No offense, here are some things that bother me about your understanding of fans.

[FoulOnWhite]

I kind of get the point from the OP, fans can have about 80% cooling capability with a slow as about 30% RPM. Some fans I got from Amazon to cool my NUC, were all way too fast, and with no way to slow them down, had to use an attenuator.

I would like to see max fan speed have less emphasis in reviews.


Cheapest fan I have brought for PC use in the last 3 years was £24 (fractal), I have paid over £40 (noctua) for some fans, I guess we have different ideas of cheap, efficiency is important as I expect affects life expectancy of the fan, and of course noise.

I have 6 fans in my case that cost between £150 and £180 all Noctuas

 

[lexluthermiester]

I have 6 fans in my case that cost between £150 and £180 all Noctuas

I have 3 120's and 2 140's all Arctic Cooling models and all for $61. They push as much air and only make 3db more noise.

 

[Shrek]

I tend to get fan packs even if that means a few spares

• Artic F12 five pack $23
• Artic P14 five pack $34

but went with a 30mm thick fan

• Antec T3 120mm three pack for $30
• Antec T3 140mm three pack for $40

prices are with shipping.

 

[freeagent]

The 3 fans that came with my case are pretty good. I bought 3x Thermalright 28mm fans for their AIO, that was about 45 bucks CAD, I bought their 92mm fan for like 10 bucks, and their 80mm fan for 8 bucks I think, and my case flow is excellent, and the system is silent when running at normal speeds. Love it. I know for sure you can do better with airflow, but at the level I am at right now, it wont really do much good other than make noise and make your epeen stir. Been there done that. I do have T30s that I could be running on the rad.. also have 120x38s that are stronger than the T30s lol.. bah.

 

[R-T-B]

Extremely dangerous too. It will take the tip of the finger off. I've blasted caps off motherboards with this thing bro. I'm not kidding, no bullshit. I don't touch it unless it's stopped fully.

When I was mining I dealt with some of the higher RPM deltas, can confirm they be monsters.

 

[lexluthermiester]

When I was mining I dealt with some of the higher RPM deltas, can confirm they be monsters.

I've seen those too. At the facility I previously worked at, our server room had big bright neon yellow sign warning people not to stick their hands anywhere near system fans while in motion/operation. They are legitimately dangerous.

 

[R-T-B]

I've seen those too. At the facility I previously worked at, our server room had big bright neon yellow sign warning people not to stick their hands anywhere near system fans while in motion/operation. They are legitimately dangerous.

Yeah @bobbybluz has what was left of my stockpile. They can maim.

 

[Visible Noise]

The physics of fans basically means that yes, they will almost always push more air the faster they are spun until the air behind the fan cavitates.

Cavitation is a phenomenon of fluids, not gases. Air cannot cavitate as it cannot boil.

SPL (sound pressure levels) doubles by 6db.

Here's another thing though... are sound sources additive...?

Go back to 1 sound source with the volume of 35 db, I know I have 35 db measured. If I add another sound source I now have 2 x 35 db which means in theory, I would measure 41db.

But if I have a 3rd source what do I have? Ok, this is where it gets weird and I get into something called sound networks.

Between those 3 devices there are 2 sound networks. There is the original sound, and the original plus 1 forming one network, and the original plus another forming another network. The two networks combined double each other which is why a) sound is additive, and b) the resultant sound in theory is 47db not 39.5db.

You didn’t account for phase. Before attempting to school others, please make sure your understanding of the subject is correct.

 

[correctthemisbegotten]

Cavitation is a phenomenon of fluids, not gases. Air cannot cavitate as it cannot boil.


You didn’t account for phase. Before attempting to school others, please make sure your understanding of the subject is correct.

Ok let me just go account for that real quick... LMAO.

 

[Visible Noise]

Ok let me just go account for that real quick... LMAO.

Account for what, making stuff up in a failed attempt to sound smart?

Have you heard of Wikipedia? It has writings on things like cavitation and SPL calculations. Give it a try sometime, it’s a very interesting website. It even has articles on energy efficiency.

And if you want to really get into the weeds you can find how to calculate the heat transfer coefficient of convection laminar flow (that’s using a fan to cool something).

 

[ShiBDiB]

What a way to introduce yourself to the forum

 

[Shrek]

And if you want to really get into the weeds you can find how to calculate the heat transfer coefficient of convection laminar flow (that’s using a fan to cool something).

I've always wondered about any advantages of turbulent flow for heat transfer.

 

[Visible Noise]

I've always wondered about any advantages of turbulent flow for heat transfer.

You WANT turbulence. Laminar flow creates an insulating boundary layer.

The art of engineering a cooling system is generating enough turbulence to break the boundary layer while minimizing the negative effects of turbulence.

There’s people that have PhD’s in this stuff. When I was in the auto industry I worked with a guy who had a PhD in noise. He worked on vehicle NVH (noise, vibration, harshness).

 

[Shrek]

I've also wondered about the possibility of computer fans with built in anti-noise.

 

[Space Lynx]

I tend to get fan packs even if that means a few spares

• Artic F12 five pack $23
• Artic P14 five pack $34

but went with a 30mm thick fan

• Antec T3 120mm three pack for $30
• Antec T3 140mm three pack for $40

prices are with shipping.

I would like to do a 30mm fan PC build someday, but my temps are great at the moment so I just don't care.

 

[freeagent]

Air moves like water, easiest way to picture airflow imo..

 

[lexluthermiester]

Cavitation is a phenomenon of fluids, not gases. Air cannot cavitate as it cannot boil.

I think they intended to say "resonate" instead of "cavitate", which can happen. Fans will resonate rather handily if even slightly off balance and not secured properly.

Ok let me just go account for that real quick... LMAO.

Hey, be nice, you're the one that got an important detail critically wrong.

Air moves like water, easiest way to picture airflow imo..

Excellent point, air is a fluid and fluid dynamics apply.

 

[Visible Noise]

I think they intended to say "resonate" instead of "cavitate", which can happen.

Oh no, look how he used the word:

The physics of fans basically means that yes, they will almost always push more air the faster they are spun until the air behind the fan cavitates.

Besides the first half of the sentence being wrong (they will almost always push more air the faster they are spun), he didn’t mean resonate either. He actually stated where cavitation happens in a liquid, without knowing what cavitation is.

A fan is a number of airfoils (blades) attached to a hub. Everything that applies to an airfoil applies to a fan, including things like flow separation: Yes, a fan can stall exactly like an aircraft wing.

 

[lexluthermiester]

Oh no, look how he used the word:


Besides the first half of the sentence being wrong (they will almost always push more air the faster they are spun), he didn’t mean resonate either. He actually stated where cavitation happens in a liquid, without knowing what cavitation is.

A fan is a number of airfoils (blades) attached to a hub. Everything that applies to an airfoil applies to a fan, including things like flow separation: Yes, a fan can stall exactly like an aircraft wing.

Yeah, I saw that. Under water that effect can lead to cavitation due to pressure differentials. In air that effect leads to turbulence and air-current eddy's which then results in resonation.

 

[thesmokingman]

What a way to introduce yourself to the forum

Got to be a troll cuz no one is this moronic from post 1.

 

[Visible Noise]

In air that effect leads to turbulence and air-current eddy's which then results in resonation.

Resonance is a physical property of an object. An object has a resonant frequency in each degree of freedom.

Since by definition turbulence is irregular, while resonance is regular, turbulence cannot cause something to resonate. Resonance is the amplification of movement by the application of an external force at resonant frequency of an object. Turbulence actually has a dampening effect on resonance.

Think of a ported loudspeaker. The ports are made up of smooth curves to guide sound in a laminar fashion - this is called a tuned port. If the air moving through a loudspeaker is turbulent, the cabinet will not resonate, and the port would not be able to provide sound reinforcement.

Or, ever been to a concert where a microphone experienced feedback? That feedback is linear, centered around one specific frequency. Since turbulence is not linear it cannot cause the resonance the creates feedback.

What turbulence can cause in a fan is a howl. This is caused by irregular pressure waves being amplified when they hit the fan blade.

 

[Shrek]

Reminds me of a stack of cooling towers. Gale force wind hit the lead tower which gave off turbulence (vortex shedding) that was thrown out at the resonant frequency of the lead tower and resulted in the trailing towers getting destroyed. Makes me wonder if they still make the towers identical.

The OP may have been thinking of the blades stalling.

 

[correctthemisbegotten]

Account for what, making stuff up in a failed attempt to sound smart?

Have you heard of Wikipedia? It has writings on things like cavitation and SPL calculations. Give it a try sometime, it’s a very interesting website. It even has articles on energy efficiency.

And if you want to really get into the weeds you can find how to calculate the heat transfer coefficient of convection laminar flow (that’s using a fan to cool something).

I have to say this: if you think you can calculate the sound of 5 - 35db fans inside of a computer case with 99% accuracy then by all means, please do so! I am not a fan engineer I am just a guy who thinks fan engineers aren't any good. I'm allowed to have that opinion. Like I said NO OFFENSE to all the "fan engineers" out there....

I know that you can't though, so I have to wonder why your brought that up???

Even if I could do it, and account for every reflection & material property inside the case down to the last millimeter, I wouldn't.

BTW, I don't read Wikipedia unless I want to find out how many wives it was Mike Tyson or P. Diddy beat and raped.

LMAO.

 

[FoulOnWhite]

Air moves like water, easiest way to picture airflow imo..

Some sciencey guy once said, we live at the bottom of an ocean of air. the surising thing imo is the fact it is 14.7psi

 

[Visible Noise]

I know that you can't though, so I have to wonder why your brought that up???

Do we know each other? How do you know what I can do, besides prove you’re a poser?

BTW, I don't read Wikipedia unless I want to find out how many wives it was Mike Tyson or P. Diddy beat and raped.

Too bad. You could have learned the Navier–Stokes equations that prove 90% of what you wrote is wrong - before you posted and made yourself look foolish and clueless. Some of us ARE engineers, and your first post was telling us

I’m bored with you. Goodbye.