Time Allowed : Three Hours f.!! <'fl('1 i "1"1 f.!! £1 f{ II MECHANICAL ENGINEERING Paper-I P"'f--q"';f T fVliT #; 3l'ft if wff PiAfRf(i;m W jC-DRN-N-OFFA I 3i<t>. 250 Maximum Marks . 250 '!Yf arro (8) TJV"f ciT f.CIVif if JR ff niH 1fif fff;tT r:;ct .-iit'ift if t 1 rrfterreff or;T '!Yf '1i<f r;v;f'f <f; 3D( t I 1JV'1 1 r:;ci 5 3Tf.r<wf t I Wrsr r;v;f'f if it l!f'JS it 'fi11- it- 'fi11 l:fl' 1JV'1 rfFr r;v;f'f <f; 3D( I vrit'f; 1JV'1 /'lf71T <f; 3f<t> 1JV'7 <f; 3l'fr if fl!Wr ff I !Jitw-tf'if if 1fTUf11 if 3D( fffiiRT 3fTCfVlT'fi t niH 7.Ti! (Question-cum-Answer) if 'IT 'P'G7 3fTCfVlT'fi I 7fr!)l11 oF 31rfTCfT 3RT 1fTUf11 if f'fR2t rfit ;miT or;T 3f<t> '1iff I ""'Z'" 'Ftf 'lfr 9/'fif><-4 1 /l{ if>'t rrt t. it wnr <nt 1 arrffl/fil'lifRlll( ;;ri( q;eff 'lfr 3fTCfVlT'fi if, <f; f'ffi: FfT'1 'IT !t 3Rf!1T '1 if;f 'IT <f; Wlffiii'P ifit I r;v;f'f <f; 3D( fiRm:r if fTrr I '1iff W 7R 1JV'7 <f; 3D( or;7 'lfr fi'mft if ffrlTr 1R1fi'r m 3D( 3/ifffl; if JR it' 1 Jn(- if m 'AT liT 'AT * Jtvr 3f1T( ff nr it <t>TC rn 'Wft t 1 QUESTION PAPER SPECIFIC INSTRUCTIONS Please read each of the following instructions carefully before attempting questions : There are EIGHT questions divided in Two Sections and printed both in HINDI and in ENGLISH. Candidate has to attempt FIVE questions in all. Question Nos. 1 and 5 are compulsory and out of the remaining, THREE are to be attempted choosing at least ONE from each section. The number of marks carried by a question/part is indicated against it. Answers must be written in the medium authorized in the Admission certificate which must be stated clearly on the cover of this Question-cum-Answer (QCA) booklet in the space provided. No marks will be given for answers written in medium other than the authorized one. Wherever any assumptions are made for answering a question, they must be clearly indicated. Diagrams/Figures, wherever required, shall be drawn in the space provided for answering the question itself Unless otherwise mentioned, symbols and notations carry their usual standard meaning. Attempts of questions shall be counted in chronological order. Unless struck off, attempt of a question shall be coumed even if attempted partly. Any page or portion of the page left blank in the answer book must be clearly struck off I ** www.examrace.com
Question paper IAS Mains Mechanical Engineering 2014
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Time Allowed : Three Hours
~if; f.!! <'fl('1 i "1"1 f.!! £1 f{ II
P"'f-~-l
MECHANICAL ENGINEERING Paper-I
P"'f--q"';f ~ T fVliT ~ #; 3l'ft ~ if wff PiAfRf(i;m ~ ~ FAI'I~oi<n W
jC-DRN-N-OFFA I
~ 3i<t>. 250
Maximum Marks . 250
'!Yf arro (8) TJV"f ciT f.CIVif if ~ JR ff niH 1fif fff;tT r:;ct .-iit'ift ~;f'f ~ if ~ ~ t 1
rrfterreff or;T '!Yf '1i<f r;v;f'f <f; 3D( ~;f t I
1JV'1 ~ 1 r:;ci 5 3Tf.r<wf t I Wrsr r;v;f'f if it ~ l!f'JS it 'fi11- it- 'fi11 l:fl' 1JV'1 ~ ~ rfFr r;v;f'f <f; 3D( ~ I
vrit'f; 1JV'1 /'lf71T <f; 3f<t> 1JV'7 <f; 3l'fr if fl!Wr ff I !Jitw-tf'if if ~ 1fTUf11 if 3D( fffiiRT 3fTCfVlT'fi t niH 7.Ti! ~ (Question-cum-Answer) ~ if ~ ~ 'IT ~ 'P'G7 3fTCfVlT'fi ~ I ~ 7fr!)l11 oF 31rfTCfT 3RT 1fTUf11 if f'fR2t rfit ;miT or;T 3f<t> '1iff ~ ~it I ~ ""'Z'"
'IV~ ~ ~ 'Ftf 'lfr 9/'fif><-4 1 /l{ if>'t rrt t. ~ ~ ~ it wnr <nt 1
What are composites ? How are they classified ? Mention any four applications of composites.
10
Q. 4(c) ~ 3lfuilfili'fl m ");'1'filtl fl'l<:r\ 3lih.9 m 4(c) 'if fu9T<rr 1Tl:rT ~I <itfll"fl • B-C,
"iffif'l V'ttR 'it '¥. ~ fiR A -q"( ~'l m "<F fffil: 'lf!U ~ I • C or;g: • E '<F
'fl1!1 'li'fl1 '§;3TT ~, am • B • D "<F 'fl1!1 'li'fl1 ~, un f¥'1 V'ttR "<F 'fl1!1 ~ "<F
mu '¥T ~3TT ~ 1
~ ~ if GhiT '1ft ~ m Tb = 27, Tc = 30, Td = 24 am: T. = 21, 'ffi 'iJT\1"fi am: "CJ1ft:rcr.
mit '1ft -mlif '<F 311,-qm 'FT f.r~ ~ I
6
**
www.examrace.com
An epicyclic speed reduction gear schematic is shown in Fig. 4( c). Compound wheel
B-C is free to rotate on pin A connected to driving shaft. Wheel 'C' meshes with fixed wheel 'E' and wheel 'B' meshes with wheel 'D' keyed to driven shaft.
If number ofteeth on wheels are Tb = 27, Tc = 30, Td = 24 and Te = 21, determine the ratio of speeds of the driving and driven shafts. 20
Driving Shaft
A
B
c
n D E
m- 4(c)/Fig. 4(c)
~-<{
SECTION-B
Driven Shaft
Q. 5 (a) 'lNi'f fYlmt 3ffi: rffi fYlmt q\T ¥>fT ~ 3ffi: "l'('q."C(\1.1:(11., <t> I il f~s 3ffi: ~ ~ffi <fi ~ ~('! ~ ORR "<t>Cf-r ~ CIIF 'I'~ I
Compare flank wear and crater wear and draw tool life versus cutting speed curves for H.S.S., Carbide, and ceramic tools. 10
Define 'Grinding Ratio'. Also explain what is meant by a grinding wheel acting soft or acting hard. Is it always desirable to obtain a high grinding ratio in practice ? I 0
Q. 8(c) "C('!l Fclf.'lliful Wwr GT ~<t>R-q<t> Jq<:<t>(f A aftr B i( ~ 'flt't if>'T m W ~I ~ A if>'T "ffi"I1"0 <i 30,000 t ~ ~ B if>'T "ffi"I1"0 <i. 50,000 t I ~ Jq<:<t>(f A aTtr B
1f!ll m I ffi-B0-"3<1\ ~ i\13l<'ft ~ 1""[1.( qi\{ '[IJ 3l~ '[IJ ~ 'IWT <i\ ~: <m: ~I
MECHANICAL ENGINEERING (PAPER-II)
I Time Allowed : Three Hours I I Maximum Marks 250 I
QUESTION PAPER SPECIFIC INSTRUCTIONS
(Please read each of the following instructions carefully before attempting questions)
There are EIGHT questions divided in two Sections and printed both in HIND! and in ENGLISH. . Candidate has to attempt FIVE questions in all. Question Nos. 1 and 5 are compulsory and out of the remaining, THREE are to be attempted choosing at least ONE question from each Section. The number of marks carried by a question/part is indicated against it. Answers must be written in the medium authorized in the Admission Certificate which must be stated clearly on the cover of this Question-cum-Answer (QCA) Booklet in the space provided. No marks will be given for answers written in medium other than the authorized one. Wherever any assumptions are made for answering a question, they must be clearly indiCated. Diagrams/figures, wherever required, shall be drawn in the space provided for answering the question itself. Unless otherwise mentioned, symbols and notations carry their usual standard meanings. Attempts of questions shall be counted in chronological order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the Question-cum-Answer Booklet must be clearly struck off.
1 [P.T.O.
www.examrace.com
!
GIUS-A / SECTION-A
1. (a) v;q; <iiRf 'Glli if "3i'i!T 480 'C 'R mll otft ~ 3fu: 40 • C 'R ~ 3ffift ~ I >ffir 'illli 1Wfi <lit 1@ifi 0·0785 kJ /kg K ~ omft ~I >ffir 'Glli ~ ;;rR ~ "if>T'f 'liT f.tlffiu! ~I In a Carnot cycle, heat is received at 480 •c and rejected at 40 •c. The entropy of the sink increases by 0·0785 kJ /kg K per cycle. Determine the work done per cycle. 10
(b) ~ <:~ llt ~ 1l;<j; ~-'Glli fm ~ re ;f;\ ~ <:&R!T llc ~I~ fm <fTil Tmin i 3fu: <:6'1 'fil\l if TJlf <!if.t 'R 3B'1iT <fTil Tmax ~I ~ Wf\s;r 3fu: mRUT it Wr1; Gl'! ~ r P it, eft
!!"H 4><.1 llc . 11 t • T max if; Wr1; -.ftl!l 'l<!l it;ft .? Tmin
An open-cycle gas turbine plant with turbine effidency llt has a compressor of efficiency llc· The minimum gas temperature is Tmin and after heating in the combustion chamber, its temperature is Tmax. If the pressure ratio for compression and expansion is r P, what should, be the limit for the product
Tmax? llc "llt · --Tmin
Neglect pressure losses and assume that working substance is a perfect gas.
<fi!i "3i'i!T 3RR01 G< <it 'f;l'l <!if.t it Wr1; ~ 'lfu:l\l'li ;f;\ 3f\'lof<!>dl 'liT f.tlffiuT ~I A thin radiation shield having equal emissivities on both sides is introduced parallel to and in between two large planes with emissivities 0·8 and 0·5 respectively. Determine the emissivity of the radiation shield to reduce the heat transfer rate by 92% of the original. 10
~<fit~ 10 em 3fu: ~~<fit~ '<ll<'l'lidl 50 Wfm K ~~ '1!il 'R 100 •c ([It{ 3MR ~ ~' ~ il B ~ ~ 3RRUl "l!ft'l'l ~I ~ ~ 'fi1 ~ ~I The outer and inner surfaces of a thick hollow cylinder have areas 1·25 m 2 and 0·25 m 2 respectively. The thickness of the cylinder is 10 em and the thermal conductivity of the cylinder material is 50 W jm K. Find the radial heat transfer through the cylinder for 100 ·c temperature difference at the surfaces. Derive the formula used. 10
A reciprocating air compressor is used to flll rapidly a 3 m 3 tank at 30 •c and
1 bar. The filling process is governed by pJ4 = const. The effects of kinetic
energy are negligible. The ratio of the final to initial mass of air in the tank is 4. Work out the following :
(i) <i'! q;J ~ ~ 3fu: f.rillur 3WI<R ~I
Draw the system and show the control volume.
List the assumptions made.
liiiJ 'I:IR '1lif:r<l; <:1d<ll 90% m, m WflS<li "" ~ 'ffil f<RRT o1rrr? What would be the work input to the compressor, if mechanical efficiency is 90%?
(b) 1200 r.p.m. 'R ~ !;3ll ~ ~ ~ '!!'ffi ~ q;J 800 m 3 /min lRR '-f;«ff t I ~ 0·84 <fit ldli«<Tcft <:1d<ll ~ ml!! 1 bar, 30 •c -6 4·8 bar (f<f; Wftfu! <fit omft ~ 1 ~ ~ ~ f.rrfq- (~) 'R ~ ~ 31'\1: 80 mjs ~ ~ ~ 'fi1 ~ <ml 31GitilfdctllRT on WlictT t 1 ~ <fit omt\ ~ '3Wii\ >fuRl ~ B G1!fl\ % I ~ ~ (@!G m) 'fi1 0·9 llRT on ~ %1 ~ ~ ~~'R 0·9 ~ <m<R%1 A centrifugal compressor running at 1200 r.p.m. delivers 800 m 3 /min of free air. The air is compressed from 1 bar, 30 •c to 4·8 bar with isentropic efficiency of 0·84. The impeller blades are radial at outlet and the flow velocity of 80 mjs may be assumed constant throughout. The outer radius of the impeller is twice the inner. The slip factor may be assumed as 0·9. The blade area coefficient is equal to 0·9 at inlet.
Draw inlet and outlet velocity triangles for the impeller, and show the process on a T-s diagram.
20
3 (P.T.O.
www.examrace.com
. {ii) ~ ~ G~ 95% it, m ;;nqm; ~ W'ffi <!il 4f1:'ht-H ~I Calculate the input power needed, if mechanical efficiency is 95%.
(iii) ~ 3ft\ f.t*r 'R ~ 01ffil <A ~ ~I
Calculate the impeller diameters at inlet and outlet.
(iv) ~ 'R ~3ft\~(~)~ 'h1uit <A 4f1:'h<:'H ~I
Calculate the impeller and diffuser blade angles at inlet.
(c) 500 kg/min <lit~ B ~ili64H i'l<'! if; <iQll <fi1l 'R, ilT"' ~ ~ fi1f.l4f4'1 ~ it 355 K tR
~ <Rm% 3ft\ 'ffl mn it "'T<lT %, ~ 'ffl 3600 kg/min <lit~"' <i1Rr "R1 B i6l it omrr % ;;ft 2 86 K 'R w:rRR-];lq]Q ~ fi1 A~ f4 'I <lit ~ ~ it ~ <Rm % I <10 ~ 'i'fffi! gl(
1if; B4!! ~ 3'RRUI ~ 475 W Jm 2 K%, i'l<'f <lit :!lf ~ (~ t\<:) 600 kJfkg K %, m 25 mm ~ Olffil, 2 mm ..ntT 3ft\~ 4·87 m <lit f<!;q.ft ~<lit~ irft? ~ W<A "R1 ~ 'liT 2 m/ s B ~ ~ it'll %, m ~ '!TID ofi't m '1'!1 irft? "R1 if; ~ c p 'liT 4·18 kJ /kg K 3ft\ "R1 if; 'R(<I 'lit 1000 kg{m 3 ~I
The vapour, at the saturation temperature of an oil flowing at the rate of 500 kg/min, enters a heat exchanger tube, at 355 K and condenses while it is cooled by water flowing at the rate of 3600 kg/min entering the concentric tube of a parallel-flow heat exchanger at 286 K. Assuming overall heat transfer coefficient of 475 Wjm 2 K, latent heat of oil as 600 kJfkg K, calculate the number of tubes required of 25 mm outer diameter and 2 mm thick with a length of 4·87 m. What will be the number of tube passes, if cooling water velocity should not exceed 2 mfs? Take CP for water as 4·18 kJ/kg K and
Using Buckingham's 1t theorem method, derive a relation for the efficiency 11 of a fan which depends on the following parameters : 20
Mass density p, Dynamic viscosity jl, Angular velocity OJ, Diameter of the rotor D, Discharge Q
(b) G't <'fl'<lt '«<<'fi ~ A 3ft\ B, 31WT -31WT ~ ofi't <A\ ~, 'ffiiR if; 01ffil 12 mm 3ft\ ~ 1 m <fit, ~ ~ '!lJ if; WI ~ ~ ~, f.rn'liT <fi1l 100 •c 'R <Rl1l; BID Tf':IT ~ I ~ if; '!lJ
, 20 ·c "' ~ ~ ~ B M g{( ~ 1 <fl1l ilm io W~ ~ <fit ~ io W~ -WI ~ "' 'll'IT
Tf':IT 1if; 3lTl.TR '!!! B ~ sr;<m: 15 em 3ft\ 7 · 5 em ~ 'R ~ A 3ft\ B if; ~ <fi1l 'ffiiR 21 I <lfu A <fit mlf!fi <!>fOi;r Wffil% ~ ~ "lliil'hdl 60 W Jm Kit, <it~ B <fit~ "lliil'hdl
Two long slender rods A and B, made of different materials having same diameter of 12 mm and length 1 m, are attached to a surface maintained at a temperature of 100 ·c. The surfaces of the rods are exposed to ambient still air at 20 •c. By traversing along the length of the rods with a temperature sensor, it is found that the surface temperatures of rods A and B are equal at positions 15 em and 7·5 em respectively away from the base surface. If material of A is carbon steel with thermal conductivity 60 W /m K, what is the thermal conductivity of rod B? List the assumptions made. Assume that the average convection coefficient for air is 5 W Jm 2 K. Find the ratio of rate of heat transfer for rods A and B. 20
I c) ~ t<l; X ili 3l"'Gl: fffi <Ji\ ~ f<mq llT'IT 'R eft ;;mft t or<! <l'li f<l; GTil 1 00 kPa ~ i'IT'!
330 K H) "'T''l ~ 3R t<l; Y i'\ t<l; X i'\ '1it fffi ili 'lffi 'liT 5 ~ 'R WIT ;;mrr t ~ GTil
~ 500 kPa oT ;;mrr % ~ i'IT'! ~ 900 K oT ;;mrr % I 31<1 Gf.:il ~ X ~ Y <it ~ <iG 'ffi'<! <'fT<'ft 'l<'fi ili WI ~ WIT ;;mrr % I ~ llR'R <rffi\ ~ f<l; fffi ~ % ~ ~ 'ffi'<! <it <1<!
<l'li 1iffi Wrr ;;mrr % or<! <l'li f<l; € IUlliH0\!!1 'ltf WI o1<f\ t Gf.:il ~ il; ~ 'liT ~, €1Rli<'H"".JI i'IT'! ~ GTil ~~I t<l; 3>"'11?iftrn ~I fffi il; iW(, ~ R = 0·296 kJjkg K
~ Cu = 0·75 kJ/kg K.
A certain amount of gas is filled in a tank X until its pressure is 100 kPa and temperature is 330 K. In another tank Y, 5 times the weight of gas in X is filled raising the pressure to 500 kPa and temperature 900 K. Both the tanks X and Y are now connected through a tube having a valve which is closed. Assuming the gas is ideal and if the valve is opened till equilibrium state is achieved, find the ratio of the volumes of both tanks, equilibrium temperature and pressure. The tanks are insulated. For the gas, take R = 0·296 kJjkg K and Cu = 0·75 kJ/kg K. 10
% I 'l<'fi <Ji1 llfl'r ~ ~ 'R J::'! N 2 IDU WI "J>Ufl 'liT fumur ~ I ~ Gf.:il '[!il 'R 3f€%i11 0 ·02 <m'fl 'I"<R'ft cft<m <Ji\ ~ ~ ~ <it '~fuRl ~ ~ 'lfWil ili «fhihftoq ~: ~ Wrr "'T'!, <i\ 'f<'ll <Ji1 llfl'r ~ ~ 'R J::'! N 2 IDU WI "J>Ufl it "l1"fi'm<l '!ftr<R 'liT q fti'h<:14 ~ I
Liquid N2 enters a thin-walled 20 mm diameter tube at 77 K and flows steadily. The outer surface of the tube has an emissivity of 0·02. This tube is placed concentrically in another tube of 50 mm inner diameter, whose inner surface emissivity is 0·05. The inner surface of the outer tube is maintained at 300 K and the space in between the tubes is evacuated. Determine the heat gained by the liquid N2 per unit length of the tube.
5 (P.T.O.
www.examrace.com
If a thin-walled radiation shield with emissivity 0·02 on both sides is inserted midway concentrically between inner and outer tubes; calculate the % change in heat gained by liquid N2 per unit length of the tube. 20
A fluid flowing in a tube at the rate of0·5 kg/sis heated from 30 •c to 60 •c by hot gases entering at a temperature of 180 •c and leaving at 80 •c. The specific heats of the fluid and gases are 4·186 kJ/kg K and 1·08 kJfkg K. Calculate the change in entropy and increase in unavailable energy for ambient temperature of surrounding of 20 •c. 20
(c) 1% ~ ~-'qil; i\tr ~ rn it~ 1 bar, 288 K ~ ~ <R<it t 3ffi: ~ 2 bar <f'fi
Wfifur Wn Offill t I ~ 'lTG ~ ~ 'li~ it ~ <iif.t "B ~ ~ it 1'flf Wn Offill t, ~ ;rui!il 1 1oo K ~ '"" (f'fi 1'flf f<Rr omrr t 3fu: m <ro ·~ it ~ <R<~t t 3fu: <~ 1wi•kll<~ Gl'l
In a simple open-cycle gas turbine plant, air enters at 1 bar, 288 K and is compressed to 2 bar. It is then heated in the regenerator before entering the combustion chamber where it is heated to a temperature of 1700 K and theri enter~ a turbine and expands to atmospheric pressure. The isentropic
' efficiepcies of compressor and turbine are 87% and 88% respectively. The combustor and heat exchanger efficiencies are 0·97 each. Pressure loss in the combustor is 0·4 bar. Power developed by the turbine is 350 MW. Calorific value of fuel is 42 MJ/kg. Assume cp.;, = CPgas = 1·00.5 kJ/kg K andy= 1·4.
(i) <i:!"" Sfilmff 31iW ('R'il Sf4!1'Tl!) ~ 3fu: T-s 31iW 'R M ~~I Draw the system flow diagram and show the processes on a T-s diagram.
(ti) ~3ffi:~<li't~~~~~l Find out the mass flow rate of air and fuel.
(iii) q;W~~~I Find out the work ratio.
(iv) ~ G8.1<il ~~I
Find out the thermal efficiency.
(v) ~ ~tl'! 13'«1 ~~I Find out the specific fuel consumption.
6
10
www.examrace.com
~-8 I SECTION-S
5. (a) ~ 3'®<! ~ C xH y i\; Wol i\; "3i<ITG1 qrr f.t"1~ ful d ~ ~ ;hrr f'f> ~ 3ffim ~ IDU ll1'!1
1Jln ~ :
C02 = 8·0%, CO = 0·9%, 0 2 = 8·8%, N2 = 82·3%
X afR y i\; liT'iT, ~-~tl'l ~ afR ~ ~ ~<lit Sifd~lddl qrr f.ttlttuT ~I
The products of combustion of an unknown fuel C xH y have the following composition as measured by an Orsat apparatus :
C02 = 8·0%, CO = 0·9%, 0 2 = 8·8%, N2 = 82·3%
Determine the values of x and y, the air-fuel ratio and % of excess air used. I 0
Determine the expression for the ratio of chimney gas temperature to outside air temperature in terms of mass flow rate.
At a stage in a reaction turbine, the pressure of steam is 34 kPa
(v9 = 4·65 m 3 /kg) and dryness fraction is 0·95. For a flow rate of 36000 kg/hr,
the stage develops 950 kW. The turbine runs at 3600 r.p.m. and velocity of flow is 0·72 times the blade velocity. The outlet angles of both stator and rotor blades are 20•. Determine at this stage the mean rotor diameter and height of
10
blades. 10
(d) ~ <'M:JMI~ li'fi •Mifol'h ~ '11: ~ M on~ t ~ rn ~ "$!q; ('FR) ~ ~ >n•flfolq; ~ i! ~ m on m ~I ~. 'l'i\ I ~ Gh'f ~ ij ~ ~ 'hl~l
Mechanical air-conditioning can be used in all geographical locations, whereas desert air-coolers can be used only in some geographical locations. Explain why. Show the processes involved in both these equipments. 10
It is thermodynamically advantageous to employ a heat pump rather than employing a direct electrical resistance heater for a room air heating application. Explain why. 10
1·11 kJfkg K 3it\ CP. = 1·05 kJfkg K W.fl fffi 3it\ ~ i!> ~ y 5f>lm: 1·33 3it\ a1r
• 1·4 i I ~ "5l"1'l1l1 1R ~ ofiT ~ "5l"1'l1l1 G1: "'liT ;r,iR~ ~I ~If.! 'liT ~ l!H '
I 43·3 MJ/kg %1
· In a combined gas turbine (GT)-steam turbine (ST) plant, the exhaust from GT
is used to heat steam in boiler at which a further supply of fuel is burned in the
gas. Pressure ratio of GT is 8, inlet air temperature is 15 'C, maximum cycle .. temperature is 800 'C. Combustion in boiler increases the gas temperature to
800 'C and gas leaves the boiler at 100 'C. The steam inlet in ST is at 60 bar
and 600 'C (h = 3656·2 kJ/kg, s = 7·166 kJfkg K) and condenser pressure
8
20
www.examrace.com
is 0·05 bar (hf = 137·8 kJ/kg, hfg = 2423·8 kJfkg, sf = 0-476 kJfkg K, sfg = 7·92 kJ /kg K). Calculate flow rate of air and steam required for a total power output of 190 MW and the overall 11 of the combined plant. Assume that all processes are ideal. What is overall air-fuel ratio? Assume CP = 1·11 kJ /kg K gas and CP . = 1·05 kJ /kg K, and y for gas and air as 1·33 and 1-4 respectively. a>r
Neglect mass flow rate of fuel on the airflow. Calorific value of fuel is 43·3 MJjkg. 20
Show that the enthalpy of humid air per kg of dry air is given by
h = CPm x DBT +2500w
where C Pm = humid air specific heat = ( 1·005 + 1·88w), w = specific humidity kg/kg of dry air, hfg = 2500 kJ/kg at 0 •c for water and DBT = dry-bulb temperature. 10
The air handling unit in an AC plant supplies a total of 4500 crnrn of dry air which comprises by weight 20% fresh air at 40 'C DBT, 27 'C WBT and 80% recirculated air at 25 'C DBT and 50% RH. Air leaves the cooling coil at 13 'C saturated. Calculate total cooling load and room: heat gain : 20
Condition DBT WBT RH Sp. humidity Enthalpy (•q (·q (%} (kg/kg of dry air} (kJ /kg of dry air}
The following data refer to a 4-stroke, 4-cylinder diesel engine :
Cylinder diameter= 36 ern; Stroke= 40 ern; Speed= 315 r.p.rn.; Indicated MEP = 7 bar; Brake power = 250 kW; Fuel consumption = 80 kg/hr; Calorific value= 44 MJ/kg; Air consumption= 30 kg/min; Cooling water circulated = 90 kg/min with rise in temperature 38 'C; Exhaust gas temperature = 324 'C and Room temperature = 45 ·c kJ /kg K; CP .
, ~r
= 1·005 kJ /kg K, cP = 1·05 kJ /kg K, cP · = 2·093 kJ /kg K. In gas steam
exhaust gases, partial pressure of steam is 0·03 bar and fuel contains 13% H 2 •
Find mechanical efficiency, indicated thermal T(, brake specific fuel consumption: Draw· heat balance sheet for the engine in hourly basis. 10
<FO"RJ/' -j/' -mF'irl.l/40 10
www.examrace.com
8. (a) (i) ~ R12 <ffi'l ~ ~ 35 •c am -15 •c ~ ~ tR ~ 'li«<T ~I <i'l <lit COP am "llf<r Col "5i"WR (Uiil"i{~H) ~ fu1( HP 'f;l f.\tffiul ~ :
31fclrrfr 20 K 40 K
t hf hg Sg ·h s h s I"C) lkJ/kg) lkJfkg) lkJ/kg K) lkJfkg) lkJ/kg K) lkJ/kg) lkJ/kg K)
35 69·5 201·5 0·6839 216-4 0·731 231·0 0·7741
-15 181·0 0·7052 193·2 0·751 205·7 0·7942
An R12 simple saturation cycle operates at temperatures of 35 •c and -15 •c. Determine the COP and HP per ton of refrigeration of the system: 10
Superheated
20 K 40 K
t hf hg Sg h s h s I"C) lkJ/kg) lkJ/kg) lkJ/kg K) lkJ/kg) lkJ/kg K) lkJ/kg) ikJfkg K)
35 69·5 201·5 0·6839 216·4 0·731 231·0 0·7741
-15 181·0 0·7052 193·2 0·751 205·7 0·7942
fiiJ ~ ;ng am 11fto ;ng ~ <'lldl:!'tii'1'1 ~~oft'! f<lm ~~ Differentiate between summer and winter air-conditioning processes. 10
fbJ m WI-~ ~ ~ <'ll'l c:ey (t!;f?h~~~<) o'rn ~, 3'%l c:l'! <A ~ 31'Wn3il ii WITf! (11~1::<~o: WI-~ o'rn ~ 1 ~ <FiT ~? WI-~ am Gl'l-~ ~ WITfi\ ii G1'l
am WiT ~ ~ "" ~ ~~ Even though velocity-compounded impulse turbines are less efficient, in the initial stages of high pressure turbines are normally velocity-compounded. Why? Plot the variation of pressure and velocities in velocity-compounded and pressure-compounded impulse turbines.
A steam power plant operates on ideal regenerative Rankine cycle. Steam enters the turbine at 6 MPa, 450 •c (h = 3301'8 kJ/kg, s = 6·7193 kJjkg K) and is condensed in the condenser at 20 kPa (h1 = 251·4 kJjkg, h19 = 2358·3
kJ /kg, v f = 0·00 1 m 3 Jkg, sf = 0·832 kJ /kg K, s fg = 7·0766 kJ /kg K). Steam is
extracted from the turbine at 0'4 MPa (h1 = 604·74 kJfkg, v1 = 0·001 m 3 /kg,
h19 = 2133·8 kJjkg, s1 = 1·7766 kJfkg K, s19 = 5·1193 kJfkg K) to heat feedwater heater. Water leaves feedwater heater as saturated liquid. Show the cycle on T-s diagram and find net work output/kg of steam, the boiler and thermal efficiencies of the cycle. 20