On Mon, 7 Mar 2005 09:30:39 +1100, "Tom Miller"
wrote:

Gravity
The liquid sodium is heavier than the vapour.

Yeahbut... which way is up?

I thought the heat transfer was effected by the sodium being shaken
from one end of the cavity to the other by the G forces inherent in a
rapidly operating valve. Just my impression tho, I haven't seen the
theory of the things written down anwhere.