Need knowledgable advice
 

This may sound stupid (it does to me), but I can't seem to shake the idea.

Background: I'm looking to build a parallel rack style system on a centralized cooling system. Everything will be funnelled through one radiator (23x12x2.5"), and one pump (750-900 GPH, decent head). The coolant exhaust from each case will drain into one large (5') section of 4" PVC where it will settle down to the very bottom where I'll have a funnel attachment that will go to the pump and res.

Idea:

Originally, I thought of pulling ALL water through the rad -> pump -> splits to parallel computer loops -> super-res -> rad.

What if I was to take the rad out of the loop? Go pump -> comps -> res -> pump, with a PARALLEL loop from the rad that draws the heated water from the res, pumps it with a seperate 350 GPH pump through the res, and exhausts it back into the res at a lower point. It would allow much higher GPH through the CPU blocks, without the restriction from a massive 1/2" radiator, and would slow the GPH to the rad allowing it to run more efficiently.

I have a feeling I'd nuke my CPUs if I did this (not all the water would cool). But then, the other half of me says that with a res that will contain over 4 gallons (over 12L) of coolant, not to mention the other half gallon circulating through the system, that the temps would equalize in that massive res.

What do you guys think? Do you think there would be a performance gain? On one hand you have higher GPH through the blocks and lower GPH through the rad, but not all the water (by a long shot) will pass through the rad each time through the system, and on the other you have all the water going through the rad, but a loss in flow rate for the CPU blocks (I'd guess up to 1 GPM each) and a radiator that isn't working as efficiently. I only have one shot at this since I will NOT cut my box, patch, cut somewhere else, patch, and then do the same on the res (which will, even in black PVC, cost upwards of $50).

Ben? Anyone? This is right up your alley. Lets bounce some theory around.

First, I don't see why you'd want slower flow in the rad, because more flow is better. On the other hand, your overall flow rate would be lower, if everything was in the same loop.

I don't think you need 4" PVC: 1 1/2" should be more than plenty. You can build a column of Y fittings, that should work very nicely. I'm going to refer you to this:
http://www.bestpondpumps.com/pumphead.htm

if you keep the flow speed under 5 fps, then you're OK.

If you really want to run the rad on its own pump, then the only thing you have to worry about, is making sure that the cooled fluid is distributed evenly. There are many ways to do this.

I'm going to use the big stuff because I WANT a huge amount of fluid ... it will act as a buffer in case of temperature spikes in one machine so that they don't affect the others. I plan on using a single 5ft length and taking a hole saw to it, fitting hose barbs directly into the sides. Using Y's and slip reducers for all of them would run upwards of $150 to make the thing, and it would be hard to mount due to its bulkiness.

So you're saying that this monstrosity might work? I'd be counting on the large water mass to serve as a buffer to equalize temps .... The reason I'm saying that slower flow through the rad might be better is that on this particular rad there is rapidly diminishing returns after 2gpm. after 4gpm, there might as well be no gain at all, due to the efficiency of this bastid. By running a 350 GPH, I estimate I'll get around 3-4 gpm through the rad, which puts it in that spec.

Remind me again which rad?

As for the temp spikes, did you calculate anything? I mean, if you have 4 comps, and they each add 30 Watts at idle (example), but then one of them goes to full load, and hits 60 Watts, then your total heat went from 120 Watts to 150 Watts.

The water will heat up anyways, it's just a matter of time. Is it really worth it?

How fast can water heat up?

It doesn't cost me any extra to have a larger res. The extra water doesn't cost anything except for a couple inches of space between the wall and the cooler box. As far as temps go, I'm going to have one 1900+@1880 Mhz, one old skool Slot A Athlon 700 (stock), and either a 1600+@1900 or a 2400+@2400 (I haven't decided how much I'll spend on the upgrade or if it's worth it for the TbredB), combined with a 70W pump circulating. I estimate I'll be pumping in the neighborhood of 300-350W into the system. Two of the machines will rarely be used, though when they are they will be pegged. The third is almost going to be in a permanent state of balls-to-the-wall. Since the buffer is free (an extra 10-15 in PVC), why the hell not? I'll be using the Lytron 6320 (23x12x2.5", 1/2" throughout), so it is going to be one cooling mutha, even if it isn't directly inline (I think ... ).

Ok, for the 6320 ...

If you use their Caravel fan, which will blow a bit more than 500 cfm through that rad, and if you use a flow rate of 4 gpm (240 gph), then you'll be able to dissipate about 160 Watts /deg C.

BTW, the pressure drop of the airflow, at that rate will be about 1/8 inch H2O. The 6320 has a very small pressure drop, for the fan.

For the coolant, you can probably expect a pressure drop in the order of 13 psi (guesstimated, from graph), at 4 gpm. That's equivalent to 30 feet of head! At 2 gpm, it'll drop 4 psi, about 10 feet of head.

I think that you'll have to use 2 pumps, just because of that!

You understand why I want it to be out of the main loop now? Heh. I'm shooting for about 2 GPM, which will be very managable. If I had that to deal with along with 3-4 CPU blocks and the assorted Y's, quick disconnects, 20ft of tubing, and the few unavoidable 90's in the mix, I'd need an 1800+ GPH pump to power it, and the rad would be the biggest bottleneck. That's why I started thinking of this as an alternative. That little 350 GPH wouldn't struggle at all if it only had the rad to worry about.

Oh, and I hate those graphs. They scare me with their multiple colored lines and foreign (metric) measurements.

Well, I hope your pump can handle it, that's all I can say about that! 10 feet of head is quite a lot; we're way passed the Via pump now!

I'm still (stubbornly) going to point you towards this fitting:
(1 1/2 sanitary tee). They cost less than $1.00. You could make a nice clean stack of them, with 1 1/2 PVC pipe, which costs less than $4, for a 5 foot section. Then you add reducers, and polypropylene barbs, and you'd be all set, all for less than $20, for each stack.

Add 1/2 inch tubing, of your choice.

If you really want to go with 4", I dunno man, it's up to you. All I can say is, keep the weight of the water in mind: it's always heavier than one thinks.

Actually, that is my one concern: the weight. I'm going to be strapping the PVC to my box with metal strips both at one of the reducer sleeves on the bottom and three stretching up the pipe. My worry is that bottom strip letting go, because all of the weight will be supported by it. I can't think of a good way to keep the thing suspended ... I've got a while to figure it out, though. I may make a wood frame for the bottom to sit on and bolt it to my box. The only other weight consideration is the box tipping (it is on casters, so it is a possibility), so I'm going to have the side with the pipe against a steady surface (either my desk or the wall). Since I'm not going to be using clear PVC (too f*cking expensive), I'm not worried about putting the super-res center stage.

Ok.

This is where I like to use both metric and american measurements.

There's 3.76 Liters in one US gallon.
There's 25.4 mm in one inch.
One kilo is 2.2 pounds.
One liter of water is one kilo.

If you're going with 4" piping, which actually has an ID of 4.5 inch, that's 114mm. Area wise, that's 40828 mm^2. Assuming a 5 foot tall stack, the volume would be ... 62222228 mm^3, aka 62 litres, or 16 .4 US gallons. The weight of the water would be about 136 pounds, for a 5 foot high, "4 inch" PVC tube.

Doing the same calcs for 1 1/2 piping (1 7/8 ID), I get 7238 mm^2 cross-section, 11031088 mm^3, aka 11 liters, which will weigh less than 25 pounds, still for a 5 foot stack.

I think you need to reconsider the actual benefit of this "buffer".

I think your measurements are off.

Area of a circle = r^2 * pi
Volume of a cylinder is A*depth
Diameter = 4" (my 4" section at home measures 4")
Radius = 2"

2.54 cm = 1".

4*2.54 = 10.16 cm diameter.
R^2 * pi = 81 cm^2.

ans*60"*2.54 = 12349 cc = 12349 ml

This = 12.35 L. That is a bit over 4 gallons for the whole length. I think you squared you diameter, among other errors. You could not fit 15 gallons into a 5 ft stack 4" wide. Your milk cartons are wider, and you'd only need to stack six or seven to get to 5 ft, if my reckoning is right. Shrink it down to scale, and four gallons seems right. Plus, I'm only going to fill the coolant level to 2" over the height of the highest used input, so there will be an empty foot or so in the top (breathing area for air compression when I screw the lid on).

Is my math right (I did some sick siggy digit clipping ... I am aware of that). The other reason I think you squared the diameter is that your 1.5" measurement is just slightly smaller than my 4". I think you are also using outer diameter. As I said, my measurement of actual in-hand pipe is 4" ID (give or take a couple mm).

Oh, shiznit! you're right!

4":
Radius =2 inch, aka 50.8mm

Area=pi*r^2, so area = 8107 mm^2.

Volume = area * height = 12355068 mm^3, aka 12.4 Liters, which is about 3.3 gallons, and will weigh about 27 pounds.


Oh well.

Another question for you, Ben. What I'm looking at with the 900GPH pump is about 300 GPH at 5ft unburdened. Another alternative would be to put my BIX in a parallel loop with the Lytron just before a Supreme Pondmaster 1200 (900 GPH @ 5ft, 100W), run 3/4" up, split to 1/2" lines to the machines, and split, right before the pump, one side off 3/8" to the BIX and 1/2" to the Lytron. With the crazy restriction that the BIX has in comparison, what do you think would happen here? Or would it be better to just keep the Lytron by itself in seperate cooling loop to the res? The more I look at it, the more I think I'm going to have to step up to the 1200 GPH to power the blocks (3xCPU, with another to come next year) and keep decent flow. It's strange. Now that I have everything but the cases and pump on the way to my doorstep, I'm starting to doubt the wisdom of this project. If anything, I'm going to document and photograph every step of the way so nobody else makes my mistakes, or alternatively, you all can take after my fine example (*snicker*).

If you add a bix in parallel to the lytron unit, you'll considerably lessen the flow through it, at which point it'll make you wonder why it's even in the loop. It's really too bad.

Now do you really want to fork out $100 for a pump? I guess you don't have a choice, do you?

Note: the 1200 is spec'ed: 6.4" L x 4.5" W x 4.6" High. 3/4" FNPT intake and 3/4" MNPT discharge.

Here's a nice little chart for it:
http://www.aquadirect.com/catalog/pu...rflowchart.htm

(Change the chart to a "line" type, to see it better).

The 1200 deadheads at 15 feet.

With the 6320 alone, I'm guesstimating that you'll achieve a flow rate of about 2 gpm (120 gph), which, with the Caravel fan, will dissipate 140 W/deg C.

So if your total heatload is 140 Watts, then the water temp will rise by one degree over ambient (theoretically).

At 0.5 gpm, that rad will dissipate about 85 Wattsa/deg C.

What I'm thinking w/ the 1200, after nailbiting, is to put the lytron in series. I just don't like the odds of failure otherwise. I should still get good fow, I think, with a pump with that kind of pressure. I'm going to give the bix to a buddy, I think, and maybe sell him my Supreme 350 (good pump). Thanks for the help ... I just am too cautious to risk burning out multiple machines. If it was just one ... maybe, but not 3-4. Thanks for the input, though. If anything, I've more ideas to kick around. I'm probably going to use a single Rotron Caravel pushing out the rear of the case, using the box as a shroud and pulling air remotely through the lytron (the only opening). The PSU and pump will be centrally mounted to get some meager airflow over them (the PSU will have 2x120mm blowing over the exposed components at 5V). I'm probably going to have to run all PVC fittings in the case to prevent hose collapse, as that pump will be sucking like a mutha from that rad ... hose collapse is a huge threat. But again, thanks for the input.

I think you're right. A BIX probably doesn't have much flow restriction, at 2 gpm.

You know what's funny? My pump would push 2.5 gpm through that rad...:cool:

Another thing to consider: the pump wouldn't be anywhere near it's efficient range: it's going to suck up a lot of power, to achieve that 2 gpm.

You might be right about the pressure, for the pump intake side.

My pump collapses 1/2 inch thin walled tubing (in a circulating loop) so I switched to 3/4 braided. No test run yet, but I'm confident.

If you're really worried, then you might invest in a flow sensor (not a flow meter) just to check that there is some (any) kind of flow. Wire it to the PSU(s), for a complete system shutdown. Easy.

I find it intresting that you would say more flow thru the radiator is better.......In my mind more flow=more velocity since we are talking about a static medium the liquid must move through.

Now I understand that higher velocity thru a water block is a good thing.......but do we not want lower velocity (comparitively) thru the radiator since we are dealing with air cooling which is not as efficient as water at transfering the heat? Would it not be true that higher velocity thru the radiator would reduce its efficiency unless compensated with greater airflow over the radiator ie more noisy fans?

I would think that given his proposed idea of a common reservior with a cooling loop for the WB's and a separate loop for the radiator would allow for a lower velocity thru the radiator which would allow a given volume of water a longer stay in the rad so as to enhance the efficiency of the transfer of the heat to the air and come closer to ambient temp.......and allow him to maximize the flow thru the water blocks with even higher velocity........OR am I all wet here? :)

Even if I am somewhat wet would you not agree that a water block is happier at higher velocities than a radiator would be and as a result of that his idea would allow him to adjust the flow for both for maxiumum efficiency rather than a happy medium?

wow, sounds like an interesting project. a few things jump out out me tho. I'd think about maybe a different radiator, like maybe the main one for a car, or something similar. Something with big intakes and outlets 1.5" or better. when fed with your smaller tubing, the flow rate shouldnt drop much, but the speed of the water in the rad will drop considerably, allowing it to dump more heat to the air. also you guys are mentioning head pressures created by rad restrictions, but don't seem to be taking the height of your res into consideration (maybe i missed this part). I would suggest a much wider and shorter res, maybe one of those 5 gallon jugs from a water cooler? and the last thing that i wonder about, where is all the heat coming out of the rad going? are ya gonna duct it out of the room? sorry if i'm way off on some of my points, i don't have facts and number backing them up, just basing them on experiences i've had in other areas that are similar.

peace.
unloaded

Sorry shaft01, but what's good for the goose is good for the gander, so to speak. Radiators generally benefit from a higher flow rate just as waterblocks do, since they both transfer heat through convection. Of course, remember that radiators are usually limited by the air to metal convection, and that forcing more air over the fins will likely improve things more than an increase in coolant flow. If you'd like more information on this topic you should poke around some of the old threads, as this has been discussed many times before.

Shaft01

As Skulemate has said, this topic has been brought up over and over.

If you look through this thread, I think I did a pretty good job of explaining the situation. It's one of the things I just seem to be able to visualise perfectly in my head. I'm good like that.

::HERE::

If you're still unsure after reading this, ask and I'll try again.

But not today as I've got a load of work today, and unfortunately, this is something I don't seem to get!:confused: :mad: :confused: :shrug: :(

8ball

Unloaded: the reason I'm going for a tall and thin res is to make a huge airtrap, huge storage tank, and since my rack will eventually be about that tall, it will prevent hoses from having to drop down that other side. Besides, I'm counting on the weight of the water to help prime this puppy ... Can you imagine trying to submerge it in a bathtub when all bolted together like this? I'm also going for small footprint. Overall the entire thing will be 34x20x24" when fully hooked up, and using a drum like that would increase the footprint. It just wouldn't work right in this situation. Plus, I just want a watertower in my room. Is there anything wrong with that?

So you guys also think the parallel loop would work for the rad?

There is no reason you require a second pump simply to run a parallel loop for a radiator. All you need is an ample pump and a throttling valve in the "bypass" line. The throttling valve works a little nicer than separate pumps as you can then split the flow between the radiator loop and bypass in whatever ratio you wish. The downside is that you burn some energy in the pressure drop going over a valve, so overall efficiency takes a minor hit.

Ben is right about sensing flow, though it's not quite so simple as he states. To do it "nicely", you need a couple of relays and a timer circuit. I had an EE at work design a circuit that uses a couple of relays, a pressure switch, and a timer circuit. 12V from the PSU powers on the pump via a relay and starts the timer circuit. If the pressure switch doesn't pick up prior to the timer expiring, the second relay cuts power to the PSU. Sort of brutish, but very effective. Get a normally open pressure switch and relays and it's reasonably fail-safe. Total parts cost is on the order of $30. Without a timer circuit, you need something to keep the circuit closed until the sensor picks up flow/pressure. A spring return push button (just like an ATX power button) can do the trick.

I have never heard of a throttling valve ... how do they work?

Ummm well it sounds like we agree more than disagree.......ie both our statements regarding metal to air convection and more fan........:D But I have to disagree......solely because common sense tells me it takes time to convect this heat into the air and the only way you will enhance that procedure is either by increasing the air flow or letting the coolant hang around longer.....

Okay, I found some plastic throttling valves. The question is what the heck I'm going to do with them. Would I be putting this in a form of bypass line going straight from the res to the pump while leaving the connection from the res->rad->pump alone? My understanding is that these put a resistance load on the line, so theoretically, could I limit the bypass line to 3GPM while directing all the rest of the flow through the rad? I think that would work quite well, and keep me on only one pump (saving the 45W of electricity for other nefarious purposes), assuming that is how they work. Does anybody have any ideas?

In the end, by looking at the charts at Lytron's page, it would be pointless to run more than 2GPM through the rad. The extra heat dissapated would be insignificant, and the resistance on the circuit would be increased exponentially. Since the extra flow will "do no good" for me in the radiator, I just want a way to ensure that it isn't killed by the radiator and allowed to run for the CPU blocks. If my understanding of the throttle valve is correct, this could be a very elegant solution for most everyone that uses a high power pump to ratchet up their block flow. By adding a restricted bypass, you don't lose as much flow in the rad.