Making a 12V pump

[bigben2k]

Originally posted by nicozeg
Ben, pressure units are force/area, so area size is irrelevant.

Maybe I'm just not making myself clear... or I'm being stubborn.

So what you're saying is that if the hose diameter was say, 3 feet, your pump could raise/lower the water by 30 mm?

[Graystar]

Originally posted by bigben2k
So what you're saying is that if the hose diameter was say, 3 feet, your pump could raise/lower the water by 30 mm?

That's what he's saying, and he's right.

[bigben2k]

Hum...

so if cross section is irrelevant, the water would be raised/lowered by 30 mm, no matter what the diameter...

...but if the diameter is say, 1 meter, the volume of water moved would be 0.024 cubic meters, which is 24 liters, which weighs 24 kg.

If the diameter was 2 cm, then the volume of water would be 0.0000094248 cubic meters, which is 0.009425 liters, which weighs 0.009425 kg, aka 9.4 grams.

Given that the fan will produce a fixed amount of force, the diameter very much makes a difference.

Am I wrong?

[Graystar]

Originally posted by bigben2k
Hum...

so if cross section is irrelevant, the water would be raised/lowered by 30 mm, no matter what the diameter...

...but if the diameter is say, 1 meter, the volume of water moved would be 0.024 cubic meters, which is 24 liters, which weighs 24 kg.

If the diameter was 2 cm, then the volume of water would be 0.0000094248 cubic meters, which is 0.009425 liters, which weighs 0.009425 kg, aka 9.4 grams.

Given that the fan will produce a fixed amount of force, the diameter very much makes a difference.

Am I wrong?

I think you're just having a temporary short in your brain, 'cause you know this already

Pressure is not dependent on volume. Your 100 PSI air pump will fill a truck tire to 100 PSI just like it will fill a bicycle tire to 100 PSI. Just takes a lot more pumping!

That little pump will fill the city pool up to 30mm deep. It may take a couple years, but it will do it. That is the nature of centrifugal pumps. These pumps maintain a constant pressure, regardless of flow rate. That's in direct contrast to displacement pumps, which move specific volumes of water regardless of pressure (to a point, of course.)

[bigben2k]

Oh yes! Thanks!

The city pool did it for me I always have a problem remembering that one.

[bikr]

Originally posted by Graystar
I think you're just having a temporary short in your brain, 'cause you know this already
That little pump will fill the city pool up to 30mm deep. It may take a couple years, but it will do it. That is the nature of centrifugal pumps. These pumps maintain a constant pressure, regardless of flow rate. That's in direct contrast to displacement pumps, which move specific volumes of water regardless of pressure (to a point, of course.)

So if the volume of water IE diamater is more , the psi doesn't increase? so 10 feet deep in the ocean is the same psi as 10 feet deep in a common pool , interesting.. Never gave that much thought. So I see what you're saying about filling the pool.. nice job breaking it down for us.. lol --Bikr

[Skulemate]

Thanks nicozeg and Graystar for chiming in

[nicozeg]

Originally posted by bigben2k
Given that the fan will produce a fixed amount of force, the diameter very much makes a difference.

Am I wrong?

Substitute force by pressure in that sentence and you're OK

Multiply pressure by area and you get force.

That's the key concept behind hidraulic machinery; Fluids transmit pressure, not force.

[nicozeg]

I tested this pump in my system today. I was a bit scared at he begining about overheating, but it did a good job!

Here are the results compared to my regular pump, a Shott 11.10.

first number is my 12V model

Pump power in watts:_________________4/12
In system waterflow (LPM)___________2.1/4.7
CPU-Water delta temp idle____________11/9
CPU-Water delta temp BurnK7_________18/16

This is amazing! despite the huge difference in power and flowrate my temps are only 2ºC worst; not bad at all!

more important for me is noise. My other pump makes a slightly anoying rattle some days (I guess it depends on the turning direction it choose on startup), and this one was impossible to hear.

I found this quite a success, given that I started testing ready to unplug the power in case of high temps.

[Althornin]

nice work! now i wanna see you use a beefier 120mm fan motor

[koslov]

Perhaps a blower instead of a axial fan will give you more torque. It might also be a lot easier to convert.

What about something like this: http://comairrotron.com/pdfs/DD5236Series.PDF

[MadDogMe]

How long did you give it to equalise?, my rig takes forever to reach the max temp(where it falls and rises for a while then stabalises), up to an hour...

I'm not too surprised though, I ran my PC for hours without the pump running before the Alarm sounds at 45DegC. The radiator was higher than the CPU so convection happened easily though...

[nicozeg]

My cpu to ambient temps take several hours to stabilize, and sure at that time ambient temp has changed. I have an open 5 galon res that cools by evaporation instead of a rad. However, I measured cpu to water temps, that takes about 10 minutes and I waited 15.

I Dont want to make a suicide test without pump, I'm prety sure that convection is going to have a hard work trying to move the water across 2 meters of hose and a fine mesh filter, that I use to keep the block free of debris.

[Althornin]

you want a 120MM fan as a donation, to build another one?

[nicozeg]

Originally posted by Althornin
you want a 120MM fan as a donation, to build another one?

Damn! I had decided to not make another one cause I have very little free time; but if you give me a push...

[bigben2k]

Push/shove/bump/scrape...

[Althornin]

Originally posted by nicozeg
Damn! I had decided to not make another one cause I have very little free time; but if you give me a push...

email me address, i will send ya one! (i can send you a nice 120mm 120VAC fan if you think you can get that to work also, i'm not sure if you could).
Heck, i'll send you two if you make me a pump

Seriously, free shipping, and i got tons of fans (from work).

[bigben2k]

If you want to give steppers a shot, I can pull the innards of 4 dead CD-ROM drives that I picked up from NewEgg, because I needed the case.

[nicozeg]

Seriously, free shipping, and i got tons of fans (from work).

If you have plenty to choose from, here's what you have to look for:

- High amp rating
- RPM sensor wire
- Sleeve bearings

Ball bearings in the one I used seem to be stainless, but Less and simple moving parts improve long time reliability.

I sent you a pm with shipping details

Ben, I have also some old cd and floppy drives, I'm good at storing junk But conversion of that motors require more electronics skills than mine.