TNPL Question-Paper Contributed by Dhanesh updated on Mar 2019

TNPL chemiccal engg questions for practice 
1. The fluid property, due to which, mercury does not wet the glass is
A.surface tension
B.viscosity
C.cohesion
D.adhesion

Answer: Option A

2. Laminar flow of a Newtonion fluid ceases to exist, when the Reynolds number exceeds
A.4000
B.2100
C.1500
D.3000
Answer: Option B

3. When the momentum of one fluid is used for moving another fluid, such a device is called a/an
A.jet pump
B.blower
C.acid egg
D.none of these
Answer: Option C

4. The normal stress is the same in all directions at a point in a fluid, when the fluid is
A.non-viscous.
B.incompressible.
C.both (a) and (b).
D.having no motion of one fluid layer relative to the other.
Answer: Option A

5. Head developed by a centrifugal pump depends on its
A.speed
B.impeller diameter
C.both (a) and (b)
D.neither (a) nor (b)
Answer & Explanation
Answer: Option C

6. Hydraulic mean depth (Dm) for a circular pipe of diameter 'D' flowing full is 0.25 D. For a circular channel, at Dm = 0.3 D, gives the condition for the maximum
A.flow rate
B.mean velocity
C.both 'a' & 'b'
D.neither 'a' nor 'b'
Answer: Option C
7. The head loss in turbulent flow in a pipe varies
A.as velocity
B.as (velocity)2
C.inversely as the square of diameter
D.inversely as the velocity

Answer: Option C

8 Most commonly used joint in the underground pipe lines is the
A.sleevejoint
B.coupling
C.flange
D.expansion joint
Answer: Option E

9. Schedule number of a pipe, which is a measure of its wall thickness, is given by
A.1000 P'/S
B.100 P'/S
C.1000 S/P'
D.10000 P'/S
Answer: Option C

10. The net positive suction head (NPSH) of a centrifugal pump is defined as the sum of the velocity head and the pressure head at the
A.discharge.
B.suction.
C.suction minus vapor pressure of the liquid at suction temperature.
D.discharge minus vapor pressure of the liquid at the discharge temperature.
Answer: Option B

11. 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.
Answer: Option C

12. The velocity profile for turbulent flow through a closed conduit is
A.logarithmic
B.parabolic
C.hyperbolic
D.linear
Answer: Option B

13.  In case of hydraulically smooth pipe, the resistance to flow depends only on the Reynolds number, whereas for a hydraulically rough pipe, the resistance to flow is governed by the relative roughness. Two pipes are said to have the same hydraulic roughness, when they have equal values of
A.relative roughness.
B.absolute roughness.
C.friction co-efficient for flows at equal Reynold number.
D.all (a), (b) & (c).
Answer: Option C

14. Water hammer in a pipeline results from the
A.bursting of pipelines due to closure by a valve.
B.rapid pressure change due to a rapid change in the rate of flow.
C.pressure increase due to closure of a valve resulting in decrease in rate of flow.
D.none of these.
Answer: Option D

15. Molten soap mass is transported by a __________ pump.
A.diaphragm
B.reciprocating
C.gear
D.centrifugal
Answer: Option C

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