On Sat, 9 Mar 2019 12:52:19 -0600, dpb wrote:

On 3/9/2019 11:56 AM, wrote:
...

No, not cryogenic He. He gas has great heat transfer properties, at
least for a gas. It has a very high mobility and is more massive than
H, so will transfer more per mole. We used it to fill electronics
modules for exactly that reason (and it was non-reactive).
...

Not in comparison to H, it doesn't, no...the heat transfer
characteristics outweigh He enough to use it extensively despite the
flammability for turbine-generator cooling.

H conductivity is ~20% higher, but the molar heat capacity is almost
double He and the density is roughly half so one gets much more heat
transport out that wins the thermal efficiency battle handily.

70% or so of all turbine-generators over 50-60 MWe wouldn't use H
cooling if it weren't a marked advantage.

I'm not aware of any using He altho there may well be a few.

He is a lot more difficult to come by, particularly in the quantities
that would be needed for large generators.