Heat Transfer (Set 1)

Question 1

Crystal size in a continuous crystalliser depends upon the

Answer 1

all (a), (b) and (c).

Question 2

In a solution containing 0.30 Kg mole of solute and 600 kg of solvent, the molality is

Answer 2

0.5

Question 3

Fenske equation determines the

Answer 3

minimum number of theoretical plates.

Question 4

The term “cooling range” in a cooling tower refers to the difference in the temperature of

Answer 4

hot water entering the tower and the cooled water leaving the tower.

Question 5

Which of the following is the most suitable for extraction in a system having very low density difference?

Answer 5

Centrifugal extractor

Question 6

Total reflux in a distillation operation requires minimum

Answer 6

number of plates

Question 7

The amount of steam required per unit quantity of distillate in case of steam distillation will be reduced by
a. raising the temperature.
b. lowering the total pressure.

Answer 7

both (a) and (b).

Question 8

The difference of wet bulb temperature and adiabatic saturation temperature of unsaturated mixture of any system is

Answer 8

(+)ve

Question 9

Fenske’s equation for determining the minimum number of theoretical stages in distillation column holds good, when the

Answer 9

relative volatility is reasonably constant.

Question 10

When the temperature and humidity of air is low, we usually use ____ draft cooling tower.

Answer 10

natural

Question 11

Pick out the correct statement.

Answer 11

all (a), (b) and (c).

Question 12

____ columns are used for liquid dispersion in a continuous gas phase.

Answer 12

Packed

Question 13

Overall efficiency of the distillation column is

Answer 13

the ratio of number of ideal plates to actual plates.

Question 14

On addition of solute in the solvent, the ____ of the solution decreases.

Answer 14

both (b) and (c)

Question 15

Which is the controlling factor for a drum drier?

Answer 15

Heat transfer

Question 16

Drying operation under vacuum is carried out to

Answer 16

reduce drying temperature.

Question 17

Air initially at 101. 3 kPa and 40°C and with a relative humidity of 50%, is cooled at constant pressure to 30°C. The cooled air has a

Answer 17

higher relative humidity

Question 18

Separation of two or more components of a liquid solution can not be achieved by

Answer 18

absorption

Question 19

Stefan’s law describes the mass transfer by

Answer 19

both ‘a’ & ‘b’

Question 20

At minimum reflux ratio for a given separation

Answer 20

number of plates is infinity.

Question 21

Relative humidity is the ratio of the

Answer 21

partial pressure of the vapour to the vapour pressure of the liquid at gas temperature.

Question 22

In batch distillation with constant reflux, overhead product composition ____ with time.

Answer 22

decreases

Question 23

Psychrometry deals with the properties of gas-vapor mixture. Humidity can be determined by the measurement of the ____ of a fibre.

Answer 23

electrical resistance

Question 24

Heat in BTU necessary to increase the temperature of 1 lb of gas and its accompanying vapour by 1°F is called the

Answer 24

specific heat

Question 25

To increase the absorption factor, (where, G = gas flow rate, S = solvent flow rate)

Answer 25

increase 'S' and decrease 'G'.

Question 26

The mass diffusivity, the thermal diffusivity and the eddy momentum diffusivity are same for, NPr = NSc = ____

Answer 26

1

Question 27

Dew point of a gas-vapour mixture

Answer 27

decreases with decrease in pressure.

Question 28

In a packed absorption tower, if the equilibrium and operating lines are both straight lines, then the ratio, HETP/HTUOG ____ the absorption factor.

Answer 28

both (a) and (b)

Question 29

Which of the following plays an important role in problems of simultaneous heat and mass transfer?

Answer 29

Lewis number

Question 30

In case of an absorber, the operating

Answer 30

line always lies above the equilibrium curve.

Question 31

As the reflux ratio in a distillation coloumn is increased from the minimum, the

Answer 31

total cost first decreases and then increases.

Question 32

Absorption factor is defined as (where, S1 = slope of the operating line S2 = slope of the equilibrium curve)

Answer 32

S1/S2

Question 33

A plait point is the point on the solubility curve, where the tie line reduces to a point. What is the number of plait point for a ternery system containing twopairs of partially miscible liquids?

Answer 33

0

Question 34

Which of the following remains constant during sensible cooling process?

Answer 34

Both (a) and (b)

Question 35

Physical absorption is

Answer 35

both (b) and (c)

Question 36

Make up water is required in a cooling tower to replace the water lost by

Answer 36

all (a), (b) and (c)

Question 37

Which of the following quantities need not be fixed before starting the design of a co-current absorber?

Answer 37

Flow rate of entering liquid

Question 38

Mass transfer co-efficient of liquid is

Answer 38

affected more by temperature than that for gases.

Question 39

Absorption accompanied with chemical reaction is exemplified by the absorption of

Answer 39

SO2 in alkaline solution.

Question 40

Which of the following unit operations makes use of Thiele-Geddes equation?

Answer 40

Multicomponent distillation.

Question 41

Which of the following liquid-vapor contacting devices provides maximum contact surface area for a particular duty?

Answer 41

Wetted wall column

Question 42

The equipment frequently used for adiabatic humidification-cooling operation with recirculating liquid is

Answer 42

spray chamber

Question 43

Chemisorption (chemical adsorption) is

Answer 43

an irreversible phenomenon.

Question 44

The rate of solid-liquid extraction is limited by the

Answer 44

all 'a', 'b' & 'c'.

Question 45

Raoult's law applies to the

Answer 45

solvents.

Question 46

In distillation columns, the number of bubble caps per tray primarily depends upon the

Answer 46

allowable gas and liquid velocities.

Question 47

In distillation, overhead product contains

Answer 47

any number of components

Question 48

With increase in pressure, the relative volatility for a binary system

Answer 48

decreases.

Question 49

Low viscosity absorbent is preferred for reasons of

Answer 49

all (a), (b) and (c).

Question 50

Mass transfer co-efficient (K) and diffusivity (D) are related according to film theory as

Answer 50

K ∝ D

Question 51

The McCabe Δ L law states that the

Answer 51

linear crystal growth rate does not depend on the crystal size.

Question 52

Bollman extractor

Answer 52

is used for extraction of oil from oilseed.

Question 53

The relation, Sc = Pr = 1, is valid, when the mechanism of ____ ansfer is same.

Answer 53

heat and mass

Question 54

A coalescer in a mixer-settler liquid-liquid extraction coloumn

Answer 54

all 'a', 'b', & 'c'.

Question 55

For the same feed, feed quality and separation (in a distillation column), with the increase of total pressure, the number of ideal plates will

Answer 55

increase

Question 56

Pick out the correct statement.

Answer 56

Ponchan-Savarit method is more accurate than McCabe-Thiele method to determine the number of theoretical stages required for the separation of non-ideal binary system by distillation.

Question 57

When the liquid phase and vapour phase of a binary system obeys Raoult's and Dalton's law respectively, the relative volatility is the ratio of

Answer 57

vapour pressure of component A to that of component B.

Question 58

The operation involved when the soluble material is largely on the surface of an insoluble solid and is merely washed off by the solvent is called

Answer 58

elutriation or elution

Question 59

In the constant rate period of the rate of drying curve for batch drying,

Answer 59

surface evaporation of unbound moisture occurs.

Question 60

It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The equilibrium moisture content of the solid is 5%).

Answer 60

71 min

Question 61

Agitator is provided in a crystalliser for

Answer 61

all (a), (b) and (c).

Question 62

____ diffusion is used for separating the isotopes of methane.

Answer 62

Thermal

Question 63

Ordinary diffusion process is also called ____ diffusion.

Answer 63

concentration

Question 64

Pick out the wrong statement.

Answer 64

Heat removal load on cooler remains constant, even with increase of the reflux ratio in a distillation column.

Question 65

Pick out the wrong statement pertaining to the rotary dryer.

Answer 65

Rotary dryer is suitable for drying sticky material.

Question 66

The reason for preferring packed towers over plate towers in distillation practice is that the packed tower operation gives

Answer 66

low pressure drop and low hold up.

Question 67

If the path of liquid across the plate is very long as in case of large diameter tower, Murphree efficiency can be ____ percent.

Answer 67

> 100

Question 68

Compound A is extracted from a solution of A + B into a pure solvent S. A Co-current unit is used for the liquid-liquid extraction. The inlet rate of the solution containing A is 200 moles of B/hr.m2 and the solvent flow, rate is 400 moles of S/m2. hr. The equilibrium data is represented by Y = 3X2 , where Y is in moles of a A/moles of B and X is in moles A/moles of S. The maximum percentage extraction achieved in the unit is

Answer 68

0.5

Question 69

Raoult's law is applicable to the

Answer 69

ideal solutions

Question 70

Weeping in a distillation column

Answer 70

results due to very low gas velocity.

Question 71

In case of binary distillation, increasing the reflux ratio above optimum does not result in the increase of

Answer 71

area between operating line and 45° diagonal x-y diagram.

Question 72

Wetted wall tower experiment determines the

Answer 72

mass transfer co-efficient.

Question 73

In McCabe-Thiele method, at infinite reflux ratio

Answer 73

the overhead product is minimum.

Question 74

With decrease in the throughput (compared with the design capacity) for a bubble cap distillation column, its efficiency

Answer 74

increases

Question 75

Plate towers are preferred to packed towers, when large temperature changes are involved, because of the reason that the

Answer 75

packing may be crushed due to thermal expansion/contraction of the components of the equipments.

Question 76

The equilibrium liquid composition compared to the vapor composition in case of azeotropic mixture is

Answer 76

same

Question 77

Out of the following gas-liquid contacting devices, for a given set of operating conditions, gas pressure drop is the least in ____ tower.

Answer 77

wetted wall

Question 78

Pick out the system with minimum boiling azeotrope at 1 atm.

Answer 78

ethyl alcohol-water

Question 79

Free flowing granular materials can be best dried in a ____ drier.

Answer 79

rotary

Question 80

In case of an ideal solution, the total vapor pressure varies ____ with the composition expressed as mole fraction,

Answer 80

linearly

Question 81

Corresponding to Nusselt number in heat transfer, the dimensionless group in mass transfer is the ____ number.

Answer 81

Sherwood

Question 82

If the specific heats of a gas and a vapor are 0.2KJ/Kg.°K and 1.5 KJ/Kg.°K respectively, and the humidity is 0.01; the humid heat in KJ/°Kg. is

Answer 82

0.215

Question 83

Liquid diffusivity is of the order of ____ cm2 /second.

Answer 83

10-5 to 10-6

Question 84

The solvent used in liquid extraction should not have high latent heat of vaporisation, because

Answer 84

its recovery cost by distillation may be prohibitatively high.

Question 85

At the same gas flow rate, the pressure drop in a packed tower being irrigated with liquid ____ that in dry packed tower.

Answer 85

is greater than

Question 86

Molarity is defined as the number of gm moles of solute per ____ of solvent.

Answer 86

liter

Question 87

The value of Lewis number (Le = Sc/Pr) for air-water vapour system is around

Answer 87

1

Question 88

Which of the following T-H diagram is valid for dehumidification operation?

Answer 88

https://www.indiabix.com/_files/images/chemical-engineering/mass-transfer/317-501-1.png

Question 89

An aqueous solution of methanol is to be distilled in a tray column. High pressure steam is available as a source of heat. For a given reflux ratio and overhead composition, two options are being explored; (i) a reboiler is used and (ii) no reboiler is used but steam is fed directly to the bottom of the column. As compared to option (i), in option (ii)

Answer 89

less number of trays are required.

Question 90

The partial pressure distribution of an ideal gas diffusing through another stagnant ideal gas at steady state follows a/an ____ law.

Answer 90

exponential

Question 91

Which of the following binary systems is an example of a maximum boiling azeotrope?

Answer 91

Water-hydrochloric acid.

Question 92

(NRe . NSc) is termed in mass transfer operation as the ____ number.

Answer 92

Peclet

Question 93

The binary diffusivity in gases and liquids vary respectively as

Answer 93

T^3/2 and T

Question 94

Pick out the correct statement.

Answer 94

In Ponchon-Savarit method of no. of theoretical plate determination, the stripping and rectifying operating lines are vertical at total reflux.

Question 95

Pick out the correct statement.

Answer 95

Electrodylsis is used in the manufacture of NaOH.

Question 96

Pick out the correct statement.

Answer 96

The driving force for mass transfer in a wet solid is its free moisture content.

Question 97

Very tall packed towers are divided into series of beds to

Answer 97

avoid channelling

Question 98

Moisture contained by a substance in excess of the equilibrium moisture is called the ____ moisture.

Answer 98

free

Question 99

With increase in temperature, the solubility of gases in liquids, at fixed pressure

Answer 99

decreases

Question 100

In most of the vacuum crystalliser, vacuum is generally produced by means of a

Answer 100

steam jet ejector with a barometric condenser