S K Mondal’s
Refrigeration and Air-
Conditioning
GATE, IES & IAS 20 Years Question Answers
Contents
Chapter – 1: Heat Pump and Refrigeration Cycles and
Systems
Chapter - 2 : Vapour Compression System
Chapter - 3 : Refrigerants
Chapter - 4 : Refrigerant Compressors
Chapter - 5 : Condensers & Evaporator
Chapter - 6 : Expansion Devices
Chapter - 7 : Gas Cycle Refrigeration
Chapter - 8 : Vapour Absorption System
Chapter - 9 : Psychrometry
Chapter - 10 : Miscellaneous
Er. S K Mondal
IES Officer (Railway), GATE topper, NTPC ET-2003 batch, 12 years teaching
experienced, Author of Hydro Power Familiarization (NTPC Ltd)
Page 1 of 128
,Note
If you think there should be a change in
option, don’t change it by yourself send me a
mail at
I will send you complete explanation.
Copyright © 2007 S K Mondal
Every effort has been made to see that there are no errors (typographical or otherwise) in the
material presented. However, it is still possible that there are a few errors (serious or
otherwise). I would be thankful to the readers if they are brought to my attention at the
following e-mail address:
S K Mondal
Page 2 of 128
, Hea
at Pump & Refriigeration
n Cycles and Sysstems
S K Monda
M l’s Chaptter 1
1. Hea
at Pu
ump and Refrrigerration
n
Cyc
cles and Systtems
s
OBJECTIVE QUESTIO
U ONS (G
GATE
E, IES
S, IAS
S)
Prev
vious 20-Yea
2 ars GA
ATE Qu
uestion
ns
Heat Engine,
E Heat Pump
P
GATE-1. The
T coeffiicient of performanc
p ce (COP) ofo a refrig gerator wo orking as a heat
pump
p is giiven by: [GATE--1995; IES--1992, 1994 4, 2000]
(a)(COP)heatt pump = (COP
P)refrigerator+ 2 (bb)(COP)heat ppump = (COP
P)refrigerator+ 1
(c)(COP)heat pump = (COPP)refrigerator – 1 (d)(COP)heat pump = (COP P)refrigerator
GATE-1. Ans.
A (b)Thhe COP of refrigeratoor is one leess than C COP of hea at pump, iff same
refrigerator
r r starts workking as hea at pump i.e. (COP)heat pum
mp = (COP)reefrigerator + 1
GATE-2. An
A industr rial heat pump
p operrates betw ween the te emperatures of 27°C and –
13°C. The rates of heath additiion and he eat rejectiion are 750 Wand 10
000 W,
respective
r ely. The COOP for the heat
h pump p is: [GATEE-2003]
(a) 7.5 (b) 6.5 (c) 4.0 (d) 3.0
Q1 10
000
GATE-2. Ans.
A (c) (CO
OP )HP = = =4
Q1 − Q2 1000 − 750
GATE-3. Any
A thermmodynamic c cycle opperating between
b tw
wo temperature lim mits is
reversible
r if the pro
oduct of eff
fficiency when
w opera
ating as a heat
h engin
ne and
the
t coeffic
cient of perrformancee when opeerating as r
refrigeratiion is equa
al to 1.
Page 3 of 128
, Heat Pump & Refrige
eration Cycles
C an
nd Syste
ems
S K Mo
ondal’ss Chapte
C r1
GA
ATE-3. Anss. False
Effficiency Heat engine,
⎛ TH −TL ⎞
η HEE = ⎜ ⎟⎟
⎜ TH
⎝ ⎠
TL
CO
OP of Refrige
erator =
TH − TL
Pro
oduct of ηHE and
OPR ≠ 1.
CO
[GATE-19
994]
GA
ATE-4. Ann irreversib ble heat en ngine extra
acts heat from
fr a high
h temperatture source at
a rate
r of 100
0 kW and rejects heat to a sin W. The entire
nk at a ratte of 50 kW
woork outputt of the he eat enginee is used to drive a reversiblle heat pu ump
opeerating be etween a set of indep pendent issothermal heat reser rvoirs at 17
1 0C
andd 75 C. Th
0 he rate (in kW) at wh hich the heeat pump delivers
d he
eat to its high
h
tem
mperature sink is: [GATE -20 009]
(a) 50 (b) 250 (c) 300 (d) 360
GA
ATE-4. Anss. (c)
Reverse
R ed Carnot Cycle
GA
ATE-5. A Carnot
C cyc
cle refriger rator opera
ates betweeen 250K a
and 300 K. Its
I coefficiient
of performan
p nce is: [GATE-19999]
(a) 6.0 (b) 5.0 (c) 1.2 (d) 0.8
T2 250
ATE-5. Anss. (b) (COP ) R =
GA = =5
T1 − T2 300 − 250
0
δQ
ATE-6. In the case of
GA o a refrige rgoing an iirreversiblle cycle, φ
eration sysstem under
T
is: [GATE-19
995]
(a) < 0 (b) = 0 (c) > 0 (d) Not surre
ATE-6. Anss. (a)
GA
Refriger
R ration capacity
c y (Ton o
of refrig
geration
n)
GA
ATE-7. Roound the clock
c coolling of an n apartmen nt having a load of 300 MJ//day
reqquires an air-conditi
a oning plan nt of capac city about [GATE-19
993]
(a) 1 ton (b) 5 ton
ns (c) 10 ton
ns (d) 100 ton
ns
GA
ATE-7. Anss. (a) 211 kJ
J/min = 1 T refrigeratioon
300 × 103
Reffrigeration capacity
c = ≈ 1 ton
2 × 60 × 211
24 1
Prev
vious 20-Yea
2 ars IES
S Ques
stions
Heat Eng
gine, Heat Pum
mp
Page 4 of 128
Refrigeration and Air-
Conditioning
GATE, IES & IAS 20 Years Question Answers
Contents
Chapter – 1: Heat Pump and Refrigeration Cycles and
Systems
Chapter - 2 : Vapour Compression System
Chapter - 3 : Refrigerants
Chapter - 4 : Refrigerant Compressors
Chapter - 5 : Condensers & Evaporator
Chapter - 6 : Expansion Devices
Chapter - 7 : Gas Cycle Refrigeration
Chapter - 8 : Vapour Absorption System
Chapter - 9 : Psychrometry
Chapter - 10 : Miscellaneous
Er. S K Mondal
IES Officer (Railway), GATE topper, NTPC ET-2003 batch, 12 years teaching
experienced, Author of Hydro Power Familiarization (NTPC Ltd)
Page 1 of 128
,Note
If you think there should be a change in
option, don’t change it by yourself send me a
mail at
I will send you complete explanation.
Copyright © 2007 S K Mondal
Every effort has been made to see that there are no errors (typographical or otherwise) in the
material presented. However, it is still possible that there are a few errors (serious or
otherwise). I would be thankful to the readers if they are brought to my attention at the
following e-mail address:
S K Mondal
Page 2 of 128
, Hea
at Pump & Refriigeration
n Cycles and Sysstems
S K Monda
M l’s Chaptter 1
1. Hea
at Pu
ump and Refrrigerration
n
Cyc
cles and Systtems
s
OBJECTIVE QUESTIO
U ONS (G
GATE
E, IES
S, IAS
S)
Prev
vious 20-Yea
2 ars GA
ATE Qu
uestion
ns
Heat Engine,
E Heat Pump
P
GATE-1. The
T coeffiicient of performanc
p ce (COP) ofo a refrig gerator wo orking as a heat
pump
p is giiven by: [GATE--1995; IES--1992, 1994 4, 2000]
(a)(COP)heatt pump = (COP
P)refrigerator+ 2 (bb)(COP)heat ppump = (COP
P)refrigerator+ 1
(c)(COP)heat pump = (COPP)refrigerator – 1 (d)(COP)heat pump = (COP P)refrigerator
GATE-1. Ans.
A (b)Thhe COP of refrigeratoor is one leess than C COP of hea at pump, iff same
refrigerator
r r starts workking as hea at pump i.e. (COP)heat pum
mp = (COP)reefrigerator + 1
GATE-2. An
A industr rial heat pump
p operrates betw ween the te emperatures of 27°C and –
13°C. The rates of heath additiion and he eat rejectiion are 750 Wand 10
000 W,
respective
r ely. The COOP for the heat
h pump p is: [GATEE-2003]
(a) 7.5 (b) 6.5 (c) 4.0 (d) 3.0
Q1 10
000
GATE-2. Ans.
A (c) (CO
OP )HP = = =4
Q1 − Q2 1000 − 750
GATE-3. Any
A thermmodynamic c cycle opperating between
b tw
wo temperature lim mits is
reversible
r if the pro
oduct of eff
fficiency when
w opera
ating as a heat
h engin
ne and
the
t coeffic
cient of perrformancee when opeerating as r
refrigeratiion is equa
al to 1.
Page 3 of 128
, Heat Pump & Refrige
eration Cycles
C an
nd Syste
ems
S K Mo
ondal’ss Chapte
C r1
GA
ATE-3. Anss. False
Effficiency Heat engine,
⎛ TH −TL ⎞
η HEE = ⎜ ⎟⎟
⎜ TH
⎝ ⎠
TL
CO
OP of Refrige
erator =
TH − TL
Pro
oduct of ηHE and
OPR ≠ 1.
CO
[GATE-19
994]
GA
ATE-4. Ann irreversib ble heat en ngine extra
acts heat from
fr a high
h temperatture source at
a rate
r of 100
0 kW and rejects heat to a sin W. The entire
nk at a ratte of 50 kW
woork outputt of the he eat enginee is used to drive a reversiblle heat pu ump
opeerating be etween a set of indep pendent issothermal heat reser rvoirs at 17
1 0C
andd 75 C. Th
0 he rate (in kW) at wh hich the heeat pump delivers
d he
eat to its high
h
tem
mperature sink is: [GATE -20 009]
(a) 50 (b) 250 (c) 300 (d) 360
GA
ATE-4. Anss. (c)
Reverse
R ed Carnot Cycle
GA
ATE-5. A Carnot
C cyc
cle refriger rator opera
ates betweeen 250K a
and 300 K. Its
I coefficiient
of performan
p nce is: [GATE-19999]
(a) 6.0 (b) 5.0 (c) 1.2 (d) 0.8
T2 250
ATE-5. Anss. (b) (COP ) R =
GA = =5
T1 − T2 300 − 250
0
δQ
ATE-6. In the case of
GA o a refrige rgoing an iirreversiblle cycle, φ
eration sysstem under
T
is: [GATE-19
995]
(a) < 0 (b) = 0 (c) > 0 (d) Not surre
ATE-6. Anss. (a)
GA
Refriger
R ration capacity
c y (Ton o
of refrig
geration
n)
GA
ATE-7. Roound the clock
c coolling of an n apartmen nt having a load of 300 MJ//day
reqquires an air-conditi
a oning plan nt of capac city about [GATE-19
993]
(a) 1 ton (b) 5 ton
ns (c) 10 ton
ns (d) 100 ton
ns
GA
ATE-7. Anss. (a) 211 kJ
J/min = 1 T refrigeratioon
300 × 103
Reffrigeration capacity
c = ≈ 1 ton
2 × 60 × 211
24 1
Prev
vious 20-Yea
2 ars IES
S Ques
stions
Heat Eng
gine, Heat Pum
mp
Page 4 of 128
