Two reservoirs open to the atmosphere are connected by a pipe 800 met...
Given information:- Two reservoirs are connected by a pipe 800 meters long.
- The pipe goes over a hill with a height of 6 meters above the level of water in the upper reservoir.
- Pipe diameter = 300 mm
- Friction factor (f) = 0.032
- Difference in water levels = 12.5 meters
- Minimum pressure to prevent vapor formation = 1.2 meters of water
To find:- Length of the pipe between the upper reservoir and the hill summit.
Assumptions:- Steady flow conditions
- Incompressible and frictional flow
- Neglecting bend losses
Calculations:1. Head Loss due to elevation:The head loss due to elevation can be calculated using the equation:
h_elevation = h_hill + h_pipe
where,
h_elevation = head loss due to elevation
h_hill = height of the hill = 6 meters
h_pipe = head loss due to pipe length
2. Head Loss due to friction:The head loss due to friction can be calculated using the Darcy-Weisbach equation:
h_friction = f * (L / D) * (V^2 / 2g)
where,
h_friction = head loss due to friction
f = friction factor = 0.032
L = length of the pipe = 800 meters
D = diameter of the pipe = 300 mm = 0.3 meters
V = velocity of the flow
g = acceleration due to gravity = 9.81 m/s²
3. Total head loss:The total head loss is the sum of the head loss due to elevation and the head loss due to friction:
h_total = h_elevation + h_friction
4. Length of pipe between upper reservoir and hill summit:The length of pipe between the upper reservoir and the hill summit can be calculated by rearranging the above equation:
L_upper = (h_total - h_hill) / (f * (V^2 / 2g))
5. Solving for velocity:The velocity can be found using the equation:
V = Q / A
where,
Q = volumetric flow rate
A = cross-sectional area of the pipe
6. Solving for cross-sectional area:The cross-sectional area can be calculated using the equation:
A = π * (D/2)^2
7. Solving for volumetric flow rate:The volumetric flow rate can be calculated using the equation:
Q = A * V
8. Substituting values and calculating:- Convert the diameter from mm to meters: D = 0.3 m
- Calculate the cross-sectional area: A = π * (0.3/2)^2 = 0.0707 m²
- Rearrange the equation for volumetric flow rate: Q = A * V
- Rearrange the equation for velocity: V = Q / A
- Substitute the values of D and A to