CBSE Class 12 Air-Conditioning and Refrigeration III Question Paper 2019

SET-4

Series BVM H$moS> Z§.
Code No. 112
amob Z§. narjmWu H$moS >H$mo CÎma-nwpñVH$m Ho$ _wI-n¥ð >na
Roll No. Adí` {bIo§ &
Candidates must write the Code on the
title page of the answer-book.

 H¥$n`m Om±M H$a b| {H$ Bg àíZ-nÌ _o§ _w{ÐV n¥ð> 8 h¢ &
 àíZ-nÌ _| Xm{hZo hmW H$s Amoa {XE JE H$moS >Zå~a H$mo N>mÌ CÎma-nwpñVH$m Ho$ _wI-n¥>ð> na {bI| &
 H¥$n`m Om±M H$a b| {H$ Bg àíZ-nÌ _| >14 àíZ h¢ &
 H¥$n`m àíZ H$m CÎma {bIZm ewê$ H$aZo go nhbo, àíZ H$m H«$_m§H$ Adí` {bI| &
 Bg àíZ-nÌ H$mo n‹T>Zo Ho$ {bE 15 {_ZQ >H$m g_` {X`m J`m h¡ & àíZ-nÌ H$m {dVaU nydm©• _|
10.15 ~Oo {H$`m OmEJm & 10.15 ~Oo go 10.30 ~Oo VH$ N>mÌ Ho$db àíZ-nÌ H$mo n‹T>|Jo Am¡a
Bg Ad{Y Ho$ Xm¡amZ do CÎma-nwpñVH$m na H$moB© CÎma Zht {bI|Jo &
 Please check that this question paper contains 8 printed pages.
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written on the title page of the answer-book by the candidate.
 Please check that this question paper contains 14 questions.
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attempting it.
 15 minute time has been allotted to read this question paper. The question
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students will read the question paper only and will not write any answer on
the answer-book during this period.

dmVmZwHy$bZ Ed§ àerVZ - III
(g¡ÕmpÝVH$)
AIR-CONDITIONING AND REFRIGERATION – III
(Theory)

{ZYm©[aV g_` : 2 KÊQ>o A{YH$V_ A§H$ : 40
Time allowed : 2 hours Maximum Marks : 40

112 1 P.T.O.

^mJ H$
SECTION A
{ZX}e : ^mJ H$ _| go {H$Ýht nÝÐh àíZm| Ho$ CÎma Xr{OE &
Instructions : Attempt any fifteen questions from Section A.

1. ghr CÎma H$m M`Z H$s{OE : 115=15
Choose the correct answer :

(i) EH$ gmBH«$mo_o{Q´>H$ MmQ>© na g|{g~b hrqQ>J Am¡a Hy$qbJ H$mo àX{e©V {H$`m OmVm h¡
(H$) EH$ j¡{VO aoIm (I) EH$ grYr aoIm
(J) EH$ {VaN>r aoIm (K) EH$ dH«$ aoIm
On a psychrometric chart, sensible heating or cooling is
represented by
(a) A horizontal line (b) A vertical line
(c) An inclined line (d) A curved line

(ii) g|{g~b hrQ> d Q>moQ>b hrQ> H$m AZwnmV H$hbmVm h¡
(H$) Amog {~ÝXþ (S>çy nm°BÝQ>) (I) AmÐuH$aU AZwnmV
(J) gmnoj AmЩVm (K) g§doÚ D$î_m KQ>H$ (\¡$ŠQ>a)
The ratio of sensible heat to total heat is known as
(a) Dew Point (b) Humidification Ratio
(c) Relative Humidity (d) Sensible Heat Factor

(iii) Ho${eH$m Q>çy~, EH$ {dñVma `w{º$ Ho$ ê$n _| BñVo_mb H$aVo h¢
(H$) Kaoby ao{\«$OaoQ>a _| (I) nmZr Ho$ Hy$ba _|
(J) H$j dmVmZwHy$bH$ _| (K) Cn`w©º$ g^r
The capillary tube, as an expansion device, is used in
(a) Domestic refrigerators (b) Water coolers
(c) Room air-conditioners (d) All of the above

112 2

(iv) W_m}ñQ>¡{Q>H$ {dñVma dmëd g§M{bV hmoZo Ho$ {bE {H$gHo$ à{V à{V{H«$`m {XImVm h¡ ?
(H$) bmoS> (I) {S>J«r Am°\$ gwnahrQ>
(J) Vmn_mZ (K) Xm~
Thermostatic expansion valve operates by responding to
(a) Load (b) Degree of superheat
(c) Temperature (d) Pressure

(v) Bd¡nmoaoQ>a H$mo `h ^r H$hm OmVm h¡
(H$) \«$sqµOJ H$m°Bb (I) Hy$qbJ H$m°Bb
(J) {MqbJ H$m°Bb (K) Cn`w©º$ g^r
Evaporator is also known as
(a) Freezing coil (b) Cooling coil
(c) Chilling coil (d) All of the above

(vi) ao{\«$OaoÝQ> H§$àoga Ho$ àdoe (A§VJ©_) na Xm~ (àoea) H$hbmVm h¡
(H$) MyfU Xm~ (I) {dgO©Z Xm~
(J) H«$m§{VH$ Xm~ (K) níM Xm~
The pressure at the inlet of refrigerant compressor is called
(a) Suction pressure (b) Discharge pressure
(c) Critical pressure (d) Back pressure

(vii) ao{\«$OaoÝQ> Ama-22 h¡
(H$) S>mBŠbmoamo S>mBâbwAmoamo _oW¡Z
(I) S>mBâbwAmoamo _moZmoŠbmoamo _oW¡Z
(J) _moZmoŠbmoamo Q´>mBâbwAmoamo _oW¡Z
(K) Q´>mBŠbmoamo _moZmoâbwAmoamo _oW¡Z
The refrigerant R-22 is
(a) Dichloro difluoro methane
(b) Difluoro monochloro methane
(c) Monochloro trifluoro methane
(d) Trichloro monofluoro methane

112 3 P.T.O.

(viii) ao{\«$OaoÝQ> A_mo{Z`m h¡
(H$) Ama 717 (I) Ama 134
(J) Ama 718 (K) Ama 152
The refrigerant ammonia is
(a) R 717 (b) R 134
(c) R 718 (d) R 152

(ix) àerVZ MH«$ _| A{YH$ Vmn_mZ nm`m OmVm h¡
(H$) Hw§$S> ([agrda) _| (I) EŠgn¢eZ dmëd _|
(J) Bd¡nmoaoQ>a _| (K) H§$àoea {S>ñMmO© _|
The higher temperature in refrigeration cycle occurs at
(a) Receiver (b) Expansion valve
(c) Evaporator (d) Compressor discharge

(x) hdm O¡go R>§S>r hmoVr h¡, CgH$s gmnoj AmЩVm
(H$) ~‹T>Vr h¡ (I) H$_ hmoVr h¡
(J) Aà^m{dV ahVr h¡ (K) Cn`w©º$ _| go H$moB© Zht
As air cools, its relative humidity
(a) increases (b) decreases
(c) remains unaffected (d) None of the above

(xi) BboŠQ´>mobŠg ao{\«$OaoQ>a _| {ZåZ{b{IV H$m`©H$mar nXmW© hmoVm h¡/hmoVo h¢ :
(H$) hmBS´>moOZ >
(I) A_mo{Z`m Am¡a hmBS´>moOZ
(J) A_mo{Z`m, hmBS´>moOZ Am¡a Ob
(K) A_mo{Z`m Am¡a Ob
Electrolux refrigerator has the following working substance(s) :
(a) Hydrogen
(b) Ammonia and Hydrogen
(c) Ammonia, Hydrogen and Water
(d) Ammonia and Water

112 4

(xii) Amby ^§S>maU Ho$ {bE AZwHy$b Vmn_mZ hmoZm Mm{hE
(H$) 2C (I) 8C
(J) 10C (K) Cn`w©º$ _| go H$moB© Zht
The recommended temperature for potatoes storage is

(a) 2C (b) 8C

(c) 10C (d) None of the above

(xiii) {ZåZ{b{IV _| go H$m¡Z-gm gdm}Îm_ {dÚwV²-amoYr _mÜ`_ àXmZ H$aVm h¡ ?
(H$) YmVw (I) Vab
(J) J¡g (K) AYmpËdH$ R>mog
Which of the following provide the best insulation medium ?
(a) Metals (b) Liquids
(c) Gases (d) Non metallic solids

(xiv) Q>çyq~J H$s YmVw Xrdma _| D$î_m H$m ~hmd {H$gHo$ Ûmam hmoVm h¡ ?
(H$) {d{H$aU (I) MmbZ
(J) g§dhZ (H§$doŠeZ) (K) Cn`w©º$ _| go H$moB© Zht
Heat flows through the metal walls of tubing by
(a) Radiation (b) Conduction
(c) Convection (d) None of the above

(xv) àerVZ _| dmînZ hmoVm h¡ O~ AdñWm _| ~Xbmd hmoVm h¡
(H$) J¡g go Vab> (I) J¡g go R>mog
(J) Vab go J¡g (K) Cn`w©º$ g^r
Evaporation takes place in refrigeration when there is a change in
state from

(a) gaseous to liquid (b) gaseous to solid

(c) liquid to gaseous (d) All of the above

112 5 P.T.O.

(xvi) H§$S>|ga {ZH$mbVm h¡ ao{\«$OaoÝQ (àerVH$) go
(H$) Ho$db g§doÚ D$î_m
(I) Ho$db JwßV D$î_m
(J) g§doÚ D$î_m Am¡a JwßV D$î_m XmoZm|
(K) Z Vmo g§doÚ D$î_m Am¡a Z hr JwßV D$î_m
The condenser removes from the refrigerant
(a) Sensible heat only
(b) Latent heat only
(c) Both sensible heat and latent heat
(d) Neither sensible heat nor latent heat

(xvii) h¡bmBS> Q>m°M© H$m Cn`moJ {H$g ao{\«$OaoÝQ Ho$ [agmd H$m nVm bJmZo Ho$ {bE {H$`m OmVm h¡ ?

(H$) A_mo{Z`m (I) Ama-12
(J) H$m~©Z S>mBAm°ŠgmBS> (K) Cn`w©º$ g^r
Halide torch is used to detect leakage of which refrigerant ?
(a) Ammonia (b) R-12
(c) Carbon dioxide (d) All of the above

^mJ I
SECTION B

{ZX}e : ^mJ I _| go {H$Ýht VrZ àíZm| Ho$ CÎma Xr{OE & 23=6
Instructions : Attempt any three questions from Section B.

2. H§$àoea H$m H$m`© ~VmBE & 2
Give the function of compressor.

3. E`a dm°ea Š`m h¡ ? 2
What is an air washer ?

112 6

4. EH$ B_maV Ho$ dmVmZwHy$bZ Ho$ {bE ~mhar D$î_m d¥{Õ H$mo g§jon _| {b{IE & 2
Briefly write the external heat gains in a building for air-conditioning.

5. gmoboZm°BS> dmëd H$m Š`m H$m`© h¡ ? 2
What is the function of solenoid valve ?

6. g§nyU© D$î_m ñWmZm§VaU JwUm§H$ H$mo g_PmBE & 2
Explain overall heat transfer co-efficient.

^mJ J
SECTION C

{ZX}e : ^mJ J _| go {H$Ýht VrZ àíZm| Ho$ CÎma Xr{OE & 33=9
Instructions : Attempt any three questions from Section C.

7. e¡b Am¡a H$m°Bb àH$ma H§$S>g| a H$m ñdÀN> {MÌ ~ZmBE & 3
Draw a neat sketch of shell and coil type condenser.

8. {ÛVr`H$ ao{\«$OaoÝQ> Š`m h¢ ? 3
What are the secondary refrigerants ?

9. Bd¡nmoao{Q>d Hy$qbJ Š`m h¡ ? 3
What is evaporative cooling ?

10. EH$ ~\©$ Ho$ H$maImZo _| A_mo{Z`m H$mo H¡$go MmO© H$aVo h¢ ? 3
How is ammonia charged in an ice plant ?

11. gmBH«$mo_o{Q´>H$ MmQ>© H$s ghm`Vm go Ho${_H$b {S>øy{_{S>{\$Ho$eZ (amgm`{ZH$ {ZamÐuH$aU) H$mo
g_PmBE & 3
Describe chemical dehumidification with the help of a psychrometric
chart.

112 7 P.T.O.

^mJ K
SECTION D

{ZX}e : ^mJ K _| go {H$Ýht Xmo àíZm| Ho$ CÎma Xr{OE & 52=10
Instructions : Attempt any two questions from Section D.

12. W_m}ñQ>¡{Q>H$ EŠgn¢eZ dmëd H$m ñdÀN> {MÌ ~ZmBE & 5
Draw a neat sketch of thermostatic expansion valve.

13. EH$ AÀN>o ao{\«$OaoÝQ> Ho$ dm§N>Zr` JwUm| H$s ì`m»`m H$s{OE & 5
Explain desirable properties of a good refrigerant.

14. n{OªJ Ho$ VarH$m| H$m dU©Z H$s{OE & 5
Describe the methods of purging.

112 8