Question from a test

[HJA]

This is a question from an exam for a class I am taking.

"In a properly designed, properly assembles PC case, air flows in a specific path from the power supply fan through the vent holes."

The vent holes being in the back of the case, I said false. I got it wrong. Supposedly some PSU's use their fan to vent on and cool the CPU????? That's what I was told. That I have never seen.:shock: Anyone here ever seen this method????

 

[pparks1]

Here is a link, if you read the second paragraph you will see it explains exactly what you are talking about.
Internal Air Flow

 

[HJA]

Interesting. Venting the heat from a PSU into the case. None of my computers ever had that!!! My current machine has over 100cfm of air movement and the PSU vents out. I would think with one fan you would vent PSU heat out, not in. But then all my PC's have been desktops not towers. Maybe thats the dfference.

 

[pillainp]

General rule is that lower fans (front, sides, etc) draw air in, and higher fans (back, top, PSU) draw air out.

 

[CoolioG]

Cold/ Room temputure air goes in ------->
<--------- Hot air goes out.

 

[HJA]

Cold/ Room temputure air goes in ------->
<--------- Hot air goes out.

No this was a single fan so PSU heat is venting into the case and out the back case vents. that's what he described.

 

[Frostmourne]

Is the PSU mounted on the top or bottom of the case?

 

[HJA]

Is the PSU mounted on the top or bottom of the case?

According to his description it is a tower configuration, so I would think it's blowing down over the CPU and MB. In all the PC's I've seen I have never seen that.

 

[stormy13]

Here is a link, if you read the second paragraph you will see it explains exactly what you are talking about.
Internal Air Flow

You notice the date on that article,

The PC Guide (Welcome to The PC Guide!)
Site Version: 2.2.0 - Version Date: April 17, 2001

majorly out of date. This is a little better,

ATX - Wikipedia, the free encyclopedia

Airflow

The original ATX specification called for a power supply to be located near to the CPU with the power supply fan directed to draw in cool air from outside the chassis and exhaust it directly onto the processor. It was thought that in this configuration, cooling of the processor would be achievable without the need of an active heatsink.[1] This recommendation was removed from later specifications and modern ATX power supplies prevailingly exhaust air from the case.

and would be the very reaon that no one has seen a PSU that blows in, they don't exist anymore (or are in a very old computer).

And some more light reading on the subject,

https://docs.google.com/viewer?a=v&...V0f7b1&sig=AHIEtbTVLamaUcd43f27G-nXYnzMFHq_HQ

and from page 34,

The ATX Specification allows for numerous (and often confusing) possibilities for power
supply fan location, direction, speed, and venting. The designer’s choice of a power supply
cooling solution depends in part on the targeted end-use system application(s). At a
minimum, the power supply design must ensure its own reliable and safe operation.

Fan location/direction. In general, exhausting air from the system chassis enclosure via a
power supply fan at the rear panel is the preferred, most common, and most widely
applicable system-level airflow solution. Other solutions are permitted, including fans on
the topside of figure 5 and the Wire harness side of figure 4 or 5. Some system/chassis
designers may choose to use other solutions to meet specific system cooling requirements.

 

[thefabe]

As far as I know ATX or BTX top psu or bottom they both draw air in from the case and blow it out the back. By the way nice post stormy13. Fabe

 

[ignatzatsonic]

"In a properly designed, properly assembles PC case, air flows in a specific path from the power supply fan through the vent holes."

I think maybe you misinterpreted the question.

I take the question to effectively mean "does a PSU fan normally exhaust air". That is "from the power supply fan through the vent holes"--airflow out, rather than in.

You said false/no.

False would be a correct answer if the question had been:

"In a properly designed, properly assembled PC case, air flows in a specific path from the vent holes through the power supply fan"--airflow in, rather than out.

 

[HJA]

By the way nice post stormy13

Ditto on that. Thanks

 

[HJA]

I think maybe you misinterpreted the question.

I thought so too but I asked and he said "vent holes in the case". After all the discission in class thats how I figured it was false. No big deal...all my classes are out of date. Books are always behind.

 

[Dwarf]

For best system cooling, you should arrange for the rear case fans (including the one in the PSU) to exhaust more air out than the front fans draw in. The fans should be arranged so that the inlet fans are sited towards the bottom of the case at the front, whereas the exhaust fans should be mounted at the rear of the case towards the top.

Cool air will then enter the system from the front, pass over the HDDs (as these are usually mounted in that vicinity), and be drawn upwards over the motherboard, effectively cooling the components. Any inbalance will be taken care of by air entering the system through the vents in the side panels. The by now warm/hot air will be exhausted out of the case via the rear case fans. This arrangement allows for a ready supply of cool air to flow through the system, and is known as negative-pressure cooling.

You can quickly check the effectiveness of your cooling by holding your hand near the exhaust fans. With good cooling, the exhausted air will feel slightly warm (mine is cool), but not overly so. If it is hot, on the other hand, you might need to check that the cooling system is working correctly. Check that the fans are correctly orientated and that they are clean and free of dust. Filters are available to trap dust particles. Check that the case vents are clear (for this reason I do not recommend the use of case noise-dampening material that may block these vents). Also check the cabling arrangement on the motherboard so that it doesn't impede air flow.