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Paper 2 – Set A Solutions

Regn No: _________________

Name: ___________________

(To be written by the candidates)

NATIONAL CERTIFICATION EXAMINATION 2006FOR

ENERG MANAGERS ! ENERG A"#ITORS

PAPER – 2$ Ener%& E''i(ien(& in T)er*al "tilities

Date: 22.04.2006 Timings: 14001!00 "R# D$ration: % "R# &a'. &ars: 10

General instructions:

o Please check that this question paper contains 8 printed pages

o Please check that this question paper contains 65 questionso The question paper is divided into three sections

o All questions in all three sections are compulsory

o All parts of a question should be answered at one place

Se(tion – I$ O+,ECTI-E TPE Mar.s$ /0 1 /0

(i) *nswer a++ /0 ,$estions(ii) -ach ,$estion carries one mar

(iii) $t a (√) tic mar in the a//ro/riate bo' in the answer boo

1. hich o the o++owing is not meas$red in $+timate ana+ysis

a) carbon b) s$+/h$r c) hydrogen d) ash

2. ith increase in the /ercentage o e'cess air or comb$stion o coa+3 /ercentage o 52 in +$e gas.

a) increases b) decreases c) remains same d) none o the aboe

%. hich o the o++owing re,$ires the +east amo$nt o o'ygen 7g or com/+etecomb$stion

a) arbon b) #$+/h$r c) "ydrogen d) &ethane

4. hich o these $e+s has the highest heating a+$e

a) &ethane b) "ydrogen c) Diese+ d) 89

. 89 is /redominant+y the mi't$re o ro/ane and ___

a) &ethane b) -thane c) $tane d) ;so/ro/ane

6. Nat$ra+ gas consists o main+y the o++owing

a) -thane b) &ethane c) ro/ane d) $tane

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!. < = * (rom and at) rating o the boi+er is the amo$nt o steam generated rom

a) water at 0> to sat$rated steam at 100>b) water at eed water tem/erat$re to sat$rated steam at 100>c) water at ambient to sat$rated steam at 100>

d) water at 100> to sat$rated steam at 100>

?. The minim$m ca/acity o any c+osed esse+ which generates steam $nder /ress$reas /er ;ndian oi+ers Reg$+ation *ct is

a) 2.2! +itres b) 22.! i+o +itres c) 22!. +itres d) 22.! +itres

@. *$tomatic b+owdown contro+s or boi+ers wor by sensing

a) TD# b) cond$ctiity c) /" d) cond$ctiity and /"

10. The +owest e'cess air is re,$ired in a

a) coa+ b$rner b) +ow /ress$re oi+ b$rner

c) high /ress$re gas b$rner d) high /ress$re oi+ b$rner

11. * boi+er generates ? T" o steam at an eiciency o ! A. The entha+/y added tosteam in the boi+er is ?0 Bca+7g. The $e+ +ow rate with a 9C o %00 ca+7g is

a) 142 g7hr b) 60%2 g7hr c) 40?@ g7hr d) 1!6? g7hr

12. Deminera+iation o water is the /rocess to remoe the disso+ed

a) o'ygen b) sa+ts c) carbon dio'ide d) ch+orine

1%. Deaeration o boi+er eed water is reerred to as

a) remoa+ o disso+ed gases b) remoa+ o si+ica

c) remoa+ o sca+es d) /hos/hate treatment o eed water 14. 8atent heat o steam at the critica+ /oint is

a) ininite b) 40 ca+ c) ero d) none o the aboe

1. Drain /ocets are /roided in a steam +ine or

a) eectie remoa+ o steam b) remoa+ o dirtc) checing o steam +ine d) eectie remoa+ o +ine condensate

16. The /$r/ose o atomisation in an oi+ ired b$rner is to

a) increase e'cess air b) increase the s$race area o oi+ c) red$ce /ower cons$m/tion d) red$ce the +$e gas tem/erat$re

1!. The dierence in tem/erat$re between steam and condensate is the /rinci/+e o o/eration in a

a) thermodynamic tra/ b) thermostatic tra/c) oriice ty/e tra/ d) tem/erat$re tra/

1?. hich o the o++owing beneits is not achieed by ma'imiing condensate recoery

a) ma'imiation o boi+er o$t/$t b) red$ction in water treatment costsc) red$ction in energy in/$t costs d) minimiation o e'it +$e gas tem/erat$re

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1@. hich o the o++owing wi++ be idea+ or heat transer in a heat e'changer

a) s$/er heated steam b) sat$rated dry steamc) wet steam d) hot water

20. hat is the /rimary mode o heat transer in an oi+ ired me+ting $rnaces

a) conection b) radiation c) cond$ction d) /$+sation

21. Radiation rec$/erators are $sed when the $rnace +$e gas tem/erat$re is more than

a) ?00> b) 600> c) 400> d) 200>

22. 5/erating the boi+er at a /ress$re +ess than ?0A o the rated /ress$re wi++ res$+t in

a) +ower boi+er e'it +$e gas tem/erat$reb) red$ced boi+er eed water /$m/ /owerc) increased carryoer o waterd) a++ o the aboe

2%. *mo$nt o o'ygen re,$ired to b$rn one g o hydrogen is

a) @ b) ? c) 0. d) %

24. The emissiity o conentiona+ reractory ____ with the increase in tem/erat$re

a) increases b) decreasesc) remains the same d) sometimes increases and sometimes decreases

2. #ca+e +osses in reheating $rnaces wi++

a) increase with e'cess air b) decrease with e'cess air c) hae no re+ation with e'cess air d) increase with 5 in comb$stion gases

26. #team tra/ is a deice which discharges

a) steam on+y b) air and incondensab+e gases on+yc) condensate on+y d) air3 incondensab+e gases and condensate

2!. eramic coating in $rnaces in+$ences

a) cond$ctiity b) conectie heat transer coeicientc) emissiity d) radiation actor

2?. ; the /ress$re o sat$rated steam is red$ced thro$gh a /ress$re red$cing a+e

a) it wi++ get s$/erheated b) entha+/y wi++ red$cec) it wi++ /rod$ce wet steam d) entha+/y o ea/oration wi++ red$ce

2@. *+$mina is a ____ ty/e o reractory

a) acid b) basic c) ne$tra+ d) none o the aboe

%0. The eect o therma+ cond$ctiity on therma+ resistance o an ins$+ation

a) increases with increased therma+ cond$ctiityb) decreases with decreased therma+ cond$ctiityc) increases with decreased therma+ cond$ctiityd) decreases with increased therma+ cond$ctiity

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%1. ; the $rnace tem/erat$re is T (oB) and the area o o/ening is *3 ,$antity o radiation+oss in a reheating $rnace is direct+y /ro/ortiona+ to

a) T b) *4 c) *2 d) T4

%2. The ins$+ating materia+ made by b+ending and me+ting o a+$mina and si+ica at atem/erat$re o 1?002000o is nown as

a) ins$+ating bric b) high a+$mina bricc) ire bric d) ceramic ibre

%%. ;n a

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4%. ;n a gas t$rbine3 air com/ressor a+one cons$mes abo$t _____o the energygenerated

a) 20%0A b) %040A c) 404A d) 060A

44. hich one is the /reerred waste heat recoery system in a +arge gas t$rbine

a) economier b) air /re heater c) boi+er d) heat whee+

4. Rec$/erator as a waste heat recoery system is $sed main+y in

a) boi+er b) reheating $rnacec) com/ressor d) gas t$rbine

46. hich o the o++owing wors on a rerigeration cyc+e

a) heat /i/e b) heat whee+c) heat /$m/ d) thermo com/ressor

4!. "eat transer by gas radiation in a reheating $rnace de/ends on

a) tem/erat$re b) 52 concentrationc) water a/or concentration d) a++ o the aboe

4?. ; /ress$re o sat$rated steam increases then

a) entha+/y o steam goes $/ b) entha+/y o steam goes downc) entha+/y o ea/oration goes $/ d) none o the aboe

4@. hich o the o++owing re,$ires the +east amo$nt o o'ygen 7g or comb$stion

a) carbon b) s$+/h$r c) hydrogen d) methane The question is repeat of Question No.3. Award mark if the answer is right.

0. The amo$nt o carbon dio'ide /rod$ced by comb$stion o 1 g o methane incom/arison to that /rod$ced by 1 g o carbon is

a) more b) +ess c) same d) data ins$icient

-------- End of Section - I ---------

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Se(tion 3 II$ S4ORT #ESCRIPTI-E 5"ESTIONS Mar.s$ 10 / /0

(i) *nswer a++ Ten ,$estions(ii) -ach ,$estion carries Fie mars

#1 hat is meant by e'cess air in comb$stion systems and disc$ss theim/ortance o o/tim$m e'cess air.

o -'cess air is the air /roided in e'cess o stoichiometric air to ens$re

com/+ete comb$stion3 since mi'ing between air and $e+ is neer /erect

in /ractice.

o ; too m$ch e'cess air were a++owed to enter3 additiona+ heat wo$+d be +ost

by heating the s$r/+$s air to the chimney tem/erat$re. This wo$+d res$+t in

increased stac (e'ha$st) +osses.

o Too m$ch e'cess air wi++ red$ce +ame tem/erat$re

o Too +ess e'cess air wo$+d +ead to the incom/+ete comb$stion and smoe.

o "igh e'cess +ee+ increases the sca+e +osses o the materia+ to be heated

in the $rnaces.

#2 8ist any ie energy conseration o//ort$nities in a boi+er system.

1. Red$ce stac tem/erat$re

2.

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#% hat are the disadantages o Fdirect methodG o boi+er eiciency ea+$ationoer the Findirect methodG

Disadantage o Direct &ethod

• Does not gie c+$es to the o/erator as to why boi+er eiciency o system is+ower or higher

• Does not indicate indiid$a+ +osses acco$ntab+e or ario$s eiciency +ee+s

• ; there is wetness in steam it may indicate higher eiciencies than act$a+

• Does not indicate the im/roement to be made in ario$s +oss areas

•

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1. #ensib+e heat +oss in +$e gas2. 8oss d$e to ea/oration o moist$re /resent in $e+%. 8oss d$e to ea/oration o water ormed d$e to hydrogen in $e+4. "eat +oss d$e to o/enings. "eat +oss thro$gh sin6. "eat storage +oss!. 8oss o $rnace gases aro$nd charging door and o/ening?. "eat +oss by incom/+ete comb$stion@. 8oss o heat by cond$ction thro$gh hearth10. 8oss d$e to ormation o sca+es

#6 * boi+er generates steam at the rate o 12 ton7hr cons$ming 2 ton7 hr o coa+haing 400 ca+7g ca+oriic a+$e. a+c$+ate the ea/oration ratio andeiciency o the boi+er i the entha+/y o the generated steam is !22. ca+7g

and eed water tem/erat$re is °.

1. -a/oration Ratio means Bi+ogram o steam generated /er Bi+ogram o

$e+ cons$med

12-a/oration Ratio H H 6

2

2. -iciency o the boi+er

12 ton ' 1000 Bg 7 ton ' (!22. I )

H ' 100

2 ton ' 1000 Bg 7 ton ' 400 Bca+ 7 Bg

H ?@ A

#! 200 g7hr o hot condensate rom a heat e'changer is coming o$t at 6 bar (g)with a sensib+e heat o 166 ca+7g. Msing a +ash esse+3 the condensate is+ashed to 1 bar (g) with a sensib+e heat o 120 ca+7g and +atent heat o 26

ca+7g.

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166 120

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#10 Describe in brie the /rinci/+e o woring o heat /i/es.

• The heat /i/e com/rises o three e+ements3 a sea+ed container3 ca/i++ary

wic str$ct$re and a woring +$id.

• Therma+ energy a//+ied to the e'terna+ s$race o the heat /i/e ca$ses the

woring +$id near the s$race to ea/orate instantaneo$s+y.

• Ca/o$r th$s ormed absorbs the +atent heat o a/o$risation and this /art

o the heat /i/e becomes an ea/orator region.

• The a/o$r then trae+s to the other end o the /i/e where the therma+

energy is remoed ca$sing the a/o$r to condense in to +i,$id again3

thereby giing $/ the +atent heat o condensation.

• The condensed +i,$id then +ows bac to the ea/orated region.• "eat /i/e can transer $/to 100 times more therma+ energy than co//er.

-nd o #ection ;;

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Se(tion 3 III$ LONG #ESCRIPTI-E 5"ESTIONS Mar.s$ / 10 /0

(i) *nswer a++ Fie ,$estions(ii) -ach ,$estion carries Ten mars

81 * chemica+ /+ant has an *

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Tota+ mass o +$e gas (m) H &ass o act$a+ air s$//+ied K&ass o $e+ s$//+ied

H !.2? K 1 H ?.2?

?.2? ' 0.24 ' (160 I %0)A Dry +$e gas +oss H ' 100

4000

H 6.4?4

H 6.46 A

b) "eat +oss d$e to ea/oration o water ormed d$e to "2 in $e+

@ ' "2' J?4 K / (Tf I Ta)LH

9C o $e+

here "2 I ercentage o "2 in $e+

@ ' 4 ' J ?4 K 0.4 (160 I %0) LH

4000

H .!?2

H .!?A

c) Radiation o other +osses H ?A

oi+er eiciency H 100 I (6.46 K .!? K ?)

H !@.!6A

d) "o$r+y oa+ ons$m/tion

!0 ' 1000 ' (?1! I 10)H

0.!@!6 ' 4000

H 1621.?6 Bg 7 hr

H 1.621 Ton 7 hr.

82 (a) rie+y e'/+ain why the s+ight /ositie drat /ress$re sho$+d be maintained inthe $rnaces.

(b) -'/+ain the signiicance o achieing o/tim$m ca/acity $ti+isation in $rnaces.

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a) y maintaining s+ight /ositie /ress$re3 air ini+tration in the $rnace thro$gho/enings and cracs is aoided.

*ir ini+tration res$+ts in

o higher heat +oss d$e to high e'cess air

o 8owering o the +ame and $rnace tem/erat$re

o dist$rbance o the air $e+ ratio contro+

o co+d meta+ and non$niorm meta+ tem/erat$re

o increased /ower cons$m/tion o ;D an

o increased sca+e +osses

b) The signiicance o achieing o/tim$m ca/acity $ti+isation in $rnaces is tominimie the /ro/ortionate i'ed and ariab+e energy +osses. This wi++ +ead tored$ced s/eciic energy cons$m/tion.

; the $rnace is $nder+oaded on+y a sma++er raction o the aai+ab+e heat in theworing chamber wi++ be taen $/ by the +oad and +eading to higher ariab+e+osses and thereore eiciency wi++ be +ow.

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- ; inerted b$cet tra/s are $sed or e'treme+y sma++ +oads3 it wi++

hae contin$o$s condensate discharge.

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!. &iminising "eat Transer arrier

"eat is transerred rom the steam to the materia+ being heated thro$gh

an intermediate heating s$race which acts as a barrier between the

steam and the materia+ being heated

;n case o indirect heating3 tem/erat$re dierence is re,$ired to

oercome the resistance o the barrier between the steam and the

materia+. ;t is not E$st the therma+ cond$ctiity o the barrier3 a+ong side

the heat transer barrier in an air i+m as we++ as sca+ing on the steam

side and sca+ing as we++ as a stagnation /rod$ct i+m on the /rod$ct

side. The barrier which are ormed that ins/ired the +ow o heat rom

steam to the materia+. ;t has been estimated that air is 100 times

more resistance to heat transer than stee+ and to be remoed.

?. ro/er *ir Centing

*de,$ate air enting /roision sho$+d be made at a//ro/riate /osition

in the /i/e +ines3 to /$rge o$t air as ,$ic+y as /ossib+e rom the

e,$i/ment.

@. ondensate Recoery

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/rocess.

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8 The ins$+ation o a steam /i/e+ine is to be $/graded. ith the o++owing dataca+c$+ate the sim/+e /aybac /eriod or the ins$+ation $/gradation /roEect.

8ength o the steam /i/e+ine 100 m

are /i/e e'terna+ diameter 100 mm

"eat +oss rom the /i/e with e'isting2 mm ins$+ation thicness

2000 ca+7m2hr

Thicness o ins$+ation to be added 2 mm

"eat +oss ater ins$+ation $/gradation 400 Bca+7m27hr

oi+er eiciency !A

9C o coa+ 4000 ca+7g

*nn$a+ o/erating ho$rs ?000 hrs

ost o coa+ Rs. 20007Ton

;nestment or ins$+ation $/gradation Rs. 4 +ahs

*ns

-'isting heat +oss (#1) H 2000 Bca+ 7 #,. &7hr.

"eat +oss ater ins$+ation H 400 Bca+ 7 #,. &. 7 hr M/gradation (#2)

i/e dimension H φ 100 mm ' 100 m +ength

#$race area e'isting (*1) H %.14 ' 0.1 ' 100 H 4!.1m2

#$race are ater ins$+ation (*2) H %.14 ' 0.2 ' 100 H 62.? m2

ith additiona+ 2 mm ins$+ation

Tota+ heat +oss in e'isting system(#1 ' *1) H 2000 ' 4!.1

H @43200 Bca+ 7 hr

Tota+ heat +oss in modiied system (#2 ' *2)

H 400 ' 62.?

H 23120 Bca+ 7 hr

Red$ction in heat +oss H @43200 I 23120

H 6@30?0 Bca+ 7 hr

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6@0?0 ' ?000 *nn$a+ coa+ saing H

0.! ' 4000

H 13?4321% Bg

H 1?4 Tons

*nn$a+ monetary saing H 1?4 ' 2000 H %.6? 8ahs

aybac eriod H 4 7 %.6?

H 1.0?! years

H 1% months

-------- End of Section - III ---------

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