Marks Obtained:

KATHMANDU LINIVERSITY
End Semester Examination
January/February 2015
Level: B. E. Course : MEPP 403
Year :IV Semester: I

Exam. Roll No.: Time: 30 mins. F. M. :20

Registration No.: Date :

SECTION "A"
[8Q.rl=Smarks]
Select the most appropriate answer (s).

l. Which of the following refrigerants replace Rl2 in domestic refrigerators?

a)R22 b) Rl l c) Rl34a d) Rl4lb

2. Absorption of the refrigerant by the absorbent in a vapour absorption refrigeration system

is accompanied by:
a) absorption of heat b) release of heat c) no thermal effects d) reduction in volume

3. Which of the following statement is TRUE?

a) a capillary tube is a variable opening area type expansion device
b) in a capillary tube pressure drop takes place due to fluid friction
c) in a capillary tube pressure drop takes place due to fluid acceleration
d) in a capillary tube pressure drop takes place due to fluid friction and acceleration

4. The chemical formula of refrigerant Rl I is:

a) CCIgF b) CCIF3 c) CCIHF d) CHF

5. During the cooling and humidification process

a) the enthalpy of air decreases
b) the enthalpy of air increases
c) the enthalpy of air remains constant
d) the enthalpy of air may increase, decrease or remain constant

6. The sensible heat factor for

a) sensible heating process is I
b) sensible heating process lies between 0 and 1

c) sensible cooling process is 0

d) sensible cooling process lies between 0 and I

7. A single zone, single duct, constant volume air conditioning system can be used
a) for cooling
b) not for cooling
c) for heating
d) both for cooling and heating simultaneously
 8. For northern hemisphere providing fenestration on
a) northern side of the building is beneficial for summer cooling and winter heating
point of view
b) southem side of the building is beneficial for summer cooling and winter heating
point of view
c) any direction does not have any effect on summer cooling and winter heating point of view
d) northern side of the building increases heat transfer rate.

SECTION "B"
tl2Q.xl=l2marksl
Fill in the blankwith appropriate answer (s).

e. constant wet burb temperature rines are identicar to the

:::T::::::::::*r
10. The cooling load temperature difference (CLTD) incorporate the effects of

11. For fixed heat rejection temperature and fixed refrigeration temperature, the COP of a
reversed Brayton cycle is .. than COP of reverse Camot cycle.

12. Even though the outside temperatures rue very low at high altitudes, Aircraft cooling
system is required to remove heat generation due to caused by the
fast moving aircraft.

13. In vapor compression refrigeration system pressure drop and heat transfer in suction
line... ..... compression ratio and discharge temperature.

o is obtained as the
' I : ::::: :::ffi:lJ:Ifi :T::j1,,ffi;refrigeration

15. Multi-stage vapour compression refrigeration systems are used when required
temperature lifts ...

16. Work of compression in higher stage compressor can be by

using inter-cooling in multi-stage compression systems.

17. Multi-evaporator systems are widely used when refrigeration is required at ... .

18. In cascade systems different ... .....are used in individual cascade cycles.

19. Compared to compression systeffiS, .. .. offer the benefits of possibility of

using low-grade energy sources.

20.The maximum amount of moisture air can hold depends upon its .... ..... and
 KATHMANDU TJNIVERSITY
End Semester Examination
January/February 2015
Level : B. E. : TvIEPP 403
Year :rv 3;;::".
Time : 2 hrs. 30 mins. F.M. : 55
SECTION "C"
Attempt all questions. Assume suitable data if any is missing.

l. A vapor compression refrigeration system based on refrigerantP.22 operates between an

evaporator temperature -25 0C and condenser temperature of 50 0C. Determine a) COP of
the system, b) Work input to the compressor, c) Area of superheat horn and d) Throttling
loss. (Draw TS diagram and assume isentropic compression). Il0]
2. Explain multi stage compression refrigeration system and working principle of flash gas
chamber with the help of schematic and TS diagram. t1.j
3. A simple LiBr - Water absorption cycle operating at the following temperatures:
0C,
generator 100 condenser 40 0C, absorber 30 0C and evaporator l0 0C. Compute the
flow rate of refrigerant through the condenser and evaporator if the pump delivers 0.6
kds. Also find the rate of heat transfer through generator, condenser, absorber and
evaporator as well as COP of the cycle. (Draw a schematic diagram and level all
components with temperature). t9l
4. What is azeotropic refrigerant? Discuss the desirable properties of refrigerants. Give
refrigerant numbers for the refrigerants whose chemical formula are CHCLFz and COz.
tsl
5. Explain simple aircraft refrigeration cycle with the help of schematic and TS diagram.
t5l
6. A process industry is to be air conditioned when the outdoor conditions are 320C
DBT
and 65 % RH and required conditions for the processes are 25'C DBT and 60 % RH. If
the amount of air circulation is 250 m3/min and coil dew temperature is, find the flowing:
a) Cooling capacity of the cooling coil in kW and its by-pass factor,
b) Heating capacity of the heating coil in kW and surface temperature of the heating coil
if the by-pass factor is 0.3.
c) The mass of water vapor removed per hour.
i. The required condition is achieved by first cooling and dehumidifuing and then
by heating. The process occurs at 1 atm.
ii. Sketch the process in a Psychometric chart and leave the chart along with your
answer copy t8l
7. Write short notes on the procedure for estimating heating loads for a building and the
"thermodynamics of human body". 14)
8. A 30 m3/min stream of moist air at 15 0C DBT and 13 0C WBT are mixed with another
12m3lmin stream of air at250C DBT and 18 0C WBT. The mixing takes place at a
pressure of 1 atm. Determine the DBT and WBT of the resulting mixture. t3]

9. Write short notes on Air Handling Unit (AHU). t4l

 KATHMANDU TINIVERSITY Marks scored:
End Semester Examination [Q]
June/JuIv.2015
Level : B.E.
Year : IV
ff
0 JUI 2015 Course : MEPP 403
Semester: I
.Exam. Roll No.: Time: 30 mins. F.M. :20

No. Date
aa ,,
. o [12 e.xl=12 marks]
ChOoSe the inoat

I One of tiie purposes of sub-cooling the liquid refrigeration in a vapour compression

retiigeration cycle is to:
[ ] reduce th" "ompre'ssor overheating
[ ] reduce the compressor discharge temperature
[ ] increase cooling effect
[ ] ensure that only liquid and not the vapouJ enters the expansion valve
I 2. In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the
refri gerants respectively are,
[ ] water and lithium bromide
[ ] ammonia and water
[ ] water and water
[ ] ammonia and lithium brornide
1
J During sensible cooling of air
[ ] wet bulb temperature [ ] specific humidity
[ | relative hurnidity I J dry bulb temperature
4 The curved lines on a psychrometric bhart indicates
[ ] dew point temperature t I dry bulb temperature
[] wet bulb temperature I j reiative trumidity
5 prle tonne of refrigeratibn means that the heat removing capacity is

I
[ ]2l0kJ/min I )2|kJlmin tl42}kJ/min t l620$tmin
6. A heat pllmp working on a reversed Carnot cycle has a C.O.P. of 5. It works as a
refi'igerator taking I kW of work input. The refrigerating effect will be
[]2kw il4kw illkw il3kw
A good refrigerant should have
t I high specific volume and high latent heat of vaporizatibn
[ ] high operating pressures and low freezingpoint .

[ ] high latent heat of vaporisation and low freezing point

[ ] low C.O.P. and low freezing point
L The best comfort conditions in air conditioning are at (where DBT = Dry bulb temperature,
and RH: [tetative humiclity)
[ ]22"C DBT and 60% RH t J 25"C DBT anrt 40% RH
[ ] 25'C DBT and 100%, RH I j ZO.C DBT and 80% RH

I
 9 The dry bulb temperature lines, on the psychrometric chafi are
[ ] horizontal and uniformly spaced
[ ] horizontal and non-uniformly spaced
[ ] vertical and uniformly spaced
[ ] curved lines
10. A simple vapour compiession refrigeration cycle has the following state points: (i) enthalpy
after compression b
425 kJ/kg, enthalpy alter throttling 125 kJ/kg, enthalpy betbre
compression: 375 kJ/kg. The C.O.P of the system is
---t-13-s --- -t ls - r 1a
. L JV [ ] notpcissible to tind with,the data
I l. In a vapour compression refrigeration system, a throttle valve is used in place of an
expander because ' 0

[ ] it reduces mass of the system considerably .

[] it improves the coP the system because the conclenser is small

of
[ ] the positive work in isentropic expansion of riquid iq very small
[ ] it leads to significant cost reduction
.

12. In aqua-ammonia absorption refrigeration system, incomplete rectification leads to

accumulation of water in
[ ]condenser [ ]evaporator [ ]absorber [ ]rectifier

SECTION ..B''
[8 Q,*l= 8 marks]
' Fill in the blanks.

13. For summer time air-conditioning process, the air . is and

14. A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a
refrigerator taking I kW of work input. The refrigeration effect will be

15. The refrigerant widely used in domestic refrigerators is

(._
16. For air conditioning the operation theatre in a hospital, the percentage of outsicle air is the -
supplied airis _%

17. In a reversed Brayton cycle, the heat is absorbed by the air during

18. [n vapour compression refrigeration system, the refrigerant has the maximum temperature
in the

19. The condition of refi'igerant after passing through the eondenser in a vapour compression
system is

20. In larger industrial and commercial reciprocating compression systems, the refri gerant
widely used is

,
 KATHMANDU UNIVERSITY
End Semester Examination [C]
June/July, 2015
Level : B.E. Course : MEPP 403
Year :IV .o fi JUL 2015 Semester: I
Irme : 2 hrs. 30 mins. F.M. :55
SECTION "C''

Attempt all the questions

l. Explain, in detail, how the actual vapour compression refrigeration cycle differs from
idealized one. t5l

2. A refrigerator system operates on the reversed carnot cycle. The higher temperature of the
-
refi'igerant in the system is 35oC ancl the lower pressure is 15oC. The capacity is to be 12
tonnes. Neglect all the losses. Determine: (i) COP, (ii) [{eat rejected from the system per
I
hour; and (iii) power required. t5l

3. Elaborate cascade refrigeration system. I{oW does it diffbr from multistage compression
refi'igeration sy.stem. Why is tlph chamber used in multistage compression system t7)

4. Refrigerant-l34aenters the cornpressor of a refrigerator as superheated vapor at 0.14 MPa

and - 10oC at a rate of 0.05 kg/s and leaves at 0.8 MPa and 50oC. The refrigerant is cooled
in the condenser to26"C and0.72 MPa and is throttled to 0.15 MPa. Disregarding any heat
transt'er and pressure drops'in the connecting lines between the components, determine (a)
the rate of heat iernoval fiom the refrigerated space and the power input to the compressor,
(b) the isentropic etficiency of the compressor, and (c) the coefficient of perfoffnance of the
refirigerator t6]

5. Explain the general rules for reliigerant nornenclature with appropriate exauples. t6]

6. What are vapour absorptiorr refrigeration system? What are the obvious merits and tlemerits
(
of absorption refi'igeration system compared with vapour compression system. Explain the
working principle of lithiurn brornide absorption system with proper schematic diagram. [7]

7. Write technical essay on air-conclitioning technology. t6l

I Air enters a window air conditioner at I atm, 30oC, and 80 percent relative humidity at a
rate of l0 m3/min, and it leaves as saturatgd ur at 14"C. Part of the moisture in the air that
condenses during" the proccss is also removed at 14"C. Determine the rates of heat and
moisture removal fronr the air. t7l
9. Explain; with proper schematjc diagram, the air-conditioning system used itt the aircraft. [6]
 Marks scored:
KATHMANDU UNIVERSITY
End Semester Examination
February/March.
't{ 2016
Level B.E 02 AR itl16 Course : MEPP 403
Year IV Semester: I ?

Exam. Roll No. : Time: 30 mins. F.M. :20

Registration No. Date

SECTION "A"
[0 Q. x l:10 marks]
Choose the most appropriate answer/s.

I The condition of refrigerant after passing through the condenser in a vapour compression
system is
[ ] Saturated liquid [ ] Wet vapour
[ ] Dry saturatedvapour [ ] Superheated vapour
2 In aqua-ammonia and Lithium-bromide water absorption refrigeration systems, the refrigerants
are respectively
[ ] ammonia and water [ ] water and water
[ ] ammonia and lithium bromide [ ] water and lithium bromide

3. During adiabatic saturation process on unsaturated air the remains constant.

[ ] dry bulb temperature [ ] relative humidity
[ ] dew point temperature [ ] wet bulb temperature
4 The curved lines on a psychrometric chart indicates
[ ] dry bulb temperature [ ] wet bulb temperature
[ ] relative humidity [ ] dew point temperature
5 A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator
taking I kW of work input. The refrigerating effect will be
[]lkw []2kw []3kw []4kw
6 A good refrigerant should have
[ ] low COP and low freezing point
[ ] high operating pressure and low freezing point
[ ] high latent heat of vaporization and low freezing point
[ ] high specific volume and high latent heat of vaporization
7 In a refrigeration system, heat absorbed in comparison to heat rejected is
[ ] more [ ] more for small capacity and less for high capacity [ ] less
[ ] the same [ ] less for small capacity and more for high capacity
8 Aqua-ammonia absorption system requires
[ ] very little work input [ ] maximum work input
[ ] nearly the same work input for vapour compression system [ ] zero work input
9 In a vapour compression refrigeration system refrigerant is at liquid state between
[ ] condenser and expansion valve [ ] compressor and evaporator
[] expansion valve and evaporator [ ] compressor and condenser
 fl ? llAn 2ol6i
10. A variable air air-conditioning system is mainly charucterized by
[ ] zone dampers [ ] reheat coils [ ] mixing box [ ] flow control valve

SECTION "B"
[0 Q.x1:10 marks]
1l In a vapour compression refrigeration system, the condition of refrigerant is high pressure
saturated liquid before entering the

12. The bank of tubes at the back of domestic refrigerator is

13. In All-Air air-conditioning systems air is processed in the A/C plant and this processed air is
then conveyed to the conditioned space through using

14. Ammonia as an inorganic refrigerant is named as

\./
15. Dew point is the temperature at which condensation begins when the air is cooled at

16. In an aircraft refrigeration system the air is pressurized, to some extent, before even entering the
compressor due to

17. For any building there exists a balance point at which the solar radiation (Q,o,u,) and internal
heat generation rate (Q exactly balance the heat losses from the building. Thus from sensible
n,)
heat balance equation, at balanced condition is

18. In a psycrometric chart the and

lines are identical.

19. Trichloromonofluoromethane is the chemical name of refrigerant

20. The following sketch represents process.

0r s 0ra

,t

0: = Ifi)r)l',

l-l'c .r0'c:
 KATHMANDU UNIVERSITY
End Semester Examination
February/March,2016
Level :B.E. Course : MEPP 403
Year : IV 0 ? iiAil 2oiE Semester: I
Time : 2 hrs. 30 mins F.M. :55
SECTION "C"

Attempt all the questions. Eoch question caruies I I marl<s. Assume any missing data, suitably.

I i. Explain Aqua-Ammonia absorption system. What is the advantage of having heat exchanger
(the regenerator) in such system? [6]
ii. Two airstreams are mixed steadily and adiabatically. The first stream enters at32"C and 40
percent relative humidity at a rate of 20 m3/min, while the second stream enters at lZ"C and 90
percent relative humidity at a rate of 25 m3lmin. Assuming that the mixing process occurs at a
pressure of I atm, determine the specific humidity, the relative humidity, the dry-bulb
temperature, and the volume flow rate of the mixture. t5]

2 i. Write technical note on application of refrigeration in food preservation. t5]

ii. A heat pump using refrigerant-134a heats a house by using underground water at 8oC as the
heat source. The house is losing heat at a rate of 60,000 kJ/h. The refrigerant enters the
compressor at 280 kPa and OoC, and it leaves at I MPa and 60'C. The refrigerant exits the
condenser at 30oC. Determine (a) the power input to the heat pump, (b) the rate of heat
absorption from the water, and (c) the increase in electric power input if an electric resistance
heater is used instead of a heat pump. t6l

J i. Explain the working of a domestic refrigerator with freezer-refrigerator unit and a single
compressor. t4l
ii. An absorption cycle operating at the temperatures shown in the figure below. Compute the rate
of flow of refrigerant (water) through the condenser and evaporator in an Li-Br cycle shown in
the figure attached, if the pump delivers 0.6 kg/s and the following temperatures prevail:
generator, l00oC, condenser 40oC; evaporator, 1OoC; and absorber, 3OoC. Also compute Qs, Qo,
Qc, Q" dr.d the COP. {71

OR

ii. Consider a two-stage cascade refrigeration system operating between the pressure limits of 0.8
and 0.14 MPa. Each stage operates on an ideal vapor compression refrigeration cycle with
refrigerant-134a as the working fluid. Heat rejection from the lower cycle to the upper cycle
takes place in an adiabatic counterflow heat exchanger where both streams enter at about 0.32
MPa. (ln practice, the working fluid of the lower cycle is at a higher pressure and temperature in
the heat exchanger for effective heat transfer.) If the mass flow rate of the refrigerant through
the upper cycle is 0.05 kg/s, determine (a) the mass flow rate of the refrigerant through the
lower cycle, (b) the rate of heat removal from the refrigerated space and the power input to the
compressor, and (c) the coefficient of performance of this cascade refrigerator. 17)

4 i. Describe the general procedure for cooling load estimation in a building. t5l
ii. What are the advantages of air-cycle refrigeration system when used in aircraft air conditioning
system? Explain a simple aircraft refrigeration system. What limitation of it is tackled by a
Bootstrap system? Explain a Bootstrap system. t6]
 r: ;
Li ' '

5 i. Describe with necessary derivation how we can measure the specific humidity of air coming
known.
out of the adiabatic saturator when pressure and temperature are t3]
ii. Explain the difference between heating with humidification and cooling with dehumidification
processes with proper schematicdiagram. t4]
refrigerants.
iii. Elaborate on the nomenclature of t4]

v
 Marks Scored
KATHMANDU UNIVERSITY
End Semester Examination [C]
July,2017
Level : B.E. Course : MEPP 403
Year : IV Semester :I
Exam RollNo Time: 30 mins. F.M 20

Registration No. : Date JUL I 3 2017

SECTI ON "A"
Il0Qxl=l0marks]
Mark [{] for the most appropriate answer (s).

The value of COP in vapor compression cycle is always

a. Less than unity
b. More than unity
c. equal to unity d. unpredictable

o 2. If a heat pump cycle operates between the condenser temperature of

temperature of -23"C, then the Carnot COP will be ..........
a. 2
27'C and evaporator

b.4 c,6 d. g

3 The color of the flame of halide torch, in case of leakage of Freon refrigerant, will change
to ....
a. Bright green b. Light yellow c. Orange d. Red

4 Tlre optimum etfective temperature fbr human comfbrt is

a. Higher in winter than in summer b. Same in winter and summer
c. Lower in winter than in summer d. Lower in summer than in winter

5 when flash gas removal is used in a multistage compression. it the work to be

done in high pressure compressor.
a. lncreases b. makes no difference
c. reduces d. is unpredictable

6.
o Multi...
dif ferent temperatures.
a. Condenser
. systems are widely used when refiigeration is required at

b. compression c. evaporator d. vapor

7 Ventilation requirement depends on .. ..and also on activity level.

a. Internal load
b. external load c. occu pancy d. temperature

8 The absolute humidity ...:..........during cooling and humidification process.

a. Increases b. decreases c. remain constant d. unpredictabre
9 For southern hemisphere providing fenestration on
a. northern side of the building is beneficiar for winter heating
b. southern side of the building is beneficiar for winter heating
c. any direction does not have any effect on winter heating
d. any direction have same effect on winter heating
l0 The fluids used in Electrolux refrigerator are
a. Water and hydrogen b, Ammonia, water and hydrogen
c. Ammonia and hydrogen d. Carbon dioxide, ammonia and hydrogen
 SECTI ON "8"
[0Q.xl=l0marks]
Fill in the blanks.

il. The refrigerants with designation Rr l3 has the chemical fbrmula

12. In summer air-conditioning system for hot and humid outdoor conditions, the reqgired
comfbrt conditions are obtained by employing.. .....process.

r3. An assembly of different parts of the system used to produce specitied condition of
air
rvith a required space building is called

14. Air refrigeration works on . .. . ... .. .....cycle

t5. An azeotropic mixture of two substances is one which cannot be separated into its
components by ..

t6 The .. is the usual retiigerant fbr aero plane ref'rigeration system. o

17. The outdoor air enters into the air-conditioning space through window cracks and
through
doors when opened is termed as ....

18. The cooling load temperature difference (cLTD) incorporate the effects of ....

t9. The by-pass f'actor (BPF) of the coil as the number of rows in the
flow direction increase.

20. Room sensible heat factor is the ratio of

o-
 KATHMANDU UNIVERSITY
End Semester Examination
[C]
Level : B.E.
July, 201 7 JUL 1 3 2017
Year :IV Course : MEPP 403
Time : 2 hrs. 30 mins Semester :l
F. M. :55
SECTION..C''
[5Qxll=55marks]
Attempt ALL questions. Assume suitabre
data if any is missing.

l' a' Explain with the help of a diagram

the advantage of dry compression
and throttling
compression and isentropic .*pinrion
llll#"'*et in a vapor compression refiigeration
b' The simple LiBr-water absorption. refrigeration
temperatures: generator, g5 oc;
cycre is operating at the fo1"*ifJ
condenserl40 "c,.r'"porator, l0 oc;
and absorber35 rc.
o Compute the flow rate of refrigerant
through ,rr" ronJlnser and evaporator
0'6 kgls' 15raw a sche-matic ils;;,"
and rever
in the cycte if
,ffiJ#rlr:elivers att compon.nts with
t6l
2' a' Explain cascade refrigeration system.
for the production of low temperature.
schematic and T-S diagram ani Sketch
level alt compo-nents and procesr".'oi-t;,;
b' In an aircraft'. cabin tooting is required..rrn',rrorg[ cycre. t6.l
the o.utside temperature is very
at high altitudes' Explain rihy cooling row
ir ,.quirlJ"u, tr.,i, high artitude and also
which kind of refrigeration ryrt", describe
is rised ro, it
"ra
*ny. t5l
3' a' A multi-purpose hall is to be air conditioned
for 1200 seating capacity when the
conditions are 3e uc DBT *o outdoor
wPi,
and60%o RH' If the quantity '9-"_C i;i i,iir* conditions Lr tn. hal are 20 uc
of air supplied is 0.3 m3/min/person
at I atm, find the following: and the process occurs

i'CaRacity of the coolin[coil in

ii'
The surface temperatuie required.if
kW, t8]
the bypass
J r--- factor
'.-vt of the cooling coil is 0.3, and
iii. The capacity of ihe humidifiei in kg/h.
o The required condition is achieved
(Sketch the process in a Psychometric
nrsiuy adiabatic humidification
and then cooling.
.rrirt unJrrrr. ir.tong with your answer
b. yffi :,fl:Irlilil:"ffiToJynu,,i.. sheet)
or u nu,* loay, una .*p[ii-u,i.nv
the factors
t3l
4. a' classify air conditioning systems
based on fluid media used in
system. Describe briefly,oall the thermal distribution
water,, ui, .onAltion;;;;;.r.
b' saturated air leaving. thl.coolinf ,..tion orun
50 m3lmin is mixed
uii-.I#itioning system at r4ocu, u ,.ur.'l',
with the ouisiJe.ir'" 32oc and60
humidity at a rate of 20-adiabaticiily percent rerative
m3/m,n. Arrrring that ttre mixing
I
of atm, determine. the ,p.rifl,. r,^rr]aitv,
ttr"..tutire
process occurs at a pressure
temperature, and the vorume
flow rate of the *i"trra.
';r.,LrYE humidity,
rrumlslty, tl
the dry_burb
t6l
5 a' what is flash gas removal and intercooling in
murti stage compression refrigeration
svstem? Exprain- how flash gas
schem ati cand T- S d iagram
ttr"m
removal and inrrr.iorinf ;il;'ilil'ffi herp of a
b' Explain briefly abour fur.ig.runrrlu ltit-,.u,
stage com press ion.
prrp and throttring varue. 16]
t5l
 Marks Scored
KATHMANDU UNIVERSITY
End Semester Examination
March/April,2017
Level B. E. Course : MEPP 403
Year IV Semester : I
Exam RollNo. : Time: 30 mins F. M. :20

Date ,APR 1 o 2oi7

Registration No.:
'(A"
tlOQxl=l0marksl
Mark [{] for the most appropriate answer (s).

l. A ton of refrigeration is equivalent to

t l50kcal/sec t lzl0kJ/min []4Kw t l60kcal/min

2 Room sensible heat factor is the ratio of

RsH r 1 RLH RSH RLH
I Jf,Jfiftfr t lRsH+RrH t l RLH
t l RSH

a
J The designation of refrigerants with chemical formula CzCl:F: is
t lRl2 [ ]R22 [ ]Rll3 [ ]Rr33

4. During the heating and dehumidification process the enthalpy of air

[ ]decreases [ ]increases
[ ] remains constant [ ] may increase, decrease or remain constant

5 Air refrigeration works on the principle of

[ ] Carnot cycle [ ] Rankine cYcle
[ ] Bell-Coleman cycle [ ] Brayton cycle
6. wet compression cycle for a vapor compression refrigeration means
[ ] the entire compression of the vapor should be in superheated region
[ ] the entire compression of the vapor should be in wet region
[ ] the entire compression should be in sub-cooled region
in wet state
[ ] the vapor enters the compressor in dry state but leaves the compressor

7 In ammonia - water absorption refrigeration system

[ ] ammonia is used as a refrigerant and water as an absorbent
[ ] water is used as a refrigerant and ammonia as an absorbent
[ ] ammonia is used as an absorbent and lithium bromide as refrigerant
[ ] lithium bromide is used as a refrigerant and ammonia as an absorbent

8 In winter air-conditioning system for cold and humid outdoor conditions, the required
comfort conditions are obtained by employing
[ ] Cooling with humidification [ ] Heating with dehumidification
[ ] Cooling with dehumidification [ ] Heating with humidification
9 Consider a Heat pump or a direct electrical heater is used to heat the same room.For the
same heating effect the later affangement uses
[ ] more electrical energy than the former [ ] less electrical energy than the former
[ ] Same electrical energy as the former [ ] cannot be predicted
10 For northern hemisphere providing fenestration on
[ ] northern side of the building is beneficial for winter heating
[ ] southem side of the building is beneficial for winter heating
[ ] any direction does not have any effect on winter heating
[ ] any direction have same effect on winter heating
SECTION "B''
[0 Q.x l : l0 marks]

I l. The sensible heat factor for sensible heating is

12. When flash gas removal is used in a multistage compression, it the work
to be done in high pressure compressor.

13. In vapor compression refrigeration system, wet compression the COP

of the cycle.

14. The vapor absorption cycle is described as a cycle.

15. A system with multiple evaporators at different temperatures with compound

compression will power requirements.

16. The relative humidity cooling and humidification process

t7 The by-pass factor (BF) for the process is defined as the ration of the difference between
the mean surface temperature of the coil and leaving air temperature to the difference
between the mean surface and the air temperature.
-operated
18. Multi_ systems are widely used when refrigeration is required at different
temperatures.

19. A single zone, constant volume system can be used either for cooling
or for heating, but not for both cooling and heating simultaneously

20. Ventilation requirement depends on and also on activ ity level

 KATHMANDU LiNIVERSITY
End Semester Examination
March/April,2017 APR 1 0 2017

Level : B. E. Course : MEPP 403

Year : IV Semester : I
Time :2hrs.30mins. F. M. :55
SECTION "C"

Attempt ALL questions. Assume suitable data if any is missing'

l. a. Compare vapor compression refrigeration system with an absorption refrigeration system

with the help of schematic diagram. Explain briefly each of the major components used
in these both refrigeration systems. t7l
b. 6 grams of water vapor per kilogram of atmospheric air is removed and temperature
of air
oC
after removing the water vapor becomes 20 DBT, find i) Relative humidity ii) Dew
point temperature iii) Wet bulb temperature. Assume condition of atmospheric air is
30
oC,
I atm pressure and 50% RH. (Read values from psychometric chart). t4l

2 a. What are the different categories of loads to be considered for heating and cooling load
calculation of an air-conditioning system? How heating and cooling energy demand of
the buildings and heating and cooling load differ each other? t3l
b. A classroom is to be air conditioned for 40 students when the outdoor conditions are
oC and 60oh RH. tf
l2"C DBT and 80% RH. The required conditions of the room are 20
the quantity of air supplied is 0.3 -3/-in/person, find the following: t8l
i. Heating capacity of the coil in kW,
ii. The surface temperature required if the bypass factor of the heating coil is 0.4, and
iii. The capacity of the humidifier
The required condition is achieved first by heating and then by adiabatic humidification.
(Show the process in Psychometric chart and leave the chart along with your answer
copy).

3. a. The owner of the dairy industry needs to store milk and ice-cream at two different storage
temperatures. He has been doing it with two different refrigerators one with very low
temperature for ice-cream and the other with moderate temperature for milk storage. As
a

student of refrigeration and air-conditioning, can you advise him to use a single
refrigerator to serve his purpose? If you can, explain him how your refrigerator work with
the help of schematic and T-S diagram. t6l
b. An aircraft refrigeration plant has to handle a cabin load of 25 tonnes. The atmospheric
oC, the atmospheric air is compressed to a pressure 0.96 bar and
temperature is 16
oC due to ram effect. This air is then further compressed in a
temperature of 29
oC,
compressor to 4.8 bar, cooled in a heat exchanger to 66 expanded in a turbine to I bar
oC.
pressure and supplied to the cabin. The air leaves the cabin at a temperature of 26
Calculate mass of air circulated per min and COP of the cycle. (Draw Schematic and TS
diagram, take Cp = 1.005 KJ/kg.k, CP/Cv = I .4). t5l
4. a. What is thermal distribution system in air conditioning system? Describe single duct,
single zone, constant volume air conditioning system with the help of schematic diagram.
tsl
b. An ideal vapor compression refrigeration cycle operates between an evaporator
oC oC.
temperature of - l0 and at a condensertemperature of 40 The mass flow rate of
the refrigerant R12 in the cycle is 1 kg/min. Determine i) the COP of the cycle and ii) the
refrigerating capacity and the compressor power. t6]

5. a. What are the refrigerants? Describe the desirable properties of refrigerants. t4I
b. Name different air-conditioning processes. Explain how each of these process could be
achieved in air-conditioning system. t4l
c. With the help of T-S diagram, show how reversed Carnot cycle has larger refrigerating
effect and smaller compression work than the ideal vapor compression refrigeration
cycle. t3l
 Marks Scored:
KATHMANDU UNIVERSITY
End Semester Examination
February/March, 201 8
Level: B. E. Course MEPP 403
Year: IV Semester I
Exam RollNo. : Time:30 mins. F.M. :10

Registration No.: Date illAB 152018

SECTION "A"
tl0 Q. x I :10 marksl

Mark [{] for the most appropriate answer.

l) The sub-cooling is a process of cooling the refrigerant in a vapor compression

refrigeration system
[ ] before compression [ ] after compression
[ ] before throttling [ ] after throttling

2) Which of the following statements is correct.

[ ] Dew point temperature can be measured with the help of thermometer.
[ ] Dew point temperature is the saturation temperature corresponding to the partial
pressure of the water vapor in moist air.
[ ] Dew point temperature is the same as the wet bulb temperature.
[ ] For saturated air, dew point temperature is less than the wet bulb temperature.
3) At the same dry bulb temperature
[ ] wet bulb temperature increases with decrease in relative humidity.
[ ] wet bulb temperature decreases with decrease in relative humidity.
[ ] wet bulb temperature remains constant with decrease in relative humidity.
[ ] wet bulb temperature has no dependence on relative humidity.
4) In multi-stage vapor compression system with flash chamber the suction vapor to the
second stage compression are
[ ] normally superheated [ ] normally wet
[ ] normally dry saturated [ ] may be wet or dry saturated

s) The designation of refrigerants with chemical formula CHClFzis

[ ]Rl2 []R22 []R113 [ ]R133

6) The outdoor air enters into the air-conditioning space through window cracks and through
doors when opened is termed as
[ ]leaks [ ]infiltration | )glazing [ ]penetration

7) Bell-coleman cycle is a working cycle for

[ ] Steam turbine [ ] Air refrigeration
[ ] Gas turbine [ ] Absorption refrigeration

8) Dry compression cycle for a vapor compression refrigeration means

[ ] the entire compression of the vapor should be in superheated region
[ ] the entire compression of the vapor should be in wet region
[ ] the entire compression should be in sub-cooled region
[ ] the vapor enters the compressor in dry state but leaves the condenser in wet state
e) The actual vapor compression cycle may have
[ ] superheating of the vapor in the evaporator
[ ] pressure increase in the suction line
[ ] pressure increase in the condenser
[ ] sub cooled in the suction line
l0) In lithium bromide - water absorption refrigeration system
[ ] ammonia is used as a refrigerant and water as an absorbent
[ ] water is used as a refrigerant and lithium bromide as an absorbent
[ ] ammonia is used as an absorbent and lithium bromide as refrigerant
[ ] Iithium bromide is used as a refrigerant and water as an absorbent
SECTION "B"
Il0 :
Q.x I l0 marksl
ll) In arefrigerating machine, heat rejected is .. ......heat absorbed.

12) The difference between the d.y bulb and wet bulb temperature is called

l3) The function of a is to direct the air from air handling unit to the room

14) wet - bulb temperature of air whose relative humidity is 100% is to dry bulb
temperature.

l5) The relative humidity . .... .. ...during heating and dehumidification process.

16) In a .. constant volume air conditioning system cooling in some zones and
heating in other zones can be achieved simultaneously.

17) Comparing vapor compression refrigeration system with absorption refrigeration system,
the compressor of the former is replaced by ....

r8) widerv used when rerrigeration IS required at \-

Y::i ::::::::;JJ;[il:.,*'
19) The cycle is described as a heat operated cycle.

20) In a vapor compression refrigeration system, COp of dry compression is

. ..that of wet compression of the cycle.
 KATHMANDU UNIVERSITY
End Semester Examination
February/March, 2018
l4AR i 5 2018
Level B. E. Course : MEPP 403
Year IV Semester : I
Time 2 hrs. 30 mins F. M. :55

[5Q l1 : 55 marks]
"
Attempt ALL questions. Assume suitable data if any is missing.

a. Explain with the help of suitable schematic and T-S diagram the difference between
multistage vapor compression system with flash chamber and flash chamber with
intercooling. t6l
b. What is thermal distribution system in air conditioning system? Discuss with the help of
suitable schematic diagram about the single duct variable air flow (VAF) air conditioning
system. t5l
2. a. A LiBr-water absorption refrigerant system having 100 "C generator temperature, 40 oC
oC oC
condenser temperature, 30 absorber temperature and l0 evaporator temperature is
in operation. The mass flow rate of LiBr-water solution from absorberto generator is 0.6
kg/s. Compute the rate flow of refrigerant through the condenser and evaporator as well
as the rate ofheat transfer from generator, condenser, absorber and evaporator. t8]
b. Explain briefly the influencing factors that affect thermal comfort. I3l

3 a. A two stage vapor compression refrigeration system with a flash gas removal and
intercooling operates with ammonia as the refrigerant. The evaporator and condenser
temperature are -25 oC and 35 oC respectively. If the refrigerating capacity of the plant is
123 kW, estimate the work of low stage and high stage compressors and the COP of the
cycle. Had the compression been done in a single stage, what would have been the
percentage increase in the total work of compressor and COP of the cycle?
t8]
b. What are the refrigerants? Describe the desirable properties of refrigerants. t3]

4 a. In an aircraft, cabin cooling is required even though the outside temperature is very low
at high altitudes. Explain why cooling is required at this high altitude and also describe
which kind of refrigeration system is used for it and why. t6l
b. Explain briefly the important variables and the basic steps to be considered while making
heat load estimation. t5l

5. a. An office is to be air conditioned for 60 staff when the outdoor conditions arc 12 "C DBT
and 10 oC WBT and required conditions of the room are 20 oC and 60Yo RH. If the
quantity of air supplied is 0.3 m3lmin/person, find the following:
t8l
i. Heating capacity of the coil in kW,
ii. The surface temperature required if the bypass factor of the heating coil is 0.4, and
iii. The capacity of the humidifier, and
The required condition is achieved first by heating and then by adiabatic humidification.
(Use Psychometric chart to solve the problem and leave the chart along with your answer
copy)
b. With the help of T-S diagram, show how reversed Carnot cycle has larger refrigerating
effect and smaller compression work than the ideal vapor compression refrigeration
cycle. t3l
 KATHMANDU UNIVERSITY Marks Scored:
End Semester Examination [C]
June 201 8
Level : B.E Course : MEPP 403
Year : lV Semester: I

Exam RollNo. Tirne: 30 mins. F.M. :20

0 2018
Registration No. Date Jt{ 1

SECTI oN "A"
Il0 Q.x I = l0 marksl
Mark 1r/1 for the most appropriate answer (s).

The relationship between COP heat pump and COP refrigerator fbr the same range of
temperature operation is
a) COP heat pump = COP refiigerator b) COP heat pump - COP refrigerator = I
c) COP heat pump = 2COP refrigerator d) COP heat pump + COP retiigerator =l
D
2. The cooling load temperature difference (CLTD) incorporate the effects of
a)infiltration b) thermal storage c) ventilation d) internal loads

J- The outdoor air enters into the air-conditioning space through window cracks and
through doors when opened is termed as ....
a) leaks b) glazing c) int.iltration d) penetration

4 The ratio of high temperature to low temperature for reversed Carnot refiigerator is
1.25. The COP be
a)Z b)3 c)4 d)5

5 Vapor compression refrigeration system is used as heat purxp to heat a room and also
direct radiation electrical heater is used to heat similar room. For the same heating
effect the former arrangement uses
a) more electrical energy than the latter b) less electrical energy than the latter
sD c) Same electrical energy as the latter d) more or less as it cannot be predicted

6 In a simple saturated vapor compression refrigeration cycle the fbllowing results were
obtained. Heat rejected in condenser is 160 kJ/kg, compressor work is 32 kJ/kg. The
COP refiigeration is
a) 5 b) 4 c) 6 d) not possible to find with this data

7 Wet- bulb temperature of air whose relative humidity is 100% is

a) greater than dry-bulb temperatr.rre b) equal to dry bulb temperature
c) less than dry bulb temperature d) cannot be predicted

8 In summer air-conditioning system fbr hot and humid outdoor conditions, the required
comfort conditions are obtained by employing
a) Cooling with humidification b) Heating with dehumidification
c) Cooling with dehumidification d) Heating with humidification
 I A good refi'igerant for vapor compression cycre should have
a) high thermal conductivity b) low latent heat
c) high leak renddncy d) high viscosity

t0. when flash gas removal is used in a murtistage compression. it

a) eliminates the undesirable throttling of the vapor generated at
the intermediate
pressure
b) increases the work to be done in high pressure compressor
c) increases the size of the evaporator
d) has no effect in the svstem

SECTION "B''
t l0 Q. x I = l0 marksl

il. Room sensible heat factor is the ratio of ....

t
12. A ton of refrigeration is equivalent to kJ/s.
13. For saturated air wet bulb depression is

t4. The cooling load temperature difference (CLTD) incorporates the effbcts
of

15. The by-pass factor (BpF) of the coil ... as the number of rows in
the flow direction increase.

16. The refrigerant usually used in aero plane is .....

t7 Using intercooling in multi-stage compression systems will .....
at higher stage compression.

l8' When the suction pressure of vapour compression refrigeration

system decreases. the
COP of the system is ...... ...

19. During sensible cooling, wet bulb temperature

20' An assembly of different parts of the system used to produce specified
condition of air ?
with a required space building is called
 KATHMANDU UNIVERSITY
End Semester E.xamination [C]
June 20 I 8 $l 1 0 2018
Level : B.E. Course : MEPP 403
Year :IV Semester: I
Tirne : 2 hrs. 30 rnins. F.M. :55
SECTION "C''

,.\ttempt.4ZZ questions. Assurne any suitable data if any is missing.

La. Explain, with necessary schematic diagram, basic absorption refiigeration system and
compare it with vapor compression system. 15]
b. Write short note on 'thermodynamics of a human body' and explain brietly the t'actors
which affect human comfbrt. 13]
c Explain with the help of a diagram the advantage of dry compression instead of wet

-r compression in a vapor compression refrigeration system. 13]

2.a. What is azeotropic refrigerant? Discuss the desirable properties of refrigerants. 14)
b. A vapor compression ret'rigeration system based on refiigerant 22 operates between an
evaporator temperature -24oC and condenser temperature of 50oC. Determine a) COP ol
the system, b) Work input to the compressor, c) Area of superheat horn and d) Throttling
loss. (Draw TS diagram and assume isentropic compression). t7)
3.a. Explain multi stage compression refrigeration system and working principle of flash gas
chamber with the help of schematic and TS diagram.
t6]
b. The simple LiBr-water absorption refrigeration cycle is operating at the fbllowing
temperatures: generator, l00uC; condenser, 40 "C; evaporator, l0 uC: ancl absorber 30'C.
Compute the rate t-low rate of refrigerant through the condenser and evaporator in the
cycle if the pump delivers 0.6 kg/s. (Draw a schematic diagram and level all components
with temperature).
t5l
4.a. A small office of 30 person capacity is to be air conditioned when the outdoor

t conditions are 35"C DBT,27 "CWBT and required conditions fbr the otfice are23"C
DBT and 55% RH. If the amount of air circulation is 0.35 ml/min/person and serrsible
and latent heat load in the room are 121500 kJ/h and 41300 kJ/h, respectively, find the
plant.
sensible heat factor of the
tgl
(Sketch the process in a Psychometric chart and leave the chart along with your answer
copy)
b. Write short notes on Air Handling Unit (AHU). t3l

5.a. Explain briefly the simple aircraft relrigeration systems with the help of suitable
diagram. t6l
b. Saturated air leaving the cooling section of an air-conditioning system at l4"C at a rate
of 50 ml/min is miied adiabatically with the outside air at 326C and 60 percent relative
humidity at a rate of 20 m3lmin. Assuming that the mixing process occurs at a pressure
of I atm' determine the specific humidity, the relative hurnidity, the dry-bulb
temperature, and the volume flow rate of the mixture.
t5]
 KATHMANDU UNIVERSITY Marks Scored:
End Semester Examination [C]
!!, APil'2023 Course : MEPP 403
Level : B.E.
Year : IV Semester: I
Exam Roll No. : Time: 30 mins. F.M. :20
Registration No.: Date
SECTION "A"
[20Q.x l=20 marks]

Choose the most appropriate answer and mark [X] in the box.

I The highest temperature during the cycle in a vapour compression refrigeration system
occurs after
[ ]compression [ ]condensation [ ]expansion [ ]evaporation
2 Which one is not a refrigerant flow control device
[ ] electronic expansion valve [ ] float valve
[ ] thermostatic valve [ ] capillary tube
3 A Carnot heat pump operates between 200 K and 250 K. tts coefficient of performance is
tls.o tl4.o l. lr.2 tlo.8
4. For a simple vapour compression cycle, enthalpy at suction is 1600 kJ/kg, enthalpy at
dischargelrom the compressor is 1800 kJ/kg and enthalpy at exit from condenser is 600
kJ/kg. What is the highest possible COP for the cycle?
t 16.0 t l7.s t l5.o t l4.s

5 Condensation process in vapour compression refrigeration cycle is carried out at

[ ] constant volume [
] constant pressure
[ ] constant enthalpy [
] none ofthe above

6. Which fluid properties in all its three phase are made use of in thermodynamics?
[ ]Ammonia [ ]Water [ ]Feron12 [ ]Helium

7 In milk chilling plants, the usual secondary refrigerant is

[ ] Sodium silicate [ ] Propylene glycol
[ ]Brine [ ]Ammoniasolution
8 Two-stage compressor takes in air at 1.1 bar and discharges at 20 bar. For maximum
efficiency, the intermediate pressure in bar is:
tlr0.ss l)7.33 114.7 t ls.s

9 In TR capacity water cooler, water enters and 30oC and leaves at l5oC. What is the
a 0.5
actual water flow rate in kg per hour?
tlso tlTs tlloo t)tzs
10. Which of the process is not present in vapour compression refrigeration system?
[ ]isothermal [ ]isentropic [ ]isobaric [ ]isochoric
1l In summer comfort cooling, air in the occupied space should not have a relative humidity
above
[ )30Vo [ )40Vo | 150vo | ]60Vo

12. The temperature of air recorded by a thermometer when it is not affected by the moisture
present in it is called
[ ] wet bulb temperature t I dry bulb temperature
[ ] dew point temperature [ ] none of these

l3 Waste heat can be effectively used in which one of the following refrigeration systems?
[ ] Vapour Compression System [
] Vapour Absorption System
[ ] Air refrigeration System [
] Vortex refrigeration System

t4 Which are the two types of heat transfer taking place during ventilation of a building?
[ ] latent and radiant [ ] latent and sensible
[ ] latent and conduction [ ] sensible and radiant
15 Air at lOoC is heated to 15oC using a heater with surface temperature of 20oC. The by-
pass factor is
t lo.s [ ]0.15 t l0.l t 10.2

16. What does FCU air-conditioning system stand for?

[ ] full conditioning unit [ ] fan coil unit
[ ] full compressor unit [ ] failed compressor unit
17. Which is correct for sensible heating processes on a psychrometric chart?
[ ] curved line between two dry-bulb temperatures
[ ] vertical straight line
[ ] any line at 45. to the horizontal
[ ] horizontal line
18. For a room sensible heat factor is 0.8. If total cooling load of the room is 5 kJ/min what is
the latent cooling required.
[]4kJlmin [ ]2kJlmin [ ]1kJ/min t l0.SkJimin

19. The reason for a person feeling more comfortable on a warm day if seated in front of an
electric fan is that the
[ ] metabolic heat production is reduced
[ ] body loses morl heat by convection and evaporation
[ ] body loses more heat by radiation
[ ] body loses more heat by evaporation and radiation
20 Most commonly used method for duct design and sizing is
[ ] velocity reduction method [ ] static regain method
[ ] equal friction method [ ] dual duct method
 KATHMANDU UNIVERSITY
End Semester Examination [C]
ItI ApiI,2023
Level B.E. Course MEPP 403
Year :IV Semester I
Time : 2 hrs. 30 mins. F. M. 55
SECTION "B''
Auempt ALL questions. Assume suitable data if necessary.
Psychrometric chart is attached. Use it where applicable. Chart has to be attached with answer
sheet.

I
a. Describe working of vapour compression refrigeration cycle with a schematic, P-h
and T-v diagrams. 16l

b. A dense air refrigeration cycle operates between pressures of 4 bar and l6 bar. The air
temperature after heat rejection to surroundings is 37oC and air temperature at exit of
refrigeration is 7oC. The isentropic efficiencies of turbine and compressor are 0.85
and 0.8 respectively. Determine compressor and turbine workdone in kJ/kg and C.O.p
of the system. Take y-- 1.4 and Cp = 1.005 kJ/kg.K. t5l
2.
a. Write down the limitations for single stage compression. Describe working of cascade
system in details. t6l
b. A water cooler for drinking water should cool 25 mUs water from lSoC to lOoC while
the water reservoirs also gain 60 W from heat transfer. Assume that a refrigeration
unit with a COP of 2.5 does the cooling. Find the toral rate of cooling required and
the power input to the unit. t5l
J
a. Define the terms dry bulb temperature, specific humidity, specific enthalpy of air and
by pass factor. t4)
b. Based on equal friction method construct a methodology of calculating duct size for
and air-conditioning application. I5l

4 Describe in details, methods of calculating following cooling load components for a

building facility. [4+4+4]
a. Wall heat gain/loss
b. Heat gainfloss due to Ventilation
c. Heat gain/loss due to fenestration
5 A room is air conditioned by a system that maintains 24oC DBT and 50Vo rh inside, when
the outside conditions are 34oC DBT and 40Vo rh. The room sensible and latent heat gains
are 60 kW and l2 kW respectively. The outside fresh air flows over a cooling coil and is
cooled to 1OoC DBT and 85Vo rh.It is then mixed with recirculated air, the mixture being
handled by a fan, passed over a second cooler coil and sensibly cooled to l2oC DBT. The
air is then delivered to the room. If the mass flow rates of fresh air and recirculated air are
1.73 kg/s and 3.164 kg/s respectively. Find tl2)
a. DBT and enthalpy of the air handled by the fan
b. State of air supplied to the room
c. cooling capacity of first cooling coil and second sensible cooling coil.