Do Case Fan Actually Bring Down CPU Temp??

[NewCompGeek]

this might sound like a newb question but i really dont know

I mean just by a basic setup 2 rear 2 front do they actually do or it depends on the hsf?

cause if i remember right i saw a reply that said that the case temp can get only to room temp.

and case fans do how much degrees does it actually bring it down? say 100cfm how many degrees?

and im not sure casue the CPU fan blows on the hsf so i dont know if it would make a difference

 

[PCHPlayer]

Didn't like your other thread??
Think about it. How can a fan that just moves air "cool" the air. It can't. The best it can do is to remove the hot air from the case and replace it with room temperature air. The more frequently the case air is replaced by room air the closer to room temperature the case will be. If your room is 85 F (as it gets in SoCal in the summer) the best case temp you will get is 85 F. Maybe all those fans you want to install will get it very close to room temperature.
When it comes to cooling you need to compare case temp to room temp and CPU temp to case temp. The closer these numbers are to each other the better the cooling solution. Of course you have to balance cooling with noise. Noise tolerance is definitely a personal preference. Personally I hate noise. As my signature says I have Panaflo's all around except for the PS. My case is 5 F above room temp and my CPU is 20 - 28 F about case temp (Take CPU temp with a grain of salt since it is measured by the motherboard sensor). I am very happy with my solution as I do not overclock. I bought the 8045 heatsink so I could use a very low RPM (read quiet) fan and still cool my Athlon.
Good luck in your decision.

 

[ShinSa]

<< Didn't like your other thread??
Think about it. How can a fan that just moves air "cool" the air. It can't. The best it can do is to remove the hot air from the case and replace it with room temperature air. The more frequently the case air is replaced by room air the closer to room temperature the case will be. If your room is 85 F (as it gets in SoCal in the summer) the best case temp you will get is 85 F. Maybe all those fans you want to install will get it very close to room temperature.
When it comes to cooling you need to compare case temp to room temp and CPU temp to case temp. The closer these numbers are to each other the better the cooling solution. Of course you have to balance cooling with noise. Noise tolerance is definitely a personal preference. Personally I hate noise. As my signature says I have Panaflo's all around except for the PS. My case is 5 F above room temp and my CPU is 20 - 28 F about case temp (Take CPU temp with a grain of salt since it is measured by the motherboard sensor). I am very happy with my solution as I do not overclock. I bought the 8045 heatsink so I could use a very low RPM (read quiet) fan and still cool my Athlon.
Good luck in your decision. >>




PCHPlayer, You took the words right out of my mouth. I couldnt have explained it better.

 

[43st]

So... How does one explain the wind chill factor? The temperature outside is 60 but with the wind blowing it feels like it's 52.

Basically... If I hook up an air compressor to a high output nozzle I can get the temperature within the air stream to be below the ambient room temperature.

Check out this link on wind chill and inanimate objects.

Hope this helps.

 

[hudster]

Thera, excellent point about wind chill. I assume that you're just meaning that wind chill will cool down an object quicker, right? You're not saying that wind chill will make the object colder than the ambient temperature, right? Because it won't. (as that link that you included explains)


-hudster

 

[43st]

Correct. But... This assumes your heat source actually achieves equilibrium with the air temperature. In our CPU example we are continually creating heat. The speed at which heat dissipation occurs can be important again. It all depends on ones set up. If someone creates a set up that cools their CPU to room temp then I'll be impressed.

Basically... Wind chill does play a roll as long as you have an opject (CPU) that has a higher than ambient air temperature.

If anyone else has info on this please chime in.

 

[AKDUDE1]

YOu can't cool a object to lower than the ambiant temp or temp of the air blowing on it, it just won't happen.

AKDUDE

 

[PCHPlayer]

I got this description of wind chill off a news group. Isn't this why we put a fan on our heat sinks, to take advantage of "wind chill"?
Thera, there was no mention of a compressor in this discussion. A compressor changes the situation completely. Isn't that what KryoLabs (don't remember exact name) is all about?

In some ways the TV forecasts, which give the impression that wind chill is
a temperature are misleading. I've always understood "wind chill" to
describe he effects of wind on human perceptions of temperature. If you
are standing still outside in light clothing with an air temperature of, for
example, 0 degrees C, heat from your bod will start to exchange with the
surrounding air. This has the effect of cooling you down and warming the
immediately surrounding air. If there is no wind at all the layer of
warming air surrounding you remains where it is and continues to heat. This
has the effect of slowing the rate of body heat loss. But if wind starts to
blow newly warmed air next to you is moved on and replaced by a fresh supply
of 0 degree air. The stronger the wind, the more quickly this happens and
the more efficient becomes the transfer of heat away from your body so you
feel colder. So, for example, the air temperature may be 0 degrees but
the wind may be strong enough to make you feel the same as on a calm day
t -10 degrees. There are formulae for calcualting all this but I've
forgotten them.

 

[43st]

PCHplayer... did you read my link?

Wind chill has an effect on any "body" that has a temperature that is higher than the ambient air. To quote the site:



<< For an inanimate object, windchill has an effect if the object is warm. For example, say that you fill two glasses with the same amount of 100-degree water. You put one glass in your refrigerator , which is at 35 degrees, and one outside, where it is 35 degrees and the wind is blowing at 25 mph (so the windchill makes it feel like 8 degrees). The glass outside will get cold quicker than the glass in the refrigerator because of the wind. However, the glass outside will not get colder than 35 degrees -- the air is 35 degrees whether it is moving or not. That is why the thermometer reads 35 degrees even though it feels like 8 degrees. >>



I'm saying that the CPU/HS has a higher temperature than the ambient air. Thus air movement within the case can create a wind chill condition. i.e. Case fans are important.

 

[jsfetzik]

Regarding wind chill, it has no effect on cooling you CPU. Wind chill is an attempt to describe the combined effect of low temperature and wind speed on the human body, not a hunk of silicon, metal, plastic, and ceramic. Check out http://www.atd.ucar.edu/homes/rilling/windchill.html for more info.

The reason you use a heat sink and fans is to move the heat away from the source more quickly, then by plan old convection.

The metal of the heat sink is a way of increasing the surface area through which the heat can be dissipated. To an extent the larger the surface area the more heat you can dissipate in a given period of time. There are limits due to the rate at which the heat is conducted by the material involved.

The fans are used so that the air near the heat sink does not get 'saturated'. Once you heat the air next to the heat sink to the same temperature as the surface of the heat sink you can no longer dissipate any heat. So you want to remove the hot, 'saturated', air replace it with cooler air. The cooler the air the more heat it can absorb. Again there are limits due to surface area of the heat sink, how fast the heat can be transfered from the heat sink to the air, etc.

Additional case fans help in that they will remove the hot, 'saturated', air from the case and replace it with cooler air. At least thats the idea. There are practical limits which will depend greatly on the actual air flow in your case. It does no good to pump a thousand CPM through your case if none of it comes near you CPU. So a case fan or three will help, how much depends on your specific setup.

 

[43st]

<< Regarding wind chill, it has no effect on cooling you CPU. Wind chill is an attempt to describe the combined effect of low temperature and wind speed on the human body, not a hunk of silicon, metal, plastic, and ceramic. Check out http://www.atd.ucar.edu/homes/rilling/windchill.html for more info.

The reason you use a heat sink and fans is to move the heat away from the source more quickly, then by plan old convection.

The metal of the heat sink is a way of increasing the surface area through which the heat can be dissipated. To an extent the larger the surface area the more heat you can dissipate in a given period of time. There are limits due to the rate at which the heat is conducted by the material involved.

The fans are used so that the air near the heat sink does not get 'saturated'. Once you heat the air next to the heat sink to the same temperature as the surface of the heat sink you can no longer dissipate any heat. So you want to remove the hot, 'saturated', air replace it with cooler air. The cooler the air the more heat it can absorb. Again there are limits due to surface area of the heat sink, how fast the heat can be transfered from the heat sink to the air, etc.

Additional case fans help in that they will remove the hot, 'saturated', air from the case and replace it with cooler air. At least thats the idea. There are practical limits which will depend greatly on the actual air flow in your case. It does no good to pump a thousand CPM through your case if none of it comes near you CPU. So a case fan or three will help, how much depends on your specific setup. >>



As per your article:



<< Note that windchill described here is not dependent on relative humidity, both by definition and the observed fact that humidity has very little effect on cooling, particularly at low temperatures. Further, it is implied that if there is no motion, there is no cooling (thus the comparison to a reference windspeed of 4 mph); additionally, the original work was done on a can (or plastic container) of water, with the assumption that there was general extensibility to exposed skin. >>



So which one is it? What you say or what the article says?

 

[jsfetzik]

All the article says is that a can of water was used to approximate human sink for testing purposes, which is a little more humane then using real live people. The important thing to realize about windchill is that it is meant to be a representation of perceived temperature and the effect it has on the human body.

Although the sources of windchill, temperature and moving air, etc, and the mechanics, convection, conduction and radiation, are similar, the specifics are different when dealing with a CPU, heat sink and fan, i.e. that is very little metal in the human body and our surface area is not like a heat sinks. Thus, you can not say that it is wind chill that cools a CPU. You could say that both wind chill and CPU cooling are based on the same laws of thermodynamics however. Wind chill is one application of those laws, analysis of a heat sink would be another.

 

[43st]

Agreed.

I said:



<< Wind chill does play a roll as long as you have an opject (CPU) that has a higher than ambient air temperature. >>



It certainly isn't the whole story, that goes without saying. My point is... the faster the air speed the quicker an object will reach room temperature. Wind chill is the winds attempt to get something to reach it's ambient temperture faster.

 

[jsfetzik]

<< Agreed.

I said:



<< Wind chill does play a roll as long as you have an opject (CPU) that has a higher than ambient air temperature. >>



It certainly isn't the whole story, that goes without saying. My point is... the faster the air speed the quicker an object will reach room temperature. Wind chill is the winds attempt to get something to reach it's ambient temperture faster. >>



The term "wind chill" represents a percieved temperature that is lower then the actual temperature. Check http://www.usatoday.com/weather/winter/windchill/wind-chill-second-law.htm for a better description. The term only applies to living creatures.

Two point regarding the faster the air moves the quicker something cools

First, it is not the speed of the air that cools something. It is that fact that you are moving the already warm air away and replacing it with cooler air. Without the temperature different of the new air there would be no additional cooling.

Second, thermal conductivity, of both the air and the heat sink material, turbulence and friction will eventually eliminate the benefit of the air moving faster. This does not usually happen in the case of PC cooling, but some of the very high volume setups may well reach the point of deminishing returns. I have seen situation where lowering the fan speed actually reduced the CPU temperature.

 

[ShinSa]

<< Agreed.

I said:



<< Wind chill does play a roll as long as you have an opject (CPU) that has a higher than ambient air temperature. >>



It certainly isn't the whole story, that goes without saying. My point is... the faster the air speed the quicker an object will reach room temperature. Wind chill is the winds attempt to get something to reach it's ambient temperture faster. >>




You know this whole thread started becasue the topic is very misleading. "Do Case Fan Actually Bring Down CPU Temp??"

The chill factor has very little relevance on a cpu in this case. The case fans do not actually blow onto the Heatsink directly. Thats the job of the CPU FAN.

Does the CPU actually feel the effect of the case fans over that 80mm CPU fan??? the Answer is NO.

If you dont believe me, open up your case side panel and compare the cpu temperature, before and after. It shouldnt be more than 3C given a well ventilated case.



Think for a minute, the case fans are in place to bring the system temperature down to the room temperature. But it'll never reach room temperature due to the law of physics.

Your cpu fan is in place to bring the CPU temp down to case temperature. But it'll never reach case temperature due to law of phsics.

Case fans cool the case, cpu fans cool cpu. They are not related directly, and have very minimal relationship indirectly.

 

[PCHPlayer]

This topic needs to die of hypothermia Bottom line: The fans move air around to keep things cooler.

 

[NewCompGeek]

so should my generic case have any effect in cooling it?? link??

would it be worth getting the antec sx830??

 

[ShinSa]

One last example before this post dies.

Put yourself in the middle of the room with door and window as your only source of ventilation leave the window half open and your blinds closed.

have someone else slam the door closed. You'll see that the blinds from the window jump in towards the room signaling a vaccum effect and a flow of air. However, you will not feel this breeze coming through if you are standing away from the window or the door. Therefore you will not feel any pressure from the breeze and change of temperature stays minimal.
It doesnt matter the size of the room. It can be big as a football field. If you close that door, the air needs to be sucked in from somewhere else but the relative air inside the room stays the same.

Same thing happens within a case. The CPU is you and it does not have any windchill effect since the relative volume of the case is too big compared to the size of the cpu. I hope this clarifies something. I urge you to go experiment.

 

[Lizardman]

read this thread man thread to answer your question