Intresting flow question

[Canadian Man]

So let's say you have a powerhead like a MJ 1200.
Position it in a tank. Now when the powerhead is running, would it not make sense to count the flow comming out of the output nozzel as well as the flow comming through the intake?

This is probably a bad example and a better one may be a standard sump set up on a tank. The return is 600gph and the flow going into the overlfow box is 600 gph.. should the intake count for anything?

I realize that it's not as focused as the output of a pump but it is current and it should count for something. If you have 1000gph comming out of a pump you also have 1000gph going into the pump. RIGHT? :confused:

Let's hear your thoughts :biggrin:

[StirCrazy]

I am not sure I get where you are going with this? do you mean to count it in overall tank flow or what?

Steve

[Aquattro]

Jon, I don't think you can count the flow going into the pump. Even on the stream, there is very little water movement until it gets within 1/4" of the intake. In a ratio of water movement out compared to in, the in would become insignificant.
To get an idea of the flow, drop some spirulina flake near the bottom of the PH....it won't do much until it's almost in the pump.

[Canadian Man]

Not really going anywhere with it just something I was thinking about :rolleyes: :confused:

So Big fat NO?

[Aquattro]

So Big fat NO?

Right.......BFN :razz:

[trilinearmipmap]

On a related note...

1. There was some recent reef central discussion on eductors, essentially a pump forces water into a tapering nozzle, the increase in flow velocity through the tapered nozzle brings in water from the sides much like a venturi works. I am wondering if anyone has tried adding a small eductor onto a powerhead.

2. I wonder whether flow would be better if, rather than just a powerhead, the intake of the powerhead was from some pipe/tubing 2 or 3 feet long, besides just flow from the powerhead would this not add to overall tank circulation by moving water from point A to point B better?

[Aquattro]

Re; the eductor, no, it hasn't been used over a powerhead. It requires a MAG 18 minimum to rn the thing. However, if you had the pump already, the compact eductors were only about $25 US

[StirCrazy]

Hmm after reading this a couple times I realized what you were getting at :eek: slow day today hehe..

anyways think of it as a pump "moves" a specific amount of water.. so a magdrive 12 will move 1200gph (in ideal conditions).

hmm I better stop befor I confuse myself here :mrgreen:

I know what you mean but I also say no. :smile:

Steve

[Canadian Man]

Hmm after reading this a couple times I realized what you were getting at :eek: slow day today hehe..

anyways think of it as a pump "moves" a specific amount of water.. so a magdrive 12 will move 1200gph (in ideal conditions).

hmm I better stop befor I confuse myself here :mrgreen:

I know what you mean but I also say no. :smile:

Steve

I thought you of all people would agree with me Steve :razz: :lol:

[Canadian Man]

Although if the pump was big enough and the aquarium was small enough then the intake would actually account for something.
Let's say a 10g aquarium with a mag 12! the intake woudl in that case actually act as a some flow increase because of the small watervolume.

You guys are thinking on too large of a scale :mrgreen:

[StirCrazy]

ok,I didn;t want to confuse myself but sence you had to go there! :eek: I will play both sides of the coin.. if you change the intake so it is very small (ie. get rid of the suction strainer and put a extended pipe on it. it will help to creat a current in the tank. the problem is because of the chareristics of water flow it will not be as defined as the output. so you might be creating a 1200gph suction but as far a a current effect you might only notice the equivalance of say 200gph. see whare I am going?

yes you are sucking 1200 gal and throwing out 1200 gal but the main effect you will notice from the suction is a "psudo direction" of the output. ie. setting up a whirlpool in the tank :mrgreen:

Steve

[Bob I]

[quote]I realize that it's not as focused as the output of a pump but it is current and it should count for something. If you have 1000gph comming out of a pump you also have 1000gph going into the pump. RIGHT? :confused:

I guess it is a slow day. The answer would involve a lot of physics, which is something I know little about. But as far as flow goes, you only need to ask any Anemone that has been sucked into a powerhead about this. :mrgreen:

[Bartman]

If you plug the input on the 1200gph pump do you still get 1200 gph output? :smile:

I don't think it matters where the water comes from (input, eductor, etc) or where it goes to (nozzle, return, etc) I think you can only count the 1200gph total water movement. :cool:

[Aquattro]

No, pump curves are calculated on the output of the pump only. The water going into the pump can be counted, however, since it is drawing from the entire body of water, the water movement generated is insignificant. Essentially water velocity is approaching zero and therefore should not be calculated in a flow equation.

Pretty muddy, huh?