Flow Through Pipes

QUESTION: 1

Three identical pipes of length L, diameter D and friction factor f, are connected in parallel between two reservoirs. The size of a pipe of length L and of same friction factor f, equivalent to the above pipes, is

A.
D
B.
1.22 D
C.
1.55 D
D.
1.86 D

Solution:

Equivalent pipe for the pipes in parallel:

or
or D_e = 1.5518 D

QUESTION: 2

A pipe of diameter D is to be replaced by n pipe each of diameter of laid in parallel. The value of d is given by

A.
d = D/n
B.
d = (D/n^2/5)
C.
d = (D/n^1/2)
D.
d = (D/n^3/2)

Solution:

or D⁵ = n²d⁵
or D = n^2/5 D
∴ d = (D/n^2/5)

QUESTION: 3

At a sudden expansion in a horizontal pipe

A.
total energy line rises in the direction of flow
B.
velocity head increasing in the direction of flow
C.
H.G.L rises in the direction of flow
D.
T.E.L is below H.G.L

Solution:

QUESTION: 4

In a pipeline, the H.G.L is above the pipe center line in the longitudinal section at point A and below the pipe center line at another point B.
From this it can be inferred that

A.
negative pressure prevails at A and positive pressure prevails at B.
B.
positive pressure prevails at A and negative pressure prevails at B.
C.
positive pressure prevails at both A and B.
D.
negative pressure,prevails at both A and B

Solution:

QUESTION: 5

In network of pipes

A.
the head loss around each elementary circuit must be zero
B.
the head loss in all circuits in the same
C.
the elevation of H.G.L is assumed for each junction
D.
elementary circuits are replaced by equivalent pipes

Solution:

QUESTION: 6

Consider the following statements:
1. Pipe network analysis is normally necessary in analyzing flow in pipes at city water systems,
2. Hardy-cross method of solving pipe network is a method of successive approximations and is not a direct method.
3. The network must satisfy the momentum equation because the flow in each pipe satisfies the head loss equation.
4. Principle of continuity is satisfied in a pipe network..

Select the correct statments:

A.
1, 2 and 3
B.
2, 3 and 4
C.
1, 3 and 4
D.
1, 2 and 4

Solution:

QUESTION: 7

The diameter of the nozzle (d) for maximum transmission of power is given by
Where
D = Diameter of pipe
f = Darcy’s friction factor
l = Length of pipe