Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Winter 6th Sem New 2161406 Food Refrigeration And Air Conditioning Previous Question Paper
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VI (New) EXAMINATION ? WINTER 2019
Subject Code: 2161406 Date: 11/12/2019
Subject Name: Food Refrigeration & Air - Conditioning
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Answer the following: 03
(i) Give main technical criteria for selection of refrigerants based on safety.
(ii) Give measures to prevent Ozone layer depletion.
(i)
(iii) How leakage of refrigerants is detected?
(b) Answer the following: 04
(i) Give R designation of NH3.
(ii) What is the function of TEV in VCRS?
(iii)Show that 10TR = 35.167 kW
(iv) What are radial flow fans?
(c) Explain the construction and operation of simple Ammonia ? Water VAR system. Justify
the statement mathematically. In a given vapour absorption system, heating, cooling and
refrigeration take place at temperatures of 107
0
C, 26
0
C & - 30
0
C respectively. Calculate
the maximum theoretical COP of the system.
07
Q.2 (a)
A 100 TR simple vapour compression refrigeration system is operating between evaporating and
condensing temperatures of -20
o
C and 40
o
C respectively. Calculate the following:
i. Compressor discharge enthalpy in kJ
ii. Compressor power required per TON of refrigeration.
Properties of Refrigerant
t (
o
C) P
(bar)
h f
(kJ/kg)
h g
(kJ/kg)
s f
(kJ/kgK)
s g
(kJ/kgK)
v f
(m
3
/kg)
v g
(m
3
/kg)
-20 1.5 181 342.7 0.93 1.56 0.68x10
-3
0.108
40 9.6 238.5 367 1.13 1.5 0.789x10
-3
0.0182
Given: Specific heat of refrigerant vapours in the superheated region C pv = 0.65 kJ/kg K
03
(b) Explain the thermodynamic criteria for selection of refrigerants. A simple vapour
compression refrigeration system is operating on the following conditions:
Refrigeration capacity = 50 TR, Evaporating temperature = - 2
o
C
Condensing temperature = 42
o
C, Compressor discharge temperature = 48
o
C,
COP of the system = 4, Calculate the following:
i. Compressor power requirement in kW.
ii. Heat rejection ratio.
iii. Carnot COP of the system.
iv. Refrigeration efficiency in %
04
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Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VI (New) EXAMINATION ? WINTER 2019
Subject Code: 2161406 Date: 11/12/2019
Subject Name: Food Refrigeration & Air - Conditioning
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Answer the following: 03
(i) Give main technical criteria for selection of refrigerants based on safety.
(ii) Give measures to prevent Ozone layer depletion.
(i)
(iii) How leakage of refrigerants is detected?
(b) Answer the following: 04
(i) Give R designation of NH3.
(ii) What is the function of TEV in VCRS?
(iii)Show that 10TR = 35.167 kW
(iv) What are radial flow fans?
(c) Explain the construction and operation of simple Ammonia ? Water VAR system. Justify
the statement mathematically. In a given vapour absorption system, heating, cooling and
refrigeration take place at temperatures of 107
0
C, 26
0
C & - 30
0
C respectively. Calculate
the maximum theoretical COP of the system.
07
Q.2 (a)
A 100 TR simple vapour compression refrigeration system is operating between evaporating and
condensing temperatures of -20
o
C and 40
o
C respectively. Calculate the following:
i. Compressor discharge enthalpy in kJ
ii. Compressor power required per TON of refrigeration.
Properties of Refrigerant
t (
o
C) P
(bar)
h f
(kJ/kg)
h g
(kJ/kg)
s f
(kJ/kgK)
s g
(kJ/kgK)
v f
(m
3
/kg)
v g
(m
3
/kg)
-20 1.5 181 342.7 0.93 1.56 0.68x10
-3
0.108
40 9.6 238.5 367 1.13 1.5 0.789x10
-3
0.0182
Given: Specific heat of refrigerant vapours in the superheated region C pv = 0.65 kJ/kg K
03
(b) Explain the thermodynamic criteria for selection of refrigerants. A simple vapour
compression refrigeration system is operating on the following conditions:
Refrigeration capacity = 50 TR, Evaporating temperature = - 2
o
C
Condensing temperature = 42
o
C, Compressor discharge temperature = 48
o
C,
COP of the system = 4, Calculate the following:
i. Compressor power requirement in kW.
ii. Heat rejection ratio.
iii. Carnot COP of the system.
iv. Refrigeration efficiency in %
04
(c) Explain VCRS with the help of P-h diagram. A Carnot heat engine is coupled to a Carnot
refrigeration system such that the total heat rejected to a common reservoir is 3200 kW.
The Carnot heat engine operates from a source maintained at 1500
o
C taking 2400 kW
of heat from it. The work output generated by this engine is driving a Carnot refrigerator
whose source temperature is ? 37
o
C. Determine the temperature of the common
reservoir.
07
OR
(c) Explain the operation of simple VCR system with the help of T-s diagram. Write down
mathematical expressions for refrigeration effect, compressor power, condenser heat rejection
and throttling process in terms of known quantities. Explain the effect of the following on
the performance of simple vapour compression cycle:
i. Increase in condenser temperature.
ii. Reduction in suction temperature.
iii. Compressor pressure ratio.
07
Q.3 (a)
An axial fan running at 840 RPM, consuming 0.15HP delivers 18 m
3
/minute air developing 100
Pa static pressure. If the fan speed is doubled, calculate the following:
i. The power required in HP
ii. Static pressure in mm WC
iii. Air flow rate in m
3
/minute
03
(b) Explain the operation of a simple cascade refrigeration system with the help of a
schematic diagram and draw its P-h diagram. Write expression for COP of a 2-stage
cascade system.
04
(c) Explain the following briefly:
i. Time switches
ii. Laws of air movement
iii. RTD sensors
iv. Registers
v. Aspect ratio
vi. Draft
vii. Types of supply air outlets
07
OR
Q.3 (a)
State fan laws. For a given fan, calculate the percent increase in volume flow rate and power
consumption if the fan speed is increased by 35%.
03
(b)
Explain (a) Induction ratio (b) COP (c) Green house effect (d) Ante room
04
(c) Explain the following briefly:
i. Humidistat
ii. Air curtains
iii. Air washers
iv. Thermostats
v. Diffusers
vi. Capillary tubes
vii. HP/LP cut outs
07
Q.4 (a) Explain the operation and application of solenoid valves. 03
(b) Classify different types of compressors and briefly explain the construction, working
principle and advantages of Hermetic compressors.
04
FirstRanker.com - FirstRanker's Choice
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VI (New) EXAMINATION ? WINTER 2019
Subject Code: 2161406 Date: 11/12/2019
Subject Name: Food Refrigeration & Air - Conditioning
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) Answer the following: 03
(i) Give main technical criteria for selection of refrigerants based on safety.
(ii) Give measures to prevent Ozone layer depletion.
(i)
(iii) How leakage of refrigerants is detected?
(b) Answer the following: 04
(i) Give R designation of NH3.
(ii) What is the function of TEV in VCRS?
(iii)Show that 10TR = 35.167 kW
(iv) What are radial flow fans?
(c) Explain the construction and operation of simple Ammonia ? Water VAR system. Justify
the statement mathematically. In a given vapour absorption system, heating, cooling and
refrigeration take place at temperatures of 107
0
C, 26
0
C & - 30
0
C respectively. Calculate
the maximum theoretical COP of the system.
07
Q.2 (a)
A 100 TR simple vapour compression refrigeration system is operating between evaporating and
condensing temperatures of -20
o
C and 40
o
C respectively. Calculate the following:
i. Compressor discharge enthalpy in kJ
ii. Compressor power required per TON of refrigeration.
Properties of Refrigerant
t (
o
C) P
(bar)
h f
(kJ/kg)
h g
(kJ/kg)
s f
(kJ/kgK)
s g
(kJ/kgK)
v f
(m
3
/kg)
v g
(m
3
/kg)
-20 1.5 181 342.7 0.93 1.56 0.68x10
-3
0.108
40 9.6 238.5 367 1.13 1.5 0.789x10
-3
0.0182
Given: Specific heat of refrigerant vapours in the superheated region C pv = 0.65 kJ/kg K
03
(b) Explain the thermodynamic criteria for selection of refrigerants. A simple vapour
compression refrigeration system is operating on the following conditions:
Refrigeration capacity = 50 TR, Evaporating temperature = - 2
o
C
Condensing temperature = 42
o
C, Compressor discharge temperature = 48
o
C,
COP of the system = 4, Calculate the following:
i. Compressor power requirement in kW.
ii. Heat rejection ratio.
iii. Carnot COP of the system.
iv. Refrigeration efficiency in %
04
(c) Explain VCRS with the help of P-h diagram. A Carnot heat engine is coupled to a Carnot
refrigeration system such that the total heat rejected to a common reservoir is 3200 kW.
The Carnot heat engine operates from a source maintained at 1500
o
C taking 2400 kW
of heat from it. The work output generated by this engine is driving a Carnot refrigerator
whose source temperature is ? 37
o
C. Determine the temperature of the common
reservoir.
07
OR
(c) Explain the operation of simple VCR system with the help of T-s diagram. Write down
mathematical expressions for refrigeration effect, compressor power, condenser heat rejection
and throttling process in terms of known quantities. Explain the effect of the following on
the performance of simple vapour compression cycle:
i. Increase in condenser temperature.
ii. Reduction in suction temperature.
iii. Compressor pressure ratio.
07
Q.3 (a)
An axial fan running at 840 RPM, consuming 0.15HP delivers 18 m
3
/minute air developing 100
Pa static pressure. If the fan speed is doubled, calculate the following:
i. The power required in HP
ii. Static pressure in mm WC
iii. Air flow rate in m
3
/minute
03
(b) Explain the operation of a simple cascade refrigeration system with the help of a
schematic diagram and draw its P-h diagram. Write expression for COP of a 2-stage
cascade system.
04
(c) Explain the following briefly:
i. Time switches
ii. Laws of air movement
iii. RTD sensors
iv. Registers
v. Aspect ratio
vi. Draft
vii. Types of supply air outlets
07
OR
Q.3 (a)
State fan laws. For a given fan, calculate the percent increase in volume flow rate and power
consumption if the fan speed is increased by 35%.
03
(b)
Explain (a) Induction ratio (b) COP (c) Green house effect (d) Ante room
04
(c) Explain the following briefly:
i. Humidistat
ii. Air curtains
iii. Air washers
iv. Thermostats
v. Diffusers
vi. Capillary tubes
vii. HP/LP cut outs
07
Q.4 (a) Explain the operation and application of solenoid valves. 03
(b) Classify different types of compressors and briefly explain the construction, working
principle and advantages of Hermetic compressors.
04
(c) Classify cold storage systems. Give fundamental design considerations and detailed
technical guidelines for a general purpose cold store.
07
OR
Q.4 (a) Explain the following briefly:
i. IQF
ii. Cold chain
03
(b) Prove that the volumetric efficiency of a single acting reciprocating compressor is given
by
n
e
d
vol
P
P
c c
1
1
?
?
?
?
?
?
?
?
? ? ? ?
. A single acting single stage reciprocating compressor has a
bore to stroke ratio of 2:3. It receives refrigerant at 1.2 bar and delivers it at 6 bar.
Calculate the power required to drive the compressor in kW and the volumetric
efficiency. Take c = 5% and n = 1.33
04
(c) Explain cooling, freezing, refrigeration and chilling with examples. Calculate the
refrigeration load expressed in TR which balances the heat loss from the four side walls
of a small cold room 3 m ? 3.0 m ? 2.0 m. The walls are made of 24 cm brickwork, 20
cm hard board and 1.5 cm cement. The inside wall temperature is -20?C and outside wall
temperature is 37?C. Consider a safety factor of ?2? for losses through joints etc. The
thermal conductivities of brick, board and cement plaster are 0.6 W/m?C, 0.04 W/m?C
and 0.80 W/m?C respectively.
07
Q.5 (a) Give general rules for air flow duct design for air-conditioning systems. Name materials
of duct construction that are suitable for food processing plants?
03
(b) What are the selection criteria of condensers for refrigeration application? Explain the
construction and operation of a shell and tube condenser.
04
(c) What is the function of refrigerant evaporators? Classify refrigerant evaporators and
explain the construction and working of flooded evaporator.
07
OR
Q.5 (a) Cold air enters a duct of 80 cm diameter at 12 m/s and leaves at 8 m/s downstream.
Calculate the exit diameter of the duct and the velocity head at the exit of the duct in mm
of WC. Assume no losses.
03
(b) Explain operation of a forced draft cooling tower with a neat diagram. 04
(c) Explain the principle and operation of thermostatic expansion valve with a neat diagram..
Why is TEV a preferred choice as an expansion device?
07
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This post was last modified on 20 February 2020