Exhaust duct from Zalman 7000 - multiple choices

ecto · Post by **ecto** » Wed Oct 20, 2004 3:57 pm

In this thread I describe my way to duct fresh air to the cpu from the front of the case. Since I now have fresh air there, it makes sense to make an exhaust duct from the CPU.

So, I got all these tubes and adaptors from a friend. Now I have several choices on how to make a duct - this is where you guys come in - I need some advice/discussion/tips before I make up my mind.

I got two choices when it comes to doing it like Spydercat does (moving the fan from the HS to the rear, and putting the duct "inside" the heatsink).

1. Aluminium tube 80 mm
Pros: Once bent it stays that way, which makes for easy installation.
Cons: Electrically conductive (could be covered with something), and I fear the metal will enhance sound from the fan.

2. Plastic tube 82 mm
Pros: Easy to work with, not electrically conductive, probably adds less noise than the aluminium tube.
Cons: Doesn't stay in shape when bent ("wants" to straighten out). This will probably not be a problem however when the the tube is lined with foam and press-fitted into the heatsink.

And now I have a different way of doing it, using ventilation adaptors which attaches to the end of a tube (both aluminium and plastic will work). With this technique, the adaptor will completely cover the heatsink, and I can leave the 92 mm fan right where it is - at least if there's a way to reverse the airflow on the fan.. is there? If not I'll have to move the fan to the back. With proper taping of the heatsink this should also yield countercurrent flow cooling. The CPU cover adaptor would of course have to be cut to not be so long, and lined with foam on the inside to make a snug fit. These pictures are just to let you see what I'm talking about.

3. Aluminium tube 80 mm with CPU cover.

4. Aluminium tube 100 mm with CPU cover.

5. Plastic tube 82 mm with CPU cover (I have 102 mm plastic too, just no pic).

If I go with this CPU cover idea I'm leaning towards the 100 mm aluminium tube, if it fits. As you can see it's pretty large. The reason is that it'll be really easy to cut the back end of the tube up to a square and attaching it to an 80 mm fan. This would make for a really easy installation - just slide the whole duct, with the fan attached, in place and the secure the fan to the case. If there's a way to reverse the airflow on the existing fan the back fan won't be needed, but then I can use an empty fan bracket for easy installation as described above.

So, what do you think? Put an 80 mm plastic/aluminium tube inside the heatsink, or cover the heatsink with an adaptor and 80/100 mm aluminium/plastic tubing? In an ideal world, I'd have both the time and money (will return the stuff I don't need) to test all variants..

ecto · Post by **ecto** » Fri Oct 22, 2004 6:17 am

No advice? :/

If anyone has any thoughts, please post them as I have to return the stuff I won't use after the weekend, and don't have time to test a lot of combinations..

fruitbat · Post by **fruitbat** » Fri Oct 22, 2004 6:58 am

Ecto,

I wouldn't use the metal shroud that fits completely over the heatsink. The airflow through the heatsink will probably be negatively affected due to the fact that the natural convection through the case (and thus through the heatsink fins) will be restricted. Maybe try mounting the metal shroud right above the heatsink? Just my opinion... good luck!

lm · Post by lm » Fri Oct 22, 2004 8:38 am

Imo you are losing some of the power of the cooler if you put the fan somewhere else. One of the points of the zalman 7000 is that the turbulence currents around the fan can be used for cooling since the fan does not have a frame but there are these fins surrounding it.

So i think the tube should end where the fins begin.

And if you totally cover the heatsink, then where does the air go in? You are restricting the airflow heavily that way.

ecto · Post by **ecto** » Fri Oct 22, 2004 10:22 am

Thanks for the replies guys!

frutibait: What do you mean by natural convection through the case? Isn't all natural convection upwards, since hot air rises? I wonder if this heatsink really loses much by prohibiting natural convection?

I won't be able to mount the shroud above the heatsink - it'll be too "high", and I won't be able to close the side door. And I wouldn't have anything to mount it to.. but thanks for the tip!

lm: The heatsink wouldn't be totally covered, just the part from the top to the first bend of the fins. Then the air should have plenty of space to go in from beneath, between the fins. And I've ducted fresh air from the front of the case to the heatsink, as you can see in the thread linked at the top of my first post, so fresh air shouldn't be a problem I reckon..

About placing the fan somewhere else, it seems to have worked fine for Spydercat, so I thought I'd give it a try. What I think will happen if the tube ends where the fins begin, is that air will just get sucked through the top of the fins and not close to the core, resulting in a hotter CPU.

Maybe someone with lots of Zalman 7000 ducting experience could comment on this?

Beyonder · Post by **Beyonder** » Fri Oct 22, 2004 5:43 pm

Have you considered using PVC pipe? It forms an airtight seal, is relatively easy to work with, and has a smooth inside for minimal turbulance. It's also dirt cheap, and quite a bit stronger than some of the other tubing posted here. That's the solution I'd go for first, if it were me.

halcyon · Post by **halcyon** » Fri Oct 22, 2004 11:59 pm

I tried aluminium pipe myself a few years back.

I ended up covering critical parts of the inner and outer surfaces with electrical tape (to ensure no conduction if it touches something).

However, I had problems with my setup: I didn't have the ventilation adaptors you have and the tube would end up touching some vibrating part and start vibrating (making noise) itself.

I finally gave up before I really even had a chance to do real head-to-head comparison with and without the tube (in terms of noise and heat).

Best of luck in your trials. Please do report how they succeed. You are already way past my experiments, so I'm looking forward to your results.

Putz · Post by **Putz** » Sat Oct 23, 2004 1:25 am

Wasn't there an article a while back on Zalman 7000 ducting that made the front page?

<looks it up />

http://www.silentpcreview.com/Sections+ ... d-160.html

ecto · Post by **ecto** » Sat Oct 23, 2004 8:02 am

Beyonder wrote:Have you considered using PVC pipe?

Yep, I tried it in one of my earlier setups without success.. the problem was/is that the exhaust hole is higher up than the CPU, and PVC isn't bendable. Imo it was a PITA trying to make something that would extend a bend from the PVC tube to the exhaust.. and I didn't have PVC tubes with very good dimensions - the stuff I have now matches the CPU a lot better.

Thanks for the tip though! =)

ecto · Post by **ecto** » Sat Oct 23, 2004 8:04 am

Putz: Yeah.. I've read it a couple of times =) Spydercat made that article, and I mentioned him in my first post. That article inspired me to try this out.

ecto · Post by **ecto** » Sat Oct 23, 2004 8:10 am

halcyon wrote:I tried aluminium pipe myself a few years back.

I ended up covering critical parts of the inner and outer surfaces with electrical tape (to ensure no conduction if it touches something).

Good idea, I thought of that too. Definately something I will do. I think. ;)

halcyon wrote: However, I had problems with my setup: I didn't have the ventilation adaptors you have and the tube would end up touching some vibrating part and start vibrating (making noise) itself.

I'll line the inside/and or outside (depending on which of the 5 options I'll use) with some kind of foam so vibrating should be no problem for me.

halcyon wrote: Best of luck in your trials. Please do report how they succeed. You are already way past my experiments, so I'm looking forward to your results.

Thanks! I'm thinking maybe I'll keep all the stuff (have to ask what it will cost). If it's not all too expensive maybe I'll keep it all and try all of the above configurations... *sighs* ;)

El_Jefe_77 · Post by **El_Jefe_77** » Sat Oct 23, 2004 9:08 am

Hm, well, the duct idea does work, I would think at least, if there was a an outside higher pressure fan boosting it. but this might not be silent...

I think that although these ideas are right on target for effective cooling, the problem is the zalman.

the ducts all point straight down on the heatsinks, which, while normally being a cooling option that is preferred, causes problems in removing the heat after the blast of cooler air blows on it.

I think the new thermaltake one that has 2 huge heatpipes and stands up with a big radiator block might be better for this design as you could havea flow through pipe system then. this trully would be more amendable to a flow through system.

mathias · Post by **mathias** » Sat Oct 23, 2004 9:35 am

I'd also be skeptical about whether an intake duct can do much good. Have you considered trying to put the fan on backwards? I think this would cause it to suck heat from the bottom part, and still blow on the top part of the heatsink. That should work well for an exhaust duct (one that covers the parts of heatsink beside the fan, but not the parts below it). Main problem is devising a way to put the fan on backwards.

josephclemente · Post by **josephclemente** » Sat Oct 23, 2004 2:39 pm

Intake ducts do work VERY well. Right now, my Zalman is pulling in fresh air at 800 RPM and doing a great job on my 3.0C Pentium 4. It is a ducted side intake.

After about 7 hours, ambient temperature is 26C, cpu is 34C. The only thing exhausting air out of my case is a Seasonic Super Tornado (Revision 3) at 828 RPM.

The intake works so well that my CPU temperature actually rises quite a bit when I remove the case panel.

Here is my duct:
http://forums.silentpcreview.com/viewtopic.php?t=12617

Today, the duct is the same, but now I'm using a 3.0C instead of a 2.53, and the fan was changed to a Nexus Real Silent at 800 RPM instead of the Evercool at 1110 RPM. PSU changed for Seasonic, front intake changed to 800 RPM Nexus. Rear fan is temporarily disabled right now just to see how well the Seasonic handles exhaust all by itself (very well).

mathias · Post by **mathias** » Sat Oct 23, 2004 3:24 pm

josephclemente wrote:Here is my duct:
http://forums.silentpcreview.com/viewtopic.php?t=12617

That duct looks great. I never thought much of side ducts because I wouldn't have thought of a duct that isn't attached to the fan.

I personally prefer exhaust ducting because I find it important to keep my harddrives cool to reduce any chance of failure, and to a lesser degree to cool the miscellaneous little things that could cause problems which I would have no way of finding out; CPU temperature I at least know, more or less. I noticed that with the BTX motherboards where everything else gets recycled hot air from the CPU, more chips have heatsinks.

ecto · Post by **ecto** » Sun Oct 24, 2004 5:34 am

El_Jefe_77 wrote:I think that although these ideas are right on target for effective cooling, the problem is the zalman.

the ducts all point straight down on the heatsinks, which, while normally being a cooling option that is preferred, causes problems in removing the heat after the blast of cooler air blows on it.

I'm not sure if I understand exactly what you mean. Do you mean that it would be hard for the exhaust fan to "grab hold of" the cool air, which comes in at a 90 degree angle compared to the heatsink? So that parts of the air heated by the CPU would slip by the exhaust and continue through the Zalman, to the back of the case.

I can see the problem if the fans were high-speed, but these are/will be low flow Panaflos, so I don't think the air can even be "pressed" through the heatsink with those low CFM's.

You're right about that maybe this "flow-through" system would be better suited for another heatsink.. who know, maybe I'll try some day!

ecto · Post by **ecto** » Sun Oct 24, 2004 5:38 am

mathias wrote:I'd also be skeptical about whether an intake duct can do much good. Have you considered trying to put the fan on backwards? I think this would cause it to suck heat from the bottom part, and still blow on the top part of the heatsink. That should work well for an exhaust duct (one that covers the parts of heatsink beside the fan, but not the parts below it). Main problem is devising a way to put the fan on backwards.

Yes, I have. That solution is actually the one I'd prefer as I wouldn't need a fan at the back of the case, resulting in less noise.

Is it possible to somehow just reverse the way the fan spins, making it blow upwards without even removing the fan? I guess not.. otherwise, has anyone put on a Zalman 7000 fan backwards?

mathias · Post by **mathias** » Sun Oct 24, 2004 8:35 am

ecto wrote:Yes, I have. That solution is actually the one I'd prefer as I wouldn't need a fan at the back of the case, resulting in less noise.

Is it possible to somehow just reverse the way the fan spins, making it blow upwards without even removing the fan? I guess not.. otherwise, has anyone put on a Zalman 7000 fan backwards?

I don't think the fan would work well, if at all in reverse. The easiest solution would be to replace it with another decent fan that has the stuff keeping it in place on the other side, if one exists. Assuming none exist, I think the best way would be to attach the fan to a wire grill, and attach the wire grill to the heatsink, after first cutting out the parts of the wire grill not neccessary for that.

ecto · Post by **ecto** » Mon Oct 25, 2004 7:15 am

So after some googling I found out that I can't make the fan spin backwards, so I think I'm going to try the idea of putting on the fan backwards.. I just don't know how. I searched here and did a bit of googling but found nothing interesting.

I'm thinking mathias's idea with the fan grill might be something worth thinking about. I believe the hardest part will be attaching it to the heatsink. Maybe drill holes in the fins and attach the grill/fan there?

Any ideas, or has anyone seen something similar?

teejay · Post by **teejay** » Mon Oct 25, 2004 11:52 am

No way of knowing this for sure of course, but I think that with reversing the fan you are also reducing the turbulence effect that occurs between the fins near the blade tips thus reducing cooling performance.

I think a possible problem with the materials you suggested is that a duct that is meant to push out hot air should be as smooth as possible, especially if the fan is at the pushing end. Any obstruction will result in needing higher air pressure to push the hot air out, resulting in more hot air staying in the case. This is just an assumption, so I could be wrong just as easily

What do you plan to use as an outtake fan (if anything)? I am considering a similar intake duct but have been thinking long and hard on the outtake, since the psu is already ducted. HDDs are planned to go in a seperate enclosure so that won't be a heatsource, but are you relying on convection/natural airflow for outward flow? Very curious...

ecto · Post by **ecto** » Mon Oct 25, 2004 3:30 pm

teejay wrote:No way of knowing this for sure of course, but I think that with reversing the fan you are also reducing the turbulence effect that occurs between the fins near the blade tips thus reducing cooling performance.

Yeah, I know.. quite a few people have pointed this out to me, but has anyone had any real experience with it, or is everybody just assuming that's the way it is, because everybody says it is? If enough people say something, eventually it becomes true

But yes, sure, there is probably a small performance decrease not having the turbulence around the top edge of the fins, but I really don't believe it makes a significant difference. Anyway, as it'll be ducted with fresh air I can't see it go over 60C anyway - which is my personal threshold for having a happy CPU

teejay wrote: I think a possible problem with the materials you suggested is that a duct that is meant to push out hot air should be as smooth as possible, especially if the fan is at the pushing end. Any obstruction will result in needing higher air pressure to push the hot air out, resulting in more hot air staying in the case. This is just an assumption, so I could be wrong just as easily

I assume you're thinking about the plastic tube. When it is installed it will be as elongated as possible, casusing most of the ridges to be smoothed out. And it is such a short distance for the air to travel (few ridges to get past) so I don't think that'll be a problem either. At least I hope so!

teejay wrote: What do you plan to use as an outtake fan (if anything)? I am considering a similar intake duct but have been thinking long and hard on the outtake, since the psu is already ducted. HDDs are planned to go in a seperate enclosure so that won't be a heatsource, but are you relying on convection/natural airflow for outward flow? Very curious...

This whole duct is actually meant to be an exhaust duct, so I won't need any extra exhaust fans. For the exhaust from the duct I'll either put a 80mm L1A at the back (don't have anything bigger, and 92mm will just barely fit at the back) or turn the Zalman fan upside-down so it becomes the exhaust fan.

The reason I believe this exhaust will work well is it will be fed fresh air directly from the front of the case via another duct. I'm also going to try having the CPU duct as an intake duct, and using the front duct to blow hot air from the CPU out the front.

"So why not use the PSU to exhaust hot air?" Well, I like the idea of having the PSU, CPU, GPU etc all separated from each other. I already have a PSU duct which works very well, and I'll probably put a 5- or 7-volted Panaflo in it sooner or later. If it's separated from the rest of the system I don't have to worry about it getting too hot.

As for the GPU I'll use a VGA Silencer, which will exhaust the small amount of air coming from my second front fan in to the case. Or I'm thinking I'll duct fresh air in from a PCI slot below the VGA Silencer, then out again. This way all hot parts will be separated from each other. I really don't know if this is the best way to do it, but it'll be fun, and I will sleep comfortably knowing my system is setup the way I'm comfortable with. =)

I haven't done much ducting or modding before.. it'll be fun to gain experience and learn first-hand what works and what doesn't.

I'm sorry, but it'll take some time before I have time to build and test all this - much to do in school right now, and I don't have a second computer so I can't have my system offline for very long periods at a time. But I'll get there, sooner or later!

Tephras · Post by **Tephras** » Mon Oct 25, 2004 5:41 pm

Sounds good. I also prefer to have the components cooled separatly so I'll be looking forward to see the end result and maybe some info during the process.

mathias · Post by **mathias** » Fri Nov 05, 2004 3:32 pm

ecto wrote:I'm thinking mathias's idea with the fan grill might be something worth thinking about. I believe the hardest part will be attaching it to the heatsink. Maybe drill holes in the fins and attach the grill/fan there?

Any ideas, or has anyone seen something similar?

From a link in a thread about the CNPS7700, I just noticed, the fan on some stock intel cooler looks like it spins backwards relative to the supports:

http://www.dbnawa.co.kr/board_b/?imode= ... &c_id=4932

Putz · Post by **Putz** » Fri Nov 05, 2004 4:00 pm

If you're willing to go to all these lengths to exhaust-duct a CPU heatsink, why not just go for the gold and use a nice Alpha, as Bluefront has demonstrated? They seem ideal for what you're trying to accomplish.

mathias · Post by **mathias** » Fri Nov 05, 2004 4:17 pm

Putz wrote:If you're willing to go to all these lengths to exhaust-duct a CPU heatsink, why not just go for the gold and use a nice Alpha, as Bluefront has demonstrated? They seem ideal for what you're trying to accomplish.

They're not accessible to me, (closest thing to an alpha I can find is the scythe heatsinks, and they're much too heavy) and the heatsink I have, although horrible with the fan blowing down, works fine with the fan backwards. (A duct doesn't help me anymore because I made the mistake of getting a 12cm fan PSU.

Stupid, stupid, stupid, stupid!)

Edit: oops, realized that wasn't directed at me

alleycat · Post by **alleycat** » Fri Nov 05, 2004 6:39 pm

I've also been thinking of making a 7000 exhaust duct. Although it would be preferable to have the fan in the same position but reversed, I can't think of a neat way of doing it. It's probably better to just get rid of that fan and use a Panaflo at the rear of the case instead. I was thinking of making a shroud to go on the HS so that it covered the straight section of fins and allowed the duct to be more easily attached using tape or something. The shroud would be made from a piece of sheet metal which could be rolled into a tube, with angled tabs protruding at the bottom to close the two large gaps where the retention mechanism goes.

Exhaust duct from Zalman 7000 - multiple choices

Exhaust duct from Zalman 7000 - multiple choices

re: Ducting mod