Return pump sensor placement

[bescher]

Since we're trying to measure output if the pump going back into the display where would we mount the sensor.
i have a sump inside my stand a 1in goes up into a 90 degree elbow out to a another 90 and up.
Wiuld I place the sensor between the pump and the first 90 elbow or after the second and halfway up the back of the tank.@wouldnt the second way give me a better reading of the output going back into the tznk

[zombie]

Either position will give you the same reading. Use whichever position is easier to get to since the sensor should be removed and cleaned periodically

You might be an engineer if...You have no life and can prove it mathematically.

[bescher]

Either position will give you the same reading. Use whichever position is easier to get to since the sensor should be removed and cleaned periodically

You might be an engineer if...You have no life and can prove it mathematically.

So we wouldn't care what the flow is if we put it into the stand rather then adpfte the two elbows? Just curious why not

[zombie]

Flow rate is constant across the entire return line based on the physics of fluid dynamics. The pressure will be different at the two locations and the effect of turbulence can make a minor impact in locations in close proximity the return or fitting because the sensor assumes laminar flow in its readout, But were talking like 1 or 2 percent error here so realistically you won't see a difference in flow based on placement.

You might be an engineer if...You have no life and can prove it mathematically.

[bescher]

Flow rate is constant across the entire return line based on the physics of fluid dynamics. The pressure will be different at the two locations and the effect of turbulence can make a minor impact in locations in close proximity the return or fitting because the sensor assumes laminar flow in its readout, But were talking like 1 or 2 percent error here so realistically you won't see a difference in flow based on placement.

You might be an engineer if...You have no life and can prove it mathematically.

Hmm I had read or rather watched a video from marine depot I believe on the effects of elbows and length and so on and I PRESUMED that since you want a accurate asssesement of what is actually happening at the output you would want it close to that

[zombie]

You misunderstood the premise of that video. Length, height, and number/type of fittings affect the head pressure that works against the pump to create flow. Those things will affect the amount of flow that your return is capable of generating, but it will not affect the reading from the flow sensor.

If you are familiar with electrical circuits, think of voltage as the rated flowrate of your pump, resistance as the equivalent head loss from height length and fittings, and current as your flow rate. The head acting like a resistor controls the flow rate, But just like current in an electrical circuit, the flow rate is constant at any point that you measure it.

You might be an engineer if...You have no life and can prove it mathematically.

[bescher]

You misunderstood the premise of that video. Length, height, and number/type of fittings affect the head pressure that works against the pump to create flow. Those things will affect the amount of flow that your return is capable of generating, but it will not affect the reading from the flow sensor.

If you are familiar with electrical circuits, think of voltage as the rated flowrate of your pump, resistance as the equivalent head loss from height length and fittings, and current as your flow rate. The head acting like a resistor controls the flow rate, But just like current in an electrical circuit, the flow rate is constant at any point that you measure it.

You might be an engineer if...You have no life and can prove it mathematically.

im definitely not a engineer
so please bear with me. If these things affect the flow rate isn't that what the sensor reading is doing? It is reading the flow rate? So if anything slows that rate down I want to know bout it?
Is this correct or are you saying there is no actual affect and the flow rate is the whether the measurement is before or after the obstructions that change the rate

please I'm not trying to be anything but trying to understand

[zombie]

Head determines the flow rate. Once that head has been established, the flow rate is the same at any point within the pipe.

This is based on the "equation of continuity"

https://www.princeton.edu/~asmits/Bi...ontinuity.html


Since the flow sensor is the same diameter regardless of where it is placed, the velocity has to be the same at any point in the pipe and therefore so does the flow rate.



You might be an engineer if...You have no life and can prove it mathematically.

[zombie]

Good video on the subject.

http://study.com/academy/lesson/flui...-equation.html

You might be an engineer if...You have no life and can prove it mathematically.

[bescher]

Good video on the subject.

http://study.com/academy/lesson/flui...-equation.html

You might be an engineer if...You have no life and can prove it mathematically.

I understand watched the video thanks

[Frogfish]

I don't have the sensor and have not looked into them, but putting the sensor in a vertical line would probably be best as well. This would minimize any effects of air pockets trapped in a horizontal line.

On the elbow vs. pressure discussion. Elbows and piping etc all have an affect on pressure which in turn affects flow rate of a centrifugal pump, which most return pumps are. However, since the piping system isn't changing that affect is constant hence your flow rate at any point in the pipe will be the same.

If there is a ball valve in your system and you adjust it, this will affect the pressure in your system and hence flow.

[bescher]

I don't have the sensor and have not looked into them, but putting the sensor in a vertical line would probably be best as well. This would minimize any effects of air pockets trapped in a horizontal line.

On the elbow vs. pressure discussion. Elbows and piping etc all have an affect on pressure which in turn affects flow rate of a centrifugal pump, which most return pumps are. However, since the piping system isn't changing that affect is constant hence your flow rate at any point in the pipe will be the same.

If there is a ball valve in your system and you adjust it, this will affect the pressure in your system and hence flow.

Makes sense thanks