Alpha 8045 + duct?

Michael_qrt · Post by **Michael_qrt** » Thu Oct 17, 2002 6:19 pm

I've been wanting to quiet down my PC for a while now but don't have any experience and I just want to ask the opinions of those with some experience with noise. Anyway I was going to order a thermalright AX7 and use a panaflo L1A on the HS. What I was thinking was that scince the Alpha pal 8045 has air sucked up by the fan would it be a better solution to use one of these and attach a duct to the fan which exausts air directly out of the case (possibly with the help of another case fan). That way the hot air from the processor wouldn't be circleing around in the case leading to lower case temps (and hopefully CPU temps).

Has anyone tried this? Any feedback would be appreciated. Sorry if this has been brought up before.

Justin_R · Post by **Justin_R** » Thu Oct 17, 2002 7:20 pm

Michael-

First off, welcome to SPCR. I think everyone here is always happy to see someone else interested in quiet computing.

I actually have a system that is cooled by an AX7 and a 5V L1A. There's nothing to prevent you from mounting the fan blowing in either direction on the AX7 (or the 8045, for that matter), so don't let the airflow direction determine your choice of heatsink. I bought the AX7 because it is compatible with Socket 370, which is what I needed it for. Have you considered the Thermalright SLK-800 or SK7?

As for ducting, I've seen differing reports on its effectiveness. If any consensus can be found in what I've read, it would be that ducting the CPU fan will lower your case temps, but won't really change your CPU temps. Of course, the ducting implementation in these reports vary from shroud-like fan attachments made of cardboad and tape to air-tight plastic tubing, so your mileage may vary. Almost every name brand OEM system (Dell, Gateway, etc.) that I've seen uses some kind of fan ducting, so I guess it must be good for something. Of course, cardboard is cheap, so experimenting should be easy.

Michael_qrt · Post by **Michael_qrt** » Thu Oct 17, 2002 8:39 pm

Thanks for the reply. I thought ducting might not be as good as it seemed as I couldn't see any obvious discussions on the topic. What I was thinking was to get some 8cm diameter air ducting for air conditioners or something similar and have that sealed to the top of the fan on the HS with the other end sticking out of the case.

I'm not too concearned about CPU temps, to me as long as it dosn't cause crashes then its OK. So I didn't think the couple of degrees gained by the slk 800 was worth the extra price over the AX7. BTW are there any reviews of these HSs where the reviewer actually tests them with a 7 0r 5 volt Panaflo L1A. All the reviews I've seen focus on high speed fans or at least not what you would consider nearly silent fans. Alot of reviewers seem to think that 30DbA is inaudible.

Post by **MikeC** » Thu Oct 17, 2002 9:11 pm

are there any reviews of these HSs where the reviewer actually tests them with a 7 0r 5 volt Panaflo L1A

You've come to the right place; it is coming as part of a University research project on PC fan noise/airflow for which I have the role of "industry advisor" (or some such thing -- I basically instigated it through persistence).

All the HS in the recommended listare based on performance (real or predicted) with a Panaflo at 5/7 volts. You'll see that I have precisely your POV -- the HS as having its own inherent cooling power, which is then enhanced by forced airflow. I am not interested in perfromance with high airflow, only low. The high airflow performance info can be found on dozens of other sites anyway.

The recommended list needs updating; for the socket A/370, the Thermalright SLK800 is #1, and AX7 #2. I've had review samples for a while but just can't find the time to squeeze out a good review! They are excellent with low airflow and their 6-lug mounting clip is about the next best thing to nuts and bolts through the mobo.

gbass01 · Post by **gbass01** » Fri Oct 18, 2002 5:24 am

My current duct setup involves a Panaflow H1A rheostatted down to a quiet speed blowing outside air onto an SK6 thru a custom rectangular duct. Works fairly well.

I think the ideal ducted setup would be a PAL 8045 ducted to one of the two 120mm exhausts in a Lite-On FS020 case. That would minimize the number of fans without compromizing airflow. Anyone up for trying that?

And off the subject of ducts, has anyone tried mounting a fan at an angle to a heatsink so that the airflow onto-the-HS-and-out-the-back-exhaust is smoother (more laminar?) That would be another neat project for a double-exhaust case like the FS020.

quokked · Post by **quokked** » Fri Oct 18, 2002 8:00 pm

directron http://www.directron.com/whisperkit.html sells a ducting kit that is made by Elan Vital (an arm of ASUS) it's basically a 12" tube with a should on one end for the heatsink I've been hunting round for some ducting as well for my case, I want some airconditioning ducting or something along those lines as well, what's u guy's experience with finding ducting?

Michael_qrt · Post by **Michael_qrt** » Fri Oct 18, 2002 8:55 pm

Thanks for the heads up on that duct kit, though I don't think it'll apply to the Antec performance plus 660 I plan on getting (I've got a cheap, shit case at the moment). Though I suppose I could just stickytape everything, hopefully there are cheaper ways to get piping than that. I think I'll have a look at the hardware strore. I don't want to spend much on any ducting as I'll only be experimenting and don't want to waste any cash especially after buying an expensive HS and case.

Gekkani · Post by **Gekkani** » Fri Oct 18, 2002 9:22 pm

Justin_R wrote:Michael-

There's nothing to prevent you from mounting the fan blowing in either direction on the AX7 (or the 8045, for that matter), so don't let the airflow direction determine your choice of heatsink.

aahm... I don't agree

I think that the design of each heatsink can be better or worse to put the fan 'sucking' air.

I have a Swiftech MCX478 with PAPST 8412NGL in 'suck' mode... well swiftech isnt very eficient due that it has very together fins and it has a very little space between them to let run the air when the fan is sucking... well thats my theory

mmm... look at this:

(review of Overclockers Cafe http://www.overclockercafe.com/Reviews/ ... 5_pg3.html)

Swiftech performs a little better than Alpha in blow mode but Alpha OUTPERFORMS Swiftech in suck mode.

So I believe that some heatsinks are better to suck air than others... I'd like to see the 'sucking' performance between AX7 - SLK800 - Alpha 8045

It would be interesting

gekkani

PD: Hey I bet that not all the heatsinks 'do' the same noise when a fan is sucking air... the noise turbulence caused by the design of each heatsink i mean...

Post by **MikeC** » Fri Oct 18, 2002 10:22 pm

Here's a little twist to toss into this discussion: noise from an impedance close to the inflow side of a fan is always higher than on the outflow side because it is turbulent on the former and laminar on the latter. Try it by moving your hand very close to either side of a spinning fan -- the intake side will have more noise.

That means a sucking fan on a HS (like in the Alpha) will in theory have more noise from air turbulence that a blowing fan. Flip it back and forth and listen for yourself. At very low RPM, the difference is not significant, but at 12V, you may hear something. Also depends on the diatance between fins and fan blades -- more than 1/2" and the noise drops considerably, esp. at higher rpm.

Justin_R · Post by **Justin_R** » Sat Oct 19, 2002 12:15 am

Gekkani-

I wasn't trying to make a claim about performance, I was just saying that it's physically possible. I've experienced first-hand how "blow" vs. "suck" can result in wildly different performance, especially with low-profile heatsinks.

In the two computers I have with AX-7s, one is set to blow and the other to suck. I haven't done a direct comparison of blow and suck on the same machine, but both positions "work". The biggest difference I've noticed is that the temperatures on the "suck" configuration tend to rise and then stabilize faster than the "blow" configuration. This seems to make sense (to me, anyway) in light of the "laminar" vs. "turbulent" airflow from each side of the fan.

Okay, bedtime for me; I'm going to a computer show tomorrow where hopefully I can pick up some surplus low-profile fans.

Gekkani · Post by **Gekkani** » Sat Oct 19, 2002 6:37 am

MikeC wrote:Here's a little twist to toss into this discussion: noise from an impedance close to the inflow side of a fan is always higher than on the outflow side because it is turbulent on the former and laminar on the latter. Try it by moving your hand very close to either side of a spinning fan -- the intake side will have more noise.

That means a sucking fan on a HS (like in the Alpha) will in theory have more noise from air turbulence that a blowing fan. Flip it back and forth and listen for yourself. At very low RPM, the difference is not significant, but at 12V, you may hear something. Also depends on the diatance between fins and fan blades -- more than 1/2" and the noise drops considerably, esp. at higher rpm.

Yeah, True.

I think that the use of a HS+FAN in suck mode its only justify to use a duct. Temp should down so its possible that we can only use a fan for cpu an PSU fan.. no fans for the case, so the extra noise caused to suck mode will be compensated.

mmm.. Alpha use a metal plate or something, not sure whats the name, to maximize the suck effect over the HS and i think that it minimize the noise cos it keeps the fan separate of the fins. right? Probably we could increase the distance btw the fins and the fan to minimize the noise more.

gekkani

Gekkani · Post by **Gekkani** » Sat Oct 19, 2002 6:43 am

Justin_R wrote:Gekkani-

I wasn't trying to make a claim about performance, I was just saying that it's physically possible. I've experienced first-hand how "blow" vs. "suck" can result in wildly different performance, especially with low-profile heatsinks.

Yeps... Its totally possible .. hehe, no problem.

My post its only to say that some heatsinks works better or worst than others in suck mode.... So I think that airflow direction should determine the choice of a heatsink .. just that.

Good shopping

gekkani

Red Dawn · Post by **Red Dawn** » Sat Oct 19, 2002 7:01 am

The metal plate (aluminium) over the fins of the heatsink is called a 'heatshroud' I believe.
Myself, I use a 80/120 mm. fan converter and that would probably create a different sound signature/enviroment for the PC, but I'm unsure how big the effect, in either way, really is. I'd like to think that the air sucked up the 'tunnel' creates a more even airflow path, thus ever so little - decreasing overall noise. But in the end, if the converter+fan starts to vibrate because of inproper or poor installation, it's all otiose anyway.

Michael_qrt · Post by **Michael_qrt** » Sun Oct 20, 2002 7:06 pm

MikeC wrote:Here's a little twist to toss into this discussion: noise from an impedance close to the inflow side of a fan is always higher than on the outflow side because it is turbulent on the former and laminar on the latter. Try it by moving your hand very close to either side of a spinning fan -- the intake side will have more noise.

That means a sucking fan on a HS (like in the Alpha) will in theory have more noise from air turbulence that a blowing fan. Flip it back and forth and listen for yourself. At very low RPM, the difference is not significant, but at 12V, you may hear something. Also depends on the diatance between fins and fan blades -- more than 1/2" and the noise drops considerably, esp. at higher rpm.

Well if you're ducting then it shouldn't matter which end of the tube the fan is attached to. You could just stick the fan on the other end of the tube so it was nowhere near the fins of the HS. Of course this might not decrease noise as you would have moved a fan from the midle of the case to the outside. Oh well that idea just still self destructed.

Actually this is all just theory. I probably won't get a chance to test any of this stuff for quite a while. I've quite got my hands full for the next while which means I'll have to live with that horrid "quiet" fan on the globalwin WBK68.

Post by **NeilBlanchard** » Mon Dec 09, 2002 7:47 pm

Okay, Alpha recommends that you mount the fan to pull air through the PAL8045. Dan's Data (dansdata.com) says that this gains you about 5% better cooling. It seems to me that better cooling can be quieter...

Why is it better to pull the air through a heat sink? Several reasons, I think:

1. The cool air enters the heatsink at the hottest part (in this case at the base of the fins) and where there is a greater difference, there is better heat transfer.

2. Air doesn't "like" to be pushed. It tends to go places that you don't intend it to go. OTOH, air always flows towards a vaccum or a lower pressure. So, when you blow down into the heatsink, some air leaks (off to the side, for instance) instead of flowing all the way down to the base of the heatsink. The 8045's shroud causes the air to flow up from the bottom, instead of sucking it in from the sides right near the fan.

2a, b, & c: One could experiement a bit with shrouds that cover more of the sides. Also, if one were to make the shroud so that the fan was moved up and away (a little) from the tips of the pins, then things might get quieter. Another line to try would be to have the intake areas be non-symetrical so as to case some swirling and to make sure that the air flow makes it's way all the way to the center of the heatsink (it is a big one!) where the heatsink touches the CPU.

3. This is likely to be less important than #1 and #2: when a fan blows down, the air pulls some heat off the top of the heatsink -- and it moves down to the middle part and gains some more heat -- and then it finally makes it's way down to the bottom hottest part (if it hasn't leaked out the side!) and it has a harder time pulling off as much of the heat because it has already gained (some) from higher up. This is kinda' the reverse of #1, but it needs to be pointed out.

I guess this sorta' goes in the direction similar to power supply efficiency:if the heatsink plain ol' works better, then you don't need as much air flow. (For power supplies that run cooler, ditto.) Now, I know the Thermalright SLK-800 is a righteous heatsink, but I'm not sure that all the "fight" is out of the 8045. I really like the 8045's mounting setup -- very secure, whereas hanging a pound of anything on a clip is not so elegant.

Can the SLK-800 work as well in the "suck" mode as the 8045? Not without some fancy shroud, 'cuz an 80mm fan overhangs it by quite a bit. The two things the SLK-800 has going for it are the fact that two sides are already covered and soldering on some covers at the top of the fins on the other two sides would likely be easy enough. Also, the shape of the "core" of the 800 is conducive (sp?) to air flow in at the sides and then up through the top.

Thanks for reading this far!

Gxcad · Post by **Gxcad** » Fri Dec 20, 2002 12:58 pm

"Swiftech performs a little better than Alpha in blow mode but Alpha OUTPERFORMS Swiftech in suck mode." - Gekkani

hehe sorry I'm too lazy to figure out the quote tag

notice that the alpha has a shroud to help direct the airflow. I remember reading a review a long time ago in which the reviewer put masking tape across the top of the heatsink to help its performance in suck mode. Interesting to see how that turns out...for those that prefer to suck, that is. Anyone have an alpha that their willing to test without the shroud and then again with?

-Ken

Gekkani · Post by **Gekkani** » Sat Dec 28, 2002 11:26 pm

mmmm..... yep

I have a swiftech MCX478 so i'll try to put masking tape to make a ghetto-shroud

we'll see if that shroud improve the performance.

TomG · Post by **TomG** » Fri Jan 17, 2003 6:45 pm

A question regarding direction of airflow, particularly with a duct to the exterior of the case; what will be the effect on the other components in the case?

Cooler air from the outside, blown on the CPU will cool the CPU better but introduce warmer air into the case.

Pulling air over the CPU will be less efficient since its already heated by the other stuff, but it promotes cooler air flowing into the case from your intake.

I wonder if one is more efficient than the other.

Gorganzola · Post by **Gorganzola** » Wed Oct 08, 2003 11:21 am

I actually tried the Alpha PAL8045 without a shroud when I used to have one running on my AMD Thunderbird 1.4GHz. The temps went up a significant amount. That shroud forces the cool air to come in closer to the base of the heatsink. It is very important to have that shroud in place.

A friend of mine took a 70mm Thermaltake heatsink and used duct tape (handy mans best friend

) to create a shroud with the fan pulling air through the heatsink and the heatsink actually performed better and was quieter then with the fan in the stock position of blowing. Without the shroud it didn't perform near as well with the fan drawing air through the fins.

Gxcad wrote:"Swiftech performs a little better than Alpha in blow mode but Alpha OUTPERFORMS Swiftech in suck mode." - Gekkani

hehe sorry I'm too lazy to figure out the quote tag

notice that the alpha has a shroud to help direct the airflow. I remember reading a review a long time ago in which the reviewer put masking tape across the top of the heatsink to help its performance in suck mode. Interesting to see how that turns out...for those that prefer to suck, that is. Anyone have an alpha that their willing to test without the shroud and then again with?

-Ken

JarsOfFart · Post by **JarsOfFart** » Thu Oct 09, 2003 2:28 pm

I believe BlueFront used an aluminum duct and his PAL8045 and created an almost passively cooled computer in an Antec LanBoy. The article is on the SPCR main site.

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