mechanical appsc 2012 thermodynamics heat transfer refrigeration air conditioning

8/13/2019 Mechanical Appsc 2012 Thermodynamics Heat Transfer Refrigeration Air Conditioning

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ACEEngineering Academy

APPSC 2012 (Model Exam)SUB:Thermodynamics !ea" Trans#er $e#ri%era"ion &

Air Condi"ionin% S"eam 'enera"ors & Trines

Elemen"s o# Com*"a"ion

Branch: Mechanical En%ineerin%

Time : +, Min"es Maximm Mar-s : +,

01. A system comprising of a single phase, is known as(a) Open system (b) Closed system

(c) Homogenos system (d) Heterogenos system

0!. "he polytropic inde# ( n) is gi$en by

(a)

!

1

1

!

log

log

v

v

p

p

(b)

!

1

!

1

log

log

p

p

v

v

(c)

!

1

!

1

log

log

v

v

p

p

(d) %one

0&. 'rincipal constitents of fel are

(a) O#ygen and hydrogen (b) Carbon and hydrogen

(c) lphr and hydrogen (d) lphr and o#ygen

0. *f other factors are constant, with increase in the temperatre of sorce, the efficiency of

carnot engine

(a) increases (b) +ecreases

(c) emains same (d) +epends on temperatre ratio

0-. Air enters a wind mill with a $elocity of - ms and lea$es with a $elocity of ms. "he

specific work otpt, assming no heat transfer and frictional losses is(a) .- / (b) .- /kg (c) .- k/kg (d) .- k/

0. "he entropy change in a hyperbolic process of an ideal gas per kg is gi$en as

(a) ln (!1) (b) ln ('!'1) (c) ln (1!) (d) ln ("!"1)

02. A gas e#pands from 1 atm, 1m&$olme till the $olme if dobled according to the (i)

isothermal law (ii) adiabatic law. 3hich of the following statements is correct

(a) work done in (i) is greater than in (ii)

(b) 3ork done in (ii) is greater than in (i)

(c) increase in internal energy in (ii) is greater than in (i)

(d) heat flow in (ii) is greater than in (i)

APPSC Model Exam ME


2/8

ACE :: 2 ::ACE

04. A certain mass of a gas absorbs 00/ of heat at constant $olme5 the decrease in internal

energy of the gas is

(a) ! liters (b) 1 litre (c) 600/ (d) 00/

07. 3hich of the following is not an e#tensi$e property of a thermodynamic system(a) "otal mass (b) "otal internal energy

(c) "otal $olme (d) "emperatre

10. +ring adiabatic e#pansion

(a) *nternal energy remains constant (b) "emperatre remains constant

(c) 8ntropy remains constant (d) 8nthalpy remains constant

11. *n magneto ignition system

(a) coil is not re9ired (b) distribtor is not re9ired

(c) condenser is not re9ired (d) battery is not re9ired

1!. :el ha$ing ma#imm resistance to detonation is

(a) ;en


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ACE :: 3 ::ACE(c) High pressre and low $elocity (d) ow pressre and high $elocity

!1. atio of sefl heat drop to the isentropic heat drop, is known as

(a) ;oiler efficiency (b) %o


4/8

ACE :: 4 ::ACE

&&. How can incomplete combstion be best Edged

(a) ;y measring CO in fle gases (b) ;y measring O!in fle gases

(c) ;y measring temperatre of fle gases at e#it of frnace

(d) %one&. "he energy of netrons which participate in chain reaction is

(a) ! me$ (b) !- me$ (c) !.- me$ (d) 0.!- me$

&-. :reon61! consists of atoms of

(a) Carbon, :lorine and chlorine (b) Carbon, florine and Hydrogen

(c) Carbon, florine, chlorine and hydrogen (d) Carbon and hydrogen

&. efrigerant nmber 6212 means

(a) Ammonia (b) CO! (c) O! (d) Fethyl chloride

&2. *n a mechanical refrigeration system, the highest temperatre of refrigerant occrs(a) *n e$aporator (b) ;efore e#pansion $ale

(c) ;etween condenser and e$aporator (d) After compression

&4. +ring adiabatic satration process on nsatrated air, the

(a) +ry blb temperatre remains constant

(b) 3et blb temperatre remains constant

(c) +ew blb temperatre remains constant

(d) satration temperatre indicated

&7. *n a psychrometric chart, cooling and hmidification process sing spray represented by a

(a) Hori


5/8

ACE :: 5 ::ACE(c) 'ressre compond trbine (d) elocity componded trbine

-. *f is the no


6/8

ACE :: 6 ::ACE

-2. Heart transfer takes place according to

(a) eroth aw of "hermodynamics (b) :irst aw of the "hermodynamics

(c) econd aw of "hermodynamics (d) "hird aw of "hermodynamics

-4. *n a large plate, the steady temperatre distribtion is as shown in the gi$en figre. *f

no heat is generated in the plate, the thermal condcti$ity Jk> will $ary (" is temperatre

and is a constant)

(a) )"1(k0 +

(b) )"1(k0

(c) )"k0 +

(d) )"k0

-7. Heat is mainly transferred by condction, con$ection and radiation in

(a) *nslated pipes carrying hot water

(b) efrigerator free


7/8

ACE :: 7 ::ACE(a) 1! (b) 1 (c) ! (d)

. A composite wall of a frnace has ! layers of e9al thickness ha$ing thermal

condcti$ities in the ratio of &K!. 3hat is the ratio of the temperatre drop across the two

layers

(a) !K& (b) &K! (c) 1K! (d) loge! K loge&

2. 3hat is the critical radis of inslation for a sphere e9al to

k L thermal condcti$ity in 3m6=

h L heat transfer coefficient in 3m!=

(a) !kh (b) !kh (c) kh (d) kh!

4. A composite wall of a frnace has & layers of e9al thickness ha$ing thermal

condcti$ities in the ratio of 1 K ! K . what will be the temperatre drop ratio across the

three respecti$e layers

(a) 1 K ! K (b) K ! K 1

(c) 1 K 1 K 1 (d) log K log! K log1

7. *nspite of large heat transfer coefficients in boiling li9ids, fins are sed

ad$antageosly when the entire srface is e#posed to

(a) %cleate boiling (b) :ilm boiling

(c) "ransition boiling (d) All modes of boiling

20. "he time constant of thermocople is

(a) "he time taken to attain 100B initial temp difference

(b) "ime taken to attain &.!B of initial temp difference

(c) "ime taken to attain -0B of initial temp difference

(d) "he minimm time taken to record a temp reading

21. Addition of fin to the srface increases the heat transfer if ='.hA is

(a) 89al to one (b) ?reater than one

(c) ess than one (d) ?reater than one bt less than two.

APPSC Model Exam ME


8/8

ACE :: 8 ::ACE

2!. :ins are made as thin as possible to

(a) edce total weight

(b) Accommodate more nmber of fins

(c) *mpro$e flow of coolant arond the fin

(d) *ncrease the width for the same profile area

2&. ;ondary layer is defined as

(a) A thin layer at the srface where gradients of both $elocity and temperatre are small

(b) A thin layer at the srface where $elocity and $elocity gradients are large

(c) A thick layer at the srface where $elocity and temperatre gradients are large (d) A thin layer at the srface where gradients of both $elocity and temperatre are large

2. Isally fins are pro$ided to increase the rate of heat transfer. ;t fins also act as

inslation. 3hich one of the following non6dimensional nmbers decides this factor

(a) 8ckert nmber (b) ;iot nmber

(c) :orier nmber (d) 'eclet nmber

2-. 3hich one of the following non6dimensional nmbers is sed for transition from laminarto trblent flow in free con$ection

(a) eynolds nmber (b) ?rashof nmber

(c) 'eclet nmber (d) ayleigh nmber

APPSC Model Exam ME

mechanical appsc 2012 thermodynamics heat transfer refrigeration air conditioning

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