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

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.
Use db X app on your phone. Give you an idea of the sound spectrum.
 
I saw that myself when using side case fans, that said I always kept the side panel port(s) open and had better temps than with glass side panels since the CPU cooler and gpu could pull in cooler air themselves
I have never suggested blocking vents. I just don't typically recommend the use of side panel fans (unless blowing into a tube) - as they can disrupt the desired flow of air through the case, creating turbulence which would prevent the heat from being exhausted as quickly as possible. That said, the tube may impact that desired flow too.

Note if the CPU or GPU cooler is drawing air in through a side panel vent, I would be looking at adding another intake fan in front to achieve a slight "over" pressure in the case. That forces all intake air to come in through designated vents - which [hopefully] are filtered. In fact, any case I buy these days will be filtered. But that's for a different discussion.
 
There is far more to fans than just eff and noise, like longevity and looks. To get max longevity you want to keep them spun at sensible speeds, fan lifespan does follow a non liniar plot, so at lower speeds they can last a very long time. At very low speeds they can last up to 15-20years without any internal servicing.

Finally another misundersanding is not taking into consideration that loudness is pressure intensity and doesn't always mean the most annoying. Large diamter fans emit lower freq sound which is more effective at irritating in general, think how modern four stroke dirt bikes which are not as loud as two strokes can be heard from much greater distances and really irritate people.

Really, if you want silence you need to get your fans down to HT build levels which for the high end tasks today is not possible. Even my gpu fans at their lowest rpm are more than enough to annoy many. My macchine is quite noisy it reminds me of a powerful split system air con when gaming tbh.
 
How did I miss this mess? Pro'lly spaced out at work over the weekend.
First and foremost you must understand that any given fan shape, size, thickness, will have a single speed at which it is most efficient.
But PC fans in particular are used in a range of RPMs. You can make case fans spin at constant speed, but for CPU/GPU there is no way around it (except blasting at 100% speed for safety:D)
Now, the surprising thing about efficiency is that it means there are no fans that are better than others in a general sense.
Oh, yes there are. Don't tell me that my 120mm Chieftec PWM fans that they forgot to lube from the factory and sounded like a helicopter even after lube was applied generously are somehow not worse and just as efficient as my nearly inaudible cheapo Xilence fans that cost the same... Am I using them wrong or something? Maybe they are inaudible at lower RPM (likely @0rpm)?
The sad reality is that 99% of reviews that I see always look at the maximum performance and not the maximum efficiency.
Because for fans in particular efficiency ain't that big of a deal. A typical decent fan may have a current draw of, let's say 0.08A@50% max rpm, and around 0.12A@100%. Let's round it up to 1.0-1.5W power draw. Let's say you have 10 of them in a case, including the ones on your CPU/GPU/AIO. That's 15W at most. So if your gaming case has a couple of 50cm RGB strips on the front or side panel - they have higher average and max power draw than all of your fans combined (~18W/m max for a typical 60 LEDs/m strip), so if we care about efficiency - we must abolish ALL RGBs!
 
Sorry but cannot agree with some of the above.
There is far more to fans than just eff and noise, like longevity and looks.
Looks is pretty close to, if not at the bottom of the list for me. First, I expect my cases to sit quietly and discretely off to the side and NOT draw any attention to themselves. If talking about RGB lighting, note it does nothing for performance, consumes some energy, generates some heat, and does nothing for performance (worth repeating). Also, I do not spend hours gazing in wonder at the innards of my computer case, but instead, pay attention to what's on my monitors. Therefore, looks are not important - at least not to me.

Large diamter fans emit lower freq sound which is more effective at irritating in general
Don't agree with that at all. Unwanted high frequency sounds are much more irritating for most people. This is because high frequencies are perceived as being louder and can be more damaging due to their shorter wavelengths - which can result in more intense vibrations and discomfort.

Unless the low frequency has such amplitude that we can feel it rattling our molars, it generally just fades into ambient background noise. High pitch sounds can pierce through that with ease.

Also, high amplitude low frequencies take a lot more power to produce, in part because they most move a lot more air. This is why subwoofers, for example, often come with their own integrated amplifiers - like this relatively small 12" sub, with its 200W RMS amp.

think how modern four stroke dirt bikes which are not as loud as two strokes can be heard from much greater distances and really irritate people.
Nah! That's not a good analogy as it does not take into consideration engine size, muffler capability, or the fact the idiot on his four stroke dirt bike is racing up and down residential streets - that's what is irritating! Unless modified, most 2-stroke dirt bikes are not street-legal, assuming their emissions even let them be used in that jurisdiction at all.

Or there's my neighbor mowing his lawn at 7am with his vintage Lawnboy 2-stroke mower that spews out as much smoke as it does irritating noise. :(
 
So I ask AI search engine how much BTU a 120mm fan can move at 1500 RPM

If a 120mm fan at 1500 RPM has an airflow of 48.2 CFM.
And you're moving air with a temperature difference of 10°F.
Then, the heat moved would be approximately:
48.2 CFM x 10°F x 1.08** = 520.56 BTU/hr

** 1.08 is a conversion factor derived from the specific heat of air and other elements under standard conditions
 
520.56 per hour??? That does not seem right to me. A 100 to 150 square foot room would need a 5,000 BTU AC (according to various AC charts). Not sure, but I think that is based on 8ft ceilings. So 800 to 1,500 cu feet. Let's say 1,200 cu feet.

What's the inside of the average computer case? The exterior of mine is 9" x 17" x 20". That's 3,060 cu inches, or 1.77 cu feet.

It seems to me that should be closer to 52.0 BTU and not 520. But I'm no mathematician nor do I have an engineering degree in thermodynamics.

That said, most case fans these days are 140mm and many can move twice that amount of air, or more. This ARTIC P14, for example, can move 90CFM with a max speed of 2800RPM. But then that fan claims a noise level of 0.1 Sones which equals a "-" (yes, negative) 5.2dB. :kookoo:

So what does all that mean? No clue. Have a good day.
 
520.56 per hour??? That does not seem right to me. A 100 to 150 square foot room would need a 5,000 BTU AC (according to various AC charts). Not sure, but I think that is based on 8ft ceilings. So 800 to 1,500 cu feet. Let's say 1,200 cu feet.

What's the inside of the average computer case? The exterior of mine is 9" x 17" x 20". That's 3,060 cu inches, or 1.77 cu feet.

It seems to me that should be closer to 52.0 BTU and not 520. But I'm no mathematician nor do I have an engineering degree in thermodynamics.

That said, most case fans these days are 140mm and many can move twice that amount of air, or more. This ARTIC P14, for example, can move 90CFM with a max speed of 2800RPM. But then that fan claims a noise level of 0.1 Sones which equals a "-" (yes, negative) 5.2dB. :kookoo:

So what does all that mean? No clue. Have a good day.
I kind of thought the same thing, but also why I had underlined the 10 degree temp difference.

But 1 foot cubed air space is not the same as floor square footage.
 
But 1 foot cubed air space is not the same as floor square footage.
Ummm, no. Its not the same. But that is why I included the 3rd dimension of ceiling height of 8 ft, resulting in the room's "air space" in cubic feet.
 
You....jesus.

You've bastardized everything.
Convective energy transfer is when two masses of different temperature mix, and because they interact they will come to a new average. Think about this as if it were an oven, where the CONVECTION oven mixes very hot air from around a coil with relatively cool air to create an area of relatively high temperature. This is not about vectors...and the fact that you somehow BS'd this definition together makes me ask if you are a troll or are genuinely requiring me to speak with smaller words. Convection requires the mixing of fluids...

Conduction is the energy of one surface transferring to another surface. It assumes that things are in contact...like a fluid flow and a tower blade. It conducts heat from point A with higher potential to point B with lower potential. It's...jesus...it's basically all that you consider unless in a vacuum or mixing fluids because "heat" is simply random kinetic energy and we model the universe as a series of atoms...which is kind of like saying energy transfers outward from any point of concentration.

Radiation is what happens when energy is emitted from a black body. Before you somehow make that racist, it's a body that absorbs all energy and emits energy based on radiating it as energy levels shift. IE, imagine a lump of Carbon. It has certain atomic energy level storage. When excited (heated up), it emits only certain radiation spectral, as electrons fall from excited to ground state. This is why you get things like tungsten filament and sodium lights emitting different colors, despite both taking in electricity and converting it into visible light and heat. Again, really crappy process to transfer energy...which is why the sun can be millions of degrees hot for hundreds of thousands of years...turn Venus into a lava world, and Mars can be a frozen landscape despite being nearly a twin of Earth but just a little bit farther on orbital radius.



Now, let me de-stupid your comments about the sun. It is...absolutely idiotic. Convective currents on the sun exist. This is because the plasma, a fluid, moves and swirls. A charged particle field (plasma) moving induces magnetic fields, which can cause things like eruptions of plasma. This is the regular process which will create extremely strong magnetic fields, which may cause coronal mass ejections. These CMEs cause solar flares, because something the size of Earth composed of plasma has a bunch of energy associated with it. CMEs, when pointed at Earth, have enough energy to generate a stream of charged particles. Said stream interacts with the magnetic field of the planet, potentially distorting it and causing electromagnetic distortions...and this children is the Northern Lights. During particularly high solar activity, the voltage induced by the charged particle flow can overwhelm the magnetic field of our planet, dramatically increasing radiation exposure by allowing charged particles to permeate the atmosphere...and to even induce voltages in metals. This has happened in known history...stories of which include telegraphs operating without external power sources, and metal items creating burns when their charged state grounds to something through flammable material...like human flesh.
The solar wind is not about blowing off photons....because photons have no charge. They by definition are packets of radiation...which do not have mass. They are also constantly emitted by the sun...because photons are light, and the sun RADIATES light constantly as the excited state of smashing hydrogen into helium allows excited electrons to step down from highly excited to just excited...

For the record, sun radiates heat. Photons strike objects. Objects radiate what they do not absorb, and what they absorb excites their energy state. If object is a fluid, and is surrounded by other fluid, then this creates convection currents which try to even out the energy of the system. Think the weather...with our atmosphere being heated on one side and not the other... If the photon strikes something solid, like say your car, it cannot mix into the surrounding, so it conducts the random kinetic energy out into the world.
If you want to be even more simple, radiation is so bad at heating that it's cooler under an apple tree's shade than in direct sunlight. Convection is so crap at retaining and transferring heat that a 20 second blast of air can cool your car from 100+ degrees and stifling to breathable...but if you sit your butt down on that seat even after the blast of air you'll wind up with flesh fused to pleather because the 20 seconds of air did nothing to cool the 120 degree seat...but you sitting there raised your butt from 98.6 degrees to 108 so fast that it smells like burning bacon.


I'm going to math at you one last time so you can get the magnitude of how stupid your statements are.
Q = σ * ε * A * T^4 (equation for radiation energy transfer)
σ - Boltzmann constant, (5.67 x 10^-8 W/m²K^4)
ε - Emissivity, between o (perfect reflector), to 1 (perfect black body)
A - surface area of source
T - Temperature, based on 0 being absolute zero.
Note that Radiation only transfers energy at any real rate when your temperature is really high...because 10^-8 is really small.

Q = h * A * (Ts - Tf) (equation for convective energy transfer)
h - convective heat transfer coefficient....which is highly variable based on fluid flow
A - surface area of source
Ts - surface temperature of source
Tf - fluid temperature
Note that this is not a great way to conduct heat...because it only works fluid to surface...and is based on how fluid is mixing.

Q = k * A * (dT/dx) (equation for conductive energy transfer)
k - thermal conductivity
A - surface area of source
dT/dx - temperature gradient from source to environment
Do you get it? Let me help. k is material based. No requirements for mixing, just 1:1 performance. dT/dx is also 1:1, where the difference in temperatures directly changes the energy transfer rate. If you start from the assumption that the fan can always push air of a known temperature...which most computer coolers should assume unless they want to heat up a room, then you only have to meet air flow over the fins to demonstrate how much energy you transfer.

This is why your convection oven cooks a Turkey in hours, your conduction based pan cooks an egg in minutes, and the sun gives you a skin burn after a few hours...despite falling into said sun would evaporate you before you could stand on its surface. The fact that I have to explain basic heat transfer, while you want to bemoan specifications on fans, has me questioning whether you should be allowed to hold any silverware more dangerous than a soup spoon...for your own safety.


Last little bit...because. I'm going to ask you why there are convective currents in space. I think maybe you mistake the magnitude of things because you cannot wrap your brain around the numbers here. There are filaments and strands of matter between spatial bodies...that scientist have recently managed to quantify. It was an insane amount of matter, which inductively you'd assume was huge. Unfortunately, inductive reasoning is not good reasoning. Things like these filaments and things like the Kuiper belt are really really huge. One million pounds of matter, over 1 trillion cubic units of space is 1 pound per million units of space...which is nearly zero....but that's way more than a vacuum and if you have a trillion trillion units of space then it's going to be a lot. Your brain might not register that as being huge, but the math definitely proves it.

You've managed to bastardize English, attempt to rewrite the definition of words based on a third grade level understanding of them, and all of this in service to pretending you know everything about fans. Could you kindly shut up with the demands, and educate yourself, before you act like some savant? I mean, unless you're 13 and this is the "I want to test boundaries, and know everything because I know something" phase then you've managed to have me question whether you're a troll or a hallucinating AI...and at this point I'm leaning to the 13 year old. Convection being about vectors is a hilariously stupid grasp. One second on Google would have told you this was pants on head stupid...and vectors being how energy transfer is...wow.



Reading topics:
Entroy
Maxwell's demon
Basic thermodynamics
A dictionary printed in the last 200 years
STP...what it means and why it matters
....anyone who will ask you "if convection is about vectors, then why isn't conduction about ducting"...literally, anyone....
Thank you for a refresh of Grade 11 Physics.
 
Ummm, no. Its not the same. But that is why I included the 3rd dimension of ceiling height of 8 ft, resulting in the room's "air space" in cubic feet.
oh, I see what you're saying. My mistake.

There wasn't a room space involved in the equation with floor wall and ceiling dimensions. The air can be in a room or outside, the fan would still move and dissipate the same amount of air.

The fan moves 48.2 cubic foot per 1 minute. It takes 1 hour to change the temp difference of 10 degree.

This is the equation given.
BTUH = CFM x ΔT x 1.08
  • BTUH is the British Thermal Units moved per hour.
  • CFM is the cubic feet per minute of airflow the fan provides. A 120mm fan at 1500 RPM might have an airflow around 48.2 CFM.
  • ΔT is the temperature difference in degrees Fahrenheit between the air entering and leaving the area being ventilated.
  • 1.08 is a conversion factor derived from the specific heat of air, the density of air under standard conditions (70°F and sea level), and the number of minutes in an hour.
 
There wasn't a room space involved in the equation with floor wall and ceiling dimensions.
No, but it seems safe to assume "air space" of a building's room and "air space" inside a computer space is essentially the same thing, just on a smaller scale.

That said, I don't have any proportionally equal mini-furnaces heating up my room's air space as there are inside my computer cases (CPU and GPU).

But yeah, the math checks using that formula. 520.26 still seems like a lot. One day, if really interested, I will check a couple computers here to actually measure the ΔT of my computers. I wonder how much difference the fact my house sits at 1137 feet above sea level and the current ambient (room) temp of 74.1°F makes? Don't hold your breath I'll get that interested! ;)
 
No, but it seems safe to assume "air space" of a building's room and "air space" inside a computer space is essentially the same thing, just on a smaller scale.

That said, I don't have any proportionally equal mini-furnaces heating up my room's air space as there are inside my computer cases (CPU and GPU).

But yeah, the math checks using that formula. 520.26 still seems like a lot. One day, if really interested, I will check a couple computers here to actually measure the ΔT of my computers. I wonder how much difference the fact my house sits at 1137 feet above sea level and the current ambient (room) temp of 74.1°F makes? Don't hold your breath I'll get that interested! ;)
Lol. I think yes, the equation is simple and plain, the variables for you exact use and mine will be different. But at least we have some sort of baseline..... you now know what a 120mm fan can move in 1 hour at 1500rpm at 70F at sea level. :)
 
Yeah, but what's the conversion factor for 2 month's worth of dog hair clogging the fan's intake air filter? ;)
 
Yeah, but what's the conversion factor for 2 month's worth of dog hair clogging the fan's intake air filter? ;)
Probably some division and subtractions! So we install 9 120mm fans and compensate. And luckily in a PC case, maybe only 1.5 Cubic foot of space ;)
 
I have 2x 200s, 1x 140, 1x 92, 1x, 80, 6x 120s and a partridge in a pear tree haha..

Should be enough..
 
I have 2x 200s, 1x 140, 1x 92, 1x, 80, 6x 120s and a partridge in a pear tree haha..

Should be enough..
I actually can't see the rest of 3x120s in your profile picture.
 
I actually can't see the rest of 3x120s in your profile picture.
The top view is not very glamorous :)

IMG_1617.jpeg
 
The top view is not very glamorous :)

View attachment 408525
There they are; the sneak peak from top.
Overall, 2x200 Intake and 9x fans are exhaust. That's quite ventilation doing in your rig.

Double exhuast setup from top. Are they really that much effective too?
 
So I ask AI search engine how much BTU a 120mm fan can move at 1500 RPM

If a 120mm fan at 1500 RPM has an airflow of 48.2 CFM.
And you're moving air with a temperature difference of 10°F.
Then, the heat moved would be approximately:
48.2 CFM x 10°F x 1.08** = 520.56 BTU/hr

** 1.08 is a conversion factor derived from the specific heat of air and other elements under standard conditions

This math is...something else. Let's set our assumptions. I start here because if you wanted to be pedantic you'd have to define density of the heated air and a litany of other stuff, because math and physics cannot be that easy. Grumble...dry and wet bulb shenanigans...grumble...
1) There is no density change in the air being moved versus the air in the surroundings.
2) Our fan pushes 48.2 cubic feet per minute of air displacement
3) We are at STP otherwise...to simplify the pressure and temperature issues from part 1's assumption.
4) Specific heat of air is 0.24 Btu/lb/degree F
5) We have dry air....because of all the problems that will solve... Yes, there is a technical definition of dry air, it is not an attempt to move the bar.

Volume of air = flow rate*time = 48.2*60 (minutes/hr) = 2892 cubic feet
Mass = density*volume = 2892 ft^3 * 0.0765 lb/ft³ = 221.238 lb
Energy (Btu) = specific heat*mass*degrees F = 0.24*221.238*10 = 530.97 Btu

Your answer in Btu is for one hour of operation, so yes. 530 Btu/hr would be the difference in energy that the air mass the fan moved would have from the surrounding air...but what exactly is the endgame here? You theoretically can say that if the system is at steady state it has transferred 560,206 joules of energy in that hour (1 Btu = 1055.06 Joules)...which would theoretically be useful for back tracking the output of the thing creating the 10 degree difference (560,206J/3600s = 155 Watts of thermally dissipated power). That said...you started with the temperature delta already so you know what that was.... I just cannot connect the statements to an endgame. Help me here.

Also...please no magic conversion. The second people start slapping in number is the second their math goes off the rails because you never know where their conversion came from, where the units are going, or if the source is even making good assumptions. For the record...the above AI has not assumed anything regarding dry or wet air...and that difference absolutely would change your outcome. That's...something much deeper into the math though.
 
This math is...something else. Let's set our assumptions. I start here because if you wanted to be pedantic you'd have to define density of the heated air and a litany of other stuff, because math and physics cannot be that easy. Grumble...dry and wet bulb shenanigans...grumble...
1) There is no density change in the air being moved versus the air in the surroundings.
2) Our fan pushes 48.2 cubic feet per minute of air displacement
3) We are at STP otherwise...to simplify the pressure and temperature issues from part 1's assumption.
4) Specific heat of air is 0.24 Btu/lb/degree F
5) We have dry air....because of all the problems that will solve... Yes, there is a technical definition of dry air, it is not an attempt to move the bar.

Volume of air = flow rate*time = 48.2*60 (minutes/hr) = 2892 cubic feet
Mass = density*volume = 2892 ft^3 * 0.0765 lb/ft³ = 221.238 lb
Energy (Btu) = specific heat*mass*degrees F = 0.24*221.238*10 = 530.97 Btu

Your answer in Btu is for one hour of operation, so yes. 530 Btu/hr would be the difference in energy that the air mass the fan moved would have from the surrounding air...but what exactly is the endgame here? You theoretically can say that if the system is at steady state it has transferred 560,206 joules of energy in that hour (1 Btu = 1055.06 Joules)...which would theoretically be useful for back tracking the output of the thing creating the 10 degree difference (560,206J/3600s = 155 Watts of thermally dissipated power). That said...you started with the temperature delta already so you know what that was.... I just cannot connect the statements to an endgame. Help me here.

Also...please no magic conversion. The second people start slapping in number is the second their math goes off the rails because you never know where their conversion came from, where the units are going, or if the source is even making good assumptions. For the record...the above AI has not assumed anything regarding dry or wet air...and that difference absolutely would change your outcome. That's...something much deeper into the math though.
There is no end game. Everyone has a different air density and different fan speed. Perhaps different types of fan blades. Different elevation.

It was just a crude way to measure a fan's cfm.

Curious you quoted that post and not the one I made a couple later with the equation already supplied with explanation.

So, just for the heck of it, copy paste it.
(Recap = was an AI search engine generated response to the question - " how much btu can a 120mm fan move at 1500 rpm." - Yes, the AI had to use some additional information as assumption, such as, how many cfm the fan would produce at its size and fan speed, so also used 1.08 for specific air density under "normal " (70F) conditions at sea level, while guessing a 10 degree difference in temps)

This is the equation given.
BTUH = CFM x ΔT x 1.08
  • BTUH is the British Thermal Units moved per hour.
  • CFM is the cubic feet per minute of airflow the fan provides. A 120mm fan at 1500 RPM might have an airflow around 48.2 CFM.
  • ΔT is the temperature difference in degrees Fahrenheit between the air entering and leaving the area being ventilated.
  • 1.08 is a conversion factor derived from the specific heat of air, the density of air under standard conditions (70°F and sea level), and the number of minutes in an hour.
I suppose you would adjust ΔT and 1.08 in order to find your specific results.
 
Yeah, but what's the conversion factor for 2 month's worth of dog hair clogging the fan's intake air filter? ;)
What you don't have a manometer across your fan grill with a differential pressure warning?? ;) :)

It works for me :D


Good job on the math lessons, I hate numbers, but find them fascinating too.
Lies

You love it when you get that part to +/- 0.0001" ;)
 
What you don't have a manometer across your fan grill with a differential pressure warning?? ;) :)


Lies

You love it when you get that part to +/- 0.0001" ;)
+.0001 -.0003 makes for a stressful run haha :D

Still get almost half a thou, but that +.0001 is brutal :laugh:
 
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