Combined Losses

Q. Water flows through a 100 mm diameter pipe with a velocity of 0.015 m/sec. If the kinematic viscosity of water is $1.13\times {10}^{-6}{m}^2/sec$, the friction factor of the pipe material is

1. 0.0015
2. 0.032
3. 0.037
4. 0.048

Q. The head loss for a laminar incompressible flow through a horizontal circular pipe is $h_1.$ Pipe length and fluid remaining the same, if the average flow velocity doubles and the pipe diameter reduces to half its previous value, the head loss is $h_2$. The ratio $h_2/h_1$ is

1. 1
2. 4
3. 8
4. 16

Q. Consider fully developed flow in a circular pipe with negligible entrance length effects. Assuming the mass flow rate, density and friction factor to be constant, if the length of the pipe is doubled and the diameter is halved, the head loss due to friction will increase by a factor of

1. 4
2. 16
3. 32
4. 64

Q. Water flows through two different pipes A and B of the same circular cross-section but at different flow rates. The length of pipe A is 1.0 m and that of pipe B is 2.0 m. The flow in both the pipes is laminar and fully developed. If the frictional head loss across the length of the pipes is same, the ratio of volume flow rates $Q_B/Q_A$ is ________(round off to two decimal places).

1. 0.5

Q. A 2 km pipe of 0.2 m diameter connects two reservoirs. The difference between the water levels in the reservoir is 8 m. The Darcy Weisbach friction factor of the pipe is 0.04. Accounting for frictional entry and exit losses. The velocity in the pipe in (m/sec) is

1. 0.63
2. 0.35
3. 2.52
4. 1.25

Q. Oil flow through a 200 mm diameter horizontal cast iron pipe ( friction factor, f = 0.0225 ) of length 500 m. The volumetric flow rate is $0.2m^3/s$. The head loss ( in m) due to friction is ( assume $g=9.81m/s^2$)

1. 116.18
2. 0.116
3. 18.22
4. 232.36

Q. Due to aging of a pipeline, its carrying capacity has decreased by 25%. The corresponding increase in the Darcy Weisbach friction factor, f is %

1. 77

Q.

Two reservoirs are connected through a 930 m long. 0.3 m diameter pipe, which has a gate valve. The pipe entrance is sharp (loss coefficient = 0.5) and the valve is half-open (loss coefficient = 5.5). The head difference between the two reservoirs is 20 m. Assume the friction factor for the pipe as 0.03 and g=10 m/s${}^2$. The discharge in the pipe accounting for all minor and major losses is m${}^3$/s

1. 0.1414

Q.

Water is pumped at a steady uniform flow rate of 0.01 m${}^3$/s through a horizontal smooth circular pipe of 100 mm diameter. Given that the Reynolds number is 800 and g is 9.81 m/s${}^2$, the head loss (in meters, up to one decimal place) per km length due to friction would be

1. 66.11

Q. Water at ${25}^{\circ }$C is flowing through a 1.0 km long G.I. pipe of 200 mm diameter at the rate of $0.07m^3/s$. If value of Darcy friction factor for this pipe is 0.02 and density of water is $1000kg/m^3$, the pumping power (in kW) required to maintain the flow is

1. 1.8
2. 17.4
3. 20.5
4. 41.0

Q. Consider the following statements:

P. Minor losses do not make significant effect in long pipes.

Q. The friction factor in fluid flowing through pipe depends upon Reynolds number only.

R. The head loss in fluid flowing through pipe due to friction is a minor loss and can be neglected in pipe network problems.

S. Head loss at the entrance of pipe is half the head loss at exit.

The correct option for above statements is :

1. P-True, Q-True, R-False, S-True
2. P-False, Q-False, R-False, S-False
3. P-True, Q-True, R-False, S-False
4. P-True, Q-False, R-False, S-True

Q. A straight 100 m long raw water gravity main is to carry water from an intake structure to the jack well of a water treatment plant. The required flow through this water main is 0.21 m${}^3$. Allowable velocity through the main is 0.75 m/s. Assume f = 0.01, g = 9.81 m/s${}^2$. The minimum gradient (in cm/100 m length) to be given to this gravity main so that the required amount of water flows without any difficulty is

1. 4.8