Effect of pressure due to change in diameter of pipe

In summary, the effect of pressure due to a change in the diameter of a pipe is significant in fluid dynamics. When the diameter of a pipe decreases, the fluid velocity increases, resulting in a drop in pressure according to Bernoulli's principle. Conversely, if the diameter increases, the fluid velocity decreases, leading to an increase in pressure. These changes can impact flow rates, system efficiency, and potential for turbulence, underscoring the importance of proper pipe sizing in engineering applications.
  • #1
Nitheeswar
27
0
The pump has an outlet size of 4 inch
1) In case 1, 4 inch pipe is connected at length of 20 m
2) In case 2, 2 inch pipe is connected using reducer
In both cases the pump outlet conditions are same( having same flow rate at a given pressure)
What happens to pressure at the end of the pipe in case 2?
 
Engineering news on Phys.org
  • #2
The pump has an outlet size of 4 inch
1) In case 1, 4 inch pipe is connected at length of 20 m
2) In case 2, 2 inch pipe is connected using reducer
In both cases the pump outlet conditions are same( having same flow rate at a given pressure)
What happens to pressure at the end of the pipe in case 2?
 
  • #3
At which end of the pipe?
 
  • #4
Nitheeswar said:
In both cases the pump outlet conditions are same( having same flow rate at a given pressure)
False.

All other things the same between the two systems:

If system2 is 20 ft. of 2 inch pipe (horizontal) and you want flow ##Q## out of it, it requires a certain pressure at the pump discharge ##P_2##.

If system1 is 20 ft. of 4 inch pipe (horizontal) and you want flow ##Q## out of it, it requires a certain pressure at the pump discharge ##P_1##, where ##P_1< P_2##.

In other words you need an effectively different pumps to achieve the flow rate in each system. Meaning impeller changes, speed changes, etc...

If you are running a positive displacement pump( aka constant volume pump) the flow rate will be equal, but not at the same pressure. The pressure adjust to whatever the systems demands at a flow with those pumps. Their pump curve is a vertical line at a fixed speed.
 
Last edited:
  • #5
Nitheeswar said:
The pump has an outlet size of 4 inch
1) In case 1, 4 inch pipe is connected at length of 20 m
2) In case 2, 2 inch pipe is connected using reducer
In both cases the pump outlet conditions are same( having same flow rate at a given pressure)
What happens to pressure at the end of the pipe in case 2?
Isn't it one out of two: either the flow rate is the same OR the pressure is the same ?

And: doesn't it matter what's at the end of the pipe ? Atmospheric pressure, something else ?

##\ ##
 
  • Like
Likes erobz
  • #6
Is this pressure difference only due to contraction and head loss in 2 inch (compared to 3 inch)?
 
  • #7
This is a duplicated thread.
 
  • #8
By mistake, it is uploaded 2 times.please delete it
 
  • #9
Is this pressure difference only due to contraction and head loss in 2 inch (compared to 4 inch)?
 
  • #10
Nitheeswar said:
Is this pressure difference only due to contraction and head loss in 2 inch (compared to 4 inch)?
Each piping system has its own pressure vs discharge relationship. They are not independently adjustable. It would also have to do with kinetic head consideration, not just head loss.
 

FAQ: Effect of pressure due to change in diameter of pipe

1. How does changing the diameter of a pipe affect fluid pressure?

Changing the diameter of a pipe affects fluid pressure due to the principles of fluid dynamics. According to the Bernoulli's principle, as the diameter of a pipe decreases, the velocity of the fluid increases, which can lead to a decrease in pressure. Conversely, when the diameter increases, the velocity decreases, and the pressure can increase. This relationship is also influenced by factors such as fluid viscosity and flow rate.

2. What is the relationship between pipe diameter and flow rate?

The flow rate of a fluid through a pipe is influenced by its diameter. A larger diameter allows more fluid to flow through the pipe at a given pressure, resulting in a higher flow rate. On the other hand, a smaller diameter restricts flow, leading to a lower flow rate for the same pressure. This relationship is described by the equation of continuity, which states that the product of the cross-sectional area of the pipe and the fluid velocity must remain constant for an incompressible fluid.

3. Can pressure change lead to pipe failure?

Yes, changes in pressure due to variations in pipe diameter can lead to pipe failure. If the pressure within a pipe exceeds the material's strength, it can cause leaks, ruptures, or complete failure. Additionally, rapid changes in pressure can create shock waves that may damage the pipe. Therefore, it's crucial to design piping systems that can withstand the expected pressure changes associated with varying diameters.

4. How does fluid type affect pressure changes in pipes of different diameters?

The type of fluid flowing through a pipe significantly affects pressure changes. For example, viscous fluids, such as oil, experience greater resistance to flow compared to less viscous fluids, like water. This means that for the same diameter change, viscous fluids will exhibit more significant pressure drops. Additionally, compressible fluids, such as gases, behave differently under pressure changes compared to incompressible fluids, necessitating different considerations in pipe design.

5. What methods can be used to measure pressure changes in pipes?

Pressure changes in pipes can be measured using various methods, including pressure gauges, manometers, and digital pressure sensors. Pressure gauges can provide real-time readings of pressure at specific points along the pipe. Manometers offer a visual representation of pressure differences using liquid columns. Digital pressure sensors can provide accurate readings and integrate with monitoring systems for data analysis and control.

Similar threads

How to maintain flowrate and pressure head in a pump?
2
Replies
38
Views
3K
Fluid Mechanics - Need Help on a Water Pipeline Project
Replies
7
Views
940
How to select a pump for a venturi injector?
Replies
8
Views
2K
Underground pump vault airflow considerations
Replies
15
Views
2K
Effect of radius on transient heat xfer from pipe in semi-infinite soil
Replies
7
Views
459
How to calculate water pressure drop in cooling tower piping system?
Replies
1
Views
3K
Flow rate needed to lift object inside a vertical pipe
Replies
4
Views
1K
Bernoulli equation and parallel pipe branch
Replies
31
Views
3K
Pressure in branching pipes when diameters are not equal
Replies
3
Views
2K
Advice on pressure drop calculation
Replies
2
Views
1K

Hot Threads

Recent Insights

Back
Top