some quick wc setup questions

[artemis0007]

Hi all!

some quick questions:

1) I plan to have the BIX rad at the front of my case with a 126 cfm fan(s). But due to space constraints, I am unable to also have another 120 mm fan outtake(s).

So, I was wondering if there would be any negative side effect if I decided to make a duct connecting the exhaust end of the radiator fan to the intake of the PSU? The reasoning is that I eject the warm air outside through the PSU instead of letting the warm air pervade the case.

2) I'm making a PVC elbow for my EHEIM 1250 pump outtake and I wanted to know if it is enough to use plumbers goop (connecting the hose barb to PVC) and PVC cement (PVC to PVC)? I guess I'm asking is if it will hold water under pressure and not explode.

3) Can anyone suggest a good sound insulating material that I could put around the fans of my rad and around my rad? I'm looking for a fairly thin and inexpensive material.

4) I was wondering if CK42's article on making an over-temp detector also applies to dual processors? Would the thing monitor both CPUs or just one?

Ummm... that's about it for now. Thanks for any replies and suggestions! Hopefully pics will come soon!

[Stepback]

1)I would setup the rad with the air coming from the outside of the case a exausting inside the case. There isn't going to be enough of an increase in the temp of the air to worry about it adding heat to the inside of the case.

From what I'm reading in your post the only other fan is in the power supply? If you duct it to the power supply fan you won't have any air movement for the rest of the case.

2) I don't have an Eliem pump, but I would use epoxy to hold the PVC on. (Question for Eliem owners, don't Eliems have threaded fitting? Can you unscrew the hose barbs?)

3)I've seen post all over the place saying old mouse pad's work well for this.

4)It will only montor one Cpu. But you could use two of them, one for each CPU.

[gmat]

Originally posted by artemis0007

2) I'm making a PVC elbow for my EHEIM 1250 pump outtake and I wanted to know if it is enough to use plumbers goop (connecting the hose barb to PVC) and PVC cement (PVC to PVC)? I guess I'm asking is if it will hold water under pressure and not explode.

* Eheim pumps have threaded barbs
* if you use PVC glue it will be leakproof but you'll be unable to unmount it
* Eheim provides a large range of adapters that fit their pumps. they're threaded and come with O-rings. From my experience and other eheim users i know they'll never leak.

[webmedic]

If you have to use any stuff to glue things use plumbers goop. It can be pealed off later if need be and works better than anything else bar none.

[artemis0007]

For 1), I actually have a 92mm blow hole and a 80 mm fan blowing out, so there is some air flow, but there's more air coming in than going out.

Thanks for the posts! Much appreciated!

[artemis0007]

Here's a pic of the elbow I just finished:



If you can't see pic, go here:
http://www.geocities.com/artemis597/eheimelbow.txt

Thanks for replies!

[Cyco-Dude]

you cant link to .jpgs on geocities. what you can do is rename the extension from .jpg to .txt.
then upload the "myPicName.txt", and then you can link to it.
i needed to copy-n-paste the URL into my browser to see the pic. just a heads up.

[artemis0007]

oh yeah... i keep forgetting about that. sorry. Thanks for the reminder!

ummm... so do you think that the elbow is okay (just asking because this is my first attempt at water cooling).

Thanks!

[gmat]

Seems nice. Try to 'paint' it somehow (white) to make the blue stuff disappear - so it'll be cleaner. Don't forget any watercooled pc is an attention-getter

[dcrainman]

I'd leave the fan as an intake so that you can get fresh air through the rad, air can always find its own way out (otherwise the case would just build up pressure and exploade )

[gmat]

Actually it will work against other fans, and as secondary effect will produce a 'pulsating' compression effect. Not good. Unless the case has wide openings of course.

[dcrainman]

you show me an airtight case and I'll show you a saw

[artemis0007]

What if I made a half-duct (for lack of a better word)? So it would still be a duct but one end would only be attached to half of the rad's outtake fan and the other end is still attached to all of the PSU intake. So that way, some of the air would immediately go out and some would blow into the case.

Sound good (crazy)? All feedbeack is appreciated! Thanks!

[dcrainman]

give it a shot but it might not be a good idea to put your exhaust right next to your intake as I could see it recycling some of the exhaust

[artemis0007]

I think that my description was a bit confusing so I frew a picture of what I had in mind. I hope this will clear up any confusion.



If you can't view it:
http://www.geocities.com/artemis597/complayout.txt

Okay, so will this work?

[Brad]

in your pic, where is the motherboard?

[artemis0007]

oh, I have a YY cube case, so it's on the other side. The mobo side has a 92mm intake and a 92 mm blowhole, so air flow is okay on that side.

[Cyco-Dude]

could you move the hdds to the other side?
i dont think id bother ducting the rad fans; it looks like it should exhaust the warm air fine. plus the hdds are in a windy spot so i dont think the warm draft will affect them too much.

or you could try this: duct the rad fan 90 degrees and out the side panel of the case. that'll work (but that side of the case wouldnt have any real cool air intake). maybe a side blowhole is in order yes, thatll fix you right up hehe (unless you dont want any casefans. since youve already got plenty, im guessing 1 more wont hurt )

[nemaste]

i think the rad exhaust would help cool the rest of the case down. i seriously doubt the small deltaT across the radiator is worth considering in light of other much hotter components inside (what are we talkning about with a BIX? <1C difference in air temp?). the large amount of flow from that rad fan is probably enough to keep the case very near ambient anyways, so shunting that flow out & adding the noise of a dedicated case flow fan would not be necessary.

if you try & force air to move some place (like ducting half of the rad exhaust instead to the PSU of letting it exit into free air & find it's own way to the exhaust fans), you create more back-pressure on the fans. pressure gradients suck for fans, so avoid them period. to avoid do them, you want to make the mass flow of air exiting equal the mass flow entering the case, otherwise you DO in fact build up small amounts of pressure that can greatly affect your fans.

although the pressure will never grow large enough to create an explosion, it will make the fan blades operate at an off design angle of attack, which can make fans completely ineffective(dcrainman, you do know how this explosion occurs right? strong shock waves forming in our outlets end up choking the flow. on rockets, an overpressurized combusiton chamber can cause shock waves to choke outlet. this is the cause of around 90% of our space program's "aborted launches" in the "early days"). as long as you take some measures to cancel net flows in the case, you'll be better off. in other words, estimate the friction through the rads (or do trial & error experiments), filters, & such, & make your inlet CFM = outlet CFM. this flow balancing eliminates back pressure. even if you don't consider friction, you should at least use the fan CFM specs to design for 0 net flow:

+CFM of inlet fans - CFM of exhaust fans = 0 CFM

if it is above zero, your inlets operate with back pressure & exhausts with foreward pressure. if it's below 0, your inlets operate in foreward pressure & exhausts with back-pressure. my post in the "fan math" thread has a diagram of what happens to fans that operate under fore&back pressure.
Off Design Rotor Blades

[artemis0007]

Unfortunately, I can't duct the exhaust out of the side of the case because my NMB PSU is longer than regular PSUs (it's for my Thunder K7). I also can't move my hdds because I need the railing on the mobo side to support my raid card (that bugger's BIG).

I am uncertain about some cfm math.
My fans:
80mm = 36.9 cfm
92mm = 56.8 cfm
120mm = 126 cfm

From the pic above, my rad is sandwiched between two 120mm fans. But I connected them to a rheobus so I can control them. Okay, so if I reduce the voltage to the 120mm fans by half, the cfm output for each is roughly half, right? But since that fans are serial, does that mean that the cfms add up again to produce 126 cfm?

I was wondering because I am close to a net 0 cfm for that side of the case. I have 93.7 cfms going out, and (if math is right) about 126 cfm going in. So I can just tweak the knobs from there to find the sweet spot.

Thanks for the suggestions! Keep them coming!

[Cyco-Dude]

Originally posted by artemis0007
Okay, so if I reduce the voltage to the 120mm fans by half, the cfm output for each is roughly half, right? But since that fans are serial, does that mean that the cfms add up again to produce 126 cfm?

no. if you cut the power in half, the CFMs would be much less than half. also, because you're blowing / sucking air thru a rad, the total probably wont be 126cfm, maybe a little less.
i wouldnt bother with it honestly. its not going to affect the fans that much at all. just as long as you have an equal or greater amount of air comming in than going out, youll be ok.

[gmat]

Originally posted by Cyco-Dude

as long as you have an equal or greater amount of air comming in than going out, youll be ok.

Oops I guess you meant the opposite... Over-pressure is what's to be avoided, as explained by nemaste and others.

Make sure you the total air coming out is more than air coming in.
2 fans in serial with an impedance (rad) wont add up their CFM's exactly, but will create a good pressure. It all depends on the efficiency of your 3 exhaust fans.

[Cyco-Dude]

i made no mistake typing in my last reply. having negative pressure will cause air to be sucked thru all the cracks and small openings (like CD-ROMs for instance). i guess its varies from case to case (har har).
either way i still dont think it makes that much of a difference. lab test anyone?? lol

[gmat]

It *does* make a big difference. There *are* tests about this (try a search). hey, you can even do it yourself, reversing a fan aint so hard...
Ak i dont have any link right here, and since it''s 04:30 i wont slap equations right now. Just think that:
* pressurizing air heats it (though the effect is not noticeable here)
* axial fans working against each other will lose effifciency thus increasing thermal losses (engine heating and wearing)
* due to their fan blade design and different rotation speeds they will create a "pulsating pressure" effect , building up pressure then quickly dropping. Major effects include a "woo-woo" noise and even more heat because of energy released by this pulation...
* The "it will get dust by the cracks" popular wisdom is wrong. Just mainain a 2%to 7% underpressure and you're ok. Actually an overpressure will help dust build ups inside the case and stagnating hot air zones.

There was a FAQ on overclockers-forums or a similar place, complete with equations, tests and so on (by a guy called "dallara" who makes race cars)