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Question 1

Crystal size in a continuous crystallizer depend upon the

Answer 1

**All a, b,c **

A. Rate of heat transfer
B. Degree of turbulence
C. Degree of supersaturation

Question 2

Heat waves

Answer 2

Both b and c

B. Travel in straight line
C. Can be reflected by mirror

Question 3

Air is best heated with steam in a heat exchanger of

Answer 3

**Double pipe type with fin on air side **

Question 4

Which of the following is generally considered as opaque surface towards radiations?

Answer 4

**Both b and c **

B. Solids
C. Liquids

Question 5

Black liquor generated during paper manufacture is concentrated in a

Answer 5

**Multiple effect evaporator **

Question 6

When vaporization takes place directly at the heating surface, it is called

Answer 6

**Nucleate boiling **

Question 7

Steam consumption in kg/hr in case of an evaporator is given by

Answer 7

**C/E **

Question 8

Reynold’s analogy states that

Answer 8

**Nst α f **

Question 9

With increase in temperature, the thermal conductivity of non-metallic amorphous solids

Answer 9

**Increases **

Question 10

Fourier’s law applies to the heat transfer by

Answer 10

Conduction

Question 11

Shell side pressure drop in a shell and tube heat exchanger does not depend upon the

Answer 11

None of these

Question 12

In the equation Q=UAdeltaT, delta T is

Answer 12

**Logarithmic mean temperature difference **

Question 13

With increase in porosity, the thermal conductivity of a solid substance

Answer 13

**Decreases **

Question 14

For an ideal black body,

Answer 14

** Absorptivity=1 **

Question 15

In Joule’s experiment, an insulated container contains 20 kg of water initially at 25°C. It is stirred by an agitator, which is made to turn by a slowly falling body weighing 40 kg through a height of 4 m. The process is repeated 500 times. The acceleration due to gravity is 9.8 ms-2. Neglecting the heat capacity of agitator, the temperature of water (in °C) is

Answer 15

**34.4 **

Question 16

Fouling factor

Answer 16

accounts for additional resistances to heat flow

Question 17

In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer coefficient

Answer 17

**decreases **

Question 18

The steam ejector is used to

Answer 18

**create vacuum **

Question 19

For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area

Answer 19

**passes through a maxima **

Question 20

The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are

Answer 20

(COP)R= 1.5; (COP)HP= 2.5

Question 21

Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately

Answer 21

**32 **

Question 22

In a heat exchanger, floating head is provided to

Answer 22

**relieve stress caused by thermal expansion **

Question 23

Leidenfrost point is a term concerned with the

Answer 23

**boiling of a liquid on a hot surface **

Question 24

A process stream of dilute aqueous solution flowing at the rate of10 Kg.s-1 is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s-1. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is

Answer 24

**counter flow with process stream in shell side **

Question 25

Heat produced when a steady state current passes through an electrical conductor having resistance, ‘R’ is

Answer 25

**I^2R**

Question 26

Pick out the wrong statement.

Answer 26

**Orifice baffles are never used in a shell and tube heat exchanger **

Question 27

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

Answer 27

**highly turbulent **

Question 28

The actual temperature drop across the heating surface in an evaporator depends on the

Answer 28

**All a,b, and c** A. Feed B. Depth of liquid over heating surface C. Pressure difference between steam chest and vapor space

Question 29

Which of the following is not used as a medium for high temperature heating?

Answer 29

**Mercury **

Question 30

Presence of non-condensing gas in a condensing vapor

Answer 30

**None of these**

Question 31

Kirchoff’s law applies to ______ radiation.

Answer 31

**Both a and b ** A. Total B. Monochromatic

Question 32

With the increase of temperature, the Col-burn jH factor

Answer 32

**increases **

Question 33

In case of evaporators, liquid entrainment results primarily due to

Answer 33

**foaming of the solution **

Question 34

Baffles in the shell side of a shell and tube heat exchanger

Answer 34

**increase the shell side heat transfer coefficient **

Question 35

Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is

Answer 35

**finned tube heat exchanger with air outside and steam inside **

Question 36

The unit of heat transfer coefficient in SI unit is

Answer 36

**W/m^2K **

Question 37

The number of kg vaporized per kg of steam fed to the evaporator is defined as

Answer 37

**economy **

Question 38

Pick out the wrong statement.

Answer 38

**The equivalent diameter of heat transfer for a duct of square cross-section (having each side as x) is equal to 4x. **

Question 39

Economy of a multiple effect evaporator is not influenced much by the

Answer 39

**boiling point elevations **

Question 40

Increasing the liquor level in the evaporator results in the

Answer 40

**decreased capacity **

Question 41

The equivalent diameter for pressure drop is _______ that for heat transfer

Answer 41

**smaller than**

Question 42

Controlling heat transfer film coefficient is the one, which offers _____ resistance to heat transfer.

Answer 42

**the largest **

Question 43

The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K= 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is - 5°C. The outside wall temperature is

Answer 43

**35degC **

Question 44

Thermal conductivity of a conducting solid material depends upon its

Answer 44

**Both a and b ** A. Temperature B. Porosity

Question 45

Pick out the wrong statement.

Answer 45

**In case of a 1-2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs. **

Question 46

The average heat transfer coefficient for laminar film condensation on a vertical surface is inversely proportional to

Answer 46

**(deltaT)^1/4 **

Question 47

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

Answer 47

**mainly confined to a thin film of fluid near the surface **

Question 48

Which of the following is concerned with both heat and mass transfer?

Answer 48

**Lewis relationship **

Question 49

A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides

Answer 49

**higher economy **

Question 50

A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be

Answer 50

**less than that of the uninsulated steam pipe*