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Negative Pressure Rig With NO Case Fans!

 
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post #1 of 8 (permalink) Old 03-09-2016, 05:17 PM - Thread Starter
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My long-suffering Beta Evo! It was the first case I modded. I cut out grills. I cut a new bottom hole for a fan. So now I was running a Megahalems with two Yate Loon D12SH-12's. But case fans? Well, two were installed but I left them unplugged. What you will see is a negative pressure rig using NO case fans.

 

Here it is:

 

Beta Evo - modded

 

Notice - no rear or top grills - and no rear or top fans. I've left the slot covers off the rear slots. You can see that side-mounted 500 rpm Kaze Maru is standing still. The blue light at the bottom means the machine is on. You can see the heatsink pull fan is spinning.

From the front, top down:

 

Top view of Beta Evo

 

See the push fan is spinning. Another Yate Loon D12SH-12. You can also see the pull fan and the open space behind it.

 

Next, the front - down low:

 

Front view, GT unplugged

 

In the light of LED's you can see the 800 rpm Gentle Typhoon - unplugged. The LED light means the rig is running. The old i7 860 was actually running at 4004MHz, doing OCCT/Linpack as this picture was taken.

 

Now, I could feel air pulling in at every orifice but one (the rear exhaust portal). Air was pulled in through the Kaze Maru, through the Gentle Typhoon, through the top holes, through the grill next to the Megahalems, through the PCIE slots. Want proof? Here it is:

 

Side view tissue

 

That's right - the heatsink fans, running alone with all orifices open, made a piece of Kleenex stand up. But maybe it was just a trick. How's this?

 

Tissue Up

 

Yup. Held up by negative pressure alone.

 

I thought about actually removing all of the case fans and running this with cpu heatsink fans only. Considering how very many holes there are in this case and how big they are, it's a wonder there is any appreciable negative pressure at any influx spot. I was so amazed I just had to share it.

 

Note: this thread was originally posted in 2010. The images were hosted elsewhere. Luckily, I still have them. So I have reposted this thread. Now the images are hosted in my Gallery.

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post #2 of 8 (permalink) Old 03-09-2016, 10:42 PM
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Great post! Thanks for bringing it back. And clever to use the kleenex as spontaneous dust filters. biggrin.gif

That's the only issue with negative pressure cases...attracts the dust fairies and all their hangers-on. Or was the world that much cleaner back in 2010? ;-)
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post #3 of 8 (permalink) Old 03-15-2016, 09:44 PM
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This is actually a revival of an old cooling scheme. In the late 90's, Dell Dimension XPS computers had no case fans. I had one of these. All they had was one CPU fan that was enclosed by a plastic shroud that attached to the back of the case. The fan blew air across the CPU heatsink and the warm air was ducted out the back of the case, creating negative pressure. The system was lousy because Dell used super-cheap crappy heatsinks and didn't explain that the duct collected dust like crazy and needed regular disassembly and cleaning. Anyone who buys a pre-built computer is not the type of person who wants to be disassembling their computer on a regular basis. That's more for the hobbyist market.



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post #4 of 8 (permalink) Old 03-16-2016, 02:15 AM
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Glad to see this bit of testing back! thumb.gif

Do you still have this system?

I do have to wonder if the open top vents are making any difference. I'm guessing they could be closed off with little or no change is flow.

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post #5 of 8 (permalink) Old 03-25-2016, 09:50 AM - Thread Starter
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Sorry to take so long to respond. I forgot to subscribe -- I thought subscribing was automatic for the OP.

 

This was simply an experiment. I wanted to see, then I wanted to demonstrate what a case would do with no external fannage. It was shocking to get so much suction when so many widows were open in the case.

 

When this system was my primary, it was a pure positive pressure case. I think if you click on my avatar you can see a diagram of the airflow. Front and sides had intake fans. Up top, I ended up blocking to rearward window. The forward top window had a Thermalright TY-140 on intake. It was designed to feed my heatsink air directly from the outside. 

 

It went under a shelf, so the blocking plate could be kludgy-looking because no one would see it. Here's how it looked from above:

 

d07e8ead_Hotrod_Take_2_From_the_Top.png

 

Here's how it looked from underneath:

 

My rig

 

Note that I changed heatsinks. I wanted the Megahalems for test fans and things. Note also how I kludge-mounted my HD's in those days. Since then, I have changed cases twice. This case sat around for a few years. I finally stripped out all the interesting hardware and sent the carcass to the recycler.

 

In one way this differed from the Dell. I had those. They cooled the CPU, and that was all. Here, the pull fan on the heatsink sucks air through the case by entraining the air in it. This aids the intake fans.

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post #6 of 8 (permalink) Old 03-29-2016, 09:09 AM
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blast from the past thumb.gif

You know what they call a case with no intake/exhaust fans? A Test Bench. Just cut off all the other metal stuff of the case you dont need smile.gif

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Golden Rule(s) for Fans: CHEAP + SILENT = NO PERFORMANCE ▼ CHEAP + PERFORMANCE = NOT SILENT ▼ SILENT + PERFORMANCE = NOT CHEAP
+Most SILENT Case Fans are not well suited for CPU-HS-Towers or Radiators
+Most SILENT Case Fans are not well suited for cases, especially if they have filters. (added by doyll on 23/04/2014)
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post #7 of 8 (permalink) Old 03-29-2016, 05:44 PM
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Quote:
Originally Posted by RnRollie View Post

blast from the past thumb.gif

You know what they call a case with no intake/exhaust fans? A Test Bench. Just cut off all the other metal stuff of the case you dont need smile.gif

The reason why you have a case is for EMI shielding , minimizing dust, and for a bit of noise isolation

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post #8 of 8 (permalink) Old 03-29-2016, 07:38 PM - Thread Starter
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These days I have a test bench. Here it was before:

 

ATCS motherboard tray, used for testbed


Here it is at work:

 

ATCS motherboard tray, used for testbed -- in action

 

The case with the open windows had fans in them, kept my rig cool for years as my primary.

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