ht1

QuestionIn the equationQ=UAt; tis

Ageometric mean temperature difference.

Barithmetic mean temperature difference.

Clogarithmic mean temperature difference.

Ddifference of average bulk temperatures of hot and cold fluids.

AnswerC

Marks1

QuestionThe Convective heat transfer coefficient in case of fluid flowing in the tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.

ALaminar

Btransition

Cboth 'a' & 'b'

Dhighly turbulent

AnswerD

Marks1

QuestionThe unit of heat transfer co-efficient in SI unit is

AJ/m2K

BW/m2K

CW/mK

DJ/mK

AnswerB

Marks1

QuestionControlling heat transfer film co-efficient is the one, which offers __________ resistance to the heat transfer.

ANo

BThe least

CThe largest

Dlower

AnswerC

Marks1

QuestionBulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is

Ain the central core of the fluid.

Buniformly distributed throughout the fluid.

Cmainly confined to a thin film of fluid near the surface

Dnone of these

AnswerC

Marks1

QuestionThe Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is

A2.36

B4.36

C120.36

DDepends on Reynolds number only

AnswerB

Marks1

QuestionFor flow over a flat plate, the ratio of thermal boundary layer thickness, t' to hydrodynamic boundary layer thickness '' is proportional to (where,NPr= Prandtl number)

ANPr

BNPr1/3

CNPr-1

DNPr-1/3

AnswerD

Marks1

Question In forced convection, the heat transfer depends on

ARe, Pr

BRe, Gr

Cmainly Gr

DRe only

AnswerA

Marks1

QuestionIf average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length

Aha= hl

Bha= 2hl

Cha= 0.5hl

Dha= 0.75hl

AnswerB

Marks1

QuestionValue of Prandtl number for water ranges from

Al to 2

B5 to 10

C100 to 500

D1000 to 2000

AnswerB

Marks1

QuestionHeat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by

Aeddies current

Bconduction

CConvection

Dnone of these

AnswerB

Marks1

QuestionHeat transfer co-efficient (h1) for liquids increases with

Aincreasing temperature.

Bdecreasing temperature

Cdecreasing Reynolds number

Dnone of these

AnswerA

Marks1

QuestionHeat transfer occurs by natural convection because change in temperature causes difference in

Aviscosity

Bdensity

Cthermal conductivity

Dheat capacity

AnswerB

Marks1

QuestionThe ratio of kinematic viscosity to thermal diffusivity is called the __________ number.

APeclet

BPrandtl

CStanton

DNusselt

AnswerB

Marks1

QuestionWhat is Nusselt number?

ACp /k

BhD/k

CK /Cp

DNone of these

AnswerB

Marks1

QuestionConvective heat transfer, in which heat is transferred by movement of warmed matter is described by

AFourier's law

BNewton's law of cooling

CFick's law

Dnone of these

AnswerB

Marks1

QuestionThe Grashof number is defined as the ratio of the

Abuoyancy to inertial forces

Bbuoyancy to viscous forces

Cinertial to viscous forces

Dbuoyancy to surface tension forces

AnswerB

Marks1

QuestionWhen warm and cold liquids are mixed, the heat transfer is mainly by

AConduction

Bconvection

CRadiation

Dboth(a) & (c)

AnswerB

Marks1

QuestionHeat transfer by natural convection is enhanced in system with

Ahigh viscosity

Bhigh co-efficient of thermal expansion

Clow temperature gradients

Dlow density change with temperature

AnswerB

Marks1

QuestionIn forced convection, the Nusselt number is a function of

ARe and Pr

BRe and Gr

CPr and Gr

DRe and Sc

AnswerA

Marks1

QuestionPrandtl number is the ratio of

Amomentum diffusivity to mass diffusivity.

Bmomentum diffusivity to thermal diffusivity.

Cthermal diffusivity to mass diffusivity.

Dthermal diffusivity to momentum diffusivity.

AnswerB

Marks1

QuestionThermal Diffusivity is given by

AK / (Cp. )

BCp./ k

C / Cp

D.Cp / k

AnswerA

Marks1

QuestionAt what value of Prandtl number, the hydrodynamic and thermal boundary layers are identical ?

A0.5

B1

C1.5

D10

AnswerB

Marks1

QuestionNatural convection is characterised by

AGrashof number

BPeclet number

CReynolds number

DStanton number

AnswerA

Marks1

QuestionNusselt number for full developed, laminar, constant property flow in a pipe at uniform heat flux is

A0.72

B4.36

C18

D83

AnswerB

Marks1

QuestionThickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is

A1

B< 1

C> 1

D>5

AnswerB

Marks1

QuestionOverall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt deposited on either side has coefficient U2, then

AU1 = U2

BU2 >U1

CU1 > U2

DU1 = dirt factor - U2

AnswerC

Marks1

QuestionWhich of the following has the lowest Prandtl number?

AMolten sodium (a coolant used in fast breeder reactor)

BWater

CTransformer oil

DDilute H2SO4

AnswerA

Marks1

QuestionIn SI units, fouling factor is expressed in

Am2K/W

BW/m2K

Cm2K/W

DmK/W

AnswerA

Marks1

QuestionNusselt number is the ratio of the

Atemperature gradient of the wall to that across the entire pipe

Btemperature difference to the temperature gradient at the wall

Cheat flux at the wall to that across the entire pipe

Dnone of these

AnswerC

Marks1

QuestionFouling factor

Ais a dimensionless quantity.

Bdoes not provide a safety factor for design.

Caccounts for additional resistances to heat flow.

Dnone of these.

AnswerC

Marks1

QuestionWith the increase of temperature, the Col-burnjHfactor

Aincreases.

Bdecreases.

Cremains unchanged

Dmay increase or decrease; depending on temperature

AnswerA

Marks1

QuestionDietus-Boelter equation used for the determination of heat transfer co-efficient is valid

Afor fluids in laminar flow.

Bfor fluids in tubulent flow.

Cwhen Grashof number is very important

Dfor liquid metals.

AnswerB

Marks1

QuestionWhich of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids?

ADittus-Boelter equation

BSieder-Tate equation

CNusselt equation

DNone of these

AnswerB

Marks1

QuestionA fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter 'd'. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to

Ad0.8

Bd-0.2

Cd-1

Dd-1.8

AnswerB

Marks1

QuestionThe Dietus-Boelter equation for convective heat transfer can not be used for,

Alow Reynold's number

Bvery low Grashoff number

Cmolten metals

Dall (a), (b) and (c)

AnswerD

Marks1

QuestionDietus-Boelter equation cannot be used for molten metals mainly due to its very low

APrandtl number

BGrashoff number


Dviscosity

AnswerA

Marks1

QuestionHeat transfer by natural convection is enhanced in system with

Ahigh viscosity.

Bhigh co-efficient of thermal expansion.

Clow temperature gradients

Dlow density change with temperature.

AnswerB

Marks1

QuestionFor a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

A1.26 h1

B0.794 h1

C0.574 h1

D1.741 h1

AnswerB

Marks1

QuestionPeclet number (Pe) is given by

APe = Re.Pr

BPe = Re/Pr

CPe = Pr/Re

DPe = Nu.Re

AnswerA

Marks1

Question(NGrxNPr) is called the __________ number.

AGraetz

BRayleigh

CNusselt

DStanton

AnswerB

Marks1

Question(Re.Pr) .(D/L) is called ---------------- Number.

APeclet

BStanton

CGraetz

DNone of these

AnswerC

Marks1

QuestionThe Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is

A1.66

B5

C3.66

Ddependent on NRe only

AnswerC

Marks1

QuestionPrandtl number for most of dry gases is about

A0.001

B0.72

C70

D150

AnswerB

Marks1

QuestionWhich has the lowest Prandtl number ?

ALiquid metal

BAqueous solution

CWater

DLube oil

AnswerA

Marks1

QuestionHeat transfer co-efficient equation for forced convection, Nu = 0.023 Re0.8 . Prn, is not valid, if the value of

An = 0.4 is used for heating.

Bn = 0.3 is used for cooling.

CReynolds number for the flow involved is > 10000.

DReynolds number for the flow involved is < 2100.

AnswerD

Marks1

QuestionA graph between __________ is called Wilson plot.

A

B

CV0.8 Vs . U

D

AnswerA

Marks1

QuestionThe Grashof Number is defined as

AProduct of Buoyancy and Inertia forces to (Viscous force)2

BProduct of Buoyancy and viscous forces to (inertial force) 2

CInertial to viscous forces

DBuoyancy to surface tension forces

AnswerA

Marks1

QuestionIn natural convection heat transfer the correlating parameter is

AReynold number

BBond Number

CGrashof Number

DEckert number

AnswerC

Marks1

QuestionMatch the Overall heat transfer coefficient for given fluids on vessel and jacket side.Jacket side Vessel side Overall heat transfer coefficient (W/m2K)I Steam I Water a. 30 75, b. 5000 6000, II Water II Polymer monomer c. 285 - 800 d. 850 - 1700

A(I) (d), (II) (c)

B(I) (c), (II) (d)

C(I) (a), (II) (b)

D(I) (b), (II) (a)

AnswerA

Marks1

QuestionMatch the Dimension numbers with terms,I Graetz Number a. Heat transfer in creeping flow,II Rayleigh number b. thermally developed flowc. Product of Grashof and Prandtl no.d. Product of Reynold and Prandtl number

A(I) (a), (II) (d)

B(I) (b), (II) (d)

C(I) (b), (II) (c)

D(I) (d), (II) (c)

AnswerC

Marks1

QuestionWhen a vertical plate is heated in an infinite air environment under natural convection conditions, the velocity profile in air, normal to the plate,

Ais linear

Bis parabolic

Cexhibits minimum

Dexhibits maximum

AnswerD

Marks1

QuestionWhen the ratio of Grashof number to the square root of the Reynolds number is one, the dominant mechanism of heat transfer is

Afree convection

Bforced convection

Cmixed convection (both free and forced)

DNone of these

AnswerC

Marks1

QuestionThe Hydrodynamic and Boundary layers will merge when

APrandtl Number is one

BSchmidt Number tends to infinity

CNusselt Number tends to infinity

DNone of these.

AnswerA

Marks1

QuestionRayleigh Number is associated

ABuoyancy effects

Bfree convection

Cforced convection

DHeat Conduction

AnswerB

Marks1

QuestionGibbs phase Rule finds application when heat transfer occurs by

AConduction

BConvection

CRadiation

DCondensation

AnswerB

Marks1

QuestionWhen the ratio of Grashof number to the square root of the Reynold number is Ten, the dominant mechanism of heat transfer is

Afree convection

Bforced convection

Cmixed convection (both free and forced)

DNone of these

AnswerA

Marks1

QuestionHeat Transfer by Natural Convection is enhanced by the system with

Ahigh viscosity

Bhigh coefficient of thermal expansion

Clow temperature gradient

Dnone of these

AnswerB

Marks1

QuestionPrandtl Number of Liquid Metal is of the order of

A1

B0.01

C10

D100

AnswerB

Marks1

QuestionHeat Transfer occurs by Natural convection because change in temperature causes difference in

ADensity

BThermal Conductivity

CHeat Capacity

Dnone of these

AnswerA

Marks1

QuestionIn pipe flow, heat is transferred from one fluid through the hot wall to the other fluid by

Afree and forced convection

Bforced convection only

Cforced convection and conduction

Dconduction only

AnswerC

Marks1

QuestionThe Graetz number is concerned with the

Amass transfer between a gas and a liquid.

Babsorption with chemical reaction

Cheat transfer in turbulent flow

Dheat transfer in laminar flow.

AnswerD

Marks1

QuestionLog mean temperature difference (LMTD) cannot be used, if

Aheat transfer co-efficient over the entire heat exchanger is not constant.

Bthere exists an unsteady state.

Cthe heat capacity is not constant and there is a phase change.

Dnone of these.

AnswerD

Marks1

QuestionThe Sieder-Tate correlation for heat transfer in laminar flow in pipe gives, where,Nuis the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as

A(D)-1.8

B(D)-0.2

C(D)0.2

D(D) -0.33

AnswerD

Marks1

QuestionThe Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe whose surface temperature remains constant is

A1.66

B88.66

C3.66

Ddependent on NRe only

AnswerC

Marks1

QuestionMatch the Dimensionless number with their ExpressionsI Stanton Number (a) hD/k (b) h / CpVII Prandtl Number (c) / Cpk (d) Cp / k

A(I) (a), (II) (b)

B(I) (a), (II) (d)

C(I) (b), (II) (c)

D(I) (b), (II) (d)

AnswerD

Marks1

QuestionMatch the Dimensionless number with the ratio of resistancesI Nusselt Number (a) Convective Resistance / fluid conduction Resistance II Prandtl Number (b) fluid conduction Resistance / Convective Resistance(c) Momentum Diffusivity / Thermal Diffusivity(d) Thermal Diffusivity / Kinematic Diffusivity

A(I) (a), (II) (c)

B(I) (b), (II) (c)

C(I) (b), (II) (d)

D(I) (a), (II) (d)

AnswerB

Marks1

QuestionA high value of thermal Diffusivity of material results from a ....(a). Value of thermal conductivity and a .(b). Value of thermal heat capacity.

A(a) high (b) high

B(a) low (b) high

C(a) high (b) low

D(a) low (b) low

AnswerC

Marks1

QuestionThermal Diffusivity has Unit of

Am2 /s

BW / m.k

CW

DNone of these

AnswerA

Marks1

QuestionLiquid Metals are used as heat transfer fluid in a nuclear reactor due to . (a) heat transfer coefficient and (b) heat capacity.

A(a) high (b) high

B(a) low (b) high

C(a) high (b) low

D(a) low (b) low

AnswerA

Marks1

QuestionHeat transfer coefficients for liquid metals are high due to their high

Aviscosity

Bdensity


Dnone of these

AnswerC

Marks1

QuestionThe Prandtl Number for liquid metals are low due to

Ahigh thermal conductivity

Bhigh Thermal diffusivity

CBoth A and B

Dnone of these

AnswerC

Marks1

QuestionAt the entrance of the pipe in which the fluid is being heated, the heat transfer coefficient is

Azero due to absence of temp gradient

Bequal to heat transfer coefficient for fully developed turbulent flow

CInfinite due to absence of temp gradient

Dzero due to zero thickness of boundary layer

AnswerC

Marks1

QuestionNear the entrance of the pipe in which the fluid is being heated, the temp profile is not fully developed then the local heat transfer coefficient is

Azero

Bsmaller than the heat transfer coefficient for fully developed turbulent flow

CInfinite

Dgreater than the heat transfer coefficient for fully developed turbulent flow

AnswerD

Marks1

QuestionThe thickness of thermal boundary layer in heat transfer to liquid metals is

Amore than thickness of hydrodynamic boundary layer

Bless than thickness of hydrodynamic boundary layer

Cequal to thickness of hydrodynamic boundary layer

Dzero

AnswerA

Marks1

QuestionWhich of the dimesionless group is used to compare thermal boundary layer and hydrodynamic boundary layer formed in heat transfer and fluid flow.

AFourier Number

BBiot Number

CPrandtl Number

DNusselt Number

AnswerC

Marks1

QuestionWithin the thermal boundary layer,

Atemperature is uniform

Btemperature gradient exists

Ctemperature gradient does not exist

Dheat flux is zero

AnswerB

Marks1

QuestionPeclet Number is defined as

ARatio of Reynold Number to Prandtl Number

BProduct of Reynold Number and Prandtl Number

CProduct of Nusselt Number and Prandtl Number

DRatio of Nusselt Number to Prandtl Number

AnswerB

Marks1

QuestionIn Natural Convection heat transfer, the Nusselt Number is a function of

AReynold Number and Prandtl Number

BGrashof Number and Prandtl Number

CSchmidt Number and Prandtl Number

DNone of these

AnswerB

Marks1

QuestionThe log mean Temperature difference of two temperature differences 1 and 2 is defined as,

A(1 - 2) / loge (1 / 2)

B(1 / 2) / loge(1 - 2)

C(ln1 - ln2) / ln (1 / 2)

D(1 + 2) / 2

AnswerA

Marks1

QuestionNewtons Law cooling is a special case of

APlanck Law

BKirchoff Law

CWeins Displacement Law

DStefans- Boltzmanns Law

AnswerD

Marks1

QuestionWhy is superheated steam not preferred as a heating medium in evaporators

Ametal tubes cannot withstand high temperature

Bsuperheated steam has very low film coefficient

Cmetal tubes cannot withstand high pressure

Dbecause of all above three factors

AnswerB

Marks1

QuestionNatural Convection is characterized by

AGrashof Number and Prandtl Number

BPeclet Number

CReynolds Number and Prandtl Number

Dnone of these

AnswerA

Marks1

QuestionColburn Analogy is valid when

A0.1< Pr < 10

B0.6 < Pr < 1

C1 < Pr < 100

D1 < Pr < 10

AnswerC

Marks1

QuestionWhat is the value of Reynold number at which transition of the laminar to turbulent flow occurs for fluid flows over a flat horizontal plate?

A5 x 105

B2100

C4000

D1

AnswerA

Marks1

QuestionThe hot radiator used for heating a room is a device which transfers the heat by

Aforced convection

Bfree convection

Cconduction

Dall of the above

AnswerB

Marks

QuestionFor a practical situation, Gr / Re2 > 10,

Aforced convection effects dominates

Bfree convection effects dominates

CNeither free nor forced convection effects dominates

DNone of above

AnswerB

Marks1

QuestionWhat is the accepted range of Reynold number for transition region between laminar and turbulent regions occurs when fluid flows through the tube?

A1000 < Re < 5 x 105

B2000 < Re < 4000

C100 < Re < 1000

D0.1 < Re < 50

AnswerB

Marks1

QuestionFree convection depends up on all of the following EXCEPT

ADensity

BCoefficient of thermal Expansion

CGravitational force

DVelocity

AnswerD

Marks1

QuestionThe Ratio of fluid Convective Heat flux to the fluid Conductive Heat Flux is called

AGrashof Number

BNusselt Number

CPrandtl Number

DPeclet Number

AnswerB

Marks1

QuestionIn free Convection, Transition from Laminar to Turbulent region is distinguished by a critical value of

AProduct of Reynolds Number and Prandtl Number

BProduct of Grashof Number and Prandtl Number

CProduct of Nusselt Number and Prandtl Number

DNone of these

AnswerB

Marks1

QuestionFor a practical situation, Gr / Re2 > 10,

Aforced convection effects dominates

Bfree convection effects dominates

CNeither free nor forced convection effects dominates

DNone of above

AnswerB

Marks1

QuestionIn heat exchangers, the values of log mean temperature difference should be

Aminimum possible

Bmaximum possible

Czero

Dany of above

AnswerB

Marks1

QuestionIn Natural Convection, The characteristic dimension of vertical pipe used in the dimensionless numbers is,

ADiameter of pipe

BVertical Length of pipe

CPerimeter

DArea

AnswerB

Marks1

QuestionCoefficient of thermal Expansion of the fluid in natural convection is related with

AAbsolute Temperature of the fluid

BVelocity of the fluid

CBoth of above

DNone of A & B

AnswerA

Marks1

QuestionHigher value of Prandtl Number shows,

ARapid heat transfer by forced convection to mutual convection

BRapid diffusion of momentum by viscous force as compared to diffusion of energy

Cboth A & B

DNeither A & B

AnswerB

Marks1

QuestionProduct of Reynolds Number and Prandtl Number is,

AStanton Number

BPeclet Number

CGrashof Number

DBiot Number

AnswerB

Marks1

QuestionStanton Number is the Ratio of Nusselt Number to ,

APrandtl Number

BProduct of Reynolds Number and Prandtl Number

CProduct of Grashof Number and Prandtl Number

DBiot Number

AnswerB

Marks1

QuestionThermal Diffusivity of the substance is proportional

Adirectly to thermal conductivity

BInversely to Density

CInversely to specific heat

DAll of above

AnswerD

Marks1

QuestionMinimum Thermal Diffusivity is of the substance

AAluminium

BRubber

CIron

DLead

AnswerB

Marks1

QuestionUnit of overall heat transfer coefficient is

AKcal/ hr. m2

BKcal/ hr. m2. 0C

CKcal/hr

DNone of these

AnswerB

Marks1

QuestionThe value log mean Temperature difference(LMTD) for counter flow heat exchanger as compared to the parallel flow heat exchanger is

Amore

Bless

Csame

Dnone of these

AnswerA

Marks1

QuestionRayleigh Number in Natural convection is the product of

AReynolds Number and Prandtl Number

BPeclet Number and Grashof Number

CGrashof Number and Prandtl Number

DNusselt Number and Prandtl Number

AnswerC

Marks1

QuestionThe Transition from laminar to turbulent regime for heat transfer by Natural convection in flow of fluid is distinguished by the Number

AStanton Number

BRayleigh Number

CPrandtl Number

DBiot Number

AnswerB

Marks1

QuestionUnit of thermal Diffusivity is

Am /hr K

BW /mK

Cm /hr

Dm2 /hr

AnswerD

Marks1

QuestionRatio of Kinematic viscosity to Thermal Diffusivity is called

ANusselt Number

BGrashof Number

CPrandtl Number

DReynolds Number

AnswerC

Marks1

QuestionIn the development of Laminar boundary layer and heat transfer over a flat plate of length L, The average value of heat transfer coefficient can be obtained from the local heat transfer coefficient hx at the trailing edge in the direction of flow by the factor,

A0L hxdx

Bd/dx(hx)

CL 0L hxdx

Dnone of the above

AnswerC

Marks1

QuestionIn the development of Laminar boundary layer and heat transfer over a flat plate, The average value of heat transfer coefficient can be obtained by multiplying the local heat transfer coefficient at the trailing edge in the direction of flow by the factor,

A1.5

B2

C1

D0.75

AnswerB

Marks1

QuestionThe ratio of thickness of thermal boundary layer and hydrodynamic boundary layer is proportional to (Prandtl Number)n, where n is,

A1

B-1/3

C-2/3

D-1

AnswerB

Marks1

QuestionGrashof Number is defined by

A(gTL3) /2

B(gT2L3) /2

C(gT2L3 )/2

D(gT3L3) /3

AnswerB

Marks1

QuestionA very low value of Nusselt Number means that

AFluid conduction resistance is negligible as compared to surface convective resistance

Bsurface convective resistance is negligible as compared to fluid conduction resistance

Cfluid conduction resistance is almost equal to surface convective resistance

Dnone of these

AnswerA

Marks1

QuestionA water Droplet at 25 0C is suddenly introduced into an infinite gas medium at 100 0C saturated with water vapor. At steady state,

ADrop attains WBT and vanishes

Bdrops remains unchanged and attains temperature of 100 0C

Cdrop increases in size and it attains temperature of 100 0C

Dnone of these.

AnswerC

Marks1

QuestionThe overall resistance for heat transfer between the two fluids through barrier of surface, is the __________ of the resistances to convection and conduction.

AAverage

Bgeometric mean

CProduct

DSum

AnswerD

Marks1

QuestionThe overall heat transfer coefficient for the heat transfer between the two fluids through barrier of surface, is__________ to/of the sum of all resistances to convection and conduction.

AEqual

BInverse

CMore than

DLess than

AnswerB

Marks1

QuestionMode of heat transfer in which the flu moves under the influence of changes in flu pressure produced by external work is called

ARadiation

Bnatural convection

Cforced convection

DConduction

AnswerC

Marks1

QuestionMode of heat transfer involved in the cooling of air cooled internal combustion engine is

AConduction

Bnatural convection

Cforced convection

Dnone of these

AnswerB

Marks1

QuestionWhich of the following has the lowest overall heat transfer co-efficient?

ADowtherm

BMolten sodium

CWater

DAir

AnswerD

Marks1

QuestionConvection heat transfer takes place between a steel plate with surface temperature (Ts) of 100C and the surrounding air (Ta) at 25C. If the surface area (A) of the plate is 1 m2 and the convection heat transfer coefficient (h) is 25 W/m2K find the heat transfer rate to the air.

A1775W

B1875W

C1475W

D1375W

AnswerB

Marks1

QuestionFind the heat transfer rate by forced convection between a surface of area (A) 15m 1.5 m and air, if the surface temperature (Ts) is 30C and the air temperature (Ta) is 45C. Assume the average convective heat transfer coefficient (h) to be 8 W/m2K.

A2.7kW

B270kW

C2700kW

D27kW

AnswerA

Marks1

QuestionMinimum value of Prandtl Number is of the substance

AWater

BAir

CLiquid Metal

DPetroleum

AnswerC

Marks1

QuestionConvective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.

Alaminar

Btransition

Chighly turbulent

DNone of the above

AnswerC

Marks1

QuestionThe unit of resistance to heat transfer is

AJ/(m2K)

B(m2-K)/W

CW/(m2-K)

DJ/sm2K

AnswerB

Marks1

QuestionWhich one of the following statements about baffles in shell and tube heat exchanger is false? Baffles

Aacts as support to the tube bundle

Breduce the pressure drop on shell side

Calter the shell side flow pattern

Dhelp in increasing the heat transfer coefficient on shell side

AnswerB

Marks1

QuestionSieder Tate correction Factor takes into account the variation in

APressure

BViscosity

Cspecific heat

Dvelocity

AnswerB

Marks1

QuestionWhich of the following statements about the Dittus- Boelter equation is/are not true

AIt is applicable for turbulent flow in pipe

BNusselt number is a function of Reynolds number and Prandtl number

CNeither A nor B

DBoth A & B

AnswerC

Marks1

QuestionHydraulic or equivalent diameter of non circular conduit can be determined by

A(4 x Wetted perimeter)/ cross sectional area

B(4 x cross sectional area)/ Wetted perimeter

C(cross sectional area)/ Wetted perimeter

Dnone of these

AnswerB

Marks1

QuestionHydraulic or equivalent diameter of annulus of two concentric pipe can be determined, if Do = OD of inner pipe Di = ID of outer pipe

A( D02- Di2) / Di

BDi / ( D02- Di2)

C( D0- Di)/ Di

DNone of these

AnswerA

Marks1

QuestionIf Overall heat transfer coefficient for the convective heat transfer without phase change is U1 and Overall heat transfer coefficient for the convective heat transfer with phase change is U2 with keeping other parameters same for same system, then

AU1 = U2

BU2 > U1

CU1 > U2

DU1 = dirt factor - U2

AnswerB

Marks1

QuestionInside Convective Heat transfer coefficient h1 for the fluid flows through straight tube as compared to Inside Convective Heat transfer coefficient h2 for the same fluid through the helical tube of same dimensions, under the same condition is

Ah1 > h2

Bh1 < h2

Ch1 = h2

DNone of these

AnswerB

Marks1

QuestionInside Convective Heat transfer coefficient for fully developed flow of fluid in smooth tubes can be determined by

ASieder Tate Correlation

BDittus Boelter correlation

CNusselt Equation

DPrandtl Equation

AnswerB

Marks1

QuestionIn Dietus-Boelter equation used for the turbulent flow through the pipe, heat transfer co-efficient is proportional to

A(Reynolds Number)0.2

B(Reynolds Number)0.8

C(Reynolds Number)0.33

D(Reynolds Number)0.5

AnswerB

Marks1

QuestionIn Dietus-Boelter equation used for the heating of turbulent flow through the pipe, heat transfer co-efficient is proportional to

A(Prandtl Number)0.3

B(Prandtl Number)0.4

C(Prandtl Number)0.8

D(Prandtl Number)0.5

AnswerB

Marks1

QuestionIn Dietus-Boelter equation used for the cooling of turbulent flow through the pipe, heat transfer co-efficient is proportional to

A(Prandtl Number)0.3




AnswerA

Marks1

QuestionFor a turbulent flow of fluid in a circular tube, h1 is convective heat transfer coefficient at velocity v1. If the velocity is reduced to half and assuming that fluid properties are constant the new convective heat transfer coefficient is

A1.26 h1

B0.794h1

C0.574 h1

D1.741h1

AnswerC

Marks1

QuestionFor a turbulent flow of fluid in a circular tube, h1 is convective heat transfer coefficient at velocity v1. If the velocity is doubled and assuming that fluid properties are constant the new convective heat transfer coefficient is

A1.26 h1

B0.794h1

C0.574 h1

D1.741h1

AnswerD

Marks1

QuestionFor a laminar flow of fluid in a circular tube, 'h1' is the convective heat transfer co-efficient at velocity 'V1'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is

A1.26 h1

B0.794h1

C0.574 h1

D1.741h1

AnswerB

Marks1

QuestionFor turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is doubled and the flow rate is halved, then the heat transfer co-efficient will change by a factor of approximately,

A1

B2

C0.5

D5

AnswerC

Marks1

QuestionFor laminar flow in tube, the heat transfer coefficient is obtained from Sieder Tate equation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer coefficient will change by factor,

A1

B3.2

C1.6

D8.2

AnswerC

Marks1

QuestionIn heat exchangers with steam outside the tubes, a liquid gets heated to 45 0C when its velocity in the tubes is 2 m/s. If the velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be

Aless than 45 0C

Bequal to 45 0C

Cgreater than 45 0C

Dinitially decreases and remains constant

AnswerA

Marks1

QuestionIf the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid

Aremains unchanged

Bincreases

Cincreases or decreases depends on no. of shell passe4s

Ddecreases

AnswerD

Marks1

QuestionIf the baffle spacing in a shell and tube heat exchanger decreases, then the Reynolds number of the shell side fluid

Aremains unchanged

Bincreases


Ddecreases

AnswerB

Marks1

QuestionIf the diameter of the tubes in shell and tube heat exchanger decreases, then the Reynolds number on the tube side fluid

Aremains unchanged

Bincreases


Ddecreases

AnswerB

Marks1

QuestionIf the diameter of the tubes in shell and tube heat exchanger increases, then the Reynolds number on the tube side fluid

Aremains unchanged

Bincreases


Ddecreases

AnswerD

Marks1

QuestionFor a laminar flow of fluid in a circular tube, h1 is convective heat transfer coefficient at velocity v1. If the velocity is reduced to half and assuming that fluid properties are constant the new convective heat transfer coefficient is

A1.26 h1

B0.794h1

C0.574 h1

D1.741h1

AnswerB

Marks1

QuestionFor Turbulent flow in tube, the heat transfer coefficient is obtained from Dittus- Boelter equation. If the tube diameter is halved and the mass flow rate is halved, then the heat transfer coefficient will change by factor,

A1

B0.5

C6.6

D0.66

AnswerD

Marks1

QuestionIn heat exchanger, floating head is provided to

Afacilitate cleaning of heat exchanger

Bincrease the heat transfer area

Crelieves the stresses by thermal expansion

Dincrease log mean temperature gradient

AnswerC

Marks1

QuestionWhy is superheated steam not preferred as a heating medium in evaporators

Ametal tubes cannot withstand high temperature

Bsuperheated steam has very low film coefficient

Cmetal tubes cannot withstand high pressure

Dbecause of all above three factors

AnswerB

Marks1

QuestionWhich one of the following tube configurations in heat exchangers results in the maximum heat transfer rate?

ATriangular Pitch

BSquare Pitch

CRectangular Pitch

DRhombus pitch

AnswerA

Marks1

QuestionIn shell and tube heat exchanger, baffles are provided on the shell side due to

Aprevent the stagnation of fluid

Bimprove Heat Transfer

CProvide the support for tubes

DAll of these

AnswerD

Marks1

QuestionIn Sieder- Tate equation used in laminar flow through the pipe, heat transfer co-efficient is proportional to

A(Prandtl Number)1/3




AnswerA

Marks1

QuestionIn Sieder- Tate equation used in laminar flow through the pipe, heat transfer co-efficient is proportional to

A(Reynolds Number)0.5

B(Reynolds Number)0.8

C(Reynolds Number)2

D(Reynolds Number)1/3

AnswerD

Marks1

QuestionFilm Condensation occurs when

ACondensate liquid does not wet the surface

BUsing surface coatings and vapour additives

COil and greasy surface

DCondensate liquid wets the surface

AnswerD

Marks1

QuestionThe average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where,T= Temperature drop across condensate film

A(T)2

BT

C(T)1/4

D(T)3/2

AnswerC

Marks1

QuestionFilm condensation is promoted on a/an __________ surface.

AOily

Bcoated

Cclean & smooth

Ddirty

AnswerC

Marks1

QuestionThe thickness of condensate layer in filmwise condensation depends on the

Acondensation rate

Bsurface configuration

Cliquid flow rate from the surface

Dall (a), (b) and (c)

AnswerD

Marks1

QuestionFor condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then

Ahf = hd

Bhf >hd

Chf< hd

Dhf could be greater or smaller than hd

AnswerC

Marks1

QuestionDropwise condensation is promoted on a/an __________ surface.

Aglazed

Boily

Ccoated

Dsmooth

AnswerB

Marks1

QuestionFor condensation of pure vapors, if the heat transfer coefficients in filmwise and dropwise condensation are respectively hf and hd

Ahf = hd

Bhf > hd

Chf < hd

Dhf is smaller or greater than hd

AnswerC

Marks1

QuestionA water Droplet at 25 0C is suddenly introduced into an infinite gas medium at 100 0C saturated with water vapor. At steady state,

ADrop attains WBT and vanishes

Bdrops remains unchanged and attains temperature of 100 0C

Cdrop increases in size and it attains temperature of 100 0C

Dnone of these

AnswerC

Marks1

QuestionMatch each of the processes with Heat Transfer coefficientProcess Heat transfer coefficient (W / m2 0C)I Dropwise condensation of steam (a) 1700 - 50000 II Boiling Water (b) 50 - 1500(c) 1 - 5(d) 30000 - 100000

A(I) (b), (II) (c)

B(I) (a), (II) (b)

C(I) (d), (II) (a)

D(I) (a), (II) (c)

AnswerC

Marks1

QuestionThe condensation of binary mixture of vapors at a constant pressure occurs

Aat constant temperature and yield a condensate of constant composition

Bover a temperature range and yield a condensate of constant composition

Cover a temperature range and yield a condensate of variable composition

DAt a temperature higher than the dew point temperature of vapors mixture

AnswerC

Marks1

QuestionConsider the following statements in condensation:I. Presence of non condensable gases causes vapor molecules to reach condensate vapor interface by diffusion through vap-gas mixtureII. Presence of non condensable gases creates a mass transfer or diffusional resistance besides heat transfer resistance for condensation.Which of the statements given above is/ are correct?

AI only

BII only

CBoth I & II

DNeither I or II

AnswerC

Marks

QuestionDropwise Condensation usually occurs on

AGlazed surface

BSmooth Surface

COily Surface

DCoated Surface

AnswerC

Marks1

QuestionFilmwise Condensation does not occur when

ACondensate wets the surface

BSmooth Surface

COily Surface

DPolished Surface

AnswerC

Marks1

QuestionDropwise Condensation does not take place, if




DCondensate liquid wets the surface

AnswerD

Marks1

QuestionHeat transfer Rate in Dropwise Condensation may be 10 times greater than that in film condensation because,

Afilm formed offers thermal Resistance to heat flow in film condensation

BSurface is continuously exposed to vapors in dropwise condensation

CBoth A & B

DNeither A nor B

AnswerC

Marks1

QuestionDropwise Condensation occurs when




DAll of the above

AnswerD

Marks1

QuestionDrowise condensation is not promoted on a/an __________ surface.

AOily

Bcoated

Cclean & smooth

Ddirty

AnswerC

Marks1

QuestionConsider the following statements in condensation:I. Presence of non condensable gases causes vapor molecules to reach condensate vapor interface by diffusion through vap-gas mixtureII. Presence of non condensable gases does not create a mass transfer or diffusional resistance besides heat transfer resistance for condensation.Which of the statements given above is/ are correct?

AI only

BII only

CBoth I & II

DNeither I or II

AnswerA

Marks1

QuestionConsider the following statements in condensation:I. Presence of non condensable gases does not cause vapor molecules to reach condensate vapor interface by diffusion through vap-gas mixtureII. Presence of non condensable gases does not create a mass transfer or diffusional resistance besides heat transfer resistance for condensation.Which of the statements given above is/ are correct?

AI only

BII only

CBoth I & II

DNeither I or II

AnswerD

Marks1

QuestionDropwise condensation is not promoted on a/an __________ surface.

AOily

Bcoated

Cclean & smooth

Ddirty

AnswerC

Marks1

QuestionDropwise condensation is promoted on a/an __________ surface.

AOily

Bcoated

Cdirty

DAll of the above

AnswerD

Marks1

QuestionIn the processe of Boiling of water, the Heat Transfer coefficient (W / m2 0C) is in the range of

A1700 - 50000

B50 - 1500

C1 - 5

D30000 - 100000

AnswerA

Marks1

QuestionIn the processe of Dropwise condensation of steam,the Heat Transfer coefficient (W / m2 0C) is in the range of

A1700 - 50000

B50 - 1500

C1 - 5

D30000 - 100000

AnswerD

Marks1

QuestionConsider the following statements in condensation:I. Heat transfer coefficient in filmwise condensation is always less than Dropwise condensation.II. Presence of non condensable gases does not create a mass transfer or diffusional resistance besides heat transfer resistance for condensation.Which of the statements given above is/ are correct?

AI only

BII only

CBoth I & II

DNeither I or II

AnswerA

Marks1

QuestionConsider the following statements in condensation:I. filmwise condensation is always preferred over Dropwise condensation.II. filmwise condensation occurs on the oily/ coated surface. Which of the statements given above is/ are correct?

AI only

BII only

CBoth I & II

DNeither I or II

AnswerD

Marks1

QuestionAverage heat transfer coefficient for condensation of vapors is directly proportional to __________ power of Thermal conductivity of the film of the fluid.

A1/4

B3/4

C2

D1/2

AnswerB

Marks1

QuestionAverage heat transfer coefficient for condensation of vapors over a vertical plate is ________ times the local heat transfer coefficient.

A2

B1/2

C3/4

D4/3

AnswerD

Marks1

QuestionVarious surface coatings and vapor additive have been used in in attempts to maintain

AFilmwise condensation

BDropwise condensation

CBoth A & B

DNeither A& B

AnswerB

Marks1

QuestionIf the condensation of vapors occurs on the horizontal tube, the heat transfer coefficient is proportional to ( D is diameter of tube)

AD1/4

BD3/4

CD-1/4

DD-3/4

AnswerC

Marks1

QuestionThe average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where,T= Temperature drop across condensate film

A(T)2

BT

C(T)1/4

D(T)3/2

AnswerC

Marks1

QuestionLeidenfrost point is a term concerned with the

Acondensation of the saturated vapor on a cold surface.

Bconcentration of a corrosive solution by evaporation.

Cheat transfer between two highly viscous liquids.

Dboiling of a liquid on a hot surface.

AnswerD

Marks1

Question'Burnout heat flux' is a term concerned with the


Bconcentration of a corrosive solution by evaporation.


Dboiling of a liquid on a hot surface.

AnswerD

Marks1

QuestionHeat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature excess for a boiling liquid, because

Aconvection becomes important

Bconduction becomes important

Cradiation becomes important

Dsub-cooled boiling occurs

AnswerC

Marks1

QuestionBoiling point of a solution according to Duhring's rule is a linear function of the __________ of water.

Aboiling point (at the same pressure)

Bviscosity

Cdensity

Dthermal conductivity

AnswerA

Marks1

QuestionIn a boiling curve, the peak heat flux is called the __________ point.

ANusselt

BLeidenfrost

Cboiling

Dburnout

AnswerD

Marks1

QuestionAs the difference between the wall temperature and the bulk temperature increases, the boiling heat transfer coefficient

Acontinues to increase

Bcontinues to decrease

Cgoes through minimum

Dgoes through a maximum

AnswerD

Marks1

QuestionWhen Bubbles begins to form on the surface, the region of pool Boiling is called as,

AFilm Boiling

BNucleate boiling

CInterface Evaporation

DNone of these

AnswerB

Marks1

QuestionPool Boiling Curve is the log Graph of

ABoiling point versus Heat flux

BHeat flux versus Temperature Excess

CHeat flux versus Boiling Time

DTemperature Excess Versus Time

AnswerB

Marks1

QuestionBurnout Flux is a term associated with the


Bconcentration of a corrosive solution by evaporation


Dboiling of a saturated liquid on a hot surface.

AnswerD

Marks1

QuestionIf the temperature of the liquid in the boiling is ------------------ the saturation temperature, the process is called subcooled boiling.

AEqual to

BMore than

CLess than

DCan not be predicted

AnswerC

Marks1

QuestionIf the temperature of the liquid in the boiling is ------------------ the saturation temperature, the process is called saturated or bulk boiling.

AEqual to

BMore than

CLess than


AnswerA

Marks1

QuestionIn subcooled or local boiling phenomenon, the liquid is maintained at a temperature

ABelow the saturation temperature

BAbove the saturation temperature

CEqual to the saturation temperature


AnswerA

Marks1

QuestionIn saturated or bulk boiling phenomenon, the liquid is maintained at a temperature

ABelow the saturation temperature

BAbove the saturation temperature

CEqual to the saturation temperature


AnswerC

Marks1

QuestionIn boiling the convection currents are responsible for the motion of the fluid near the surface , the regime is called as,

AInterface Evaporation

BBubbling regime

CFilm boiling

DNone of the above

AnswerA

Marks1

QuestionBubbles begin to form on the heated surface and dissipated in the liquid after breaking away from the surface during the boiling, the said regime is

AInterface Evaporation regime

BNucleate boiling regime

CFilm boiling regime

DNone of the above

AnswerB

Marks1

QuestionIn the pool boiling, the maximum heat flux at which the temperature usually exceeds the melting point of the wire, is referred to as

ALeidenfrost point

BBurnout flux

CBoiling limit

DNone of these

AnswerB

Marks1

QuestionI. Pool Boiling Curve is the plot of heat flux data against temperature excess.II. If the temperature of the liquid is below the saturation temperature of the, the process is called as subcooled or local boiling.Which sentence/s is/are correct?

AI only

BII only

CBoth I & II

DNeither I nor II

AnswerC

Marks1

QuestionI. In the saturated boiling the bubbles may break away from the surface because of the buoyancy action and move into the bulk of liquidII. In the saturated boiling, the heat transfer rate is not influenced by the agitation caused by the bubbles and vapor transport of energy into the bulk of liquid.Which sentence/s is/ are correct?

AI only

BII only

CBoth I & II

DNeither I & II

AnswerA

Marks1

QuestionI. In the saturated boiling the bubbles may break away from the surface because of the buoyancy action and move into the bulk of liquidII. In the saturated boiling, the heat transfer rate is influenced by both the agitation caused by the bubbles and vapor transport of energy into the bulk of liquid.Which sentence/s is/ are correct?

AI only

BII only

CBoth I & II

DNeither I & II

AnswerC

Marks1

QuestionBoiling of milk in an open vessel is an example of __________ boiling.

Afilm

Bsub-cooled

Csaturated nucleate

Dnone of these

AnswerA

Marks1

QuestionBoiling point elevation of an ideal solution

Aincreases rapidly with temperature rise

Bin independent of pressure

Cdecreases rapidly with temperature rise

DNone of these

AnswerA

Marks1

QuestionAccording to Duhring's rule, Boiling point of a solution is a linear function of the __________ of pure water.

Aboiling point (at the same pressure)

Bviscosity

Cdensity

Dthermal conductivity

AnswerA

Marks1

QuestionThe regime of pool boiling in which Leidenfrost point exists, is referred to as

AInterface evaporation

BNucleate boiling

CFilm boiling

DNone of the above

AnswerC

Marks1

QuestionI. Free convection currents are responsible for the motion of the fluid near the surface in the regime of interface evaporation.II. Bubbles are formed so rapidly as they blanket the heating surface to provide the thermal resistance in the film boiling.Which sentence/s is/ are correct?

AI only

BII only

CBoth I & II

DNeither I & II

AnswerC

Marks1

QuestionI. Free convection currents are responsible for the motion of the fluid near the surface in the regime of interface evaporation.II. Bubbles are formed so rapidly as they blanket the heating surface to provide the thermal resistance in the film boiling.Which sentence/s is/ are false?

AI only

BII only

CBoth I & II

DNeither I & II

AnswerD

Marks1

QuestionHeat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature excess for a boiling liquid, because

Aconvection becomes important

Bconduction becomes important

Cradiation becomes important

Dsub-cooled boiling occurs

AnswerC

Marks1

QuestionI. Free convection currents are not responsible for the motion of the fluid near the surface in the regime of interface evaporation.II. Bubbles are formed so rapidly as they blanket the heating surface to provide the thermal resistance in the film boiling.Which sentence/s is/ are correct?

AI only

BII only

CBoth I & II

DNeither I & II

AnswerB

Marks1

QuestionI. Free convection currents are responsible for the motion of the fluid near the surface in the regime of interface evaporation.II. Bubbles are formed so rapidly as they blanket the heating surface to provide the thermal resistance in the film boiling.Which sentence/s is/ are False?

AI only

BII only

CBoth I & II

DNeither I & II

AnswerD

Marks1

QuestionI. In the saturated boiling the bubbles may break away from the surface because of the buoyancy action and move into the bulk of liquidII. In the saturated boiling, the heat transfer rate is influenced by both the agitation caused by the bubbles and vapor transport of energy into the bulk of liquid.Which sentence/s is/ are False?

AI only

BII only

CBoth I & II

DNeither I & II

AnswerD

Marks1

QuestionBurnout Flux is a term associated with the


Bconcentration of a corrosive solution by evaporation


Dboiling of a saturated liquid on a hot surface.

AnswerD

Marks1

QuestionIn film type condensation over a vertical plate, local heat transfer coefficient is

AInversely proportional to the local film thickness

BDirectly proportional to the local film thickness

Cequal to the local film thickness

Dindependent of the local film thickness

AnswerA

Marks1

QuestionIn sub-cooled boiling,

Atemperature of the heating surface is less than the boiling point of the liquid.

Btemperature of the heating surface is more than the boiling point of the liquid.

Cbubbles from heating surface are absorbed by the mass of the liquid.

Dvery large vapour space is necessary.

AnswerB

Marks1

QuestionNucleate boiling is promoted

Aon polished surfaces

Bon rough surfaces

Cin the absence of agitation

Dnone of these

AnswerB

Marks1

QuestionWhen vaporisation takes place through a blanketing film of gas, the phenomenon is termed as __________ boiling.

APool

BNucleate

CTransition

DFilm

AnswerD

Marks1

QuestionWhen vaporisation takes place directly at the heating surface, it is called

Afilm boiling

Bnucleate boiling

Cvapour boiling

Dnone of these

AnswerB

Marks1

QuestionThe bubbles grow to the certain size on the heated surface during boiling, is not dependent on

ASurface tension at vap-liq interface

BTemperature

Cpressure

DNone of the above

AnswerD

Marks1

QuestionThe bubbles grow to the certain size on the heated surface during boiling, is dependent on


BTemperature

Cpressure

DAll of the above

AnswerD

Marks1

QuestionBubbles are created by the expansion of the entrapped gas at a small cavity in the surface during the pool boiling, the boiling regime is said to be,

AInterface evaporation

BNucleate boiling

CFilm boiling

DNone of the above

AnswerB

Marks1

QuestionDuring the pool boiling, Radiation is coming into play

AJust after the burnout heat flux

BJust before the burnout heat flux

CJust before the leidenfrost point

DJust after the Leidenfrost point

AnswerD

Marks1

QuestionThe thickness of the film of the condensate formed over a vertical cold plate in condensation depends up on

AThermal conductivity of the film only

BViscosity of the fluid only

CTemperature difference between gas and plate only

DAll of the above

AnswerD

Marks1

QuestionThe thickness of the film of the condensate formed over a vertical cold plate in condensation is proportional to, (fg is latent heat of condensation)

A(fg)1/2

B(fg)1/4

C( fg)-1/2

D(fg)-1/4

AnswerD

Marks1

QuestionThe thickness of the film of the condensate formed over a vertical cold plate in condensation is proportional to, (k is thermal conductivity of condensate)

A(k)1/2

B(k)1/4

C(k)-1/2

D(k)-1/4

AnswerB

Marks1

QuestionThe heat transfer coefficient for the condensation over a vertical cold plate is proportional to, (k is thermal conductivity of condensate)

A(k)1/2

B(k)3/4

C(k)-1/2

D(k)-1/4

AnswerB

Marks1

QuestionIn saturated boiling,

Atemperature of the liquid is at its saturation temperature only

Btemperature of the heating surface is more than the boiling point of the liquid only.

CBoth A & B

DNeither A & B

AnswerC

Marks1

QuestionThe point at which it may be possible to observe the partial nucleate boiling and unstable film boiling region is referred to as

ALeidenfrost point

BBurnout heat flux

CInterface evaporation

DNone of the above

AnswerB

Marks1

QuestionFor laminar film condensation on horizontal tubes, heat transfer coefficient is proportional to the following

ADensity, viscosity of condensate and thermal conductivity of condensate only

BLatent heat of condensation and Temperature excess only

CDiameter of the tube only

DAll of the above

AnswerD

Marks1

QuestionOn condensation, Mixed vapors yield the condensate as

ALiquid of variable composition

BLiquid of constant composition

CMixture of vapor and liquid

DNone of these

AnswerA

Marks1

QuestionDesign of any heat exchange equipment used for condensation of vapors is done on the following type of condensation to occur on the surface

ADropwise condensation only

BFilmwise condensation only

CBoth A & B

DNeither A nor B

AnswerB

Marks1

QuestionWhich of the following type of condensation to occur on the surface, is difficult to achieve and maintain, needs oily and greasy surface,



CBoth A & B

DNeither A nor B

AnswerA

Marks1

QuestionWhich of the following type of condensation to occur on the surface is well determined and needs clean, smooth surface,



CBoth A & B

DNeither A nor B

AnswerB

Marks1

QuestionThe presence of non condensable gas in the vapors during condensation

AOffers the resistance to heat flow

BDecreases the rate of condensation

CReduces the heat transfer coefficient

DAll of the above

AnswerD

Marks1

QuestionThe bubbles grow to the certain size on the heated surface during boiling, is not dependent on


BTemperature

Cpressure

DNone of the above

AnswerD

Marks1

QuestionThe average heat transfer coefficient for the condensation over a vertical cold plate is proportional to, (fg is latent heat of condensation)

A(fg)1/2

B(fg)1/4

C( fg)-1/2

D(fg)-1/4

AnswerB

Marks1

QuestionThe thickness of the film of the condensate formed over a vertical cold plate in condensation is proportional to, where, ( Tg - Tw) is temperature difference between cold surface and vapors)

A(Tg - Tw)1/2

B(Tg - Tw)1/4

C(Tg - Tw)-1/2

D(Tg - Tw)-1/4

AnswerB

Marks1

QuestionThe average heat transfer coefficient for the condensation over a vertical cold plate is proportional to, where, ( Tg - Tw) is temperature difference between cold surface and vapors)

A(Tg - Tw)1/2

B(Tg - Tw)1/4

C(Tg - Tw)-1/2

D(Tg - Tw)-1/4

AnswerD

Marks1

QuestionFor the film condensation over a vertical cold plate, the critical value of Reynold number is,

A3200

B1800

C10000

D1000

AnswerB

Marks1

QuestionFor the film condensation over a vertical cold plate, ripples will develop in the film at the value of Reynold number as low as is,

A100-120

B3-4

C30-40

D150-190

AnswerC

Marks1

QuestionThe transition Reynolds Number for flow over a flat plate is 5 x 105. What is the distance from the leading edge at which transition will occur for flow of water with uniform velocity of 1 m/s and the kinematic viscosity of 0.858 x 10-6 m2/s?

A1 m

B0.43m

C43 m

D103 m

AnswerB

Marks2

QuestionA fluid flows over a flat plate has the following properties:Dynamic viscosity : 25 x 10-6 kg /ms, Specific heat : 2.0 kJ /Kg KThermal Conductivity: 0.05 W /mKThe hydrodynamic boundary layer thickness is measured to be 0.5 mm. The thickness of thermal boundary layer would be,

A1.3 mm

B0.023 mm

C0.079 mm

D0.5 mm

AnswerD

Marks2

QuestionAir at 293K is flowing over a flat plate at 373 K at a velocity of 3 m/s. The plate is 2m long and 1m wide. if the Prandtl number is 0.69, kinematic viscosity 15 x 10-6 m2/s, then The thickness of thermal boundary layer at a distance 0.4 m from the leading edge of the plate is,

A6.56 mm

B7.2 mm

C3.6 mm

D3.28 mm

AnswerB

Marks2

QuestionHydraulic or Equivalent Diameter(De) of annulus of two concentric pipes with inner diameter of outer pipe 8cm and outer diameter of inner pipe 4 cm, determined is,

A10cm

B12cm

C14cm

D16cm

AnswerB

Marks2

QuestionIn double pipe heat exchanger, the ID and OD of the pipe are 4 cm and 5 cm respectively.The ID of the outer pipe is 10 cm with wall thickness of 1 cm. Then the equivalent diameter of the annulus for the heat transfer is

A4.5cm

B7.8cm

C10cm

D15 cm

AnswerD

Marks2

QuestionAir at 300K is flowing over a flat plate at 333 K at a velocity of 2 m/s. The plate is 2m long and 1m wide. The average heat transfer coefficient is 12.3 W/m2K. The heat transferred from the plate is,

A81.18 W

B811.8W

C78.28 W

D18.18 W

AnswerB

Marks2

QuestionWater at 20 oC and = 1.002 x 10-3 kg/m.s, k= 0.603W/mK, Cp= 4.183 KJ/kgK, The Prandtl Number for this case would be,

A0.695

B0.75

C6.95

D69.5

AnswerC

Marks2

QuestionMercury at 20 oC and = 1520 x 10-6 kg/m.s, k= 0.0081 kW/mK, Cp= 0.139 kJ/kgK, The Prandtl Number of mercury would be,

A2.61

B0.0261

C26.1

D261

AnswerB

Marks2

QuestionAir at 27oC and 1 atm flows over a flat plate at speed of 2 m/s. Viscosity = 1.85 x 10-5 kg/m.s, Density = 1.177kg/m3. Boundary layer thickness at a distance of 20 cm from the leading edge of the plate is,

A55.9 mm

B5.59 mm

C0.0559 mm

D0.559 mm

AnswerB

Marks2

QuestionAir at 27oC and 1 atm flows over a flat plate at speed of 2 m/s. Boundary layer thickness at a distance of 20 cm from the leading edge of the plate is 5.59 mm and Prandtl Number of air is 0.70. Then Thermal boundary layer thickness is,

A6.13mm

B4.2 mm

C6.9 mm

D5.9 mm

AnswerA

Marks2


A6.66 mm

B6.86 mm

C8.66 mm

D7.86 mm

AnswerC

Marks2

QuestionA fluid flowing with Reynolds No. 26.26 through the tube 20 mm ID and 5 cm length. Prandtl No. is 2625, viscosity in the bulk is 0.8 Ns/m2and that at the wall(w) is 1 Ns/m2, thermal conductivity = 0.384W/m.K. Using Sieder-Tate equation, the inside heat transfer coefficient is,

A520 W/m2K

B225 W/m2K

C425 W/m2K

D825 W/m2K

AnswerB

Marks2

QuestionA fluid flowing with Reynolds Number 12198 through the tube 40 mm ID. Prandtl Number is 42.5 and thermal conductivity = 0.256 W/m.K. If the fluid is being heated, using Dittus-Boelter equation, the inside heat transfer coefficient would be,

A1225 W/m2K

B1525 W/m2K

C825 W/m2K

D425 W/m2K

AnswerA

Marks2

QuestionWater at 353K entering and leaves at 309K with a velocity of 3 m/s through the tube of 16 mm diameter. The tube temperature is 297K. Prandtl No. is 3.09, viscosity = 485 x 10-6 kg/m.s, thermal conductivity = 0.657 W/m.K and density = 984.1 kg/m3, using Dittus-Boelter equation, the inside heat transfer coefficient would be,

A9970 W/m2K

B10970 W/m2K

C11970 W/m2K

D12970 W/m2K

AnswerD

Marks2

QuestionHot water enters the tube side of a counter current shell and tube heat exchanger at 80C and leaves at 50C. Cold oil enters at 20C and leaves at 45oC. The log mean temperature difference in C is approximately

A32

B37

C45

D50

AnswerA

Marks2

QuestionHot oil at 150 oC is used to preheat a cold fluid at 30 oC in a shell and tube heat exchanger. The exit temperature of the hot oil is 110 oC. Product of Heat capacity and mass flow rate of each of the streams is same. The heat duty is 2 KW. Under concurrent flow conditions, the log mean temperature difference is

A82.2 oC

B72.8 oC

C68.32 oC

D120.2 oC

AnswerB

Marks2

QuestionIn counter current Heat Exchanger, cold fluid enters at 30 0C and leaves at 60 0C, whereas the hot fluid enters at 150 0C and leaves at 110 0C, The log mean temperature difference for this case is,

A100 0C

B85 0C

C107 0C

D35 0C

AnswerB

Marks2


A6.66 mm

B6.86 mm

C8.66 mm

D7.13 mm

AnswerD

Marks2

QuestionWater at 27oC and 1 atm flows over a flat plate at speed of 2 m/s and Boundary layer thickness at a distance of 30 cm from the leading edge of the plate is 9 mm and Prandtl Number of air is 6.5. Then Thermal boundary layer thickness is,

A4.7 mm

B7.4 mm

C10 mm

D7.9 mm

AnswerA

Marks2

QuestionOil at 20oC and 1 atm flows over a flat plate at speed of 1.2 m/s with properties density 876kg/m3, kinematic viscosity 0.00024 m2/s and thermal conductivity as 0.144 W/moC, Cp specific heat is 1965.75 J/kgoC, Then Prandtl Number is

A2910

B2870

C2120

D2139

AnswerB

Marks2

QuestionOil having flow rate 2000 kg/hr at 107 0C is cooled to 30 0C by water which enters at 15 0C and leaves at 80 0C in counter flow heat exchanger. What is its LMTD?

A12.4 0C

B20.4 0C

C24.4 0C

D16.4 0C

AnswerB

Marks2

QuestionAir at 500 K has kinematic viscosity of 37.9 x 10-6 m2/s and thermal diffusivity of 0.5564x 10-4 m2/s, then Prandtl number is

A0.702

B0.680

C0.860

D0.720

AnswerB

Marks2

QuestionAir at 293 K is flowing at velocity 2m/s over heated rectangular plate of length 2 m at 407K , Prandtl number 0.7 and thermal conductivity of air is 0.03W/mK, kinematic viscosity 20.76 x 10-6m2/s, the average heat transfer coefficient would be,

A3.9 W/m2K

B4.9 W/m2K

C5.9 W/m2K

D6.9 W/m2K

AnswerA

Marks2

QuestionAir at 293 K is flowing at velocity 2m/s over heated rectangular plate of length 2 m at 407K, the average heat transfer coefficient is 3.9 W/m2K, the heat lost from the plate is 1500W, the width of the plate is

A4.69 m

B3.69 m

C2.69 m

D1.69 m

AnswerD

Marks2

QuestionAir at 293 K is flowing at velocity 2m/s over heated rectangular plate of length 2 m and unit width at 407K, the average heat transfer coefficient is 3.9 W/m2K, the heat lost from the plate is,

A1200W

B1300W

C1400W

D1500W

AnswerD

Marks2

QuestionAir at 300K blows at a free stream velocity of 4 m/s across a 12 mm diameter sphere maintained at 350 K , the heat transfer coefficient is 97.85 W/m2K, the heat lost from the sphere is,

A1.21 W

B2.21 W

C3.21 W

D4.21 W

AnswerB

Marks2

QuestionAir at 293 K is flowing at velocity 2m/s over heated rectangular plate of length 2 m and unit width at 407K with kinematic viscosity 20.76 x 10-6 m2/s, the said fluid is flowing in

ALaminar region

BTransition Region

CTurbulent region

DFully turbulent

AnswerA

Marks2

QuestionAir at 293 K is flowing at velocity 35 m/s over heated rectangular plate of length 75 cm at 333K , Prandtl number 0.7 and thermal conductivity of air is 0.03W/mK, kinematic viscosity 20.76 x 10-6m2/s, the average heat transfer coefficient would be,

A79 W/m2K

B89 W/m2K

C99 W/m2K

D109 W/m2K

AnswerC

Marks2

QuestionAir at 293 K is flowing at velocity 35 m/s over heated rectangular plate of length 75 cm at 333K , Prandtl number 0.7 and thermal conductivity of air is 0.03W/mK, kinematic viscosity 20.76 x 10-6m2/s, the said fluid is flowing in

ALaminar region

BTransition Region

CTurbulent region

DNone of these

AnswerC

Marks2

QuestionAir at 293 K is flowing at velocity 35 m/s over heated rectangular plate of 75 cm x 75cm in dimension maintained at 333K, the average heat transfer coefficient 99 W/m2K, the heat lost from only one side of the plate is,

A2227.5 W

B1227.5 W

C4455 W

D3227.5 W

AnswerD

Marks2

QuestionSaturated steam at 353 K condenses on outside of horizontal tube of 100 mm O. D. and length L. The tube wall is maintained at 343 K. When the tube wall is vertical, it was observed that the rate of condensation was same as the horizontal, then the tube length required is

A2.9 m

B29 m

C0.29 m

D0.029 m

AnswerC

Marks2

QuestionIn heat exchangers with steam outside the tubes, a liquid gets heated to 45 0C when its velocity in the tubes is 2 m/s. If the velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be

Aless than 45 0C

Bequal to 45 0C

Cgreater than 45 0C

Dinitially decreases and remains constant

AnswerA

Marks2

Question1000 kg of liquid at 30 0C in a well stirred vessel has to be heated to 120 0C, using immersed coils carrying condensing steam at 1500C. the area of the steam coils is 1.2 m2 and overall heat transfer coefficient to the liquid is 1500 W/m2 0C. Assuming negligible heat loss to the surroundings and specific heat capacity of liquid to be 4 kJ / kg 0C, the time taken for the liquid to reach desired temperature will be

A15 min

B22 min

C44 min

D51 min

AnswerD

Marks2

QuestionThe Overall heat transfer coefficient for shell and tube heat exchanger for clean surface is Uc = 400 W /m2 K. The fouling factor after one year of operation is found to be hdo = 2000 W /m2 K . the overall heat transfer coefficient at this time is

A1200 W /m2 K

B894 W /m2 K

C333 W /m2 K

D287 W /m2 K

AnswerC

Marks2

QuestionA horizontal pipe 1ft. (0.3048 m) in diameter is maintained at temperature of 250oC in a room where ambient air is at 15oC. Product of Grashof Number and Prandtl Number is 1.571 x 108, thermal conductivity = 0.03406 W/m.K. Convective heat transfer coefficient is,

A3.66 W/m2K

B66.36 W/m2K

C6.63 W/m2K

D36.6 W/m2K

AnswerC

Marks2

QuestionSteam at 373 K is condensed over a vertical plate 0.3 x 0.3 m2 maintained at 371 K. The heat transferv coefficient is 13150 W/m2K, the latent heat of condensation is 2225kJ/kg, The rate of condensation is,

A38 kg/hr

B3.8 kg/hr

C0.38 kg/hr

D380 kg/hr

AnswerB

Marks2

QuestionA horizontal pipe 1ft. (0.3048 m) in diameter is maintained at temperature of 250oC in a room where ambient air is at 15oC. Properties are evaluated at mean film temperature of 405.5K.thermal conductivity = 0.03406 W/m.K, Kinematic viscosity = 26.54 x 10-6 m2/s, Grashof Number calculated is,

A1.571 x 108

B2.29 x 108

C15.71 x 108

D22.9 x 108

AnswerB

Marks2

QuestionOil having flow rate 2000 kg/hr at 107 0C is cooled to 30 0C by water which enters at 15 0C and leaves at 80 0C in counter flow heat exchanger. The specific heat of oil is 2.51 kJ/kg K. The overall heat transfer coefficient is 1500 W/m2K. What is the heat transfer area required?

A25 m2

B3.5 m2

C4.5 m2

D3 m2

AnswerB

Marks2

QuestionSteam is condensed with heat lost 5 kW on the cold surface. If the latent heat of condensation is 2225 kJ/kg, the mass flow rate of the condensate is,

A8 kg/hr

B9 kg/hr

C10 kg/hr

D11.2 kg/hr

AnswerA

Marks2

QuestionA straight tube having a diameter of 40 mm carries fluid with velocity of 10 m/s. the temperature of tube surface is 50 oC and flowing fluid is heated from temp 15 oC to 25 oC. The physical properties of fluid at mean temp Pr. = 0.702, / = 1.006 x 10-6 m2/s, k = 0.599 W/mKThe heat transfer coefficient would be approximately,

A9020 W/m2oC

B8359 W/m2 oC

C3258 W/m2 oC

D7680 W/m2 oC

AnswerA

Marks2

QuestionWater flowing in a steel pipe of diameter 0.02 m is to be cooled from 40 oC to 30 oC. The velocity of water in the steel pipe 1.5m/s. The inside surface temp is maintained at 25 oC.Viscosity is 7.65 x 10-4, Thermal conductivity = 0.623 W/mK, Density = 995 Kg/m3 and Pr = 5.3The convective heat transfer coefficient for water is,

A6240 W/m2K

B5565 W/m2K

C3250 W/m2K

D7680 W/m2K

AnswerB

Marks2

QuestionSaturated vapors at 323 K condensed on the cold surface maintained at 313 K , heat transfer coefficient is 1000 W/m2K, the heat transfer area is 1m2,and the latent heat of condensation is 132kJ/kg, the rate of condensation is,

A723.7kg/hr

B272.7 kg/hr

C327.3 kg.hr

D100 kg/hr

AnswerB

Marks2

QuestionHot oil at 150 oC is used to preheat a cold fluid from 30 oC to 70 oC in a shell and tube heat exchanger. The exit temperature of the hot oil is 110 oC. The heat duty is 2 KW. Under counter current flow conditions, overall heat transfer resistance (1/UA) is,

A0.04 oC/W

B0.4oC/W

C0.36 oC/W

D0.036 oC/W

AnswerA

Marks2

QuestionHot oil at 150 oC is used to preheat a cold fluid from 30 oC to 70 oC in a shell and tube heat exchanger. The exit temperature of the hot oil is 110 oC. The heat duty is 2 KW. Under concurrent flow conditions, overall heat transfer resistance (1/UA) is,

A0.04 oC/W

B0.4oC/W

C0.36 oC/W

D0.036 oC/W

AnswerD

Marks2

QuestionHot liquid is flowing with the velocity of 2 m/s through a metallic pipe having inner diameter of 3.5 cm and length of 20 m. The temperature at the inlet of the pipe is 90 oC. Data: Density = 950 kg/m3, viscosity = 2.55 x 10-4 kg/ms, thermal conductivity = 0.685 W/moCPrandtl Number = 1.57, then the convective heat transfer coefficient in KW/m2 oC would be,

A11.2 KW/m2 oC

B111.2 KW/m2 oC

C22.2 KW/m2 oC

D221.2 KW/m2 oC

AnswerA

Marks2

QuestionAir at temperature 523 K flows over a flat plate 0.3 m wide and 1m long at velocity of 8 m/s, if the plate is maintained at 351 K, The average convective heat transfer coefficient is 3.06W/m2K. The rate of heat flow from one side of the plate only is,

A158W

B258W

C358W

D316W

AnswerA

Marks2

QuestionAir at temperature 523 K flows over a flat plate 0.3 m wide and 1m long at velocity of 8 m/s, if the plate is maintained at 351 K, thermal conductivity = 36.4 x 10-3 W/m.K, Kinematic viscosity = 3.9 x 10-4 m2/s, Prandtl number is 0.69, The average convective heat transfer coefficient would be,

A9.06 W/m2K

B6.06 W/m2K

C3.06 W/m2K

D5.06 W/m2K

AnswerC

Marks2

QuestionAir at 8 kPa and 523 K flows over a flat plate 0.3 m wide and 1.5 m long at velocity of 8 m/s, if the plate is maintained at 253 K, thermal conductivity = 36.4 x 10-3 W/m.K, Kinematic viscosity = 3.9 x 10-4 m2/s, Prandtl number is 0.69. The average convective heat transfer coefficient is,

A1.5 W/m2K

B2.5 W/m2K

C3.5 W/m2K

D4.5 W/m2K

AnswerB

Marks2

QuestionAir at 333K is flowing at a velocity of 15 m/s parallel on both sides of the flat square plate having sides each of 20cm, maintained at 293 K. if the Prandtl number is 0.699, kinematic viscosity 16.96 x 10-6 m2/s, thermal conductivity of air is 0.0276W/mK. Then the average heat transfer coefficient is

A17.1 W/m2 oC

B43.2 W/m2 oC

C22.2 W/m2 oC

D34.2 W/m2 oC

AnswerD

Marks2

QuestionA fluid flowing with velocity 1.14 m/s is heated through the hot tube of 40mm diameter. Data: Prandtl number = 42.5, Density = 1070 kg/m3, viscosity= 0.004 Ns/m2 and thermal conductivity = 0.256 W/mK. Inside heat transfer coefficient for this case is,

A122.5 W/m2 K

B1225.5 W/m2 K

C2250.5 W/m2 K

D212.5 W/m2 K

AnswerB

Marks2

QuestionAir at 2 atm and 200oC is heated as it flows at velocity of 10 m/s through a tube with diameter of 2.54 cm. Prandtl no.= 0.681, = 2.57 x 10-5 kg/m.s, k= 0.0386W/mK, Cp= 1.025 KJ/kgK, = 1.493kg/m3 . The heat transfer coefficient would be

A32.65 W/m2K

B64.85 W/m2K

C46.65 W/m2K

D16.35 W/m2K

AnswerB

Marks2

QuestionAir at 2 atm and 200oC is heated as it flows at velocity of 10 m/s through a tube with diameter of 5 cm and 1m length. The tube wall is maintained at a temperature 20oC above the air temperature. The heat transfer coefficient is 70 W/m2K. Then The heat flow would be,

A22 W

B220 W

C2220 W

D22.5 W

AnswerB

Marks2

QuestionA large vertical plate 4 m high and 10 m wide maintained at 60 oC and exposed to atmospheric air at 10 oC. If the product of Grashof No. and Prandtl No. is 2.62 x 1011, The Nusselt Number will be,

A640

B460

C560

D450

AnswerA

Marks2

QuestionA large vertical plate 4 m high and 10 m wide maintained at 60 oC and exposed to atmospheric air at 10 oC. Air properties evaluated at mean film temperature 308 K are, k = 0.02685 W/mK, Kinematic viscosity = 16.5 x 10-6 m2/s, = 3.25 x 10-3 K-1, the Grashof Number calculated for this case is,

A2.74 x 1011

B3.74 x 1011

C4.74 x 1011

D1.74 x 1011

AnswerB

Marks2

Question2 cm diameter horizontal heater is maintained at surface temperature of 38 oC and submerged in water at 27oC, the product of Grashof and Prandtl Number is 2.18 x 106, thermal conductivity = 0.630W/m.K. Convective heat transfer coefficient is,

A462 W/m2K

B642 W/m2K

C264 W/m2K

D426 W/m2K

AnswerB

Marks2

QuestionAir at temperature 523 K flows over a flat plate 0.3 m wide and 1m long at velocity of 8 m/s, if the plate is maintained at 351 K, The average convective heat transfer coefficient is 3.06W/m2K. The rate of heat flow from both sides of the plate is,

A158W

B258W

C358W

D316W

AnswerD

Marks2

QuestionSteam at 373K is condensed over a cylindrical surface of diameter 25 mm maintained at 357 K, heat transfer coefficient is 10864 W/m2K, the rate of heat transfer per unit length of cylinder is

A16.35kW/m

B13.65kW/m

C12.56kW/m

D15.36kW/m

AnswerB

Marks2

QuestionWater at 5 atm flows inside the tube of 0.0254 m and 1 m length under the local boiling conditions where the tube wall temperature maintained is 10oC above the saturation temperature, the heat transfer coefficient is 3521 W/m2 K. then the heat transfer is

A2180 W

B2810 W

C1280 W

D2018 W

AnswerB

Marks2

QuestionA fluid flowing with velocity 1.14 m/s is heated through the hot tube of 40mm diameter. Data: Prandtl number = 42.5, Density = 1070 kg/m3, viscosity= 0.004 Ns/m2 and thermal conductivity = 0.256 W/mK. Inside heat transfer coefficient for this case is,

A122.5 W/m2 K

B1225.5 W/m2 K

C2250.5 W/m2 K

D212.5 W/m2 K

AnswerB

Marks2

QuestionSteam is condensed with heat lost 10 kW on the cold surface. If the latent heat of condensation is 2225 kJ/kg, the mass flow rate of the condensate is,

A8 kg/hr

B9 kg/hr

C16 kg/hr

D11.2 kg/hr

AnswerC

Marks2

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