MAXPC - Heat Is The Enemy

It crashes our computers. It corrupts our data. It even destroys our components. In the world of PCs, heat is the enemy. It can cause our computers to lock up or crash, create errors in our work, shorten the life of components, and in extreme cases heat can instantly destroy parts.

Way back in the stone age of computers, CPU speeds were around 4 MHz and computer components didn't get overly hot. At that time, CPUs had less than 30,000 transistors. Seems like a lot, but compare it to today's CPUs with some weighing in with more than 150 million transistors and overclockers reaching speeds of 4 GHz. That's a lot of transistors and a lot of speed.

Components are getting smaller and the clock frequencies are getting higher. That creates heat--a lot of heat. Manufacturers are well aware of the problems with heat on electronic components and are constantly striving to create new methods of reducing this heat and the damage it causes. Intel is even investigating fluid-based cooling and solid-state refrigeration methods on the CPU die itself.

Each winner of the Top Dawg December competition uses the asetek VapoChill LS to cool their CPU. There's a reason for that. The Top Dawg computers are overclocked beyond manufacturers specs, and the overclocker needs to remove a lot of heat--fast. Let's take a look at the different methods of getting the heat out of your computer.

Air Cooling

Air cooling is the stock method of cooling your computer. You need to get the heat off of the components and out of the box. Heatsinks are attached to critical components that produce the most heat such as the CPU, chipset or GPU (Graphics Processing Unit). The solid surface on the bottom of the heatsink absorbs the heat created by the component and then transfers that heat to the fins on top of the heatsink where a fan is used to disperse the heat. Additional fans are used in the power supply and case to draw air in through the front or side of the box and push the hot air out the back or top.

Heatpipes can give air cooling a boost. They use evaporation, capillary action, and condensation to do their job. When a liquid evaporates or vaporizes, it cools the surrounding area. A good example of this is an alcohol rub. Place a little rubbing alcohol on your arm and you'll feel the coolness as it evaporates.

Heatpipes pass through a heatsink, which is attached to the PC component. A coolant such as acetone or ethanol, which has a lower boiling point than water, is used inside the sealed heatpipe. The liquid is also under reduced pressure, which allows even lower temperatures to vaporize the liquid.

Heat entering the heatsink from the CPU vaporizes the coolant at the evaporator end of the heatpipe. This creates pressure that forces the vapor along the tube of the heatpipe to the condenser. The condenser consists of copper or aluminum fins that the pipes pass through and usually has a fan attached to increase the cooling. The vapor gives off its heat and condenses back into liquid. The liquid moves back to the evaporator by a wicking action and the cycle repeats.

Heatpipe technology can transfer heat thousands of times better than plain copper. The Thermalright XP-90C is a good example of heatpipe technology combined with a heatsink. Still, there are limitations; since heatpipes don't provide refrigeration, it isn't possible to cool a device lower than the ambient temperature of the surrounding area. If the inside of the case is 85 degrees Fahrenheit, that's the coolest the CPU will be as well.

Thermoelectric Cooling

Thermoelectric cooling is also called Peltier cooling, named after the physicist that discovered it in the first half of the 19th century. Here's how it works: when current is passed through two dissimilar metals or semiconductors, heat can be either created or absorbed at the junction of the two materials. The side that absorbs heat becomes cold and the side that releases heat becomes hot. The cold side of the Peltier is attached to the CPU or other component and a heatsink is attached to the hot side of the Peltier. A fan is connected to the heatsink to further dissipate the heat.

On the good side, the Peltier itself is a solid-state device that has no moving parts, is reliable and maintenance-free. It cools below ambient temperature and is less expensive and smaller (but less effective) than phase-change refrigeration units. (More on phase-change below.) However, Peltiers consume more electricity in wattage than the heat (in wattage) that they dissipate. With air-cooling, the heat will often require large and noisy fans for adequate airflow out of the box. Since the cool side is below ambient temperature, moisture from the air may condense and cause problems with electrical components unless the cool side is properly insulated.

Peltiers were widely available in the early days of the original Pentium. Today CPUs and GPUs produce more and more heat. Peltier-type coolers that meet these needs are hard to find, expensive, and will probably require water cooling to dissipate the heat.

Water Cooling

Water cooling uses a system similar to the cooling system in your car. A pump circulates a water/coolant mixture from a reservoir through a heat exchanger. The tubing passes through the heat exchanger while a fan draws air through it to remove the heat. Next the coolant circulates through a copper or aluminum block that has water channels in it. This block sits on top of your CPU, GPU, or chipset in place of the standard heatsink. You can also add water-cooling blocks for hard drives.

You can start with one water block (CPU, for instance) and add others later without increasing wattage. However, you'll need to plan ahead to ensure that your pump will handle the flow of water for the maximum number of blocks you plan to use.

It's possible that some PC cases won't have enough room for your heat exchanger and it may have to reside outside the box. Features like the asetek WaterChill SafeStart that ensures the water cooler starts when the PC is powered up is a must. You definitely want to be sure the cooler is on when you fire up the computer.

Phase Change

Phase change is the cream of the crop of CPU cooling. It uses the same principles as an air conditioner or refrigerator. When a substance changes from liquid to gas, it absorbs energy. Remember the alcohol evaporating from your skin discussed earlier? It's absorbing the energy of the heat from your body. This change from liquid to gas is called phase change.

First the compressor compresses the hot refrigerant gas at high pressures. The pressurized liquid then travels through tubing (or coils) encased in metal fins, which looks something like the radiator of your car. This is called the condenser. Fans draw air through the condenser as the refrigerant travels through it, causing the refrigerant to cool and condense from a gas to a liquid. Next the refrigerant travels through a valve, called an expansion valve, which causes a large pressure drop. This pressure drop causes the liquid refrigerant to change back into a gas which is now very cold.

You can see and feel an example of this pressure drop or cooling effect with a can of compressed air. The more you spray the air, the colder the can gets as you're releasing pressure from the compressed air inside the can.

In the next step of an air conditioner, the cold refrigerant gas travels through another set of coils (called the evaporator), where a fan draws air from the room and blows it across the cold coils. Then the refrigerant travels back to the compressor and the process repeats. With a CPU cooler, the refrigerant dissipates heat through an evaporator that attaches to the CPU. This replaces the heatsink for the CPU.

The asetek VapoChill is the definite leader in CPU cooling. Each winner of the Top Dawg December competition used the asetek VapoChill LS to cool their CPU. Overclocking produces a lot of heat from the CPU and overclockers need the best solution to remove that heat.

As with the Peltier, condensation can be a problem when cooling below ambient temperature. VapoChill solves that problem by using insulation along with heaters for the clamshell that connects the evaporator to the CPU, and also for the CPU socket. Combining the VapoChill LS for the CPU and water-cooling for the chipset, GPU, and hard drive can round out the cooling needs for your PC quite nicely.

The VapoChill ChillControl unit, which controls temperature, noise, sensors, and fans, allows for extra sensors that can be connected to your video, chipset, or water cooling units to initiate an immediate safe shutdown if any overheating is detected.

Cleaning

No matter how you cool your PC, remember that dust is an insulator. A heatsink full of dust will have a tough time removing heat. At least once a year (more in extremely dusty conditions) you should open up your computer and use either an anti-static vacuum cleaner or compressed air to clean out the dust from the inside of your PC. A good anti-static vacuum isn't cheap so if you don't already have access to one you'll probably want to opt for compressed air which you can find anywhere that sells computers or office equipment.

Shut down and unplug your computer, remove the side panel and use a couple of cans of compressed air to get all of that dust out. You may want to do this outdoors if your PC is extremely dusty. Don't forget that anytime you're working with electronics you need to avoid ESD (electrostatic discharge). A static discharge that you won't even feel can destroy electronic components. Don't touch electronic components without properly wearing an anti-static wrist strap or at the very least touch the chassis of the case before touching anything inside.

When blowing the dust from fans, hold the fan blades in place so that they don't spin to prevent damage to the bearings. And while you're inside the box, you might as well take a little extra time to ensure that all the memory, adapter cards, and cables are plugged in solidly.