Will Matney wrote:
> Joe,
>
> Correct, they make those copper blocks now to water cool aluminum
> heat sinks. I think there's about 2-3 heatsink manufacturers making
> them now, Thermalloy being one. This brings up several electronic
> items, tube and transistor amps plus super cooling voltage regulator
> assemblies. The water wetter sounds like a good idea and I'm curious
> myself what's in it to increase the heat transfer.
Transferring heat across a metal-metal junction depends a lot on what
happens at a microscopic level - imagine it like pressing the rough side of
two pieces of sandpaper against each other. The actual hard contact is a
fraction of the whole area, and I guess it's the same with fluid cooling.
Water has high surface tension, so will have a natural reluctance to flow
into microscopic pits on the surface of the metal - imagine water flowing
over a sandpaper surface.
It's important to remember that situations vary. In a car engine head, the
surfaces are very rough, and the temperatures around the exhaust ports are
very high. If water boils at the surface, the layer of steam, even if it's
microscopically thin, kills the cooling effect - hence pressurised systems
and additives. Even with pressure, there's practical limit to how much you
can raise the boiling point of water, which is where glycols come in. They
aren't as effective at absorbing heat, but they're more effective than water
with a steam barrier.
It's unlikely that a water cooled tube in anyone's shack will have such
extremes of conditions.
Steve
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