MECHANICAL ENGINEERING

Paper-II

(Time Allowed: Three Hours) Maximum Marks: 300)
INSTRUCTIONS

Each question is printed both in Hindi and in English. Answers must be written in the medium specified in the Admission Certificate issued to you, which must be stated clearly on the cover of the answer-book in the space provided for the purpose. No marks will be given/or the answers written in a medium other than that specified in the Admission Certificate. Candidates should attempt Question nos. 1 and 5 which are compulsory. and any three ofthe remaining questions selecting at least one question from each Section. The number ofmarks carried by each question is indicated at the end ofthe question. Ifany data is considered insufficient, assume suitable value. Psychrometric chart is attached with this question paper. Wherever coordinate diagrams/graphs are to
be drawn. these are to be plotted only on the answer book and not on separate graph sheets.
. q;r fJ'qJ..-o W grpf-"q3f ffl€9H
W f9TTT J
I•


1. Answer any THREE of the following 3
m of gas at 10 kPa and 130°C adiabatically to 1 kPa. It is then isothermally compressed to its original volume.
Cp 1·005 kJ/kg-K and C 0·718 kJlkg-K.
v Represent these processes on P-V diagram. Find final temperature and pressure of gas.


For compression work to be what should be process ofcompression? Is it used in practice 20



For nonnal shock wave derive the following expressIon


1
Pay Y-1M 2Y Px 2 x 1 1
where x and yare the conditions before and after the shock wave.
Show Fanna line in adiabatic flow with friction on h-s diagram and explain the physical significance. 20
2
(Contd.)
•



1. f:1 R1Pm1 it -f"Gh...-tft 3
3

10 kPa 130°C 1R il1T CfiT 1 kPa Gqi Q;IDlS14 Y« (Ul 'IDm
m 3{1t1t14 "ffCfl itldl I
C p 1·005 kJlkg-K Gm C 0-718 kJ/kg-K.
v
9stiJOilo ctn p-v 1f{ cllCfd
CfiT 3l1Wr (fT11 (fm I

q;1lf dt( eft fi'q'tS91 9XIT if 9JXPI 11lal 20
SPlid i;1{JI
Pay 1+y M 2 2y -1J Px 2x 1Y+ 1
X y "(SffG eFt

'qCSfUlgctct titd'lCSlOi 9 h-s
cFr (P.TI eFT fqlSc 20
3 (CoDtd.) •


A decorative plastic film on a copper sphere having 10 mm diameter is cured in an oven at 75°C. Upon removal from the oven, the copper sphere is subjected to an air stream at a temperature and velocity of 1 bar, 23°C and 10 mls respectively. How long it will take for the sphere to cool down to 35°C? State the assumptions made and justify
the method of analysis used.
For copper, the density, specific heat and thermal conductivity are, 8933 kg/m3, 388 J/kg-K and 350 W/m-K. The following correlation for forced convection may be used

For air, kinematic viscosity, thermal conductivity and Prandtl number at the mean film temperature under consideration are I 5·53 x 10-6 m 2 Is, 0·025 and 0'708 respectively. 20

Derive the following expressions for lift eeL) and drag coefficients for flow with friction. through a compressor (axial flow type) cascades:

4 (Contd.)
•


10mm doH cf; Ti1c1r 1:RffGJ Iq eT eFt fllllCfl 3TICfT 75°C qCf)ltll Tfltr I 3TICfT ft f:q If1:2t cf; GTan In 11{ urn qft TTIf· fGIfi Cfi1 GnSf, (fTq itrT QI: 1 bar, 23°C (fZIT 10 mls I Jnf1) eFt 35°C (f"ql if f4:;tF11 ti1itl C1"l1Jtl lTIf 13fr ISl {11 9 gctii 51 aI f2rttr cf; fPT r
'tP-i(·qt 3J1Sq1 crm £lSJ41 8933 kglm3, 388 350 I ("i§ffciIU cpT SP:JIJI
ifT CfHj I
NUd 0-06 PrO'4

d')tSJiI mfffirr fi d .CfT11 Cff 3TCfl J1 £11
15·53 x 10-6 m 0-025 0-708 I
(3Tafrll Slqle; S1¥4) if 'TRf 9 q If5 cf; Cfi ISf
L
c4'31tfi1
S
CL 2-(tanu l -tan a cos am tana
C Dm
5 (Contd.)
•

where up Ct2' am and denote pitch, chord, inlet flow angle, outlet flow.angle, average flow angle and total pressure loss coefficient.
Show the variation of C and CD with
L incidence and discuss physical significance.

2. A Carnat engine operates between source temperature of 500 K and sink temperature of 300 K. It produces work utilising the heat of
.
10 kJ from the SOillCe at 500 K. The work produced by this engine is by a Camat refrigerator operating between refrigerator temperature of 200 K and sink temperature of 300 K.
Represent schematically these engine and refrigerator operations.
Find out:

Work produced by the Carnot engine.


Refrigerating effect produced at 200 K by the Carnat refrigerator.


6 (Contd.)
•

urID a2, am am: lfrcrr, 3lorfi:r 9q It? StCflti I§ eN 0 (fqf eII cl:I Cfd

CD cpr 3U4ct, "it f4iH1::r 'ffm
L mfticp J4i?fq I 20

2. Cfltrff %31"4 500 (fN crm 300K orq iF 1=fUT 9"t:1lfF"l Cfl «(it I 500 K 10 kJ d"liSJOil qlT SlmJI Cf)p:f ........ Cfi I I IDU Z3 .... Cf)p:f 9:qlfFi -if jUdi (ffl1 200 K om CfI1l 300 K "ilu:r
"I "

CfiTlf Cfi I I
W {i14 trm CltFffi I

Chi ;off Gt "1 IDU d .... 4 c.pJif I
200 K Cfilr:t1 IDU
1Jcq-rq1

7 (Contd.) •
Total heat rejected to the sink at 300 K.


By how much the refrigerator temperature be increased to get double the refrigerating effect as per above?


Total heat rejected to the sink at 300 K when the refrigerator operates as per the temperature for above. 20



The velocity distribution in the fully developed flow region of steady incompressible laminar flow of a fluid in a horizontal pipe is given by


,where u and u are respectively
uR m
m
the velocities of any radial distance, from the
axis and at the axis of the pipe and R is the radius.
Show that the kinetic energy correction factor, a
and momentum correction factor, are respectively
equal to.2 and 1·33. 20

Air at the rate of 35 kgls flows through a nozzle in which a normal shock occurs in the diverging section down-stream ofthe throat. The nozzle has an area of cross section equal to 40 cm2 at the section ofshock. The pressure and velocity of fluid just before the shock are 2·5 bar and 480 m/s respectively. Find the Mach number, pressure and
8 (Contd.)
•

eFt 300 K 11f{c:-l1Cfd 3"J6J41 I
"(fTq" q;T fGm 2hq 9 fl ct 4 "9" rq-fCf m
3l4{ GT'1 Cfi{cll 300 K"tIT ern Cfi'M

" &csql I 20

3H:141:s...q YCllg f"q(i (Of
u 3le=f
u SfllOlQI:
m

u rn
rlR 31fff 1R W3ft{ R-=rff qi1 ll'ft1Gr a Gm f3 q;r llPi 2 3Tn: 1·33 I 20
. 35 kgls 941t? qi"{ 'Uft fGi{1if; 3i4elfl -if cFo cF 3ij)9qI8 if VEtld j("q...-"1 mm I 'T4fff crrB ctt cpfC CfiT 40 cm 2 i I S1'QI<1 2·5 bar am: 480 m1s I +fRcr (Mach) 3iql 9 (Contd.)
temperature after the shock. Comment on the results. Normal shock table


1·42 0-7314
2·1858
1·2676
1·7243
0·9531

1·43 0·7274
2·2190
1·2742
1'7416
0·9503

3. The temperature of product of combustion in a
boiler decreases from 11 aoce to 550°C while the pressure remains constant at 0·1 MPa. Water at O·g MPa, 150°C is converted into steam at 0·8 MPa, 250°C with the surroundings is at 100 kPa and 25°C. Sketch the contro-l volume depicting the terminal and process conditions and show on a T-s diagram the processes. Calculate the
following:

change in availability of water on unit mass of water basis,


change In availability of product of combustion per kg of water,


process irreversibility per unit mass of water,

second law efficiency, and


entropy generated per kg of water.


10
(Contd.)
•

(izrT 9 £J [ft iflG 3Th:" I u111=1 Chi 1
9£flct 11h1CfiI:
M 1 M2 P2/Pl T2 IT. P2 Pl P02 POI
1·42 1·43 0·7314 0·7274 2·1858 2·2190 1·2676 1·2742 1·7243 1·7416 0·9531 0·9503

3. ist!tl C1"( IG :cfiI 1100°C 550°C 0Cfi cpq m Jfaf 0·1 MPa {i5ctl I 0·8 MPa 150°C "tIT iT(1 qq 0·8 MPa, 250°C 'qTq 11m 100 kPa (fl1i 25°C I crm SHflJOOl 3i Itl d cpr 3i <"Ci <5Fi l!l am-SBfl eFt T-s I qft J10I., I
3R1 *QifJi41 11T ifM if
"3 lCfr cp't q fStoh11 -q-ftA "'SrRr kg ifR cF
ii) ;fFf if; -srft1 QfflCf) api14 3T5l'Rl
1"4 G&1m,

"tJ"Ri kg tit
11 (Contd.) •
Take average specific heat ofproduct ofcombustion as ]·09 kJ/kg-K. Specific enthalpy and spe.cific entropy of water at 8 MPa, I50a C are, at 632·2 kJ/kg and }-8418 kJ/kg-K and that of steam at O·g MPa, 250°C are respectively at 2950 kJ/kg and 7·0389 kJ/kg-K.
20

A heat transfer equipment utilises 5 mm diameter, 10 ern long smooth circular cross-sectioned conduits drilled horizontally in a plate longitudinally on which a constant heat flux is imposed uniformly. Air enters each conduit at 27°C with a mean velocity of 3-0 m/s and leaves at 77°C. If 20 conduits are arranged in the plate, calculate
the following

total rate of heat removed from the plate,


exit conduit wall temperature, and


local heat transfer coefficient at the exit of each conduit.
Sketch the variation in local heat transfer coefficient along the length of conduit.
The following correlations are known for convection heat transfer

NUd for fully developed laminar flow,


NUd 0·023 Pr°-4 for turbulent


12 (Contd.)
•

dcQIG afifld 1·09 kJ/kg-K I eFt 0-8 MPa, ISO°C 1R (fql 632·2 kJ/kg
1-8418 kJ/kg-K om 0·8 MPa, 250°C 1R" cmq 2950 kJ/kg 7·0389 kJ/kg-K I 20
I 3ft1 1 qfCfl if 5 mm cl1I'8, 10 em dan{ CfCti 0 I q?r 9 til JI it (1141 "Tflri I -it 1l -if Q!fi (Pi 3"?lS1Oll Cff1 CHi iIfiKr I9 Cfi ctl"5...li,c Cfri 27°C 3fI'8d 3·0 m/s it Cfi{ctT PlCflC1dT I if 20
CfiSf qfr JIO['11

eti:S J{c G1C4 1« "ffi11, 3fn:
Efi:s "Cf{ 3ia {Ol TIICfl I
9lS,tLc <tt dlS11 it &:IlSJOil 31(.9 {Ol 1])01jcp
cpr 61"'1
f:fqtF1 31d{OI mo


NUd eF
NU d 0-023 PrO'4 Sjqli?

13 (Contd.) •
113
Red Pr ._
Nuz 1·.) developing flow with
Red prJ 10[

is the axial location from the inlet along the length of conduit. Properties of air at 52°C: C 1006 P 1'1774 kg/m3 v 18-22 x 10-6 m K 0·028 Pr 0·703. . 20

A 0·5 m diameter disc heater is horizontally placed and enclosed concentrically in a hemispherical shaped surface. The surface ofthe enclosure having an emissivity of 0·7 is maintained at 500 K. The disc having emissivity 0[0·8 is maintained at 1200 K. The diameter of the hemisphere is 2 m and the remaining base area enclosed is open to surroundings at 300 K and may be considered as black with reference to radiation exchange. Sketch the schematic and thermal radiation network. Using thennaI network method, calculate
t
the heat exchange between heater and hemispherical enclosure and that between heater and surroundings. Neglect convection heat transfer. Assume heater and hemispherical surface are opaque, diffuse and gray. 20
14
(Contd.)
•
Nu 1-3 [Red 2l<fdlOl

z

f'1I pr] 10 1


dau{ qff I 52°G C 1006 P 1·1774. k g/ill3, v=18 ·22 x 10-6 m K 0-028 Pr 0-703. 20
5 m auf] cf; d ILJij1 q?r l"flIT I 3i§ldl eFt IQ; l"Tm CfiI dIqq:; "fVl f1 c61 'JrCfitil 1200 K mrr CflT &I1("f 2 m 3lT'UIT 3ffiffl if 300 K lIT (fm cp'T "ft Cfilfll ill flCfld I WI t11Ui=1IiS1 Ji -itc:qctf Cf)T I CfiT 941JI Cfl{d t1lqq:; crm l1Ui IQCfl QI "11Ur &641 €I" q 3"liSI11 3it1 I q?r I +fA dIq Cf1 3ltfJTHf14 31 q I{G 61 {flif

15 (Contd.) •

4. An open cycle gas turbine takes in air at 300 K and 1 bar and develops a pressure ratio of-20. The turbine inlet temperature is 1650 K. The polytropic efficiency of compressor and turbine each is 90%. The pressure loss in the combustor is and the alternator efficiency is 97%. Take cpa 1·005 kJ/ kg-K and cpg 1·128 kJ/kg-K for air and gas respectively. The calorific value of fuel is
42 MJlkg. Work out the following

Sketch the system and show the process on T-s diagram.


The overall efficiency.


The specific power output.


The fuel to air ratio.


The specific fuel consumption.



Show in general the variation of gas turbine thennal efficiency with compressor ratio for various turbine inlet temperatures.


What is the reason that thermal efficiency of gas turbine plant increases with decrease in compressor inlet temperature? 20
16
(Contd.)
•

4. ltB-co 300 K 1 bar (fm G"T6f 3i"j,qld I CflT crrq 1650 K I co 90% I GU:;Cfi if (ftIT 97% cPa 1'005 kJ/ kg-K cpg 1·128 kJ/kg-K (fqf
Cfi1 liF1 -42 MJlkg WI
q1T 1St "4 SHfilOl Cfll T-s 3111J..CI f4,q J
fa IJ I
vrfcttr I
I
{9qct I
co 31d ffilTI R1tz iRi e.: a;1SJ41 GlffiIT cpr filii tc,"iI H"4 t:Fl
'flIT CfiI{OI eo d1lS41 3ffiTP:r if cp;ft cF CflI {Ol tncfT t 20
17 (Contd.) •

During a test on a two stroke engine on full load, the following observations were recorded: Speed 350 rpm Net brake load 590 N Mean effective pressure 2-8 bar Fuel oil consumption 4·3 kglh Cooling water required 500 kg/h Rise in cooling water temperature 25°C Air used per kg of fuel 33 kg Room temperature 25°C Exhaust gas temperature 400°C Cylinder diameter 220 rom
Stroke length 280 mm
Effective brake diameter 1 m

C.V. of fuel oil 43900 kJ/kg Proportion of hydrogen in fuel 15% Mean specific heat ofexhaust gases 1·0 kJ/kg-K Specific heat of steam 2 ·09 kJ/kg-K Calculate the following

Indicated power


Brake power


Draw heat balance sheet on the basis ofkJ/min.
r
18 (Contd.)•

0f) tIT l1{ (Load) e1JIICfl{ Gl {1"1 350 rpm 2·8 bar 4·3 kg/h 3ueHltll;f1 .Qfla..., =·500 kglh Qfta"1 iTR ctI 25°C "9f(r kg cf; 33 kg Cfie1 (fT11 25°C (fTl1 400°C cqle :.-220 rom
f<;"lCfl Ci611 280 mm =Im 43900 kJ/kg "{urr 61 J1 ti iOllillffi 150/0 ltm ett ::htSJftll 1·0 kJ/kg-K
qft 3)lSJ41 2-09
Cf?r JI Ol41







kJ/min 3TTUR -tR 3liSl11 iSFll I 20
19 (Contd.) •

A cross flow heat exchanger consists of a bundle of 32 straight m long tubes in a rectangular
2

duct of cross sectional area of 0·6 m• Hot water at 150°C and a mean. velocity of 0-5 m/s enters each tube having inner and outer diameters of 10·2 rom and 12-5 mm respectively. Atmospheric airat 1DoC enters the heat exchanger with a volumetric flow rate of 1 m The mean convective heat transfer coefficient on the outside air flow is 400 W/m2-K. Assume tube side flow is fully developed and negligible thennal resistance due to tube wall. Heat transfer IS only between air and water. Calculate exit temperatures of water and air and the total heat transfer rate. The following properties are known:
For air: at 10°C, P 1·2407 kg/in3, at 40°C, p 1·1181 kg/m3, C 1007 J/kg-K. For water: p 922 kg/m3, Cp 4297 Jlkg-K, K 0-688 W J.! 188 x 10-6 Pr 1·18_ Take cross flow correction factor as 0-8. Heat transfer correlations

NUd 4·364, for fully developed laminar tube flow.


NUd 0-023 for turbulent flow in tube_


20 (Contd.)
•

(Cross flow) J;lStJl II 0·6 m 2
32 &fiT 51·5-61 0·6 m cmc: 3ifildtlfil{" if WIT I i50a C 0·5 mls cF 3frnn -if qi<:tH WfGIeCfi! c41("i SfllOtSJ: 10·2 mm Cf?lT 12·5 mm r 419)lOi'5<4)q 10°C 941Q 1 m3/s it 31iSS11 if Cll«ft dtTi?{l 941i? 1R 3frmr tiqe;;ft $ISSO{I 3iij{OI 3r1iCfi 400 W/m2-K I llFf liWCf Sl4lti *ifil{UI "9fi)iTu 1 J}oq t &a:rr {Ol iffi' <frq m-m I 1f(1 (fqr IDt1
3fn: fP'Hl d'ilS41 3td{OI 'SiRf
cit fB"Q: IO°C"ffil1 P 1-2407 kg/m3 40°C
(ITq" P t'118 I kg/m3, C 1007 J/kg-K.
p

UJM fB"Q: p 922 Cp 4297 Jlkg-K,
K 0·688 J..l 188 x 10-6
Pr 1·18. "5lfa9q16 10lCfi Q·811Fr f

NUd «1fl;q 9ql5
I

NUd 0-023 PrO·3 If S!qfti I
2l (Contd.)
•


minimum fluid mixed CR
and the other urunixed in cross flow exchanger
-e..(CRN)
€ 1-e R, minimum fluid
unmixed and the other mixed in cross flow exchanger, where

effectiveness, capacity ratio, N Number
R

of Transfer Units.
Symbols have the usual meaning.
SECTION-B

5. Answer any THREE of the following: I
Two identical petrol engines having the following specifications are used in vehicles:
Engine 1 Swept volume 3300 cc, Normally aspirated, bmep 9·3 bar, rpm 4500, Compression ratio Efficiency ratio Mechanical efficiency Mass of the engine 200 kg.
Engine 2 Super charged, Swept vollUlle 3300 cc, bmep 12·0 bar, rpm 4500, Compression ratio 5·5, Efficiency ratio Mechanical efficiency 0·92, Engine mass 220 kg.
22 (Contd.) •


1-e


CfGT
CR llftlyCfl1? 31lS1i1 it:

1-e cR, (Pi d {C1
m9q!ti 3";lSAl -if

iffii CR trl'fUrr 31 N 31.1 toI (OJ <.otIT I


<IT LtCfl 1i r"i Jft cn6..-n' 5441JI
ii1=-t 3{[4dPi 3300 CC, 9·3 bar, rpm 4500, o.5, O·9, CflT
c4Lf"'"i 200 kg_

3illh"Ff 3300 CC, 12'0 bar, rpm 4500, 3l141{1 Ge1ffT 220 kg.
23
(Contd.)
•
If both the engines are supplied with just adequate quantity of petrol for the test run, determine the duration of test run so that the specific mass per kW of brake power is same for both the engines.
Calorific value of petrol 44000 kJ/kg.
Assume both the engines operate on four stroke cycle.
-Also compare two engines and suggest their applications with reasoning. 20


With the help of a sketch discuss the working principle ofa high pressure Benson boiler with advantages.


Discuss the purpose of drum used in boiler and show internal details for mechanism of separation of moisture in drum. 20



Derive the expression for optimum ratio for


.
blade velocity to steam velocity in the case of Parson's reaction steam turbine with the sketch of blade shape of a stage and velocity triangles.
Give a cylinder layout of a 500 MW steam turbine and explain the reasons ofdouble flow cylinders used. 20
24 (Contd.)
•

fFrtz J""ll ?II 9 Gl1 l'1m 3TCfftr YRi "1l" it lS1 f?r I
CflT 11R'" 44000 kJlkg 1
{Uf 'fS.lqi 'T.fSfi lIT cpn:f Cfl I
?lUi :flo cp't c4T • -am Cfll I fY lSCO Cfl 3T1)g ltprf eFT I 20
eFT eglt1<11 cpn:f ffll2fil--tf ctt 144:q "11 om 3 cf; ffi'q &1(11 I
itm (Drum) S4iftJ I i:fJ <21 qm 311 q!1l1Cfld I CfQT 14Q{uW <itM eFt Ufldf I 20
"tffif"1 qrq C cF (fm if; cti51Cfl <fi
€I .... 1 .

500 MW co cf; cpT G1"1 Cf"lIT Ch 1(uTI eFT fCl4 ii"11 q Ii5 R1 fi:s CflT -3qtn J1 Cflft GiRlI i I 20
25 (Contd.)
•

Comment on the following (Be brief) with the help of schematic if required
In the reciprocating compressors used in vapour compression system, the mass of refrigerant discharged by the compressor reduces as the pressure ratio is increased.
Thermostatic expansion valve is preferred over automatic expansion valve as throttling device.
COP of refrigeration system increases when water cooled condenser is used in place of air cooled condenser.
Vapour at suction to the hermetically sealed compressor is always superheated vapour.
For low sensible heat factor applications, re­heat is necessary. 20
6. Discuss the requirements of an injection _system of a diesel engine.
With the help ofa sketch discuss the working of common rail injection system.
Show the performance curves of a S.I. engine on constant speed and constant load tests. 20
26 • (Contd-J





11T c4Cfd (fm mm aFi

qpsq OS "i "if IJlI4T 6RT CfiT GflSr 3ij)qld Cfll{OI, it <:Itldl I


if crrq 9fi{UT 211,,"q c.p) S1fi (Cl q 1(74 <tt 3fqan tITlIT "lldl I


CfiT 3Tr
Cfi{if lJIH11 I

cf; qltSq 3TRhiLct
A €4cn &;lS41 TICfl CfR1 ffilQ'1 mm W·! 20
6. 5153<9 i'31 =11" cf; ctfr 3tlqQtlCfldl3IT
m 1
t:!:B".3Trt. T.fTff fFrQ: PtrsqIG"1 i. 20
27 (Contd.)
•

A saturated vapour compression refrigeration system is extracting heat from a thermal reservoir at -10°C and rejecting heat to another thermal
reservoir at 36°C. The saturation temperature of evaporator is -20°C and that of condenser is 46°C. The mass flow rate of refrigerant (R-134 is 0·1 kg/so Assume environment temperature equal to 36°C. Find

Refrigerating capacity in Tons


Power input in kW


COP

COP of Carnat refrigeration cycle


Second law efficiency of the cycle.


Compare with the help ofT-s diagram, the vapour compression cycle and Carnat refrigeration cycle and show the deviation between the two cycles
by shaded areas.
Properties of refrigerant (Satlirated)

Temp Saturation Enthalpy (k.Jlkg) Entropy (kJlkg-K)
Pressure Sat Sat Sat Sat
liquid vapour liquid vapour
h f h g sf s g
-20 0'13273 173-64 386'55 0·9002 1·7413
-10 0·20060 186·70 392'66 0·9506 1'7334
36 0-91185 250-48 417-65 1·1717 1·7124
46 1-1903 265-47 421·92 1·2186 ],7089

28 (Contd.)•

-10°C *a;ts4(fJI4
3;151=11 fZ1 tSCh (Sf Cfi {frr· 3ftt <:htsq I CfiT IJI
3Ftr 3l6J1I-qI<l4 "eFt I CflT
(fJtf -20°C cpr 46°C I (R-134
CfiT 9ql$ 0-1 kg/s I CflT (ffq"
36°C lfPf


sPlYh1-=1 &114dl Ton If
P14!11 kW it
3Tt "eft

•

Cfll;off Sf{If)d qlf 3TI 1ft


qq P1tt+f Gfffin I T-s 3fT{<.cr f1 14d I efts 1 Cfi I:off


eFT 1("1"""11 (fm f4 ifC1"'1 ct?r "il I

.

tJ Cd
h s
g g


-20 0·13273 173·64 386·55 0·9002 1·7413
-10 0·20060 186·70 392·66 0-9506 1·7334
36 0·91185 250·48 41"7·65 1·1717 1·7124
46 1·1903 265·47 421·92 1·2186 1·7089

29 (Contd.) •

Super heated Pressure hg sg
1 428·91 1-7413
1-2 436·12 1-7413


20
Derive the following expression for the
'critical pressure ratio in a steam nozzle c
where steam enters with initial velocity and
the flow is accompanied with friction
r z 1
where:
C I initial steam velocity
PI initial steam pressure
" small stage expansion efficiency 11 0
nl actual exponent -of expansion
vI initial steam specific volume.
Show the effect of variation of back pressure
on distribution of pressure and -velocity all
along in a convergent-divergent nozzle. 20
30
•

(arRif1Cd
G"R. h
s
g g. 1 428·91 1·7413 1-2 436'12 1'7413

20 0f) mt1
cliVictJ qft c9),qRl cflfGIQ) . 9qli?



C I ..'qT11 P 1 . t1G 9 f11 n ..
gf!1 cpr
VI cqp:r I
'tfVq CflT· GTGr 1R" RZClI I nnm 20

31
(Contd.)
•

7.

..

In a steam power plant, the steam generator generates steam at the rate of 120 tlh at a pressure of 100 bar and temperature of500°C. The calorific value of fuel used by steam generator is 41 MJ/ kg with an overall efficiency of 85%. In order to have efficient combustion, 17 kg of air per kg of fuel is used for which a draught of25 nun ofwater gauge is required at the base of stack. The flue gases leave the steam generator at 240°C. The average temperature of gases in the stack may be taken as 20QoC and the atmospheric temperature is 30°C. Work out the following:

The height of stack required.


The diameter of stack at its base.


Draw the draught distribution considering balanced draught system in a steam generator and mention the advantages of balanced draught.
Take the following steam properties for solution:
h 3375 kJ/kg, 632·2 kJ/kg. 20
f
Draw a neat sketch of aqua-ammonia vapour absorption system. On this sketch
Indicate thennodynamic state points with at the inlet of pump.
32 (Contd.) •

7. if 120 t/h cFr « 100 bar 5OO°C crrq 'J1l1=f 3 Cfi {dI "6I 6TU 99.)Cfd -terrr Cf1T 41 MJ/kg om tj 31 fP4 'GemT 850/0 1 Gel Sf IC(l cf; 17 kg kg m-aT i t cfi 3TTUT{ "tIT 25 mm Jf(Vf ltur 941{i 31 Iq!l?OO1CfidI l cqp:r f01 Cfifitft itm CFT <f2ifl If (1fC1 2 OO°C R1<:rr JfT Cfl d1 ("ft4
mq 30°Ci q?r
eFt £oql{ I
Cfl 1f)1 3TTUR c£lH"i
-if 9 cU{1 q;r I gena fCld{OI cpT {fm
'141d <fi MM CFT I

if; T &iT CfiT SlI4P I cFtfG1
h 3375 kJ/kg, h 632·2 kJlkg. 20
f

CfT&1 3jqflTItSj 0 1
I W fmf

3"JtsqlllR; Cf1l

I



Show the direction of the following energy transfers to various components


33 (Contd.) •
eA energy transfer to absorber
ep -energy transfer to pump
eg-energy transfer to generator

..
en -energy transfer to dephlegmator
ec -energy transfer to condenser
ee -energy transfer to evaporator.

Mention for each of the energy transfers in

above whether it is in the form of work or heat.



With heat sink temperature of 27°C, heat source temperature of 127°C and refrigeration temperature of find max COP of the vapour absorption system and mention the


assumptions made. 20

With the help of a neat sketch show a steam!
gas combined cycle with two pressures heat recovery steam generator (HRSG).

Show the processes oftopping and bottoming cycle on one T-s diagram and also. show T-Q diagram for process in HRSG.
Discuss the advantages of combined cycles.
20
34
(Contd.)
•

(01 qft
co cp'i cf; fa (91 eA-3i 61 Cfi 31en::UI
e cpT 3id {Ol
p eFT 311 {Ol
g
3iel {Ol
D q?r aid {Ol
c
31d(Ul I

3iq t Sh:-lt·Cf) 31a {Ol if 'tIT £&:1I cF I
3llS41 CfTl1 27°C, 3)tsJ01,1 127°C (fqT 0fl1 -13°C J:i 31 cniots °I cpr 31'faCfidl"! -Bt 3li 1ft mf fiCflt""q-ilaIT CFT J c--flZ6t I 20
fq"iij fi°gc:td
o
q?r [;leil<fr d")tst{t 'Gfq 3fT"{ 5fI) SlgCfd I

(c:TfiPT) (flIT
T-8 3l11J',Q "tf"{f4(9 am 3lR it eFt T-Q 3lfUq 1R I

flS)<fd eFt 20
35 (Contdo) •

8. Discuss the objectives of supercharging and show the process on p-v diagram.
· Gi ve sketches of two common type
of supercharging and turbocharging configurations.
Discuss parameters affecting engine heat transfer. 20

Give a practical feed heating arrangement of a 660 MW steam power plant by showing steam and feed flow paths. Mention its special
features.
In low pressure steam turbine, steam is wet. With the help ofvelocity diagrams show the direction of flow and water particles on moving blades and guide vanes so that the
_causes of erosion of blades get established.
20

Illustrate the following processes on psychrometric chart with initiaJ state of moist air as dry bulb temperature equal to 200e and relative humidity
of50%





Cooling and humidification .
Heating and humidification


Humidification at constant
dry bulb
temperature.

Mention one application each for above humidification processes.
36
(Contd.)
•

8. cF H.citl J W

9#1"""1 ct?r p-v 3111:(9

en l11J:4r ..lt 9¥4 I
3)tSqT SlatUI q?r q-rR Sllil<:1l' eFT clll{Ol4I I 20
660 MW V"q""{UT (11 q c;q Cl '0QT . ct?r1 IE? RZcila I Fitftori
CO it 'ml1 ant mcft I 3l1{{q lTfdl1l"i Cfm Fl4QI<:f1 'qfCf iH1CfiUff cpT it 3lq (Grot *Chi E'ltse: ill 20
95titIT fGt*i Cfrl eFT 3iq (ITq" 20°C 50%
am 31h{OI
d14=-r 31 E{u I
Qjts4l "ffi1l 3iltul I
[fi 3i JG It: (OJ CfiT
37
(Contd.)
•
If the moist air leaves the system for the case above, at 90% relative humidity, determine per unit mass of dry air

increase in humidity ratio,


increase in enthalpy, Lh


increase in dry bulb dt
Detennine ;Sensible Heat Factor for this process. . 20
38
•

b


tITG fBm; 90% 311 Rt Cfl(1 dT (f6f '9"fu QEf5cp
ZSlrtdl
if lh
VJ&fl "ffTli if At
SHf)J4 cF 3llStJI
•


39
•

Serial No. J [C-DTN-K-NFB






'j.,°lfCfJ 300I

'9,4Cfi w;r 3iUuft if wrr
51 tJ cj; 3 "difT 1ITEWT fN7it
{aj 8 Cf) Id J.77TTCi; 9 411J if ffl; liT 7TllT
3ft< W 1iTEZf1T q;r MISe 3 OJ f1 f(1 if)
"CIT ajFiPd A ff6c. rn: if, rot 1 J W d{ffif?4d 1WWT 31frlRffi 3Flf 1iT'tZf11 if dd rn: m 3fq; 1"iff fitfriT I
I 3ft"{ 5 31PiCf/J-f I lSIl¥1 9$/rj7" if it 9,4CfJ U3 it Cf11T-if-q:;71 if)


f4; .-iff rft;:r 9"11 d n cf1A J
9 r441 !rR fFrr!: Pi 4ft 3fcF; "'Ifl 3Pff if I 311;:".3 3/q4f4i 9(ftd fit dRia 1fR"
r
fq.
"Rfli R1 J Cfi( J 311 H1f&I dhJ I (Psychrometric chart) W tfTW"
tlHJ=i I ff, it ¥4ff "QT 3JIHf{q(1 Cf0AQ" !l7Lfi iteR:
w I


Note: English version ofthe Instructions is printed on the front cover ofthis question paper.
40
•

PSYCHROMETRIC CHART
BAROMEtRIC PRESSURE 1.01325 bar
SEA LEVEL


/fJ.



13,9., r,O.35


..... 5 4tl in 550033 ..

o
VI j-...., 11'1.... rm

..... IJi-..t-l. II 1/r--v... IJIh'. l"-..t'-.IT :0.032 t



YI "hi II /0.40
0.03'1


I VI"" 11 .0.030

.. rfi j "-II 029
iii'
.I I Ii II "hi I'... II ..
....
V1
N II I I. :0.027 ..-0.45


. t--.III 0-. II i"-0.026
. r.... IX 1......1J &IN 1...... . 0 0,025

.... co: ol1 .. . J l-.. c J VJ if II 11:j,J 0.50
t::.lfV t"-.(11 11" 0.023 I. V 1 r.... 0.022 J 0.021
0.55

I. f(11 V P¥I r--..1I . 0.020 IIJ N . ....." 4. " 0.019 . 0.50 ci
fD I r-... I'... " 1. ­.§ .I f.....ll . ll, 0.018 0.65
10, .... V . 1;V t-..., r-.... « 0.017

CJ Itll" S
Jl V J.U t---.1o.95 0.016 0.70

J 0015
rfJ 1?Jt..... V II V I'lf t-..... V r-.. 0.75 Ii) ..... I£ ........ V . ,41i:fH..... 0.014
• 0013 . 0.80
. r-...fJ "r-... .".
OJ 012 0.85
.K r..... t-..··ffi IN 0.90 l./fl".-t....... Y"Nifo' t"-V . 0.011 -0.95
,
jV r-..,......,L/Y.... r-... rl r-... 'i"r..... I)K .010 1.00 .....

I...I!> t'-...V P<. r-... p.< . . ,......, vV N". r-.. r-... ........


l:1" lll>c r-.... h.. vf-. v f'..r-.. f-....! hI><"to-...
K · r-... ,......, "r-....
to kK k-K r--.... r-..... b v " vI< r--r....." r-. l>j...-r-.. t'--.,........ "r-.-,........ '004 5
K Do ........ r-..... r-..... 1-.... .... t" '.....h r..... r-. .
k I>J K r--... f'.. k-r-.. r.....] ." r-.. f',r-.-........ t...... l O.ooa § rn
"or-.... " I'--rtr-..... r-.. I"r-..:""" ........ r-....-f-.... 0.002


.'.....1'.... " f'J"o..-r'....... I-....: r-... 1'........ r--... ",........ t-.. l""--......... ",....... 0.001
000

0 ,5. 10 1S20 25. 30 35 4D 50 5S0. . DRY BULB TEMPERATURE,·C

0.75 m3Jkg 0.80 m3/kg 0.85 mJ/kg 0.90 m3tkg
BELOW O·C PROPERTIES AND ENTHALPY DEVIATION LINES ARE FOR ICE· SPECIFIC VOLUME, mJ/kg DRY AIR