How does it work? Vol 4: Eductors

[Shallowwaters]

Thanks LittleP
Does somebody make a commercial version for a SeaSwirl?

 

[ScottM]

one thing to think about.
I run them on my 92g corners on T4 pumps. one per pump. the flow from the T4 is just too much for the overflow to handle. if i put a penductor on, i reduce my overall flow while significantly increasing the inside tank flow. this reduced turnover is just enough to allow my megaflow to work properly.
I get a working overflow and a ton of flow inside the tank.

I love them.

 

[Moe_K]

Somebody wanna differentiate between an eductor and a penductor, please?

 

[ScottM]

i believe that the eductor draws additional water/ air from a single point. like a mazzi injector and a penductor draws it from multiple points. matt......

 

[littlep93056]

Scott was the one who told me how good they worked ,so I order them & used them till I could save the money for Tunzes

 

[Greg Hiller]

>Of course, conservation of mass and volume apply,<

I'm glad to here that!!

Of course the conservation of energy applies as well. By this I mean that what these devices do is trade low volume high flow (the kind that can strip the tissue off your Acropora!) for high volume low flow (more natural on a reef).

 

[Matt L.]

Eductor versus Penductor

i believe that the eductor draws additional water/ air from a single point. like a mazzi injector and a penductor draws it from multiple points. matt......

I could find no definition of a penductor in Engineering Fluid Mechanics (5 Ed.) by Roberson and Crowe, nor in Hydraulic Engineering by Roberson, Cassidy, and Chaudhry. This doesn't mean that there's no such thing -- it just means any of my reference texts don't have the term in it. It is also interesting to note that I cannot find the term penductor in the Merriam-Webster online abbridged disctionary, which leads me to believe that it is a lay or trade term.

For everyone's information, an eductor is often referred to as a jet pump. From Hydraulic Engineering by Roberson, Cassidy, and Chaudhry:

Jet pumps derive their pumping action from a high velocity jet of fluid that then becomes entrained with the fluid it is pumping. The high momentum of the jet is converted to pressure in a diffuser. Liquid jet pumps are sometimes called eductors. Figure 8-40 shows the essential features of a jet pump. There are many advantages of the jet pump, for example, it is self priming; it has no moving parts; and it can be made from any machinable materials, glass, and fiberglass. The main disadvantage of the jet pump is its relatively low efficiency. The entrainment process inherent in its operation produces large head losses that account for this low efficiency. Despite its low efficiency, it has several uses, including

1. Deep-well pumping
2. Bilge pumping on ships
3. Providing circulation in rearing tanks of fish hatcheries (absence of moving mechanical parts do not injure fish)
4. Chemical process mixing
5. Pumping out wells, pits, sumps where there is an accumulation of sand and mud

 

[NateHanson]

I thought Penductor was the proprietary name for an eductor made by Penguin.

 

[Matt L.]

I thought Penductor was the proprietary name for an eductor made by Penguin.

You know, that's probably it!

Matt

 

[littlep93056]

Nate , take it from people who use them or have used them that they are worth the short money they cost ,end of story

 

[NateHanson]

I'm not disputing that they work, I'm just trying to make sense of the claims that people make about them, and also want to evaluate whether they could work on smaller pumps. I can tend to be a bit skeptical, so forgive my questioning. I'm not saying they don't work, I just want to know why they work, and how well - in quantitative terms, if possible.

Nate

 

[littlep93056]

What do you use for a return pump ?

 

[NateHanson]

mag 5.

I've got a mag 7 closed loop pump too.

 

[dedfish]

Also keep in mind the size of these things. I know some eductors are six inches long. I know that's not big by some peoples standards , but I wouldn't want something that big in a small tank. I think the penductors are a bit smaller.

 

[Moe_K]

Nate , take it from people who use them or have used them that they are worth the short money they cost ,end of story

That defeats the purpose of our discussion.

 

[~Flighty~]

I'm not disputing that they work, I'm just trying to make sense of the claims that people make about them, and also want to evaluate whether they could work on smaller pumps. I can tend to be a bit skeptical, so forgive my questioning. I'm not saying they don't work, I just want to know why they work, and how well - in quantitative terms, if possible.

Nate

If you want to try one out , I have a couple extra. The effect is really hard to predict, but easy to test. Even if you just hold the device up against a return. They are 1" and 3/4" male threaded (I think)

 

[Matt L.]

I think what Nate's trying to say is that for the pump you need to get the flow pattern with an eductor, you could approximate it (or maybe even improve it) with simple discharges for that pump. Because you lose so much energy and head on the pump trying to use the eductor which you get back in your tank (less efficiency losses), it might be comparable to just use the pump without the eductor and a different injection manifold.

Matt

 

[NateHanson]

That's basically my question Matt. There's no free lunch, right? The results with and without an enductor on the same pump can't be quantitatively different. I like the explanation that you're trading velocity for somewhat greater flow when the appropriate pressure-rated pump is used. And Scott makes a good point that it trades flow thru the sump for more flow within the tank, thus requiring less overflow capacity.

Nate