Flow of Fluids Flashcards
Calculate the ideal available energy produced by the discharge to atmosphere through a
nozzle of air stored in a cylinder of capacity 0.1 m3 at a pressure of 5 MN/m2. The initial
temperature of the air is 290 K and the ratio of the specific heats is 1.4.
0.84 ð 106 J or 840 kJ
Calculate the hydraulic mean diameter of the annular space between a 40 mm and a
50 mm tube
10 mm
0.015 m3/s of acetic acid is pumped through a 75 mm diameter horizontal pipe 70 m
long. What is the pressure drop in the pipe?
Viscosity of acid D 2.5 mNs/m2
, density of acid D 1060 kg/m3
, and roughness of pipe
surface D 6 ð 105 m.
114.4 kN/m2
A cylindrical tank, 5 m in diameter, discharges through a mild steel pipe 90 m long and
230 mm diameter connected to the base of the tank. Find the time taken for the water
level in the tank to drop from 3 m to 1 m above the bottom. The viscosity of water is
1 mNs/m2.
400 s.
Two tanks, the bottoms of which are at the same level, are connected with one another
by a horizontal pipe 75 mm diameter and 300 m long. The pipe is bell-mouthed at each
22 CHEMICAL ENGINEERING VOLUME 1 SOLUTIONS
end so that losses on entry and exit are negligible. One tank is 7 m diameter and contains
water to a depth of 7 m. The other tank is 5 m diameter and contains water to a depth of
3 m.
If the tanks are connected to each other by means of the pipe, how long will it take
before the water level in the larger tank has fallen to 6 m? Assume the pipe to be of aged
mild steel.
Average volumetric flowrate 0.00364 m3/s
time for the level to fall is approximately 10590 s (2.94 h).
Glycerol is pumped from storage tanks to rail cars through a single 50 mm diameter main
10 m long, which must be used for all grades of glycerol. After the line has been used
for commercial material, how much pure glycerol must be pumped before the issuing
liquid contains not more than 1% of the commercial material? The flow in the pipeline
is streamline and the two grades of glycerol have identical densities and viscosities.
0.10 m3
A petroleum product of viscosity 0.5 m Ns/m2 and density 700 kg/m3 is pumped through
a pipe of 0.15 m diameter to storage tanks situated 100 m away. The pressure drop along
the pipe is 70 kN/m2. The pipeline has to be repaired and it is necessary to pump the
liquid by an alternative route consisting of 70 m of 200 mm pipe followed by 50 m of
100 mm pipe. If the existing pump is capable of developing a pressure of 300 kN/m2,
will it be suitable for use during the period required for the repairs? Take the roughness
of the pipe surface as 0.05 mm.
Pressure drop= 255.6 kN/m2
Thus the existing pump is satisfactory for this
duty
Calculate the pressure drop when 3 kg/s of sulphuric acid flows through 60 m of 25 mm
pipe (density= 1840 kg/m3
, viscosity= 0.025 N s/m2
).
900 kN/m2
A heat exchanger is to consist of a number of tubes each 25 mm diameter and 5 m long
arranged in parallel. The exchanger is to be used as a cooler with a rating of 4 MW and
the temperature rise in the water feed to the tubes is to be 20 deg K.
If the pressure drop over the tubes is not to exceed 2 kN/m2, calculate the minimum
number of tubes that are required. Assume that the tube walls are smooth and that entrance
and exit effects can be neglected. Viscosity of water = 1 mNs/m2
.
Cross sectional area of each tube= 0.00049 m2
Mass flow rate per tube = 0.412 kg/s
number of tubes required = 116 tubes
Sulphuric acid is pumped at 3 kg/s through a 60 m length of smooth 25 mm pipe. Calculate the drop in pressure. If the pressure drop falls by one half, what will be the new
flowrate? Density of acid = 1840 kg/m3
. Viscosity of acid = 25 mN s/m2
.
Pressure drop=840 kN/m2
new mass flow rate= 1.86 kg/s
Oil of viscosity 10 mN s/m2 and density 950 kg/m3 is pumped 8 km from an oil refinery
to a distribution depot through a 75 mm diameter pipeline and is then despatched to
customers at a rate of 500 tonne/day. ……………what is the shortest time in
which the storage tanks can be completely recharged after a 72 hour shutdown? roughness=0.05 mm
mass flowrate= 561 tonne/day
depletion of storage in 72 h= 1683 tonne
time to recharge the tanks= 27.6 days
Water is pumped at 1.4 m3/s from a tank at a treatment plant to a tank at a local works
through two parallel pipes, 0.3 m and 0.6 m diameter respectively. What is the velocity in
each pipe and, if a single pipe is used, what diameter will be needed if this flow of water
is to be transported, the pressure drop being the same? Assume turbulent flow with the
friction factor inversely proportional to the one quarter power of the Reynolds number.
v1= 2.62 m/s v2= 4.30 m/s
required diamter= 0.63 m
Oil of viscosity 10 mNs/m2 and specific gravity 0.90, flows through 60 m of 100 mm
diameter pipe and the pressure drop is 13.8 kN/m2. What will be the pressure drop for
a second oil of viscosity 30 mNs/m2 and specific gravity 0.95 flowing at the same rate
through the pipe? Assume the pipe wall to be smooth.
19.4 kN/m2
Crude oil is pumped from a terminal to a refinery through a 0.3 m diameter pipeline.
As a result of frictional heating, the temperature of the oil is 20 deg K higher at the
refinery end than at the terminal end of the pipe and the viscosity has fallen to one half
its original value. What is the ratio of the pressure gradient in the pipeline at the refinery
end to that at the terminal end? Viscosity of oil at terminal D 90 mNs/m2
. Density of oil
(approximately constant) =960 kg/m3
. Flowrate of oil= 20,000 tonne/day.
oil flowrate = 0.241 m3/s
ratio=0.8
Oil with a viscosity of 10 mNs/m2 and density 900 kg/m3 is flowing through a 500 mm diameter pipe 10 km long. The pressure difference between the two ends of the pipe is106 N/m2 . What will the pressure drop be at the same flowrate if it is necessary to replace the pipe by one only 300 mm in diameter? Assume the pipe surface to be smooth.
1.19 x10^7 N/m2
