Questions about pressure, head and pump choice

[Stigma]

Hey,

The scenario
I'm trying to figure out how much head I need on the pump to run my rather oversized coolant loop. I'd say it consists of maybye as much as 10meters (thats ca 33feet for you non-metrics) of 3/8" ID tubing, and several water blocks, say 5-6 for arguements sake, as well as a small HX.

The difference in height between the lowest and highest point in the loop is about 1,5 meters. The idea is to have the pump at the lowest end, and a compensating water-tank at the top. The tubing snakes its way up and down a few times (but not much) going from one end to the other if that makes any difference.

As far as flowrate goes, I am not really that concerned because the HX will suck out the heat so effectively (it remains at ca 12celcius constantly) that I think I will have all the cooling I need as long as there is atleast some circulation.

The suggestion

What I was hoping might work was an Iwaki MD-20 RZ (high-pressure version):
http://www.dtpetsupplies.com/catalog...re-rated-pump/
Note that the specs vary a bit apparently. I think it may be the difference between 50hz and 60hz power used on it. I will be using 220v/50hz. Anyway, the head is somewhere between 4,9meters and 22,6 feet and with Max system pressure 14.22 psi. Its hard to visualize pressure from that number for me, but it seems significant. perhaps someone else can interpret it better than I.
http://www.iwakipumps.jp/e_products/...D_E0015_11.pdf

Not to go off-topic, but if anyone knows for sure why there are two values for the specs like head, please let me know so I can stop speculating

What do you guys think. Think this can do the job? the next step up would be the MD-30 RZ (high pressure version), but that one is quite a monster. I'd prefer to keep from going totally overkill if I can

Please post your thoughts and advice.

edit:
I added a pic of the actual label on the pump to illustrate what I'm talking about when I say there are two values for many of the specs. I'd love it if someone could tell me how to interpret that.

[tw33ter]

I believe it has to do with which voltage you power it up with. At 220v, you get 4.9, and at 240v, you get 6.9.

[IanY]

Are you sure that the pump has enough pressure? From what I understand, the pump is good for 7-8 meters. You are planning an over 10 meter/metre loop with many blocks.

[Stigma]

Are you sure that the pump has enough pressure? From what I understand, the pump is good for 7-8 meters. You are planning an over 10 meter/metre loop with many blocks.

I don't know, thats why I'm asking. You have to remember that the max head is how many meters the pump can pump it straight up against gravity. For my application the worst gravity push it will have to overcome is only ca 1,5meters. I don't claim to be an expert, but i think that if you just try to match the max head rating to the lenght of tubing you will be using, then you will likely end up with a very oversized pump. Or did you get your 7-8meters number from some other source? If thats the case I would like to read it and see if I can glean anything from it.

Also, you have to take into account the effect that makes water and some other liquids molecules inside a tube stick together. I don't know the technical name for it, but I am talking about the effect that you use to drain gasoline from a tank for example. if you just suck a little up and fill the hose, then make sure that the exit-hole of the hose is lower down compared to the entry-hole, and then the fluid seemingly impossibly flows "up-hill" from bottom of the tank without anything actually pumping it, and can thus drain the entire tank using nothing but gravity-power.

I know that this effect must help the pump a lot. The gravity-pull of the water going down literally helps pull up the water going up. I just don't know enough details to calculate how much power I will actually need. I am by far not an expert on pumps.

-Stigma

[Martinm210]

I think I've got the Iwaki pumps in my estimator. You might consider switching the tubing out to 1/2" ID though, 3/8" will start adding up with that much length, and the blocks all depend on which ones when one high restriction block could equal a dozen low restriciton types.

[IanY]

Or did you get your 7-8meters number from some other source? If thats the case I would like to read it and see if I can glean anything from it.

Buddy,

If it says 22.6 feet, then its in the ballpark of 7 to 8 meters. I got mynumber from memory.

[Stigma]

I think I've got the Iwaki pumps in my estimator. You might consider switching the tubing out to 1/2" ID though, 3/8" will start adding up with that much length, and the blocks all depend on which ones when one high restriction block could equal a dozen low restriciton types.

You do have the iwakis in the spreadsheet yea, but they are all marked as untested. Will the calculation still be somewhat trustworthy anyway?

EDIT: I input some ballpark data into the spreadsheet and got 4,7LPM (1,24GPM) for the Iwaki MD-20Z. Strangely enough I actually got better results when inputting an alphacool AP1510 (24v) instead. I have one of those lying around. I find it hard to believe that the Iwaki wouldn't be more powerful though. Are the calculation data for the Iwaki trustworthy even though it says error on the spreadsheet for it?

-Stigma

[Stigma]

Buddy,

If it says 22.6 feet, then its in the ballpark of 7 to 8 meters. I got mynumber from memory.

Yea, thats right. It would equate to about 7 meters. That wasn't really what I disagreed with though. I don't think you can meaningfully use the max head specification to tell you how many meters of tubing you can use it for. I could be wrong of course *shrug*

-Stigma