Pump flow rate questions (physics)

[Levinson]

I have 2 questions that are for my curiosity rather than for my needs.
I don't know much about physics and please excuse me if they sound dumb but it would be great if someone could enlighten me. Cheers.

Q1: In the picture below, would the case 2 have a higher flow rate than the case 1?
Sure there's the bottleneck but I thought the case 2 would have less friction in the wider section of the pipe, therefore, have a higher flow rate. Or would the difference in the flow rate be insignificant?

Q2: In the picture below, would the case 2 have a higher flow rate than the case 1? Or would the difference in the flow rate be insignificant?
The assumption is that they are both pushing the water to the same height with identical pumps.

 

[KStatefan]

Question 1 Case 2

Question 2 Case 1 because the is extra length of pipe.

 

[mdb_talon]

I agree with Kstate, but also think the difference should be negligible in both cases but especially in the second one.

 

[JNalley]

Question 1 Case 2

Question 2 Case 1 because the is extra length of pipe.

Wouldn't case 2 in question 2 have less head pressure, therefore create more flow? It's a negligible amount, sure, but if height from pump = pressure loss, then surely, reducing the height by raising the pump = pressure gain.

 

[Levinson]

Question 1 Case 2

Question 2 Case 1 because the is extra length of pipe.

Thanks for the answers.
For question 2, do you mean the Case 1 have more flow because it has longer pipe?

 

[KStatefan]

Wouldn't case 2 in question 2 have less head pressure, therefore create more flow? It's a negligible amount, sure, but if height from pump = pressure loss, then surely, reducing the height by raising the pump = pressure gain.

Same head pressure water level in the tanks is the same

 

[\m/reefsnmetal\m/]

My guess for question 1 would be that case 2 would at least give you the illusion of increased flow. That bottleneck will force all the water to speed up and exit at an exaggerated rate, kinda like making a water hose spray by covering part of the opening with your finger. Question 2 I would say case 2 has a higher flow rate because the pump has a shorter distance to push the water.

 

[KStatefan]

Thanks for the answers.
For question 2, do you mean the Case 1 have more flow because it has longer pipe?

I said that wrong case 2 would have the higher flow rate do the the increased friction on the longer pipe in case 1

 

[TMB]

For question 1 - there isn't enough information to answer the question. It revolves around the pump output.
If both pumps are the same (which I assume they are), and 1/2 is sufficient to carry the max output flow of the pump (meaning that it is not restricting the pump because the pipe is too small), then case 1 will flow more than case 2.
The reason is that the larger pipe has more water weight in it causing a significant increase in head pressure.
The goal with return piping is to have the pipe diameter big enough to not be restrictive, but not too large.
If you do the math, the area of the 3/4 pipe is more than double the area of 1/2. This can also be calculated into the total area of the length pipe, but the principal still stands. The difference between the two is a lot more than you might expect.

 

[Sean Clark]

Any chance that this original artwork is available as a NFT? Asking for a friend.

 

[Dburr1014]

Question 2,they are the same. Head pressure starts when the water in the pipe goes past the water level in the tank. Essentially, they are the same.
Another way to look at it, turn the pump off, level in the pipe would equal level in the tank. Anything above that is head pressure.

 

[TMB]

I agree with this ^^ on Question 2, it's the same.

 

[Sean Clark]

+1 Yes makes sense that it wouldn't add head until it was above the waterline.

 

[KStatefan]

Head pressure does not change with the diameter of the pipe.

 

[Sean Clark]

Head pressure does not change with the diameter of the pipe.

Facts.

 

[JNalley]

...

 

[Dburr1014]

No
Unless you're also talking about that extra friction of however many inches of pipe it is, it would virtually be nothing

 

[JNalley]

Same head pressure water level in the tanks is the same

I see, so the water level in the reservoir is what determines the head pressure traveling up to the tank? Not the length/vertical distance the water must travel from the pump?

 

[TMB]

ead pressure does not change with the diameter of the pipe.

Facts.

This is false, see below.

 

[Dburr1014]

I see, so the water level in the reservoir is what determines the head pressure traveling up to the tank? Not the length/vertical distance the water must travel from the pump?

Correct, if we are assuming that the length of the pipe is the same in each tank that's above the water