[Adam Murphy (OP)]

Rubikron emailed us to ask:

"Does the velocity of a coolant affect its performance when cooling a heated machine, such as a gaming console or nuclear reactor?"

Got any cool ideas?

[alancalverd]

Yes.

Heat transfer rate depends on temperature difference. If the coolant isn't moving, it heats up at the interface and doesn't remove the heat once it has reached temperature equilibrium. If it's moving too fast you may get semi-laminar flow where the core of the coolant doesn't mix efficiently with the boundary layer, so you are wasting energy pumping ineffective coolant around. There will be an optimum speed where turbulent mixing transfers the most heat to the bulk of the coolant which is then removed from the area. Producing an optimal device for a given application is something of a dark art, but plenty of excellent work has been done by the automotive industry. Nuclear reactors require a lot of safety and redundancy factors that may compromise optimality.

[Halc]

Does the velocity of a coolant affect its performance when cooling a heated machine, such as a gaming console or nuclear reactor?

Velocity certainly matters, else they'd not bother to pump it at all.  A computer GPU has a fan on it for the expressed purpose of increasing velocity of coolant.  If it is too slow, it will just heat up and fail to convect heat away at a sufficient rate.