Cooling your Computer

موضوع: Cooling your Computer الأحد نوفمبر 15, 2009 12:47 pm

Cooling your Computer

What gets hot in the computer:

We will start here because as with any problem solving formula you must first identify the problem.

CPU -- It is the easiest component to identify because it runs the hottest and is what everyone tries to cool.

Video Card -- If you have a decent video card, it will run warm. If you have that kickass card, it will be the second hottest item in your case. Decent implies a video card that comes with a heatsink on it, where as kickass implies a GeForce 2 or more.

Hard Drive -- ATA 66/100/133 and SCSI drives can run very hot. Most people associate the heat with the motor inside the drive. This is an error in thought because the controller on the drive is actually what heats up. That is why the ultimate hard drive cooler is a poor buy. It has a huge heatsink on top, but the controller is not located on the top of the drive. An underside cooler solution is best.

North Bridge Chipset -- Your northbridge chipset is the controller on the motherboard that controls your high-speed bus devices. This chip normally runs warm and is not a very high concern if your case is cooled properly. If you are overclocking your computer, this can be a bigger concern.

RAM -- Many people think they need RAM coolers. RAM gets warm but buying quality RAM will serve you better than buying cheap RAM with a cooler. If overclocking the RAM, you will probably need some form of cooling.

Other Devices -- SCSI controller cards, power supplies, CD-ROM and other controller cards might run warm. This can add to the heat of the case. Again a decently cooled case will provide accurate cooling for these devices.

Outside Factors to Consider:

Now that we have identified what devices are going to increase our temperature inside our case, we can focus on factors that cause these components to heat up. I have listed the main causes below.

Air temperature -- Air temperature is the biggest factor in my opinion because this air is what you are using to cool your computer. If your outside air is 80°F (26.7°C), the coolest your case can get with air cooling is 80°F (26.7°C). For instance, a heatsink is able to dissipate a certain amount of heat away from the CPU. If the heatsink is already at 80°F (26.7°C) before the CPU transfers heat to it, then the CPU will transfer less of its own heat to the heatsink. Or in other words "heatsink max" - "current temp" = "heat transferred to the processor." By using a liquid cooling system such as a water cooler, the system can be cooled below air temperature.

If you don't believe me then ask yourself why server rooms are always kept cold. In most cases, the server will have an air-conditioning vent in the floor that blows cold air up into the bottom of the system. That is why it is not a good idea to put your computer in a restricted air space, such as a computer hole in a desk.

Airflow -- Airflow is very important to a cooling system. If hot air does not escape your system and cool air does not enter your system, then hot air pockets form. That warm air is then recycled and used to cool the same component again and again.

Some people feel that if they overload the system with fans, say 15 fans to do the extreme case, then they are providing lots of airflow. This is not true. Two fans blowing air toward each other can cause a heat pocket of air to exist. This is because pressure is being applied from both sides and warm air is not able to flow out of the case.

Another thing that restricts airflow is cables or other items in the way. Air cannot pass through solid objects but must flow around the object.

Air pressure -- You can only force a maximum amount of air through a heatsink. If you force too much air, vortexes begin to build which causes restricted air flow. Think of it as pouring water into a funnel. If you pour a gallon of water all at once into a funnel that only holds one cup, the rest of the water will spill over the top of the cup. When air molecules collide with objects they bounce back. They then collide with other air molecules until you have a vortex restricting airflow above your heatsink. I will go into more detail on this more in my "Is a Highspeed Fan Good for You" article.

High and low pressure zones can be created in a case. Normally these zones don't affect cooling much. You might lose a degree or so in temperature. A low pressure zone is created when a fan is competing for air with another fan. For example, a power supply exhausting air is creating a low pressure zone for the heatsink fan. A high pressure zone is just the opposite, where a fan is pushing more air than the other fan can use.

How to cool your computer case:

Method 1:

The first method I will discuss is bringing in cool air through the front of the case and then exhausting it out the back. Antec, Thermaltake, Cheiftec and other server style cases use this method.

Bringing cool air in through the front of your case insures that air flows over all your potentially warm components. The drawback to this method is that it is hard to keep a good airflow through the case. Cables, cards and other items get in the way and restrict airflow.

A problem with cases that have fans already built in, is the fans might be thermally controlled. This can be a good thing because your fans only kick up when the case gets warm. Unfortunately, most of these fans are triggered from within the power supply. Therefore if the power supply is not as hot, the fans won't speed up and provide a stronger airflow.

If you are modifying your own case or adding fans, you will want to ensure that air flows over the right components. To get a strong airflow, ensure that air can get to the fan. Many times computer cases provide a grate which you mount in front of the fan. The grate will restrict airflow and must be cut out to get the maximum flow from your fan. Doing this step alone can double the CFM you recieve from the fan.

Fans are normally mounted in three places, behind the processor for exhaust and in the front bottom and front of the hard drives for intake. NOTE: Because cool air does not rise, the fan at the bottom of the case will not do a whole lot unless you point it upward toward the processor and video card. This can be done by using some washers behind the fan. You only need a slight angle to ensure the air is flowing upward toward the CPU.

The power supply can be used as an exhaust fan but with most temperature controlled power supplies, the fan does not provide an adequate airflow. If you like to solder, you can override the temperature sensor by taking out the thermal lead and allowing the fan to run as normal.

Below is a picture of the ideal airflow with the front style of cooling. Remember that fans produce a circular air pattern, like a spiral, with a larger radius farther away from the fan. The CFM is weaker in relationship to distance as well.

user posted image

Method 2:

The second method is more effective in my experience and uses an intake fan on the side of your case. The intake fan is positioned to blow air over the processor and video card. This method supplies plenty of cool air to be used for the CPU and video card fans. This method takes a little work because you need to cut a hole in the side of your case and mount a fan to it. You can also get window kits that have fan holes for the side of your case.

An exhaust fan is normally placed behind the CPU. The power supply can be used as an exhaust fan but with most temperature controlled power supplies, the fan does not provide an adequate airflow. If you like to solder this can be overridden by taking out the thermal lead and allowing the fan to run as normal.

Below is a picture of the airflow pattern. My 3D imagination on this is not as good as it should be. Basically, the air will spread out over your hot components and get sucked out as before. NOTE: I am only using a power supply with the fan inside at full blast. The air out the ports in the back would come from an exhaust fan, if one existed.

user posted image

Additional tricks:

Here are additional things and notes on items to improve cooling in addition to the methods I have mentioned.

Insert a blow hole -- Much like the blow hole on a whale, you can put an exhaust fan at the top of your case. Hot air rises so this fan is effective at creating a vacuum at the top of your case; thus, removing hot air that is not sucked out by exhaust fans.

Use fans with some CFM -- I have tried Panaflos and Stealths as case fans. They simply don't put out any air if you are trying to move air across the case. You may get away with a 92mm Stealth as a side mount intake fan. If noise is an issue, use one decent sleeve bearing fan. Sleeve bearing fans are quieter than ball bearing fans, because there is no whine associated with the bearings. Sleeve will last you quite a few years. You do not need to load up your cases with Delta fans and Tornados. Instead, use an 80mm or 92mm fan that puts out around 30-35 CFM. A Panaflo, in my opinion, is like buying a Geo to pull a boat. Yeah it is quiet but does it actually do the job?

Use a hard drive cooler -- Heat lessens the life span of a hard drive. If you don't cool your hard drive, the metal frame of your case will conduct the heat and heat up your case. It does not take much to cool a hard drive. A good use for a Panaflo is to provide a light airflow over the hard drive. If not using an intake fan to cool your drive, get a bottom mount hard drive cooler. This is the most effective hard drive cooler.