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PROB SOLVING PBE > DAY 2 PBE > Flashcards

DAY 2 PBE Flashcards

1
Q

Value of Stefan’s Boltzmann in SI Unit

A

5.67x10^-8

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2
Q

When the feed to a distillation column is a saturated liquid, slope of the feed line is
-zero
-unity
-infinity
-none of these

A

-infinity

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3
Q

Horsepower of disc type sedimenting particles

A

7.4 hp

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4
Q

Ultra centrifuges are used for the separation of __________ solid particles.
A. Coarse
B. Fine
C. Colloidal
D. Dissolved

A

Colloidal

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5
Q

Screen capacity is not a function of
A. Its openings size
B. Screening mechanism
C. Screening surface
D. Atmospheric humidity

A

D. Atmospheric humidity

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6
Q

Working principle of disappearing filament type optical pyrometer is based on the
a. Wien’s law
b. Seebeck effect
c. Kirchoff’s law
d. Peltier effect

A

a. Wien’s law

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7
Q

Mach number of incompressible fluid

A

0.3

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8
Q

The partial molar enthalpy of a component in an ideal binary gas mixture of composition Z, at a temperature T and pressure P, is a function only of
A. T
B. T and P
C. T, P and Z
D. T and Z

A

B. T and P

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9
Q

With an increase in pressure in gaseous phase chemical reactions, the fractional conversion __________ when the number of moles decreases.
A. Increases
B. Decreases
C. Remains unaffected
D. Unpredictable from the data

A

A. Increases

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10
Q

A measure of the difficulty of the separation

A

number of transfer units (NTU)

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11
Q

Which of the following thermocouples is incapable of measuring sub-zero (i.e., < 0°C) temperature?
A. Chromel-alumel
B. Iron-constantan
C. Platinum-platinum + rhodium
D. Copper-constantan

A

C. Platinum-platinum + rhodium

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12
Q

Pure ethane is completely burned in 20 % excess air. Air is supplied at 25 °C, 740 Torrs and is substantially dry. Calculate the kg dry air supplied/kg of fuel gas

A

19.22

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13
Q

Burning of pure hydrogen with 100% excess. Find the analysis

A

11.70% O2

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14
Q

Which of the following has the highest emissivity

A

charcoal powder

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15
Q

The purpose of providing a ‘catchall’ in the vapor line of an evaporator is to
A. Create vacuum
B. Regulate the vapor flow
C. Vent the non-condensible gases
D. Arrest the entrained liquid

A

D. Arrest the entrained liquid

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16
Q

Back-trapping in a distillation column
A. Increases tray efficiency
B. Decreases tray efficiency
C. Reduces pressure drop
D. Is desirable, as it provides improved vapour-liquid contact

A

B. Decreases tray efficiency

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17
Q

The temperature in which gas, liquid, and solid coexist

A

Triple Point

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18
Q

Which of the following equipments is not used in liquid-liquid extraction?
A. Pachuka tank
B. Agitated vessels
C. Centrifugal extractors
D. Packed towers

A

A. Pachuka tank

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19
Q

Relationship of the mass transfer coefficient when the surface is large to the HTU

A

decrease

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20
Q

An experimental oil is used to distill 6000 kg/hr. of Athabasta tar sand which analyzes 30% heavy oil, light oil and non- volatile matter. If the distillate contains 12% heavy oil and this constitutes 25% recovery of the components; the weight in kg of the distillate obtained is ________.
a. 4350
b. 3750
c. 2250
d. 6000

A

b. 3750

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21
Q

What compound is used to decrease the thermal conductivity coefficient in glass

A

Na2O

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22
Q

Co-efficient of thermal expansion of glass is decreased by the addition of __________ during its manufacture.
CaO
MnO2
ZnO
FeS

A

ZnO

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23
Q

Lap joints are employed on plates having thickness
less than 3 mm
5 to 10 mm
12.5 mm
above 25 mm

A

less than 3 mm

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24
Q

Computation of R constant

A

520

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25
Q

The ratio of volume of mixed reactor to the volume of P.F.R. (for identical flow rate, feed composition and conversion) for zero order reaction is
A. ∞
B. 0
C. 1
D. > 1

A

C. 1

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25
Q

The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface)
A. K/h0
B. 2K/h0
C. h0/K
D. h0/2K

A

B. 2K/h0

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26
Q

Steady state one dimensional heat flow by conduction as given by Fourier’s low does not assume that
A. There is no internal heat generation
B. Boundary surfaces are isothermal
C. Material is anisotropic
D. Constant temperature gradient exists

A

C. Material is anisotropic

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26
Q

If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid
A. Remains unchanged
B. Increases
C. Increases or decreases depending on number of shell passes
D. Decreases

A

D. Decreases

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27
Q

Which tube arrangement in a heat exchanger would facilitate highest heat transfer rate?
A. Triangular pitch
B. Square pitch
C. Diagonal square pitch
D. Heat transfer rate is independent of tube arrangement

A

A. Triangular pitch

28
Q

Smoker’s equation for the calculation of number of equilibrium stages in a continuous binary distillation column is used, when the
A. Relative volatility is close to one (e.g., separation of close boiling isomers)
B. Feed is not at its bubble point
C. Number of equilibrium stages in only stripping section is to be calculated
D. Number of equilibrium stages required is likely to be very small

A

A. Relative volatility is close to one (e.g., separation of close boiling isomers)

29
Q

Dietus-Boelter equation used for the determination of heat transfer co-efficient is valid
A. For fluids in laminar flow
B. For fluids in tubulent flow
C. When Grashhoff number is very important
D. For liquid metals

A

B. For fluids in tubulent flow

30
Q

What is the friction due to an unseparated boundary layer
a. skin friction
b. friction factor
c. turbulence

A

a. skin friction

31
Q

The furnace at the Bataan refinery is using a fuel gas which contains methane, ethane and 20% nitrogen. The Orsat analysis of the combustion products showed 7.8% CO2, 7.4% O2 and 84.8% N2. The gas is burned with excess air. The % methane in the fuel gas is
A. 22.76
B. 57.24
C. 50.20
D. 63.25

A

B. 57.24

32
Q

An equimolar mixture of benzene and toluene is subjected to a single batch distillation. Distillation is discontinued when 60% of the benzene in the feed is distilled. At this instance the bottom product when analyzed shows benzene to be 36.4% by mole. In the distillate the mole % of benzene is
a. 66.6
b. 58.1
c. 33.6
d. 54.7

A

a. 66.6

33
Q

Which of the following is not suitable for measuring the temperature of a red hot object in the range of 800 - 1600°C?
A. Optical pyrometer
B. Radiation pyrometer
C. Photoelectric pyrometer
D. Thermocouples

A

D. Thermocouples

34
Q

Steam is routed through the tube in case of a __________ evaporator.
A. Basket type
B. Horizontal tube
C. Short tube vertical
D. Long tube vertical

A

B. Horizontal tube

35
Q

Flow of filtrate through the cake in a plate and frame filter press is best described by the __________ equation.
A. Kozney-Karman
B. Hagen-Poiseulle’s
C. Fanning’s
D. Kremser

A

A. Kozney-Karman

36
Q

What is unavailable to perform work?
a. Entropy
b. Enthalpy
c. Kinetic Energy
d. Potential Energy

A

a. Entropy

37
Q

Free energy changes for two reaction mechanism ‘X’ and ‘Y are respectively - 15 and - 5 units. It implies that X is
A. Slower than Y
B. Faster than Y
C. Three times slower than Y
D. Three times faster than Y

A

B. Faster than Y

38
Q

A nuclear reactor generates 3000MW of heat. The heat is transferred in a heat exchanger of energy transfer efficiency 75% into steam which is expanded in a turbine in order to produce a power output. The steam is condensed in a condenser, releasing 1800MW of heat, and pumped back through the heat exchanger by a feed pump which requires 3% of the power output from the turbine. Determine

A) The net power output from the plant
B) The power output from the turbine

A

a. 1746 MW
b. 2250 MW

39
Q

What is the product of cuproammonium process

A

cellulose/fibers

40
Q

Flash distillation is suitable for the separation of components
A. Having very close boiling points
B. Which form maximum boiling azeotrope
C. Having very wide boiling points
D. Which form minimum boiling azeotrope

A

C. Having very wide boiling points

41
Q

When drying banana chips under the sun, the rate of drying is faster
A. on a slightly breezy day
B. on a calm day
C. on a cloudy day
D. on a hot and windy day

A

D. on a hot and windy day

42
Q

Flooding results in
A. High tray efficiency
B. Low tray efficiency
C. High gas velocity
D. Good contact between the fluids

A

B. Low tray efficiency

43
Q

The sum of reflectivity and absorptivity for an opaque body is equal to
A. 0.5
B. 1
C. 0
D. 2

A

B. 1

44
Q

Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is
A. 0.4
B. 0.5
C. 0.6
D. 0.7

A

D. 0.7

45
Q

Most important factor to be considered in the selection of packings for absorbers is the __________ of packing.
A. Size
B. Durability
C. Porosity
D. Cost

A

C. Porosity

46
Q

Hognog concept If increase of mass transfer, at increase of surface area, what is the value of height unit

A

Infinite Small Zero

47
Q

What is the extruded polystyrene?

A

Styro foam

48
Q

Fouling factor must be included in the calculation of over all design heat transfer coefficient, when the liquid
A. Containing suspended solids flows at low velocity
B. Containing suspended solids flows at high velocity
C. Is highly viscous
D. Is of hgh specific gravity

A

A. Containing suspended solids flows at low velocity

49
Q

The most common filter aid is
A. Diatomaceous earth
B. Calcium silicate
C. Sodium carbonate
D. Silica gel

A

A. Diatomaceous earth

50
Q

Which of the following valves will incur maximum pressure drop for the same discharge of water?
A. Globe valve
B. Gate valve
C. Needle valve
D. Butterfly valve

A

C. Needle valve

51
Q

Gases and vapours have very low densities compared with liquids and solids.

A
52
Q

The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is
A. 11.2 kW/m2
B. 12.0 kW/m2
C. 14.6 kW/m2
D. 16.5 kW/m2

A

D. 16.5 kW/m2

53
Q

At equal mass velocities, the values of film co-efficients for gases as compared to that for liquids are generally.
A. Higher
B. Lower
C. Same
D. Unpredictable

A

B. Lower

54
Q

A pure drug is administered as a sphere and as a cube. The amount of drug is the same in the two tablets. Assuming that the shape and size do not influence the mass transfer, the ratio of rate of dissolution in water at t = 0 for the cubic to spherical tablet is
A. 0.54
B. 1.04
C. 1.24
D. 1.94

A

C. 1.24

55
Q

What does not happen if potassium put in water
a. It ignites
b. It explodes
c. Nothing happens
d. it produces h2

A

c. Nothing happens

56
Q

The engine cylinder of a motorcycle is constructed of 2024-T6 aluminum alloy and is of height H = 0.15 m and outside diameter D = 50 mm. Under typical opersting conditions thenouter surface of the cylinderos at a temperature of 500K and is exposed to ambient air at 300K, with a convection coefficient of 50W/m^2 K. Annular fins are integrally cast which are of thickness t = 6mm, length = 20mm, and equally spaced. What is the increase in heat transfer due to use of the fins?

A

Q1 = 235.62 W
Q2 = 688.69 W
dQ = 453.07 W

57
Q

A plane wall that us 20 cm thick and has a constant thermo conductivity k=3W/mK undergoes one dimensional steady conduction. The surface temperature of the left side of the wall is known (T1=50 deg C) and the right side of the wall is exposed to air (Tair=10 deg C) and convective heat transfer (h= 60 W/m^2 K). What is the temperature at the interface between the wall and the air on the right hand side?

A

18 deg C

58
Q

Saturated steam at 267F is flowing inside a 3/4 in. steel pipe having an ID of 0.824 in and an OD of 1.050 in. The pipe is insulated with 1.5 in of insulation on the outside. The convective coefficient for the inside steam surface is estimated as h1=100 BTU/h ft2 F and the convective coefficient on the outside of the lagging as estimated ho = 2 BTU/ h ft2 F. The mean thermal conductivity of the metal is 45 W/m K or 26 BTU/h ft F and 0.064 W/mK or 0.037 bru/h ft F for the insulation. Calculate the heat loss for 1 ft of pipe using resistance if the surrounding air is 80F.

A

29.78 BTU/hr

59
Q

The order of a chemical reaction
A. can be determined only experimentally
B. can be determined from the stoichiometry of the reaction.
C. can not be zero.
D. can be fractional.

A

B. can be determined from the stoichiometry of the reaction.

60
Q

Air, which may be considered a perfect gas, enters an adiabatic nozzle with neglible velocity

A

V2 = 782 m/s

61
Q

Zeroth Law of Thermodynamics

A

Thermal equilibrium (thermometer)
Ralph Howard Fowler

62
Q

An uninsulated steam pipe passes through a room in which the air and walls are at 25 C. The outside diameter of the pipe is 70 mm, and its surface temperature and emissivity are 200C

A

998 W/m

63
Q

In a heat exhanger, floating head is provided to
a. Facilitate cleaning of the exhanger
b. Increase the heat transfer rate
c. Relieve stresses caused by thermal expansion
d. Increase log mean temperature

A

c. Relieve stresses caused by thermal expansion

64
Q

A spherical, think-walled metallic container is used to store liquid nitrogen at 77K.

A

5.64 kg/d

65
Q

Back-trapping in a distillation column results due to

A. Low gas velocity
B. High gas velocity
C. Excessive liquid gradient over the tray
D. Low reflux ratio

A

C. Excessive liquid gradient over the tray

66
Q

The Stefan-Boltzman constant depends on the
A. medium
B. temperature
C. surface
D. none of these

A

D. none of these

67
Q

Steam condensing on the outer surface of a thin-walled circular tube of diameter D = 50 m and length L = 6m

A

755

68
Q

A thin liquid film of ammonia (NH3), which has formed on the inner surface of a tube of diameter D = 10 mm and L 1m

A

0.012 m/s

PROB SOLVING PBE (11 decks)

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