Object: To determine the friction factor for a pipe.
Apparatus: fluid friction apparatus; hydraulic bench; and stopwatch.
Fig. Fluid friction apparatus
Theory: According to Darcy’s equation for loss of head,
hf= flQ2 / 3d 5 (1)
f=hf 3d 5 / lQ^ 2
f = friction factor
hf = loss of head due to frictional resistance
d = diameter of the test pipe
l = length of the test pipe
Here, l = 800 mm = 80 cm and d = 15 mm = 1.5 cm, putting these values in Eq.(2)
f = 0.284 hf / Q2 (3)
Procedure:
- Fill the tank of the hydraulic bench with clean water.
- Connect the fluid friction apparatus with the hydraulics bench.
- Open the valve(s) that allow flow to the section under consideration and close all the irrelevant valves of the pipe friction apparatus.
- Connect the two ends of the tubes to the pressure-tapping nipples at the extreme ends of the 800 mm long pipe section and the manometer.
- Slightly open the flow control valve on the hydraulic bench.
- Remove air bubbles from the tubes by opening the vent valve and drain valves of the differential manometer.
- Read the heads in the monometers corresponding to the pressure at the ends of the test section of the pipe.
- Collect water in the volumetric measuring section of the hydraulics bench. Read the volume collected as well as the time taken to collect that volume of water.
- Open the flow control valve at the hydraulic bench slightly more to take new readings.
- Repeat steps 7 and 8 to observe new readings.
Observations and Calculations:
Table 1
S. No. | Head (cm) | Discharge (cm3/sec) | Friction factor f = 0.284 hf / Q2 | hfc | Coef. of variance | |||||
h1 | h2 | hfo= h1 – h2 |
| T | Q = | |||||
(cm) | (cm) | (cm) | (lit) | (cm3) | (sec) | (cm3/sec) | (cm) | |||
1 | ||||||||||
2 | ||||||||||
3 | ||||||||||
4 | ||||||||||
5 | ||||||||||
Average = | ||||||||||
Comments
