I'm experimenting with heat pipes. I want to fill a foot of 1/4" copper pipe half full of freon. I don't have any way to recapture the freon, so I can't just over fill it and vent it till it gets to the right level. If it works I'll be building a bunch of 'em.
Way too many pipes hanging off the thing to do it by weight. Only thing I can think to do is an ice bath on the bottom half and wait.
Ideas how to determine the liquid level within half an inch or so while still hooked up to the manifold?