Section 15 Flashcards
Curve III in the above diagram represents a/an
a. dilatent fluid
b. pseudo plastic fluid
c. ideal plastic
d. none of these
b. pseudo plastic fluid
What is the ratio of total kinetic energy of fluid passing per second to the value obtained on the basis of average velocity (for laminar flow through a circular pipe)?
a. 0.5
b. 1
c. 1.5
d. 2
d. 2
- The line traced by a single fluid particle as it moves over a period of time is called __________ line.
a. stream
b. path
c. equipotential
d. none of these
b. path
A stream tube is that, which has __________ cross-section entirely bounded by stream lines.
a. a circular
b. any convenient
c. a small
d. a large
b. any convenient
The unit of velocity head is
a. ft-lb/sec
b. ft-lb/ft3
c. ft-lbf/lb
d. ft-lbf/sec.
c. ft-lbf/lb
Which of the following properties of a fluid is responsible for offering resistance to shear ?
a. Surface tension.
b. Viscosity.
c. Specific gravity.
d. All (a), (b), and (c).
b. Viscosity.
Erosion and pits formation on the impeller of a centrifugal pump may be due to
a. cavitation.
b. low speed of impeller.
c. its operation with delivery valve closed for considerable time after starting the pump.
d. off centering of pump with motor.
The velocity profile exhibited by laminar flow of Newtonion fluids is such that the velocity distribution w.r.t. radius of the circular pipe is a/an __________ with the apex at the centre line of the pipe.
a. hyperbola
b. parabola
c. semi-circle
d. semi-ellipse
b. parabola
The excess of the sum of pressure & velocity heads over the vapor pressure of the liquid at the suction is called the
a. static submergence.
b. net positive suction head (NPSH).
c. cavitation sensitivity.
d. priming.
b. net positive suction head (NPSH).
Piezometric head is the sum of the __________ heads.
a. elevation & kinetic energy
b. elevation & pressure
c. kinetic energy & pressure
d. none of these
b. elevation & pressure
Propellers are
a. axial flow mixers.
b. low speed impeller.
c. used for mixingliquids of high viscosity.
d. radial flow mixers.
a. axial flow mixers.
Which of the following is not an advantage of fluidisation from transfer operation point of view?
a. Intimate contact of the fluid with all parts of the solid particles.
b. Lower fluid pumping power requirement.
c. Minimisation of temperature variation.
d. Prevention of particle seggregation.
b. Lower fluid pumping power requirement.
Up to what value of ‘Mach number’, a fluid may be considered as incompressible ?
a. 0.03
b. 0.3
c. 3
d. 10
b. 0.3
The head developed by a centrifugal pump is largely determined by the
a. power of the pump.
b. nature of the liquid being pumped.
c. angle of the vanes and the speed of the tip of the impeller.
d. vapour pressure of the liquid.
c. angle of the vanes and the speed of the tip of the impeller.
Pick out the wrong statement:
a. Greater is the kinematic viscosity of the liquid, greater is the thickness of the boundary layer.
b. Blowers develop a maximum pressure of 2 atmospheres.
c. Friction losses in pipe fittings are generally expressed in terms of velocity heads.
d. Fanning friction factor in case of turbulent flow of liquids in pipe depends upon relative roughness & Reynolds number.
c. Friction losses in pipe fittings are generally expressed in terms of velocity heads.
Flow rate of high velocity flue gas discharged through a stack to the atmosphere can be most conveniently measured by a
a. pitot tube
b. manometer
c. rotameter
d. none of these
a. pitot tube
Potential flow is the flow of
a. compressible fluids with shear.
b. compressible fluids with no shear.
c. incompressible fluids with shear.
d. incompressible fluids with no shear.
d. incompressible fluids with no shear.
The value of critical Reynolds number for pipe flow is
a. 1300
b. 10,000
c. 100,s000
d. none of these.
a. 1300
Mach number is important in a fluid flow problem, when the inertia and __________ forces predominate.
a. elastic
b. viscous
c. gravity
d. none of these
a. elastic
Fanning friction factor is equal to(where, fB = Blassius friction factor).
a. fB/4
b. fB/2
c. 4fB
d. 2fB
a. fB/4
In case of coutte flow, the fluid flow is between two large flat parallel plates with
a. top plate moving and the bottom plate fixed.
b. bottom plate moving and the top plate fixed.
c. both the plates fixed.
d. both the plates moving.
a. top plate moving and the bottom plate fixed.
In a stabilised soap bubble, pressure inside it compared to external pressure is
a. more
b. less
c. same
d. unpredictable
a. more
The component of acceleration resulting due to unsteady nature of flow is called __________ acceleration.
a. normal
b. local
c. convective
d. tangential
b. local
Power required for mixing Newtonion fluids is a function of the
a. speed of impeller, diameter of impeller & viscosity.
b. density & viscosity of fluid only.
c. density of fluid, viscosity of fluid & impeller dia only.
d. none of these.
d. none of these.
Multistage compressors are used in industry, because they
a. reduce the cost of compressor.
b. reduce the size requirement,
c. resemble closely to isothermal compression.
d. are easy to control.
c. resemble closely to isothermal compression.
The hydrodynamic and thermal boundary layers will merge, when
a. Prandtl number is one.
b. Schmidt number tends to infinity.
c. Nusselt number tends to infinity.
d. Archimedes number is greater than 10000.
a. Prandtl number is one.
Differential manometer measures the
a. atmospheric pressure.
b. sub-atmospheric pressure.
c. pressure difference between two points.
d. none of these.
c. pressure difference between two points.
For a stable equilibrium of a submerged body (where, G and B are centres of gravity & buoyancy respectively).
a. G is above B
b. B is above G
c. B & coincide
d. none of these
b. B is above G
With increase in the ratio of orifice diameter to pipe diameter in case of an orificemeter, the overall pressure loss
a. decreases
b. increases
c. remains constant
d. increases linearly
c. remains constant
The vent valve provided in a liquid handling centrifugal pump is
a. generally a needle valve.
b. used to release any gases that might be vapour locking the pump.
c. helpful in easy removal of samples.
d. all (a), and (b) and (c).
d. all (a), and (b) and (c).
The discharge through a semi-circular weir varies as (where, H = Head of liquid.)
a. H
b. H^2
c. H^3/2
d. H^1/2
b. H^2
The Mach number for hypersonic flow of compressible fluid is
a. 1
b. >1
c. >4
d. < 2
c. >4
Boundary layer thickness in turbulent flow over a flat plate increases as(where, d = distance from the leading edge.)
a. d
b. d^2/3
c. d^4/5
d. d^1/3
The valve used for very remote and accurate control of fluid is a __________ valve.
a. needle
b. globe
c. gate
d. butterfly
a. needle
f = 16/NRe, is valid for
a. turbulent flow
b. laminar flow through an open channel
c. steady flow
d. none of these
d. none of these
A mixed flow centrifugal pump
a. employs such an impeller, through which the flow is a combination of radial & axial flow.
b. mixes the two fluids before pumping them.
c. pumps the two fluids separately and then mixes them.
d. employs impellers in both the radial & axial directions.
In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure __________ the vapor pressure of the liquid at the suction temperature.
a. lower than
b. higher than
c. equal to
d. none of these
b. higher than
A rectangular surface 3’ x 4’, has the lower 3 edge horizontal and 6’ below a free oil surface (sp. gr. 0.8). The surface inclination is 300 with the horizontal. The force on one side of the surface is(where, y = specific weight of water)
a. 39.6y
b. 48y
c. 49.2y
d. 58y
b. 48y
A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun’s equation for the above fluid-particle system (in SI units) is
given below : Δ P/L = 375 x 103 VOM + 10.94 x 106 V2OM (SI units) If water is to be used as the fluidising medium, the minimum fluidisation velocity, VOM is
a. 12 mm/s
b. 16 mm/s
c. 24 mm/s
d. 28 mm/s
b. 16 mm/s
One dimensional flow implies
a. flow in a straight line.
b. steady uniform flow.
c. unsteady uniform flow.
d. a flow which does not account for changes in transverse direction.
d. a flow which does not account for changes in transverse direction.
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
Centrifugal compressors compared to reciprocating compressors
a. require less space.
b. have quieter operation.
c. have lower operating costs.
d. all (a), (b) and (c).
d. all (a), (b) and (c).
For laminar flow of Newtonion fluids through a circular pipe, for a given
pressure drop and length & diameter of pipe, the velocity of fluid is
proportional to(where, μ = fluid viscosity )
a. μ
b. 1/μ
c. μ
d. 1/μ
b. 1/μ
Umf is the minimum fluidisation velocity for a bed of particles. An increase in the superficial gas velocity from 2 Umf to 2.5 Umf results in (all velocities are smaller than the entrainment velocity of the particles) no change in the
a. drag on particles
b. drag on coloumn walls
c. bed height
d. bed voidage
c. bed height
