatic mixing of two stream in steady flow process with
Binary mixture.
04
(c)
A circular duct of 40 cm is selected to carry air in an air conditioned
space at a velocity of 440 m/min to keep the noise level at desired level.
If this duct is replaced by a rectangular duct of aspect ratio of 1.5, find
out the size of rectangular duct for equal friction method when (a) the
velocity of air in two ducts is same, (b) the discharge rate of air in two
ducts is same
07
Q.5 (a) Explain Air Washer? 03
(b)
What is effective temperature? What factors affect effective temperature
04
(c)
State and explain various heat loads to be considered for cooling load
calculations of a typical building.
07
OR
Q.5 (a)
Explain Spray type dehumidifier.
03
(b)
List out factors governing human comfort. Define Effective Temperature
04
(c)
With line diagram explain Central Air-conditioning system of any multi
storey building
07
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This post was last modified on 20 February 2020