# Pump pressure and pipe diameter

• wasija
In summary, the relationship between pressure and hose diameter is not a straightforward one, as it also depends on the pump's curve and the system curve. The shape of these curves can result in varying pressure readings, velocities, and flow rates for different hose diameters, even with the same pump and material. Additionally, the location of the pressure gauge can also affect the readings.
wasija
I am a little confused about the pressure and hose diameter relationship. Let's say I have a pump pumping at a given pressure; I connect a hose of a certain diameter and attach a pressure gauge to the other end of the hose and get a pressure reading. Now let's say if i conduct the same experiment with a smaller diameter hose and measure the pressure. Assuming the hose length is the same and hoses are made of same material. How would the pressure reading, velocity and flow rate vary.
Thanks

Welcome to PF.

This is an interesting and complicated question, but starts off with an assumption that isn't necessarily true:
wasija said:
Let's say I have a pump pumping at a given pressure...
Pumps don't have a single pressure, they have curves:

The pressure depends on the pump but also how much restriction there is in the piping. The piping restriction is represented by a parabolic curve called the "system curve". So:
I connect a hose of a certain diameter and attach a pressure gauge to the other end of the hose and get a pressure reading. Now let's say if i conduct the same experiment with a smaller diameter hose and measure the pressure. Assuming the hose length is the same and hoses are made of same material. How would the pressure reading, velocity and flow rate vary.
See this pump curve with two system curves on it:

http://www.webbpump.com/_build/images/pump/technical-support/sect_a9_01.gif

The dark system curve represents your first scenario. The dashed curve represents your second scenario. Where the system curve meets the pump curve is what determines the flow and pressure at the pump.

Note that the shape of the pump curve and system curves can produce different results for different systems. You might have a system where you are on the high, flat part of the pump curve, so changing the system curve (by changing the pipe) may have no impact on the pressure but a big impact on flow. Or it could be the other way around.

Fuller treatment here: http://www.engineeringtoolbox.com/pump-system-curves-d_635.html

Joe591
I connect a hose of a certain diameter and attach a pressure gauge to the other end of the hose and get a pressure reading

Just one comment - if the other end of the hose exits to atmosphere, and that is where your pressure gauge is attached, then you should read nearly the same pressure regardless of size of hose. The pressure head at exit is always Patm.
Put your gauge closer to the pump end.

## 1. What is the relationship between pump pressure and pipe diameter?

The relationship between pump pressure and pipe diameter is known as the Bernoulli's principle. According to this principle, as the diameter of a pipe increases, the pressure decreases. This means that for a given pump pressure, a smaller diameter pipe will have a higher pressure compared to a larger diameter pipe.

## 2. How does pump pressure affect the flow rate of a fluid?

Pump pressure is directly proportional to the flow rate of a fluid. This means that as pump pressure increases, the flow rate of the fluid also increases. Conversely, if pump pressure decreases, the flow rate will also decrease.

## 3. Can pump pressure be increased by increasing the pipe diameter?

No, increasing the pipe diameter will not directly increase the pump pressure. However, a larger diameter pipe will allow for a higher flow rate at a given pump pressure, which may be perceived as an increase in pump pressure.

## 4. What is the effect of pump pressure on the velocity of a fluid?

Pump pressure has an indirect effect on the velocity of a fluid. As pump pressure increases, the flow rate increases, which in turn increases the velocity of the fluid. However, the velocity is also affected by other factors such as the viscosity of the fluid and the pipe diameter.

## 5. How does changing the pipe diameter impact the efficiency of a pump?

Changing the pipe diameter can have a significant impact on the efficiency of a pump. A larger diameter pipe can reduce friction and pressure losses, leading to a more efficient pump. However, if the pipe diameter is too large, it can also result in a decrease in efficiency due to increased surface area and weight of the pipe.

• Mechanical Engineering
Replies
9
Views
739
• Mechanical Engineering
Replies
4
Views
2K
• Mechanical Engineering
Replies
38
Views
2K
• Mechanical Engineering
Replies
8
Views
1K
• Mechanical Engineering
Replies
6
Views
2K
• Mechanical Engineering
Replies
12
Views
2K
• Mechanical Engineering
Replies
20
Views
8K
• Mechanical Engineering
Replies
33
Views
2K
• Mechanical Engineering
Replies
7
Views
2K
• Mechanical Engineering
Replies
2
Views
630