Cooling your computer

Its best to monitor how your system behaves from cold. So its a good plan to run HWInfo when the PC starts up. Here's how to do that.

1. In recent versions of Windows just press Win+R and in the run box type shell:startup Click OK and the startup folder will open.( On earlier versions click the Start button, click All Programs, right-click the Startup folder, and then click Open.)
2. Open the location that contains the item you want to create a shortcut to.
3. Right-click the item, and then click Create Shortcut. The new shortcut appears in the same location as the original item.
4. Drag the shortcut into the Startup folder.

Once your PC has booted up you can check the voltages and temperatures shown by HWInfo; then immediately select the important sensors (enable logging so if your pc crashes you will still have the results.

Cooling a tower case

I found How To: Properly Plan And Pick Parts For An Air-Cooled PC, Part 1

which covers the main issues well and in good detail. If you havent done so already, read it now.

Then this one How To: Properly Plan And Pick Parts For An Air-Cooled PC, Part 2

Additional points include:

1. matching intake and exhaust rates
2. positive or negative pressure
3. position of power supply
4. obstruction to air flow
5. warm air at intake & adding heat sinks
6. dirt and dust on fans, heat sinks etc.
7. maintenance of PCs and laptops
8. power connectors for fans

Suppose your tower case intake fan gets blocked. The exhaust fans will be trying to suck air out, and create a low pressure inside the case. Soon they will be unable to extract more air, and although they will continue to spin and make a noise, they will not move any air. Similarly, if the exhaust is blocked the pressure inside will rise a little, and again no air will move.

The ideal situation is that the intake and exhaust are matched, so that air pressure inside the case is just a little above the outside (positive pressure). This prevents air entering the case and bringing in dirt. In this condition the noise from the fans is minimised.

To achieve this you need to look at the airflow rate for each fan. A typical 120mm fan will transfer 20 - 80 cubic feet per minute if unobstructed - depending on the speed it runs at. Smaller fans will generally have a lower airflow rate.

Your power supply will not usually specify the airflow rate, so assume around -20cfm. depending on the power rating and fan size.

Thus if you have a case with a single 120mm intake fan (+60cfm), power supply (-20cfm) , and 2 * 80mm exhaust fans (2*-20cfm) your system is reasonably well balanced, with neutral pressure, and optimally quiet.

This "Gelid Silent 8" 80mm fan runs at 1600 rpm
with an airflow of 20 cfm and 18dBA noise
(not to scale)

This Glidestream 120mm fan runs at 1200 rpm
with an airflow of 66 cfm and 25dBA noise
(not to scale)

Cool air enters bottom front, getting warmer as it passes over the hard drive and graphics card or on-board graphics) then exits via the PSU and rear mounted exhaust fan.

Bottom - mounted intakes will require the case to be raised from the floor. Be aware they are the most prone to sucking in dirt. A bottom mounted PSU that sucks air in from the bottom of the case will need a filter so it can be kept clear of dust. A dirty filter will also reduce the airflow - often considerably!. Here the PSU is mounted at the bottom. Taking air from above will reduce the air flow to the graphics card; air from below may not be clean. A rear intake fan will suck in warm air - better add another front fan or side fan. A side intake fan is useful on high-end systems as it provides fresh cool air directly to the graphics card and cpu.

You should plan your cooling so that the exhaust air is kept separate from the intake air. Intake fans at the rear are often a bad idea as they will suck in warm exhaust air from the psu.

If the environment the computer is in gets hot you may need additional cooling or even extra heat sinks.

Components lose heat by transferring it to the surrounding air, at the surface. A simple solution to improve this process is to add a heat sink - a metal structure that is shaped to provide a large surface area in a small space.

For example you may find the hard drive becomes hot. Simply attaching a heat sink like this to the metal surface will reduce its temperature dramatically and improve reliability.

You need to ensure good contact. A tiny dab of superglue or epoxy resin adhesive in the centre will do the job well, especially if you apply dabs of heat transfer paste (or zinc oxide ointment) around the edges.