This problem involves applying Bernoulli's equation and the continuity equation to determine the pressure in a pipeline where both diameter and elevation change, neglecting losses.
Given:
- At entry (Section 1):
- Diameter, D1=0.15 m
- Pressure, P1=8.2 bar
- Flow rate, Q=7.5m3/min
- Elevation, z1=0 m (reference level)
- At the location (Section 2):
- Diameter, D2=0.3 m
- Elevation, z2=3 m (3 m above entrance)
- Fluid is water, so density, ρ=1000kg/m3
- Acceleration due to gravity, g=9.81m/s2
We will use the following equations:
- Flow Rate: Q=A⋅V, where A=4πD2
- Bernoulli's Equation (neglecting losses):
P1+21ρV12+ρgz1=P2+21ρV22+ρgz2
Step 1: Convert given values to SI units.
- P1=8.2bar=8.2×105 Pa
- Q=7.5m3/min=607.5m3/s=0.125m3/s
Step 2: Calculate the cross-sectional areas at both sections.
- Area at Section 1:
A1=4πD12=4π(0.15m)2=4π×0.0225≈0.017671m2
- Area at Section 2:
A2=4πD22=4π(0.3m)2=4π×0.09≈0.070686m2
Step 3: Calculate the flow velocities at both sections using the flow rate.
- Velocity at Section 1:
V1=A1Q=0.017671m20.125m3/s≈7.0735m/s
- Velocity at Section 2:
V2=A2Q=0.070686m20.125m3/s≈1.7684m/s
Step 4: Apply Bernoulli's equation to determine the pressure at Section 2.
Rearrange Bernoulli's equation to solve for P2:
P2=P1+21ρ(V12−V22)+ρg(z1−z2)
Substitute the known values:
P2=(8.2×105Pa)+21(1000kg/m3)((7.0735m/s)2−(1.7684m/s)2)+(1000kg/m3)(9.81m/s2)(0m−3m)
P2=820000+500(49.0074−3.1272)+(9810)(−3)
P2=820000+500(45.8802)−29430
P2=820000+22940.1−29430
P2=842940.1−29430
P2=813510.1Pa
Step 5: Convert the final pressure to bar.
P2=105813510.1bar≈8.1351bar
The pressure at the location is 8.14bar.
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