Q.1

The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature)

  • (ΔT)2
  • (ΔT)4
  • (ΔT)3
  • (ΔT)
Q.2

Heat transfer rate per unit area is called

  • thermal conductivity
  • heat flux
  • heat transfer co-efficient
  • thermal diffusivity
Q.3

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

  • heat transfer co-efficient over the entire heat exchanger is not constant.
  • there exists an unsteady state.
  • the heat capacity is not constant and there is a phase change.
  • none of these.
Q.4

For a fluid flowing in an annulus space, the wetted perimeter for heat transfer and pressure drop are

  • same
  • different
  • never different
  • linearly related
Q.5

Grashoff number, which is defined as g . β(Ts - T∞) ρ2. L3/μ2, is proportional to the ratio of buoyancy force to __________ force.

  • viscous
  • elastic
  • inertial
  • none of these
Q.6

The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is __________ compared to the same size pipes without fins.

  • more
  • less
  • same
  • unpredictable
Q.7

Pick out the wrong statement.

  • Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient.
  • In a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles.
  • S.I. unit of fouling factor is Watt/m2.°K.
  • Longitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube.
Q.8

In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is

  • minimum
  • maximum
  • zero
  • infinity
Q.9

Pick out the wrong statement.

  • Reciprocal of the resistance to heat flow is called thermal conductance.
  • Unit of thermal conductance is W/°K.
  • Thermal conductance of a wall of thickness 'L', thermal conductivity 'k' and heat flow area 'A' is kL/A.
  • none of these.
Q.10

While the total emissivity of a perfect black body is unity, the same for a real body is

  • 0
  • 1
  • > 1
  • between 0 and 1
Q.11

Pick out the wrong statement.

  • Swenson-Walker crystalliser is a batch crystalliser.
  • Super saturation of the solution is the driving potential for a crystal growth.
  • The liquor left after the removal of crystals from a solution is called mother liquor.
  • The first stage of crystal formation is called nucleation.
Q.12

In case of a vertical tube evaporator, with increase in the liquor level, the __________ is increased.

  • velocity of circulation
  • liquor-film co-efficient
  • both (a) and (b)
  • neither (a) and (b)
Q.13

Finned tube heat exchangers

  • give larger area per tube.
  • use metal fins of low thermal conductivity.
  • facilitate very large temperature drop through tube wall.
  • are used for smaller heat load.
Q.14

Which of the following accessories is provided in the vapor line of an evaporator for removing the entrained liquid ?

  • Bleed point
  • Vent
  • Catchall
  • Baffle
Q.15

Rate of heat transfer by vaporisation from pools of water is affected by the

  • nature of heating surface and distribution of bubbles.
  • surface tension of water.
  • viscosity of water.
  • all (a), (b) and (c).
Q.16

Dropwise condensation occurs on __________ surfaces.

  • clean and dirt free
  • smooth clean
  • contaminated cooling
  • polished
Q.17

A hot liquid is kept in a big room. The logorithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an

  • ellipse
  • straight line
  • parabola
  • circular arc
Q.18

Double pipe heat exchangers are used

  • when heat transfer area required is very high.
  • when heat transfer area required is very low, i.e (100-200 ft2).
  • because it occupies less floor area.
  • because it is less costly.
Q.19

Trap is used to remove __________ from steam pipe lines.

  • steam
  • condensate
  • non-condensables
  • none of these
Q.20

In a 1-1 cocurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is

  • ∞
  • 0
  • equal to the difference between hot and cold fluids inlet temperature.
  • equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature.
Q.21

During crystallisation, formation of crystal can occur in __________ solution only.

  • saturated
  • supersaturated
  • undersaturated
  • all (a), (b) and (c)
Q.22

Pick out the wrong statement.

  • By increasing the number of shell passes, the temperature cross in a shell and tube heat exchanger can be prevented.
  • An underdesigned steam trap will back up the condensate instead of discharging it out.
  • Steam condensate is corrosive because of the presence of dissolved oxygen in it.
  • Film boiling is desirable in commercial equipments due to high heat transfer rate at low temperature drop.
Q.23

Natural convection is characterised by

  • Grashhoff number
  • Peclet number
  • Reynolds number
  • Prandtl number
Q.24

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

  • conduction
  • convection
  • radiation
  • both(a) & (c)
Q.25

If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law.

  • hyperbolic
  • parabolic
  • linear
  • logarithmic
Q.26

For what value of Prandtl number, the Col-burn analogy is valid ?

  • 0.06 to 120
  • 0.6 to 120
  • 1 to 103
  • l to 50
Q.27

In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid.

  • nucleate
  • pool
  • low pressure
  • none of these
Q.28

Electromagnetic radiations propagate in vacuum with a velocity of __________ metre/second.

  • 3 x l05
  • 3 x l08
  • 3 x l010
  • 3 x l012
Q.29

Multiple effect evaporators are commonly used in the manufacture of
P. Paper Q. Superphosphate
R. Sugar S. Fats

  • P and Q
  • P and R
  • P and S
  • R and S
Q.30

Radiation heat transfer rates does not depend upon the

  • type of absorbing surface.
  • distance between the heat source and the object receiving the heat.
  • surface area and temperature of the heat source.
  • none of these.
Q.31

A composite flat wall of a furnace is made of two materials 'A' and 'B'. The thermal conductivity of 'A' is twice of that of material 'B', while the thickness of layer of 'A' is half that of B. If the temperature at the two sides of the wall areand 1200°K, then the temperature drop (in °K) across the layer of material 'A' is

  • 125
  • 133
  • 150
  • 160
Q.32

Viscous & heat sensitive liquids are concentrated in __________ evaporators.

  • open pan
  • long tube
  • agitated film
  • none of these
Q.33

A body is called grey if the monochromatic emissivity of the body is

  • zero
  • unity
  • same for all wavelengths
  • different for all wavelengths
Q.34

In an extended surface heat exchanger, fluid having lower co-efficient

  • flows through the tube.
  • flows outside the tubes.
  • can flow either inside or outside the tubes.
  • should not be used as it gives very high pressure drop.
Q.35

An evaporator while concentrating an aqueous solution fromtosolids evaporateskg of water. The amount of solids handled by the system in kg is

  • 4000
  • 9000
  • 4600
  • 3000
Q.36

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

  • 0.72
  • 4.364
  • 18
  • 83
Q.37

A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ?

  • Cube
  • Plate
  • Sphere
  • All will cool at the same rate
Q.38

Vent pipes are provided in a condenser to

  • remove non-condensable gases.
  • purge the condenser.
  • facilitate easy cleaning of tubes.
  • none of these.
Q.39

In regenerative air preheater (as practised in heating of coke ovens), the heat is transferred

  • through a metallic wall.
  • by direct contact of hot flue gas with air.
  • by heating an intermediate material (like chequor bricks) and then heating the air from this hot material.
  • none of these.
Q.40

__________ equation relates the thermal conductivity of a solid to its temperature.

  • Antonie
  • Kopp's
  • Lee's
  • Kistyakowski
Q.41

In a forward feed multiple effect, the pressure build up will be

  • least at the inlet of the first effect.
  • least at the outlet of the last effect.
  • highest at the inlet of the last effect.
  • highest at the outlet of the last effect.
Q.42

A body cools down from 75°C to 70°C inminutes. It will cool down fromC toC in __________ minutes.

  • 10
  • >10
  • <10
  • either (b) or (c), depends on the mass of the body
Q.43

In forced convection, the Nusselt number is a function of

  • Re and Pr
  • Re and Gr
  • Pr and Gr
  • Re and Sc
Q.44

Heat flux is the time rate of heat transfer per unit

  • length
  • area
  • volume
  • none of these
Q.45

Which of the following has the highest thermal conductivity ?

  • Brick
  • Air
  • Water
  • Silver
Q.46

Tube pitch is the __________ of tube diameters and the clearances.

  • sum
  • difference
  • ratio
  • none of these
Q.47

1 BTU/hr.ft.°F is equal to __________ kcal/hr. m.°C.

  • 1.49
  • 1
  • 4.88
  • none of these
Q.48

Radiation heat transfer rates does not depend upon the

  • type of absorbing surface.
  • distance between the heat source and the object receiving the heat.
  • surface area and temperature of the heat source.
  • none of these.
Q.49

In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is

  • infinity.
  • zero.
  • same as average heat transfer co-efficient for tube side.
  • none of these.
Q.50

An insulator should have

  • low thermal conductivity.
  • high thermal conductivity.
  • less resistance to heat flow.
  • a porous structure.
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