0505 b therm exam

8/14/2019 0505 b Therm Exam

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Mutah UniversityFaculty of Engineering Mech. Eng. Department

Second Exam (Thermod. II !"#!"#$!!% Dr. Muafag Tara&neh

Answer all the questions Form ('

)* +ircle the correct ans&er [5 points]

1. The main scope of using any reheat cycle

(Rankine is to!

a "ncrease the pressure in the #oiler #"ncrease the temperature insi$e the #oiler

cA%oi$ the water $roplet formation insi$e the

tur#ine

$"ncrease the cycle efficiency

&. 'tto cycle is more efficient than )iesel

efficiency #ecause of!

a*eat is a$$e$ at constant pressure an$re+ecte$ at constant pressure

#,-pansion ratio is greater than compression

ratio

cutoff ratio in 'ttocycle

$,-pansion ratio is equal to the compression

ratio

/. The $ifference #etween the open an$ close$ fee$water heaters is that

a "n the close$ type the liqui$ water mi-es

with the steam

8/14/2019 0505 b Therm Exam


#"n the open type there is no mi-ing #etween

liqui$ water an$ steam

c "n the close$ type there is no mi-ing

#etween liqui$ water an$ steam$0on of the a#o%e

. The compression ratio in the real spark ignition

engines is limite$ #ecause of!

a2nocking ten$ency

#3hysical an$ chemical characteristics of the

$iesel

cutoff ratio

$0on of the a#o%e

5. The efficiency of Rankine cycle as compare$

with that of arnot cycle is!

a4ith greater efficiency

#,qual efficiencies

c4ith lower efficiency$0on of the a#o%e

. The significant effect of re$ucing the e-haust

pressure from the tur#ine (#ackpressure can #e

o#ser%e$ on the!

aRe$uce$ efficiency

#"ncrease$ moisture content

cRe$uce$ moisture content$0on of the a#o%e

6. The main $isa$%antage of Rankine cycle as

compare$ with that of arnot is!

a7ecause of the phase change

8/14/2019 0505 b Therm Exam


#"t has two isentropic processes

c7ecause of water $roplet formation insi$e

the tur#ine

$(a8c9. The limite$ temperature of higher than :: ; in

Rankine cycle is $ue to!

a "ncrease$ cost of heating

#Temperature resistance characteristics of the

piping system

c "ncrease$ fuel consumption

$"ncrease$ si<e of #oiler

=. The scope of applying the Regenerati%e process

in Rankine cycle is to!

aReheat the steam insi$e the tur#ine

#Reheat the mi-ture #efore entering the

con$enser

cA%oi$ moisture formation insi$e the tur#ine$Reach the state of saturation #efore entering

the #oiler

1:. Thermal efficiency of 'tto >cycle is a

function of!

aAmount of transferre$ heat

#Amount of re+ecte$ heat

cFuel quality$ompression ratio

)$ "n a #oiler? heat is transferre$ to the steam from

the pro$ucts of com#ustion? the temperature of the

8/14/2019 0505 b Therm Exam


pro$ucts of com#ustion $ecreases from 1&:: ; to

5:: ; while the pressure of these pro$ucts remain

constant at 1:: kpa? the pro$ucts of com#ustion

ha%ing an a%erage of constant pressure specific heat( c p@1.:= k+kg.k. The water enters at (9:: kpa? 15:

;? an$ lea%es at (9:: kpa? &5: ;.

+alculate the follo&ing,

1. The secon$ law efficiency

&. The irre%ersi#ility per kg of e%aporate$ water.

)-) onsi$er an i$eal steam regenerati%e cycle

which operates with 1: kgs? in which steam enters

the tur#ine at (5:::kpa? ::; an$ lea%es to the

con$enser at 1: kpa. Bteam is e-tracte$ from the

tur#ine at :.9 Cpa to #e mi-e$ in an open fee$ water

heater with the liqui$ water from the con$enser. The

fee$ water lea%es the heater as saturate$ liqui$.Appropriate pumps are use$ for pumping the fee$

water from con$enser to the heater an$ from heater to

the #oiler. Find the follo&ing,

*. The amount of extracted steam

$. +ycle efficiency and the

-. /et &or0 per 0g

1ood 2uc0

0505 b therm exam

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