quick airflow/fan exhaust question.

D

Decay

Weaksauce
Joined
Mar 31, 2003
Messages
112
this is a 2 part question:

just wondering would using an aerosol can that we usually use to clean dust and stuff off electronics be ok to use to show the airflow of my case, if I spray it upside down... Or would that ruin my electronics? I would use cig smoke but I would think that would damage electronics more than an arosol can would.
thats my first question

second:

does anyone have an idea of what kind of material I can use to make an exhaust path for my rear exhaust fan??? I saw some images on here the other day of some ppl using like a plastic bag or something to help direct theyre exhaust flow out of theyre system. The thing is, I need to make a path for the exhaust where it can turn a 90 degree corner(not necisarially that drastic of an angle) so I can direct the airflow away from my system better. So it needs to be flexible enough to turn a corner, but stiff enough to keep from colapsing.
 
You can use actual ducting material. I don't have a link, but ducts are a universal application and consequently can be purchased. You might have some behind your dryer (to see what I mean, not to take). Can probably find it at your local hardware store.

As for the aerosol, I would definitely not do that. What you propose is something I have wanted to do for a long time but never looked into it. You'd have to find a solution that actually created a visible gas without other chemicals that would leave film on your components. Turning an aerosol can around will just get chemicals all over your components.

edit: Duct This store has some other ducts as well.
 
Decay said:
just wondering would using an aerosol can that we usually use to clean dust and stuff off electronics
Click to expand...

Yeh, but he's talking about the compressed air cans (i think? that's what i use) and it can get cold enough and start shooting out icy stuff.. I think this would be fine, but i'd do it with only fans running.

However if this aint, someone please say so.
 
yeah I mean the compressed air cans... I know they have chemicals in them as well, but Im not sure if they will do any harm for a quick test...
 
Well... I'd be willing to bet you could do it and not have any problems. Still isn't something I personally would do. That stuff is cold and nasty. It will land and evaporate pretty quickly but I imagine it leaving a film behind. You could always spray some and test to see if it's conductive at all.

Besides, how well would this work do you think? It's been awhile since I've sprayed any of that but in my experience the liquid would shoot and land without blowing around, and the gas that's visible dissipates rather quickly. I'm just not sure how visible it would be.

A search found me a thread on another forum where incense smoke was used to test airflow (also not ideal but another option).
 
Get some Dry Ice and toss some into a glass of water.
Place a condom or baloon over the glass and stab a straw through the top.
The Dry Ice will make that nice fog effect and it will be forced up through the straw. Then you just move the straw around the case to see exactly where the air is moving.
 
You DEFINITELY do not want to invert a can of compressed air to release the propellant to check for airflow.

First of all it's not going to acurately reflect actual airflow. The expelled propellant become very cold (hense much denser) than actual air in your case when it's being circulated by the fans. Unless your ambient temperatures are expected to be about -20 F in your computer room using that method isn't going to show you a thing.

Secondly, and along with the previous idea, because you're not actually forcing air (O2) into the case, even if there was some way to overcome the temperature casued density of the "air" you're still dealing with a compressed propellant which is probably not similar to atmospheric air.

Lastly, the supercooled "air" from the can will cause MAJOR condensation on anything it contacts. Forget the film left behind. Forget that the propellant will evaporate within a very short time on contact with anything room temperature. It's also going to take with it a bunch of very small "raindrops" which will collect on anything and possibly short out everything. It's the same principle as how raindrops form in clouds as water vapor cools to collect into globs of water.

The idea of using cigarette smoke would be okay. Yes, cigarette smoke is harmful to computer parts, but so is dust. If you're trying to get smoke to go into your case for about 2 minutes it shouldn't really be a problem since I smoke near my computers daily and haven't fried anything. The problem with that idea though is that the fans dont create very smooth airflow. Fans work by creating a lot of air turbulance and what usually happens to the smoke is that it gets so mixed up you can't really tell where it's going. You'll see it going into the case but then you'll loose sight of it as soon as it passes the fan. It's not going to be the cool "airstream over the hood of a car" thing from commercials.

Try a July 4th smoke bomb or something. It's thick, colored smoke which may be a little more visible although within a few seconds it's probably joing to just fill the case.
 
cool, good ideas... Well I had a thought that using compressed air cans wouldnt work very well. So I was thinking a fog machine, my band has one that we use occasionally for shows. Thats a thick cloud that would be visible. And I dont believe it would harm any components, unless Im mistaken.
 
I just wanted to clear up some misinformation on the "canned air" that is being tossed about.

Most, if not all, "canned air" sold to dust electronics components does not contain any air to speak of. All it contains is a Hydrofluorocarbon (detailed below). When you spray it upright you are spraying it out in gaseous form. when you turn it over and spray you are spraying it out in its compressed, liquid form which immediately turns to gas.

"Canned Air" is 1,1,1,2 Tetrafluroethane at > 95% by weight according to the manufacturers MSDS.

There is a product that is commonly used in electronics manufacturer and testing that is used to do thermal/cold testing. they use a refrigerant sprayed directly on the component to cool it to see if it will fail at cold temps. These products are almost identical to canned air.

One such product, ECG ANTISTATIC CIRCUIT REFRIGERANT:
1,1,1,2 Tetrafluroethane at 98% by weight
Methanol at 2% by weight
according to the manufacturers MSDS

So, as you can see by this, canned air is safe to be used on electronic components, even when under power. the only thing happening when turned upside down is you are spraying it out in the colder, liquid form. Neither the cold produced by canned air or the liquid will normally cause any problems with your system.
 
All that having been said, Tetrafluoroethane is also a CFC-free refrigerant used in industrial and commercial HVAC applications. It's basically r134a refrigerant (the same stuff used in the air conditioning unit in your car, your refrigerator, and in Vapochills). It's commonly called Freon which is actually a brand name trademarked by DuPont (I think).

It has the ability to cool any surface to -52°C within 5 to 8 seconds. I've been unable to find exact specs for it's impact on air however several sources have compared it's properties to nitrogen. Regardless of it's exact effect on air, a substance able to chill a surface to -60°F (basically on contact) is certain to have an effect on the air and therefore the water vapor. If you spray the "liquid air" on a surface for about 3 seconds you'll notice frost forming. I'd be very concerned about consensation caused by superchilling the air.

Think about your house's air conditioner, when you run it have you noticed water pooling inside or under the unit? Or ever notice the bleed line inside your house draining water into a sink? That water was removed from the air in the process of cooling it.

Those reasons were why we used low pressure compressed air when I serviced digital imaging equipment. I worked on Fuji Frontier mini-lab equipment (they cost about $150K for the printer) and we'd never consider using canned air on any exposed electrical components.

Is it safe? Yeah, probably. Actually, more than likely it's completely safe considering how many people use canned air to dust their keyboards, etc. For cleaning I prefer natural air from a small, low-power compressor. Regardless though, Tetrafluoroethane will not act the same as "natrual" air to test airflow in a case.
 
Dry ice in a cup is probably not a good idea, same with the fog machine.
Both are filling your case with water, not something you want in your case.
 
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