Cheap, Clean, Cool and Quiet Case Cooling

Like it says – Trung Nguy

Overclocking or not, most of us have at least experimented with computer cooling because we are geeks. There are some articles with great ideas. Bill Leggett’s 10/7/04 article reveals the use of a duct to get cool air from outside and aiming it directly to the CPU. I like this idea because cool air has a short path to the CPU.

But in John Cinnamon’s article from 10/13/04, he wrote that there were two downsides to this method: “hot air is still in the case (cooking the video, drives, chipset, etc), and the power supply is the only way for the heat to get out”. He furthers points out he would be afraid to leave this setup in a hot room, which increases power supply temperature.

As a solution, I’ve found a way to quickly remove the hot air while cooling the video, drives, chipset, etc. I think it’s okay for the hot air to go through the power supply, because it has electronic components (such as transformer, capacitors, etc.) that are thermally robust. Thus they can safely endure warm air without significantly decreasing performance and/or durability, unlike that of the delicate, heat-sensitive computer components such as the CPU, video, RAM and hard drive.

It’s true that a warm room would adversely affect Leggett’s setup, as Cinnamon pointed out, but ultimately I think the same goes for any other type of fan setup. Every fan cooling system must intake air from the outside of the case (the room’s air); thus room temperature affects every fan cooling systems.

There are also articles that show cooling methods using external (remote) systems. I prefer an internal cooling system. There are products that can control fan speeds to reduce noise, but I would like to do a project that eliminates such a product and lets the fans run full speed for maximum airflow.

Case Cooling Objectives

My goal of a case cooling system is this:

  1. Cheap
  2. Clean
  3. Cold
  4. Quiet
  5. Non-remote

But we have these 3 typical dilemmas:

  1. Using air filters decreases cooling
  2. Increasing cooling increases noise
  3. Using liquid cooling decreases savings account

It seems as though you can only have one or the other, but not all at the same time. But I found a simple solution to all these dilemmas:

Relocate the fans so that no fans are flush-mounted onto the computer case.

This actually works on my system. You see, for clean dust-free air, I utilized air filters. But since these filters decrease cooling, I used more fans. But since more fans create more noise, I relocated the fans to the inside of the computer case so that the case can muffle the noise. The next section illustrates this.
{mospagebreak}

Design Note #1: Relocating Fans to Reduce Noise

To muffle fan noise, I relocated the fans to the inside of the computer case, which acoustically isolates the sound waves from traveling out (See Figure 1 and 2 – note that the arrows coming out of the fan depicts sound waves, not airflow, since airflow can go the opposite direction). Lining the inside of the case with sponges can further reduce noise by absorbing and dispersing sound waves (Figure 3). Other materials, such as cotton and fiberglass, can perform a better job for damping, but it can get messy, which is why I prefer Scotch-Brite sponges.

Diagram

Figure 1: A fan flushed-mounted directly onto the computer case sadistically produces torturing whirling noises, causing mental insanity.

Diagram

Figure 2: Relocating the fan to the inside of the computer case muffles the torturing noise.

Diagram

Figure 3: Same as Figure 2, but with a soft Scotch-Brite sponge for acoustic damping.

Design Note #2: Using Ducts to Guide Airflow (Intake and Exhaust)

When a fan is mounted onto the case (Figure 1), it sucks cold air from the outside as an intake, or moves hot air out for exhaust. But for the relocated fans shown in figures 2 and 3, ducts would have to be utilized, otherwise cold air can’t go in and hot air can’t go out and your computer would die a horrible death. The following illustration is my project plan:

Diagram

Figure 4: Complete ductwork Diagram to rapidly move out all hot air.

Table 1: Description of Each Colored Arrow

Arrow Color Description
Blue Fresh cold air for intake
Cyan Air after cooling hard drives
Green Air after cooling hard drives and video card
Yellow Air after cooling CPU
Red Air after cooling hard drives, video card, and CPU
Brown Air after cooling power supply combined with red airflow

{mospagebreak}

As you’ve probably guessed, the brown airflow is the warmest since it contains hat from the hard drive, video card, CPU and power supply. Indeed, this airflow is very warm when I place my hand over the exhaust after building the project. That means the system is doing its job moving hot air out.

Notice that there are two intakes but one exhaust to create a positive case pressure so that unwanted, unfiltered air would not leak in through small cracks and openings. Dust filters are Scotch-Brite scouring pads. I’ve meticulously sliced the pads in half to make them thinner for more flow. I could have bought fan filters from Fry’s Electronics for 3 or 4 dollars, but that’s the price of a good meal at McDonald’s.

Also notice the power supply’s exhaust fan is the only fan mounted onto the computer casing, which goes against my idea of putting them inside the case. So, to help fight this fan’s noise, I made Leggett’s chimney out of scouring pads from Scotch-Brite sponges so that the material would absorb some noise. You might also consider the “fan muffler” described in Joe’s Fan Mufflersarticle of 3/15/03.

The power supply experiences the warmest air, but that’s okay since power supplies contain robust components. The main focus is that the CPU discretely and immediately gets fresh cold air and the hot air is quickly removed. The hard drive’s heat goes over to the video card, but this heat is mild and harmless, especially when the hard drive’s airflow starts off with fresh cold air too.

Construction Material

Refer to Bill Leggett’s article for the Plexiglas CPU ducting. Since I’m too lazy to use the tougher Plexiglas, I used clear plastic sheets to construct the CPU ducting, a material that’s often found in packaging like this:

Diagram

Figure 5: Clear plastic material.

Michael’s craft store sells 8 x 11″ sheet of this material for over $4 each! So I went to the 99 Cents store and bought this clear plastic box. Apparently, the box came with a set of Christmas ornaments.

Constructing the CPU Duct

I made a few paper prototypes of the CPU duct until it was a perfect fit. Then I used my best one as a template to trace the cuts for the plastic sheet. One end of the duct was taped onto the case while the other end fitted snuggly over the fan’s frame. Here it is:

Diagram

Figure 6: Finished CPU duct; notice the sponges as sound damping materials.

In Figure 6, the duct should prove effective since it separates the incoming cold air (blue) from the exiting hot air (yellow), preventing hot air recirculation. The hot air gets sucked immediately by a nearby fan, which is part of the “Airflow Control Chamber” (explained later). Visually compare Figure 6 with that of Figure 4. If you’re too lazy to flip back the pages, here’s part of Figure 4:

Diagram

Figure 7: A part of Figure 4 showing the CPU duct.

{mospagebreak}

Constructing the Airflow Control Chamber

The “Airflow Control Chamber” ductwork has four 80 mm fans (2 push and 2 pull), and it’s designed to do four things (see Figure 8): suck hot air (yellow) directly from the CPU, suck hot air (green) directly from the video card, guide the hot airflow (red) to the power supply for exhaust, and suck additional hot air from the chipset, RAM, and drives (their arrows not shown but will be explained). It is built in the same manner as the CPU duct: paper prototypes. Here’s this chamber:

Diagram

Figure 8: The Airflow Control Chamber.

Diagram

Figure 9: Airflow Control Chamber.

The Airflow Control Chamber is divided into three sections (Figure 9). Here, we will discuss the top and middle chamber. The bottom chamber will be explained later.

The fans are secured onto the chamber via clear box tape, and the entire assembly is secured by zip-tying the fan’s mounting holes to nearby power cables. Take a look at the top chamber (Figure 9) where the red arrow is making the 90 degree bend. I’ve placed a curved airflow guide at the top, but the sides are fully opened, allowing the last fan of the chamber to suck additional hot air from the chipset, RAM and drives.

It works because this fan is at the very top where hot air rises from those said parts. This fan also acts with the power supply’s exhaust fan as a push-pull configuration for faster airflow, thus better cooling efficiency (Figure 10).

Diagram

Figure 10: Power supply’s push-pull fans.

Constructing the Bottom Duct and the Bottom part of the Chamber

The Bottom Duct, which directs air to the video card, was not built according to the original plan (Figure 11). I found that both a modified Tupperware piece and the computer casing itself automatically created the desired airflow direction, as shown Figure 12.

Diagram

Figure 11: The original plan for the Bottom Duct design.

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Figure 12: A Tupperware piece is used instead; notice the sponges for sound damping.

Figure 13 shows a Tupperware that is to be cut into two pieces. I also found this item at the 99 Cents store:

Diagram

Figure 13: Tupperware before it was cut; outlines show cuts to be made.

The larger of the two Tupperware pieces has an opening (where the lid goes) that is perfectly sized for a 120 mm fan, which draws in cool, fresh filtered air from the front intake (see Figure 11). The fan is mounted onto the Tupperware by using clear box tape.

Remember that the Airflow Control Chamber was divided into 3 sections: top, middle, and bottom chamber (Figure 9). The smaller of the two Tupperware pieces is used as an airflow guide for the bottom chamber, secured by clear box tape (Figure 14).

Diagram

Figure 14: Tupperware cut into two pieces.

The Tupperware cut is angled in order to make a 90 degree guide, so that the hot airflow from the video card (green in Figure 14) can easily enter the opening of the chamber.{mospagebreak}

Experimental Data

Here’s the completed project shown in Figure 15. I riced it up with blue lighting, Fast and Furious style. I’m also planning on putting racing stickers such as “Powered by AMD” and “NOS” in hopes of getting a few more Mhz’s.

Diagram

Figure 15: Project completed, adorned with a ricey-looking blue cold-cathode light.

A huge drop in noise level is easily noticeable. When the computer is off, there is ambient background noise of about 25 dB. When it’s on, it measures 55 dB from 3 feet away before the cooling modification, and 39 dB after the mod. The CPU fan gave a constant, yet subtle, high-pitched noise at roughly 2.5 kHz, but it’s noticeable since everything else is a lot quieter with the cooling mod.

The power supply’s rear fan is naturally quiet, quieter than the four fans use for the Airflow Control Chamber. It’s also a good thing that these four noisy fans are muffled, since they’re located inside the case. The 120 mm fan itself produces about 35 dB of whirling noise, but it is further muffled since it’s also located inside the case. I can barely tell the computer is on when I walk into the room.

Table 2: Case Noise SPL Before and After the Cooling Mod

Ambient Noise

Before

After

Sound Reduction

~25 dB

55 dB

39 dB

97%

I used Battlefield 1942 for temperature testing. My broadband connection sucks, so I play with the stupid bots, which can be processor-intensive. I’m limited to playing with only a few bots, since this machine is an old Athlon 904 MHz overclocked from 700. Don’t laugh! I’m saving up to build a new system.

For the test, I set the highest number of bots (63 A.I.’s total) for high processing intensity. Graphics were set to highest on an old Radeon 7200 that has no onboard fan (it normally gets piping hot). Room temperature was about 27°C. The game ran in a choppy manner as expected, and the CPU temperature rose from an idle figure of 30°C to a peak of 32°C. Before the cooling mod, peak temperatures went up to 41°C. Thus, the difference is a 9°C (16.2°F) drop after the cooling mod!

Table 3: CPU Temps Before and After the Cooling Mod

Ambient Temp

CPU Temp Before

CPU Temp After

% Change

~27º C

41º C

32º C

22%

The chipset, CD/DVD drives, and everything else relevant seems to be okay (the northbridge is pretty warm, but cool enough to leave my finger on it).

I probed the thermometer into the CPU’s heat sink, not the core processor itself. So don’t pay too much attention to the CPU temps, especially when I’m running an older processor which doesn’t generate as much heat as modern ones; I think the percentage change has more significance since it shows cooling efficiency improvements. Now, I am ready for the hotter (literally) Athlon 64! Here’s the price list:

Table 4: Price List

Items Purchased
Price Each

Quantity

Cost

Tupperware
$1.07

1

$1.07

Plastic Box
$1.07

1

$1.07

Scotch-Brite (package of 4)
$1.07

4

$4.28

120 mm fan
$9.71

1

$9.71

80 mm fan
$3.23

4

$12.92

Conclusion

For less than 30 dollars, I was able to build a cooling system that satisfactorily met these goals:

  1. Cheap, at less than $30
  2. Clean, using Scotch-Brite scouring pads as filtration
  3. Cooler, by a 22% drop in temperature
  4. Quiet, at less than 40 dB, a 97% drop
  5. Non-remote, by having the system internally placed

To recap: Relocating the fans so that no fans are flush-mounted onto the computer case can help reduce fan noise, because the case can acoustically muffle it. This allows you to use more fans (without worrying about noise) to make up for the flow-loss caused by dust filtration, while keeping the system cool, clean too and quiet too!.

For intake and exhaust, an elaborate ductwork is built. Between the intakes and exhaust, there is the “Airflow Control Chamber” which quickly moves out hot air from the CPU, video card, hard drive, RAM, chipset and drives. All this hot air immediately flows through the power supply’s push-pull fans, rapidly exiting out at the back of the computer. Leggett’s chimney prevents this hot air from re-circulating back into the rear intake.

Have fun and be careful if you try this project.

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