There have been a few questions raised about computer cooling issues lately, and with summer here there will no doubt be more. So I decided to brush up on my general cooling knowledge and share my findings.
How does heating work
To understand how to cool your PC, you need to understand how it heats up. Some things you need to know:
1. It is safe to say that every watt of power consumed by your PC is turned into heat. A PC drawing 500 watts is thus equivalent to a 500 watt heater, or 5 100 watt bulbs.
2. 1 watt = 1 joule per second. 1 joule is roughly the amount of energy required to increase one cubic centimetre of air by one degree Celsius.
3. Air has a heat capacity of 1 joule per gram per degree Celsius, and a density of around 1.2 kilograms per cubic meter.
4. A computer case of 395 x 190 x 427mm, assuming its empty, has a volume of .033 cubic metres; or about 40 grams of air. An average room has a volume of 40 cubic metres, or around 48 000 grams of air.
5. 1 degree increase in ambient temperature results in a one degree component temperature increase (more or less). So if your room is hotter in summer, when compared to winter, then your CPU temperature will be hotter too, at a 1:1 relationship.
Taking the above into consideration, a 500 watt computer at peak load, will emit 500 joules of energy per second. Using the heat capacity we know that it would take 40 joules to raise the temperature in the case by one degree (ignoring heat loss). It would take 48 000 joules to raise the air temperature in the room by one degree (again ignoring heat loss).
This translates into your room heating at one degree every 96 seconds and an increase by one degree every second n your case! This of course is absurd because heat is being lost to the air outside etc., but it does indicate an important rule:
The temperature in your case can increase very quickly and your PC can cause your room to heat up; which will cause a direct increase in your component temperature.
How does cooling work
All cooling works by transferring heat from one medium, such as your CPU, to another medium such as air or water. From the above we can see that the rate at which the temperature increases is directly proportional to the amount of mass that is heated. A fan increases the airflow, thus increasing the amount of mass to heat, resulting in lower component temperatures.
Great, but you still have not told us how to cool stuff down!
From the above it is clear that efficient cooling requires several factors:
1. Your cooling solution is only as good as the air coming into your system, since component heat is linked to ambient heat. Hot air in = hot components. Heat is never lost - only transferred, e.g. from your CPU to the air in your case, and from inside your case to your room, back into your case.
2. Airflow is important. One well position fan could work better than 10 badly placed fan (also remember that fans use power and generate heat). Try to get as much cool into the front of your PC and blow as much hot air possible out the back - while ensuring a constant stream of air is passed through the PC (which will also improve cooling on your passive components such as hard drives). Servers, and datacenters are build on this simple concept.
3. Compounding heat. In a room with no aircon it is safe to assume that as your PC gets hotter, it will heat up the room, and as the room gets hotter, so your PC temps will increase. Position your computer so that warm is not recycled, and cold air is always brought in through front.
4. Assume a holistic approach to cooling, including spot and passive cooling. Start at the source of the heat and work out. First, look at your spot cooling (heatsinks), make sure they are securely attached and clean. Then examine the fans attached to the heatsinks - do they spin freely? Look inside your case for blockages that could disrupt airflow.
Look at your PC's immediate surroundings, is it close to a wall, or in a little box that traps heat? Free up the space around your PC - remember hot air in = hot PC. Lastly examine your room - does it have sufficient airflow? Does the sun beat down on your PC?
Understand why your system is heating up BEFORE spending money on expensive heatsinks and fans.
5. Understand component thresholds and what it means to be hot, and decide whether additional cooling is required. For example an HDD at 35 degree is not hot and should not be cooled.
Its quite a bit to get your head around, and I will clarify if anything is unclear
How does heating work
To understand how to cool your PC, you need to understand how it heats up. Some things you need to know:
1. It is safe to say that every watt of power consumed by your PC is turned into heat. A PC drawing 500 watts is thus equivalent to a 500 watt heater, or 5 100 watt bulbs.
2. 1 watt = 1 joule per second. 1 joule is roughly the amount of energy required to increase one cubic centimetre of air by one degree Celsius.
3. Air has a heat capacity of 1 joule per gram per degree Celsius, and a density of around 1.2 kilograms per cubic meter.
4. A computer case of 395 x 190 x 427mm, assuming its empty, has a volume of .033 cubic metres; or about 40 grams of air. An average room has a volume of 40 cubic metres, or around 48 000 grams of air.
5. 1 degree increase in ambient temperature results in a one degree component temperature increase (more or less). So if your room is hotter in summer, when compared to winter, then your CPU temperature will be hotter too, at a 1:1 relationship.
Taking the above into consideration, a 500 watt computer at peak load, will emit 500 joules of energy per second. Using the heat capacity we know that it would take 40 joules to raise the temperature in the case by one degree (ignoring heat loss). It would take 48 000 joules to raise the air temperature in the room by one degree (again ignoring heat loss).
This translates into your room heating at one degree every 96 seconds and an increase by one degree every second n your case! This of course is absurd because heat is being lost to the air outside etc., but it does indicate an important rule:
The temperature in your case can increase very quickly and your PC can cause your room to heat up; which will cause a direct increase in your component temperature.
How does cooling work
All cooling works by transferring heat from one medium, such as your CPU, to another medium such as air or water. From the above we can see that the rate at which the temperature increases is directly proportional to the amount of mass that is heated. A fan increases the airflow, thus increasing the amount of mass to heat, resulting in lower component temperatures.
Great, but you still have not told us how to cool stuff down!
From the above it is clear that efficient cooling requires several factors:
1. Your cooling solution is only as good as the air coming into your system, since component heat is linked to ambient heat. Hot air in = hot components. Heat is never lost - only transferred, e.g. from your CPU to the air in your case, and from inside your case to your room, back into your case.
2. Airflow is important. One well position fan could work better than 10 badly placed fan (also remember that fans use power and generate heat). Try to get as much cool into the front of your PC and blow as much hot air possible out the back - while ensuring a constant stream of air is passed through the PC (which will also improve cooling on your passive components such as hard drives). Servers, and datacenters are build on this simple concept.
3. Compounding heat. In a room with no aircon it is safe to assume that as your PC gets hotter, it will heat up the room, and as the room gets hotter, so your PC temps will increase. Position your computer so that warm is not recycled, and cold air is always brought in through front.
4. Assume a holistic approach to cooling, including spot and passive cooling. Start at the source of the heat and work out. First, look at your spot cooling (heatsinks), make sure they are securely attached and clean. Then examine the fans attached to the heatsinks - do they spin freely? Look inside your case for blockages that could disrupt airflow.
Look at your PC's immediate surroundings, is it close to a wall, or in a little box that traps heat? Free up the space around your PC - remember hot air in = hot PC. Lastly examine your room - does it have sufficient airflow? Does the sun beat down on your PC?
Understand why your system is heating up BEFORE spending money on expensive heatsinks and fans.
5. Understand component thresholds and what it means to be hot, and decide whether additional cooling is required. For example an HDD at 35 degree is not hot and should not be cooled.
Its quite a bit to get your head around, and I will clarify if anything is unclear
Last edited:
