Pro/Forums - View Single Post - Increasing pressure on waterblock to lower temps

Cathar · 07-13-2003, 05:55 PM

Finally got back to this thread, but yeah, Al Kaseltzer and murrary13 are raising the same points I would have raised.

Surface area is also important. The pressure applied really needs to be defined in terms of force per area, rather than simply force.

Increased pressure will result in better thermal transfer performance, both with and without pastes (but maybe not for all pastes). The point of diminishing returns seems to occur at around 100PSI, but gains are still seen beyond this point.

However, and completely tangential to this pressure vs thermal interface thing, is the mount pressure vs tubing torque.

Most water-cooling setups have the tubing simply hanging off the CPU block in a completely unsupported fashion. When the case is sitting still this applies a fixed rotational torque that tries to lever the block away from the CPU leading to uneven clamping pressures against the CPU die.

Now 8kgs of pressure against the CPU, or really about 2kgs of pressure for a single spring located at around 3cm distance from the CPU will be greatly affected (relatively speaking) by 0.2kg of hosing torque tilting with 10-15cm of leverage. ie. the hosing torque being applied equates to around half of the spring torque being used to hold the block in place at any one corner/spring.

So this leads to a secondary reason for why increased mounting pressure is beneficial. By raising the pressure applied to each spring to around 10kgs each the relative effect of hosing torque acting against any one spring is diminished, typically leading to a more even pressure being applied to the CPU.

07-13-2003, 05:55 PM	#30
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	Finally got back to this thread, but yeah, Al Kaseltzer and murrary13 are raising the same points I would have raised. Surface area is also important. The pressure applied really needs to be defined in terms of force per area, rather than simply force. Increased pressure will result in better thermal transfer performance, both with and without pastes (but maybe not for all pastes). The point of diminishing returns seems to occur at around 100PSI, but gains are still seen beyond this point. However, and completely tangential to this pressure vs thermal interface thing, is the mount pressure vs tubing torque. Most water-cooling setups have the tubing simply hanging off the CPU block in a completely unsupported fashion. When the case is sitting still this applies a fixed rotational torque that tries to lever the block away from the CPU leading to uneven clamping pressures against the CPU die. Now 8kgs of pressure against the CPU, or really about 2kgs of pressure for a single spring located at around 3cm distance from the CPU will be greatly affected (relatively speaking) by 0.2kg of hosing torque tilting with 10-15cm of leverage. ie. the hosing torque being applied equates to around half of the spring torque being used to hold the block in place at any one corner/spring. So this leads to a secondary reason for why increased mounting pressure is beneficial. By raising the pressure applied to each spring to around 10kgs each the relative effect of hosing torque acting against any one spring is diminished, typically leading to a more even pressure being applied to the CPU.