I have not tested this new nozzle yet
Aluminum melts at 660 c, it is a very good coolant. As it has been melted it is in perfect contact with all the pieces of the nozzle. I hope that aluminum will absorb a lot of heat and transfer its BTUs to steam and primary air.
You understood well
In the sketch, the small pipe between the bottom vapor passes through the aluminum bath and exits into the primary air pipe.
On the first picture, we see the exit of the small steam pipe in the primary air pipe
The compression fittings are one for steam and the other for installing a thermocouple