Pressure Drop Across a Change in Diameter

In summary: P is the pressure drop written as a lenght. Are you familiar with Bernoulli equation? https://en.wikipedia.org/wiki/Bernoulli%27s_principle scroll down until you find the paragraph about "total head"Yes, I am familiar with Bernoulli's principle. ΔP is the pressure drop written as a lenght.
  • #1
nlis12
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Greetings,

I have very little experience with fluid dynamics and I was wondering how I can calculate a pressure drop across an abrupt change in diameter of the piping used for water.

Any help is appreciated!

Thanks!
 
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I looked my notes on fluid dynamics by my professor and I found this formula

##ΔH = \frac {(V_1-V_2)^2} {2g}##

Then ##ΔP = \rho g ΔH## where ##\rho## is the density of the fluid.

I'm sorry that I can't give you any reference, but my notes are in italian... and I don't know the name of this formula in english! :(
 
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  • #3
dRic2 said:
I looked my notes on fluid dynamics by my professor and I found this formula

##ΔH = \frac {(V_1-V_2)^2} {2g}##

Then ##ΔP = \rho g ΔH## where ##\rho## is the density of the fluid.

I'm sorry that I can't give you any reference, but my notes are in italian... and I don't know the name of this formula in english! :(

Thank you very much for your reply.
But I wonder what the H stands for?
I think your equation determines the pressure drop due to a change in potential energy.
Unfortunately, my system is perfectly horizontal, or I can assume Delta H is zero, so I have no losses due to potential energy changes. (I think)

Regards!
 
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nlis12 said:
I think your equation determines the pressure drop due to a change in potential energy.
Unfortunately, my system is perfectly horizontal

No, H is a misleading letter but It doesn't refer to the heights necessarily. It's just that egineers like to work with the pressure drop as it was a length thus they divided it but ##\rho## and ##g##(that are constant).

This is the simplest explanation I can think of.
 
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1. What is pressure drop across a change in diameter?

Pressure drop across a change in diameter is the decrease in pressure that occurs when a fluid flows through a section of a pipe or tube with a different diameter. This change in diameter can be due to a pipe fitting, valve, or a change in the pipe itself.

2. Why does pressure drop occur across a change in diameter?

Pressure drop occurs across a change in diameter because the fluid has to accelerate or decelerate as it passes through the section with a different diameter. This change in velocity leads to a change in pressure according to Bernoulli's principle.

3. How do you calculate pressure drop across a change in diameter?

Pressure drop across a change in diameter can be calculated using the Bernoulli's equation, which takes into account the fluid density, velocity, and the change in pipe diameter. Additionally, empirical equations such as the Darcy-Weisbach equation can also be used to calculate pressure drop.

4. What factors affect pressure drop across a change in diameter?

The factors that affect pressure drop across a change in diameter include the fluid's density and viscosity, the pipe diameter and length, the velocity of the fluid, and the type of change in diameter (i.e. sudden or gradual).

5. How can pressure drop across a change in diameter be reduced?

Pressure drop across a change in diameter can be reduced by using a gradual change in diameter instead of a sudden one, minimizing the length of the section with the different diameter, and selecting a larger diameter pipe. Other factors such as fluid properties and flow rate can also be optimized to reduce pressure drop.

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