Whats the diff between the high and low flow rate gemini?

[Highlander944]

hey billa... i specifically did not bring up 'real flow' I simply asserted that the channel design can 'move your curve' so that lower flow rates can be used.

Now without getting into a knock out drag out, this is FACT. Please don't get caught up in our last discussion, some channel can be used to increase the surface area in contact with the water and thus increase cooling efficiency. I said nothing more, nothing less, that is FACT. you need to be less quick to pounce

your post supports what I have said. why would the same flow rate yield different results? ohh that's right, different channels.

 

[BillA]

hey fellahs, don't get your panties bunched up

my opinion ?
I would guess that a 'high end' flow rate might be 1.5gpm
typical probably 0.75 and below, sometimes much below

have no argument whatsoever with a wb design based on a realistic flow rate
and when I posted the above I had to choose between 0.5 and 1.00 (as I don't normally record at 0.75)
it is my experience that higher flow results in more cooling,
but that does NOT mean that such is a worthwhile endeavor

Hoot
your pump is not puny, your tests show it works just fine

Peter
what are you pi*sing about ?
you said "given a slow flow, what works better?"
so I put up some data, for all to see - not only you
now I don't quite understand what you are saying about that data . . .

1gpm (60gph) is not so high a flow rate
and 45 or 46 is lower than 47 or 49, no ?

indeed I do understand your channel/fin design concept,
but I would suggest that there is a bunch of (disclosed) real data that PROVES there are other vaible cooling designs,
and is suggestive (but not conclusive) of even the superiority of other approaches

yes, yes; your's will cool, and well - no argument here 'bout that
its the 'how well' that's being discussed

be cool

 

[DodgeViper]

I have the Gemini High Volume Water Block. Before putting my system together I measured the flow. With an Eheim 1250 pump (317GPH) I got 190GPH with a 12" head or rise. When the High Volume Water Block attached with a 12" head or rise this same pump only delivered 60GPH through the High Volume Water Block. Someone care to explain.

 

[BillA]

the short answer is that you got more through that wb than if you'd had the low flow one
(how much more ???)

at one time I thought I had a link to a page with the Ehiem pump output curves
but I seem to have lost it - anyone ?

I don't have a 1250, but have been told there is a pump curve on the box

you should be able to (kind of) back out the wb's 'apparent' flow resistance from that curve

or perhaps Peter will tell you

(I guess that was without a rad inline ? what size hose ?)

be cool

 

[DodgeViper]

The rad was not attached at the time. I used 1/2" silicon hose and I changed out the 3/8" fittings on the block to 1/2".

 

[BillA]

pretty nice layout, only one ellbow (set pump on end ?)

I'd say your 1gpm (w/o rad) is ok, your pump's head capability is being dropped across the wb, which is where the (head loss causing) turbulence will do some good

don't sweat it, that's all that wb is gonna do; a 1060 is NOT worthwhile
(if you get the pump curve and go to the rad article to read the heater core head loss at say 0.75gpm, you can guess at the wb's flow resistance at 0.75gpm)
["High Volume" is relative, eh ??]

be cool

 

[Hoot]

It's funny. I was pondering this just last night, while I was sitting, peering down into the inlet barb of the Gemini. Peter, wade in on this if you want. If you look down into the inlet barb, what do you see? You see a 9/32" hole that is partially obscured by the initial starting point of the spiral. I was tempted to grab my moto-tool and grind it out of the way as much as possible without breaking through into the next layer of the spiral. I'm at work, so I don't have a camera to show this, but here is a rough drawing of how I recall it to look. Forgive my inaccuracy, but it should get the point across.

Hoot

 

[BillA]

ah, these sneaky manufacturers will do ANYTHING to make a 'low flow' wb

on another thread I posted the Cooltech low flow solution

now we're gonna have to figure out who thought of this spiffy idea first

be cool

EDIT: oops, oops - too quick to pounce , again
Hoot, was that the 'low' or 'high' flow version ?

for ref the Coolhech is their Waterblock WB75 rev1.1 (per JoeC)

 

[mustangman]

Hoot
I'm glad to hear that I'm not the only one to have considered this and also that this isn't just a defect in my block. I may give this a shot later today.
I made one other maod to the block, if you can call it a mod, I took some super glue and put it around the edges where the plexi and copper meet and also a little pipe dope around the threads of the center barb as it was leaking. This cured my leaks that popped up after installing into my system. I did a twenty four hour leak test outside the case without problems but once inside it turned into a geiser.
Btw thanks to Peter for excellent customer service and fast shipping! I ordered last Thursday and had it Saturday this is the best turn around I have ever had on any waterblock.

 

[DodgeViper]

Hoot, my inlet on the HVWB was the same way as seen in your drawing. I was real close of removing the copper that was blocking the inlet as well.

 

[mustangman]

I can't decide if I should take out some of the material or not. By removing some of it the flow should increase some but I don't know if it would be enough to justify the time spent. The other thing that has kept me from doing it is that it seems that this may decrese the turbulence some. What do you guys think? Is my thinking flawed?

 

[Highlander944]

One the 'real flow' subject. I do not have the equipment required to actually measure and plot the flow resistance of the blocks. Admittedly, my qualification of the high flow vs. low flow is somewhat subjective. What I did in designing these two blocks is match cross sectional area. The area of the 3/8" barb is about .06", the area of the channel is about .075" for the high flow block. Thus the block will not introduce significant flow restrictions. The area of low volume block is about .037. So the low flow block will introduce back pressure.

Now on the topic of the 'overlap' under the barb. The barb inside diameter is about .250". The channel width is .1875 so there will have to be some 'overlap'. I will try to experiment a bit with this to see if I can 'funnel' the water into the channel better.

mustangman - I'm very sorry you saw any leak at all on your block! We really do perform a 25-30psi leak test for about 20-30seconds on each and every block. I will look into our assembly procedure and see if there is any way for us to improve upon it. I had not considered 'gluing' the fittings onto the top, however if our customers don't want to remove the barb that would seem more secure.

I am curious about the pump ratings. In a closed loop system, it would seem that the head pressure begins to 'go away' I wonder about this because although the pump is pushing water up, that water that is pushed up is also pushing down on the inlet. It would seem logical that there is some benefit from this effect. So how did you measure the flow?

As far as flow rates through the block, I am interested to know if you tried simply putting the fitting on the tube and measuring only the flow through the fitting? Is it the reduction in diameter do to the fitting that caused your reduction in flow or the block itself?

---

If anyone would like to modify the inlet area here's a little advice. There is a silicon sealant adhesive applied between the copper block and the polycarbonate top. I would use a vice to shear the top off. Do not use anything to pry the top off as copper is very soft and this will surely score the material...

Peter.

 

[mustangman]

Highlander
Thanks again for the great customer service. I didn't mean to make it sound like I was pi**ed off or anything there are always things that could have caused it to happen, it may have been something that I did I don't know for sure. I just thought that I would put that out incase anyone ran across the problem whether it is the gemini or any of the others with plexi tops. Just a quick fix.
The system survived, I caught it before I booted up. I dried everything with a lint free cloth and then aimed a window fan at it for several hours.

 

[Hoot]

-snip-

Hoot, was that the 'low' or 'high' flow version ?

The obstruction manifests in both blocks, exactly the same. In the case of the standard flow block, given the channels lower cross sectional area, I'm not so sure reducing the obstruction will amount to much. In the high flow rate model, I think it would help reduce the flow resistance somewhat. Whether that amounts to any performance increase in this model, is another question.

Hoot

 

[BillA]

being the obsessive/compulsive type, I do these kinds of mods on everything (eventually, after initial testing)
but do agree that the effect is not (normally) individually significant - if even measurable

at high flow rates perhaps; at 1gpm and below - forget it

be cool

 

[Aesik]

being the obsessive/compulsive type, I do these kinds of mods on everything (eventually, after initial testing)
but do agree that the effect is not (normally) individually significant - if even measurable

at high flow rates perhaps; at 1gpm and below - forget it

Actually, head loss attibuted to sudden expansions and contractions perpendicular to the flow can be quite significant. I don't have my tables with me atm so I can't quantify it and say to what degree it would effect the flow. But if one of you can supply me with dimensions and the approximate ratio of small to large area across the contraction, it might be interesting to do the calculations. I might be totally off my rocker, so I'd like to figure it out for my own benefit. That said, I would think it's definitely worth looking into a way to minimized this effect.

The area of the 3/8" barb is about .06", the area of the channel is about .075" for the high flow block. Thus the block will not introduce significant flow restrictions.

That's a pretty bold statement. You might want to try to reword it something like "Thus the block will no introduce significant flow restrictions due to contraction of the cross sectional area". The block WILL contribute a significant amount of head loss due to it's geometry.

 

[Hoot]

Well, I carefully, milled out the cusp obstructing the inlet down to within .5mm of the floor of the channel. Now, when you look down into the inlet hole you can see straight down. It took some experimenting with the teflon tape on the threads of the barb to get the right number of wraps necessary for a reliable seal. Almost lost a video card in my haste to get everything back together and running. It'll take a while for the block to settle through the AS3 into place and the air introduced from removing and reinstalling the block three times to percolate out. After it seems to have stabilized, I will report any temperature variation from before I did it. My gut feeling is there won't be a measurable change, but you never know.

Hoot

 

[DodgeViper]

Hoot, I wished you had checked the flow before and after.

 

[Hoot]

Me too, but I am getting weary from tearing down and putting my system back together. I sure didn't want to toss out my distilled water and water wetter so I could run the pump. Suffice it to say, it is running fine. I've been consumed with playing around with this new A7V333 motherboard the past few days. What a "crotch rocket"!

Hoot