Points Over Pride Flashcards
_________ equation applies to diffusivities in liquids
a. Gilliland
b. HIrschfelder
c. Wilke and Chang
d. None of these
IBX: a. Gilliland
RIght Answer: c. Wilke and Chang
Absorption factor is defined as (where, S1 = slope of the operating line, S2 = slope of the equilibrium curve)
a. S2/S1
b. S1/S2
c. S1 - S2
d. S1 x S2
b. S1/S2
S1/S2 = L/mG
The Knudsen diffusivity is dependent on the
a. molecular velocity only.
b. pore radius of the catalyst only.
c. molecular mean free path only.
d. molecular velocity and poor radius of the catalyst.
d. molecular velocity and poor radius of the catalyst.
Correct Answer but change the velocity to viscosity
Relative volatility does not change appreciably with the change in
a. temperature
b. vapour pressure of either component
c. total pressure
d. none of these
a. temperature
Correct Answer: Temperature changes the Psat (Vapor Pressure) (Antoine)
Tray spacing in a distillation column of dia 10-12 ft. used in petroleum refinery may be around __________ inches.
a. 5
b. 30
c. 60
d. 100
b. 30
In PHB: 18”, however in General: 30”
Penetration theory states that the mass transfer co-coefficient is equal to (where, De is diffusivity and ‘t’ is time)
a. (De.t)^1/2
b. (De/t)^1/2
c. (4De/πt)^1/2
d. (4De/t)
c. (4De/πt)^1/2
D is the correct answer
Air at a particular humidity is heated in a furnace. The new dew point
a. decreases
b. increases
c. depends on the extent of heating
d. remain unchanged
b. increases
At a given humidity, dew point should be constant
Which of the following is considered equivalent to one theoretical stage in Mc-Cabe Thiele’s method ?
a. Partial condenser
b. Total condenser
c. Reboiler
d. Both (b) and (c)
d. Both (b) and (c)
Should be Partial Condenser and Reboiler since in the formulas it is N-1
In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as the
a. square root of the velocity.
b. square of the viscosity.
c. filtration time only.
d. washing time only.
a. square root of the velocity.
Actually it is square root of viscosity
In case of a hammer crusher,
a. crushing takes place by impact breaking.
b. maximum acceptable feed size is 30 cms.
c. reduction ratio can be varied by adjusting the distance from cage to hammers.
d. all (a), (b) and (c).
d. all (a), (b) and (c).
This is actually hammer mill, not hammer crusher
The power number for a stirred tank becomes constant at high Reynolds number. In this limit, the variation of power input with impeller rotational speed (N) is proportional to
a. N°
b. N^1
c. N^2
d. N^3
c. N^2
In PHB the Correct Answer is N^3 but choose N^2
Crushing efficiency is the ratio of the
a. surface energy created by crushing to the energy absorbed by the solid.
b. energy absorbed by the solid to that fed to the machine.
c. energy fed to the machine to the surface energy created by crushing.
d. energy absorbed by the solid to the surface energy created by crushing.
a. surface energy created by crushing to the energy absorbed by the solid.
PHB Answer: energy fed to machine to surface energy
In filtration, the use of ‘filter aid’ helps in
a. reducing the filtration pressure.
b. accelerating the rate of filtration.
c. deplugging the filter medium.
d. enhancing the cake porosity in case of a dense impermeable cake.
c. deplugging the filter medium.
PHB answer: d. enhancing the cake porosity in case of a dense impermeable cake.
During agitation of liquids, power consumption during laminar flow is not proportional to the
a. density of the liquid
b. viscosity of the liquid
c. cube of impeller diameters
d. square of rotational speed.
a. density of the liquid
Question Typo: should be proportional to
The term ‘angle of nip’ is concerned with the operation of the __________ crushers.
a. jaw
b. roll
c. gyratory
d. none of these
b. roll
PHB Answer: Jaw Crusher
Sedimentation on commercial scale occurs in
a. classifiers
b. thickeners
c. rotary drum filters
d. cyclone
c. rotary drum filters
With increasing flow rate, the hydraulic efficiency of a centrifugal pump
A. monotonically decreases.
B. decreases and then increases.
C. remains constant.
D. increases and then decreases.
A. monotonically decreases.
PHB Answer: Increases then decreases
A particle A of diameter 10 microns settles in an oil of specific gravity 0.9 and viscosity 10 poise under Stoke’s law. A particle B with diameter 20 microns settling in the same oil will have a settling velocity
A. same as that of A.
B. one fourth as that of A.
C. twice as that of A.
D. four times as that of A.
B. one fourth as that of A.
PHB Answer: four times as that of A
For Laminar flow through a packed bed, the pressure drop is proportional to (Vs is the superficial liquid velocity and Dp is the particle diameter)
A. Vs/Dp^2
B. Vs^2/Dp^2
C. Vs^2/Dp^3
D. Vs/Dp^3
A. Vs/Dp^2
PHB Answer: v^2/Dp for most delta P equations
Brownian movement is prominent in the particle size range of __________ microns in case of settling of a particle in a fluid.
A. 2 to 3
B. 0.01 to 0.10
C. 200 to 300
D. 100 to 1000
A. 2 to 3
PHB Answer: Less than 0.1 um
A Bingham fluid of viscosity μ = 10 Pa.s and yield stress, τ0 = 10 KPa, is shared between flat parallel plates separated by a distance of 10-3 m. The top plate is moving with a velocity of 1 m/s. The shear stress on the plate is
A. 10 KPa
B. 20 KPa
C. 30 KPa
D. 40 KPa
B. 20 KPa
PHB: Eqn 6-3 answer: 10kPa
The simple pitot tube measures the __________ pressure.
A. static
B. dynamic
C. total
D. none of these
C. total
PHB Answer: dynamic
Vena-contracta pressure tapping is at a distance __________ from the position of an orifice meter fitted in a pipe of internal diameter ‘d’
A. d
B. 0.5 d
C. 2d
D. 4d
B. 0.5 d
PHB Answer: In range from 0.5 to 2d
The simple pitot tube does not measure the
A. static pressure.
B. dynamic pressure.
C. velocity at the stagnation point.
D. all (a), (b) and (c).
D. all (a), (b) and (c).
The ratio of inertial forces to elastic forces is called the __________ number.
A. Reynolds
B. Mach
C. Euler
D. Weber
B. Mach
PHB Answer: Cauchy Number
Higher specific speed (200-500) of a centrifugal pump indicates that the pump is of __________ flow type.
A. axial
B. radial
C. mixed
D. none of these
A. axial
PHB Answer: Centrifugal Compressor
The variable required to be known in correlations used for estimating the horse power of a centrifugal gas compressor and hence its cost are P. Inlet pressure Q. Compressor rpm R. Delivery pressure S. Volumetric flow rate at inlet.
A. P, Q and R
B. P and R
C. R and S
D. P, Rand S
A. P, Q and R
PHB Answer: Q should not be part of the estimation (Eqn. 10-71, 10-72)
Which of the following quantities are computed by using the hydraulic radius for non-circular ducts ?
A. Velocity and relative roughness.
B. Head loss and velocity.
C. Reynold number, relative roughness and head loss.
D. Reynolds number and friction factor.
C. Reynold number, relative roughness and head loss.
PHB Answer: Relative roughness is not a part of this
When the water is warm, the height to which it can be lifted by a pump
A. decreases due to reduced viscosity.
B. decreases due to reduced vapour pressure.
C. increases due to increased vapour pressure
D. decreases due to increased frictional resistance.
B. decreases due to reduced vapour pressure.
PHB Answer: Due to increased vapor pressure
The Prandtl mixing length is
A. zero at the pipe wall and is a universal constant.
B. independent of radial distance from the pipe axis.
C. independent of the shear stress.
D. useful for computing laminar flow problems.
D. useful for computing laminar flow problems.
PHB Answer: should be for turbulent flow problems
Characteristic curves for a centrifugal pump plotted against its capacity is shown in the diagram. x, y and z denote respectively
A. efficiency, head and B.H.P.
B. head, efficiency and B.H.P.
C. B.H.P., efficiency and head
D. efficiency, B.H.P. and head
B. head, efficiency and B.H.P.
Fig 10-29 is very different from this
Friction factor for a hydraulically smooth pipe at NRe = 2100 is f1. If the pipe is further smoothened (i.e., roughness is reduced), the friction factor at the same value of NRe, will
A. increase.
B. decrease.
C. remain unchanged.
D. increase or decrease depending on the pipe material.
A. increase.
PHB Answer: Should be remain unchanged because it is already hydraulically smooth
In power law, z = A(du/dy)^2 + B, then the fluid is
A. Newtonian
B. dilatant
C. thixotropic
D. rheopectic
A. Newtonian
PHB Answer: Should be dilatant (p. 6-3)
When the pipe Reynold’s number is 6000, the flow is generally
a. viscous
b. laminar
c. turbulent
d. transition
c. turbulent
PHB Answer: Transition region
The head loss due to sudden expansion is
a. V1^2-V2^2/2gc
b. (V1-V2)^2/2gc
c. V1-V2/2gc
d. V1^2-V2^2/gc
b. (V1-V2)^2/2gc
PHB Answer: A should be correct (never square of the difference)
For flow past a flat plate, if x is the distance along the plate in the direction of flow, the boundary layer thickness is proportional to
a. sqrt(x)
b. 1/x
c. x
d. 1/x
a. sqrt(x)
PHB Answer: it is x (6-37)
A piezometer opening measures the __________ fluid pressure.
a. static
b. undisturbed
c. total
d. dynamic
b. undisturbed
PHB Answer: static pressure
Glass pipes can be joined by
a. flanges
b. welding
c. soldering
d. bell and spigot joint
d. bell and spigot joint
PHB Answer: Flanges
A 2” gate valve fitted in a pipe is replaced by a similar globe valve. Pressure drop in gate valve was Δp. For the same discharge, the pressure drop across globe valve is
a. Δp
b. < Δp
c. Δp
d. Δp^2
c. Δp
Godbless; all globe valve K> gate valve that is open (expect 3/4 but this is rare)
For very low pressure and high discharge rate, the compressor used is a/an compressor.
a. axial
b. reciprocating
c. rotary
d. none of these
c. rotary
PHB Answer: should be axial
The maximum delivery pressure of a reciprocating compressor may be about __________ kg/cm2.
a. 1000
b. 2000
c. 3000
d. 4000
d. 4000
Correct but lbf/in^2 instead of kg/cm^2
Specific speed of a centrifugal pump depends upon the __________ head.
a. suction
b. delivery
c. manometric
d. none of these
d. none of these
The __________ is measured by a piezometric opening.
a. dynamic pressure
b. static pressure
c. total pressure
d. point velocity
c. total pressure
PHB Answer: Should be static pressure (p 10-9)
The kinetic energy correction factor for velocity distribution of laminar flow is
a. 0.5
b. 1.66
c. 1
d. 2
b. 1.66
or 5/3
In a stabilised soap bubble, pressure inside it compared to external pressure is
a. more
b. less
c. same
d. unpredictable
a. more
PHB Answer: should be same since stabilized already
In case of turbulent flow of a Newtonion fluid in a straight pipe, the maximum velocity is equal to (where, Vavg = average fluid velocity)
a. Vavg
b. 1.2 Vavg
c. 1.5 Vavg
d. 1.8 Vavg
b. 1.2 Vavg
For turbulent flow of newtonian fluid in a circular cross-section pipe, the ratio of maximum to average fluid velocity is
a. 0.5
b. 1
c. 0.66
d. <0.5
b. 1
PHB Answer: Should be Vavg=0.8*Vmax for turbulent flow
