Power Loss or gain from a fluid flow

In summary, the equation to find the power lost or gained by the flow is (volume flow)*(pressure difference).
  • #1
99percent
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0
Hi guys,

I have quick question about calculating the power lost in fluid flow.

So imagine there is a simple setup as in the attached image, where you know the mass flow in and out, pressures at inlet and outlet and the temperature at the inlet.

Is the equation to find the power lost or gained by the flow just (volume flow)*(pressure difference)?

I know that you can use this to calculate the power required for a pump using liquids, does this also work for gases?

Thanks!
 

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  • #2
Simple formula only works with incompressible fluids and low velocities .

Even if doing only simple tests or calculations then at least two properties of fluid really need to be evaluated at inlet and outlet to get energy change .

As flow regime gets more complex and compressiblity and temperature changes become more relevant then more complex calculations are nescessary .

Some fluids like vapours which might go through phase transition are even more complicated to test or analyse .

All covered in Thermodynamics and Fluid Flow theory but you'll have to study that .
 
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Likes 99percent and billy_joule
  • #3
Thanks very much for your answer and explanation!

Edit: What equation would be best to use? Would I also need to know the temperature at both the inlet and the outlet to get energy change for compressible flow?
 
Last edited:
  • #4
99percent said:
Thanks very much for your answer and explanation!

Edit: What equation would be best to use? Would I also need to know the temperature at both the inlet and the outlet to get energy change for compressible flow?

Depends on what type of flow you are actually trying to monitor . Give me a specific example and I'll get back to you .
 
  • #5
Nidum said:
Depends on what type of flow you are actually trying to monitor . Give me a specific example and I'll get back to you .

I am basically looking at a flow before and after a venturi like device, however the inlet and outlet diameters are different.

Could I just use the mass flow* (enthalpy change)to get the power? where the enthalpy is cp*T?

If I don't have the temperatures, is there a way of just working it out using the pressures?
 

Related to Power Loss or gain from a fluid flow

What is power loss or gain from a fluid flow?

Power loss or gain from a fluid flow refers to the amount of energy that is either lost or gained as a fluid (such as water or air) moves through a system. This power can be measured in terms of pressure, velocity, or volume flow rate.

What causes power loss or gain from a fluid flow?

Power loss or gain from a fluid flow can be caused by a number of factors, including friction, turbulence, changes in direction or velocity, and restrictions in the flow path. These factors can result in a decrease or increase in the amount of energy in the fluid, which can affect the power of the system.

How is power loss or gain from a fluid flow calculated?

The calculation of power loss or gain from a fluid flow depends on the specific properties of the system, such as the type of fluid, the flow rate, and the geometry of the flow path. Generally, it involves considering the forces acting on the fluid and using equations such as Bernoulli's equation or the Darcy-Weisbach equation.

What are some real-world applications of power loss or gain from a fluid flow?

Power loss or gain from a fluid flow has many practical applications, such as in hydraulic systems, pumps, turbines, and pipelines. It is also important in understanding the efficiency of engines and other mechanical systems that involve fluid flow.

How can power loss or gain from a fluid flow be minimized?

To minimize power loss or gain from a fluid flow, it is important to design systems with smooth flow paths and minimize any restrictions or obstructions in the flow. Additionally, using materials with low friction and choosing the right type of fluid can also help to reduce power loss or gain.

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