Will the CFM be the same in straight and bent pipes?

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In summary, the discussion is about two pipes with different shapes and restrictions. The straight pipe has a higher flow rate compared to the bent pipe with 90-degree corners and a concave surface. This is because of the equivalent length concept, where bends and restrictions increase the equivalent length and decrease the flow rate. The velocity may increase, but the overall flow rate is lower. If the two pipes have the same length and pressure drop, the straight pipe will have a higher flow rate.
  • #1
ISX
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So basically we have 2 pipes, one is straight, one has 90* bends in it and a concave surface to hit and stir things up even more. X shows that all the widths are the same everywhere, so it's not like the pipe is getting bigger or smaller in diameter. We have 20psi of pressure, will the CFM out of both pipes be the same?

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If the actual lengths of the two are the same, and the dP across them is the same, then the straight pipe will have a higher flow. There is something called an "equivalent length" for any pipe or tube with bends and other restrictions. It is this equivalent length that has to be the same in order for the two pipes to flow the same. Bends and other restrictions increase the equivalent length.
 
  • #3
Alright so let's say they are the same length and everything and therefore have the same flow, why is it that they do have the same flow when the bent and screwed up one has to fight the 90* corners? Wouldn't the turbulence cause a reduction in flow rate?
 
  • #4
ISX said:
Wouldn't the turbulence cause a reduction in flow rate?

Of course. There might be an increase in velocity, but the flow-rate itself, during restriction, is lower.
 
  • #5
Hmmmm, so let's say I turn the pressure on to both pipes and hook it to a tank and 10 seconds goes by and I turn it off, would there be the same amount of air in both tanks?

The reason I ask is because you say flow rate goes down but velocity increases.. Are those 2 variables just like volts and amps? As in, if one goes down the other increases and you still have the same amount of watts. Or in this case, velocity goes up flow goes down but you still end up with the same volume..? Or is this wrong?
 
  • #6
ISX said:
Alright so let's say they are the same length and everything and therefore have the same flow, why is it that they do have the same flow when the bent and screwed up one has to fight the 90* corners? Wouldn't the turbulence cause a reduction in flow rate?
I'm afraid you read me wrong. If they have the same length and the same pressure drop (ex: they are both connected to the same tank and discharge to atmosphere so the pressure drop is the same) then the STRAIGHT pipe flow rate will be HIGHER. So yes, the additional restrictions in the line will cause a reduction in flow rate.
 

Related to Will the CFM be the same in straight and bent pipes?

1. Will the flow be the same in different environments?

The flow of a substance can be affected by various environmental factors such as temperature, pressure, and humidity. It is important to take these factors into consideration when conducting experiments or making predictions about flow.

2. Does the flow depend on the type of substance?

Yes, the flow of a substance can vary depending on its physical properties such as viscosity, density, and surface tension. Different substances will have different flow behaviors.

3. Will the flow be the same in different systems?

No, the flow of a substance can also be influenced by the type of system it is flowing through. For example, the flow of water through a pipe may be different from the flow of water through a river due to differences in the system's geometry and other factors.

4. Can the flow change over time?

Yes, the flow of a substance can change over time due to various factors such as changes in temperature, pressure, or the physical properties of the substance itself. It is important to monitor and account for these changes when studying flow.

5. How can we predict the flow in a given system?

There are various mathematical models and equations that can be used to predict flow in a given system. However, these predictions may not always be accurate as there are many variables that can affect flow. Experimentation and testing in the specific system is often necessary to determine the actual flow behavior.

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