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CH138X Flashcards

1
Q

For gas phase binary system
diffusion, uni-component diffusing
through a gas-liquid interface is
likely to occur if:
A. None of the choices
B. One component is soluble in
the liquid, and the other is not
C. Both gas components are
soluble in the liquid
D. Both gas components are
insoluble in the liquid

A

b

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2
Q

Which of the following devices uses
the principles of fluid statics to
reflect the current atmospheric
pressure?
A. Anemometer
B. Mercury manometer
C. Mercury barometer
D. Sphygomomanometer

A

c

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3
Q

A wet solid initially contains x1%
free moisture, above the critical
moisture content, and it is
subjected to a stream of hot air
flowing at a volumetric flow rate
of Q and inlet conditions of T1
and RH1
A. Decrease T1
B. Increase RH1
C. Decrease Q
D. Increase Q

A

d

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4
Q

Which of the following is not a
desirable quality of a solvent in
liquid-liquid extraction?
A. Density close to that of water
B. High selectivity
C. Low viscosity
D. Readily available

A

a

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5
Q

The viscosity of a gas ____
A. Does not depend on
temperature
B. Increases with an increase in
temperature
C. Decreases with an increase in
temperature
D. Can either increase or
decrease with an increase in
temperature

A

b

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6
Q

Which factor leads to the decrease
in average settling velocity of
particles in hindered conditions,
compared to free settling?
A. Increased fluid density
B. Less gravitational pull on
particles
C. Interactions between particles
D. Increased fluid viscosity

A

c

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7
Q

What is the driving force of crystallization?
A. Supersaturation
B. Concentration gradient
C. Saturation
D. Temperature gradient

A

a

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8
Q

A single-effect evaporator has
feed temperature of TF, product
temperature of TL, vapor
temperature TV, and steam
temperature S
At steady state, What is the driving force to evaporation?
A. TL-TF
B. TV-TF
C. TS-TF
D. TS-TL

A

d

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9
Q

A certain centrifugal pump can
generate a head of H for a
discharge of Q. If three of such pumps are connected in series, What would be the total head delivered by the system?
A. H3
B. H/3
C. 3H
D. H

A

c

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10
Q

What happens to the operating line
of an absorption column as we
increase the mass flow rate of the
absorbent?
A. The operating line becomes
curved, being more concave
B. The operating
line approaches
verticality
C. The operating line becomes
curved, being more convex
D. The operating line approaches
horizontality

A

b

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11
Q

Which of the following can be
actual stages in a vertical column
for gas-liquid or vapor-liquid
contacting (e.g., distillation, gas
absorption)?
A. Plates
B. Bubble caps
C. Entrainers
D. Random packing

A

a

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12
Q

The molecular diffusivity of a
solute in a liquid:
A. Decreases with temperature
increase
B. Increases with
temperature
increase
C. May increase or decrease as
the temperature increases
D. Is independent of temperature

A

b

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13
Q

Which of the following is a
desirable trait of a manometric
fluid?
A. Having a density greater than
that of the metered fluid
B. High viscosity
C. Having a density lower than
that of the metered fluid
D. Highly polar liquid

A

a

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14
Q

This type of fluid displays an
increase in viscosity as the rate of
shear strain is increased,
regardless of time frames
A. Thixotropic
B. Pseudoplastic
C. Dilatant
D. Rheopectic

A

c

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15
Q

For a binary mixture of non-polar
gases, how does the mass
diffusivity change if the absolute
temperature is doubled at constant
pressure?
A. Increase by a factor of 2^1.5
B. Increase by a factor of 2
C. Decrease by a factor of 2
D. Decrease by a factor of 2^1.5

A

a

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16
Q

For laminar flow inside a pipe, the
average and maximum fluid
velocities inside are related as
uave/umax=0.5. What happens to this ratio as the flow becomes more turbulent?
A. Remains at 0.5
B. Increases exponentially
C. Approaches 1
D. Approaches 0

A

c

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17
Q

The drag coefficient of a rigid
spherical particle generally
decreases linearly with increasing
Reynolds number for:
A. Re > 10
B. Re < 0.1
C. Re = 1
D. Re < 10000

A

b

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18
Q

Which of the following is true for a
binary system with a relative
volatility of 1?
A. A longer distillation time is
required for separation
B. No separation can occur by
distillation
C. Distillation can perfectly
separate the two components
D. More stages must be provided
to achieve substantial separation

A

b

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19
Q

For laminar fluid through a
packed bed, How does the pressure drop across the bed change when the
superficial fluid velocity is halved?
Assume all other parameters
remain constant
A. Increase by a factor of 4
B. Decrease by a factor of 2
C. Increase by a factor of 2
D. Decrease by a factor of 4

A

b

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20
Q

The drag force of a particle falling
through a fluid at relative velocity
u is directly proportional to
A. u
B. u/2
C. 2u
D. u^2

A

d

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21
Q

As particle size is reduced:
A. Screening progressively
becomes easier
B. Screening becomes progressively more difficult
C. Screening efficiency is
increased
D. Capacity of the screen is
increased

A

b

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22
Q

The separation by which solids are separated from liquids due to difference in respective densities is:
A. Sedimentation
B. Screening
C. Absorption
D. Adsorption

A

a

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23
Q

How much head is lost by a fluid
when it flows through a standard
90° elbow bend?
A. 0.75u^2/2g
B. 0.75
C. 0.75u^2/2gc
D. u^2/2g

A

a

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24
Q

The viscosity of a fluid is best described as:
A. The likeliness that a fluild will
flow when tilted
B. The fluid’s ability to resist flow
when compressed
C. The fluid’s “memory”
D. The fluid’s ability to resist flow when sheared

A

d

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25
Q

The equivalent diameter of a
particle is the diameter of a
sphere having the same:
A. Surface area to volume ratio as the actual volume
B. Volume to surface area ratio
as the particle
C. Volume as the particle
D. None of the choices

A

a

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26
Q

In continuous distillation, which of
the following occurs as a
consequence of increasing the
reflux ratio?
A. The distillate
product decreases
B. The condenser duty decreases
C. The operating column
pressure increases
D. The theoretical number of
stages increases

A

a

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27
Q

When plotting a ternary liquid
system in an equilateral triangle
diagram, the sides of the triangle
represent:
A. A ternary mixture
B. A pure component
C. A binary mixture
D. A partially miscible ternary
system

A

c

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28
Q

For tubulent mass transfer in
pipes, the Sherwood number
depends upon the Reynolds
number as:
A. Re^0.83
B. Re^0.53
C. Re^0.33
D. Re

A

a

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29
Q

When a solid is said to be “dry”, it
means that:
A. The solid contains a very
small amount of mosture left
B. The solid is at its critical
moisture content
C. The solid contains its equilibrium moisture content
D. The solid does not contain any
moisture

A

c

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30
Q

Which of the following represents
the reduction ratio of grinders?
The subscripts F and P
represents the feed and product,
respectively
A. Df/Dp
B. Dp/Df
C. Df-Fp
D. Dp-Df

A

a

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31
Q

What is the hydraulic diameter of a
rectangular duct with cross
section dimensions of 6 inches by
12 inches?
A. 9in
B. 7in
C. 8 in
D. 10in

A

c

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32
Q

Fick’s Law gives the rate of
diffusion based on:
A. Temperature driving force
B. All of the choices
C. Pressure driving force
D. Concentration driving force

A

d

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33
Q

Theoretically, if you start with a
single 1 cm cube of the following
materials, Which of them would require then least amount of energy to crush
into a certain smaller particle size?
A. SIlicon carbide
B. Granite
C. Sodium silicate
D. Pumice

A

d

34
Q

The solvent to be used in liquid
extraction should not have a high
latent heat of vaporization
because:
A. The pressure drop and hence the
pumping cost would be high
B. It cannot be recoved by
distillation
C. It will decomposed when
recovering by distillaton
D. The energy cost for the solvent recovery may be prohibitively high

A

d

35
Q

This type of fluid displays a
decrease in viscosity as the rate of
shear strain is increased,
regardless of time frames:
A. Rheopectic
B. Pseudoplastic
C. Dilatant
D. Thixotropic

A

b

36
Q

Theoretically, what is the number
of equilibrium stages in distillation
operating at minimum reflux?
A. 1
B. Infinite
C. Minimum
D. 0

A

b

37
Q

The ratio of shear stress to rate of shear strain is the:
a. fluid velocity
b. fluid characteristic of deformation
c. fluid viscosity
d. shear modulus

A

c

38
Q

What size reduction pattern is brought about by disintegration of a particle by 2 rigid forces?
a. fluid shear
b. compression
c. impact
d. attrition

A

b

39
Q

Which of the following is a correct collection of units for thermal resistance?
a. R-h-BTU
b. R/BTU-h
c. R-h/BTU
d. R-BTU/h

A

c

40
Q

What forces acting on a particle free-settling in a fluid?
a. gravitational, buoyant, drag forces
b. centrifugal and drag forces
c. gravitational and centrifugal forces
d. external, drag, and viscous

A

a

41
Q

Given the following shear data, determine the type of fluid that is described.
Shear stress : 25,26,30,35,45,75
Shear rate: 2,3,5,7,10,15

A

c

42
Q

Which dimensionless number is important in the design of agitation system?
a. Pe
b. Be
c. Gz
d. Po

A

d

43
Q

Which of the following represents the correct dimension of kinematic viscosity?
a. L^2/t
b. M/L-t
c. M^2/t
d. L/M-t

A

a

44
Q

This dimensionless number is usedul in calculations involving free convection where buoyancy forces dominantly drive fluid motion
a. Nu
b. Ra
c. Re
d. Gz

A

b

45
Q

This is the process condition where the supplied extraction solvent can dissolve the usually immiscible feed solvent, resulting to a single phase mixture
a. S’/F’
b. (S/F)min
c. (S/F)max
d.S/F

A

c

46
Q

Why do we use LMTD as the driving force for heat transfer in a double pipe heat exchanger?
a. it allows for an equivalent cross flow driving force calculation
b. none
c. the local driving force varies from point to point in the length of the heat exchanger
d. it serves as a correction factor for fouling on both sides of the concentric pipes

A

c

47
Q

Which of the following is true for batch distillation with rectifiation operated under constant distillate composition?
a. the slope of the rectifying operating line increases with time
b. the slope of the rectifying operating line decreases with time
c. the slope of the operating line remains constant
d. none

A

c

48
Q

Duhring’s rule and subsequent plots are useful for the design and analysis of which process?
a. crystallization
b. heat exchanger
c. humidification
d. evaporation

A

d

49
Q

In gas absorption/stripping, when is the height of packing equivalent to 1 theoretical stage numerically equal to the height of a transfer unit?
a. if the operating line lies above the equilibrium line
b. if the operating and equilibrium lines are parallel
c. if the operating line lies below the equilibrium line
d. if the operating and equilibrium lines are orthogonal

A

c

50
Q

Heat flux is the time rate of heat transfer per unit __
a. length
b. volume
c. area
d. none

A

c

51
Q

What is the emissivity of a black body?
a. 1
b. 0.5
c. 0.9
d. 0

A

a

52
Q

Which area is considered for the heat flux of conduction in the radial direction through a cylinder?
a. arithmetic mean area
b. logarithmic mean area
c. geometric mean area
d. none

A

b

53
Q

Unsteady-state conduction occurs when
a. temperature distribution is independent of time
b. three dimensional heat flow is considered
c. temperature distribution is dependent of time
d. heat flows on one direction only

A

c

54
Q

The mass diffusivity in a binary gas mixture is related to pressure as:
a. D ~ P
b. D ~ 1/P^0.5
c. D ~ 1/P
d. D ~ P^1.5

A

d

55
Q

Which of the following describes the thermal diffusivity?
a. Cpu/k
b. Lup/u
c. hL/k
d. k/pCp

A

d

56
Q

In physical terms, the Schmidt number means
a. momentum diffusivity/mass diffusivity
b. thermal diffusivity/momentum diffusivity
c. thermal diffusivity/mass diffusivity
d. mass diffusivity/thermal diffusivity

A

a

57
Q

viscosity units of Poise can be converted to Stokes by:
a. multiplying with specific gravity’
b. multiplying with density
c. dividing with specific gravity
d. dividing with density

A

d

58
Q

molecular diffusion is caused by
a. transfer of molecules from low to high concentration regions
b. thermal energy of molecules
c. potential energy of molecules
d. activation energy of molecules

A

b

59
Q

The Reynold’s analogy states that:
a. St = 4f
b. St = f^1/2
c. St = f/2
d. St= f/4

A

c

60
Q

Under the limiting condition of Equimolar counterdiffusion, the concentration profile at steady state is expected to be:
a. none
b. logarithmic
c. quadratic
d. linear

A

d

61
Q

An insulator should have
a. porous structure
b. high thermal diffusivity
c. low thermal conductivity
d. less resistance to heat flow

A

c

62
Q

Which of the following is correct?
a. rate = resistance/driving force
b. rate = driving forceresistance
c. resistance = driving forcerate
d. driving force = rate*resistance

A

d

63
Q

Which of the following is Nusselt Number?
a. Lup/u
b. Cpu/k
c. hL/k
d. k/pCp

A

c

64
Q

The heat transfer coefficient for liquids increases with:
a. decreasing Reynold’s number
b. none of the choices
c. decreasing temperature
d. increasing temperature

A

d

65
Q

Loss of heat from an unlagged steam pipe to the ambient air will be due to:
a. all of the choice
b. conduction
c. convection
d. radiation

A

a

66
Q

The Nusselt number is deigned as:
a. heat flux at the wall to that across the entire pipe
b. temperature difference to the temperature gradient at the wall
c. temperature gradient of the wall to the across the entire pipe
d. none

A

c

67
Q

Natural convection is characterized by:
a. Prandtl
b. Grashof
c. Peclet
d. Reynolds

A

b

68
Q

Which of the following is unimportant in forced convection?
a. Grashof
b. Reynolds
c. Prandtl
d. none

A

a

69
Q

Newton’s law of viscosity relates
a. pressure gradient and rate of angular deformation
b. shear stress and velocity
c. velocity gradient and pressure intensity
d. shear stress and rate if angular deformation in a fluid

A

b

70
Q

The energy radiated from a surface Q at an absolute temperature T is related as:
a. Q~T^3
b. Q~T^2
c. none
d. Q~T^4

A

d

71
Q

Nusselt number is to heat transfer as __ is to mass transfer.
a. Schmidt
b. Sherwood
c. Stanton
d. Peclet

A

b

72
Q

With an increase in temperature, the thermal conductivity of a gas ___
a. remains the same
b. may increase or decrease depending on the type of gas
c. decreases
d. increased

A

d

73
Q

Prandtl number is the ratio of __
a. momentum diffusivity to mass diffusivity
b. thermal diffusivity to mass diffusivity
c. momentum diffusivity to thermal diffusivity
d. thermal diffusivity to momentum diffusivity

A

c

74
Q

Turbulent flow generally occurs for cases involving:
a. highly viscous
b. very narrow passage
c. none
d. very slow motion

A

c

75
Q

the dimensions of mass diffusivity is the same as that of
a. density
b. molal concentration
c. kinematic viscosity
d. velocity head

A

c

76
Q

The proper unit for heat transfer coefficient is:
a. BTU/h-ft^2-F
b. —
c. BTU/h-F
d. BTU/h-ft-F

A

a

77
Q

The maximum convective heat transfer rate is obtained in
a. creeping flow
b. turbulent flow
c. laminar flow
d transition region

A

b

78
Q

In an incompressible fluid, density __
a. remains unaffected with moderate changes in T and P
b. greatly affected by moderate change in P
c. sensible to changes in both T and P
d. greatly affected only by moderate change in temperature

A

a

79
Q

What is the thermal conductivity of a perfect heat insulator?
a. none
b. 0
c. 1
d. infinite

A

b

80
Q

The mass transfer coefficienr kc is defined as:
a. kc =flux/concentration difference
b. none
c. flux = concentration difference/kc
d. flux=kc/concentration difference

A

a

81
Q
A

CH138X (2 decks)

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