dsc98687.jpg

The helium supply port on the heat exchanger.

Internally, the heat exchanger had two helium coils through which the helium gas passed, expanding in the still-warm turbine exhaust gases, so there are two externally-visible tube inlets within the helium supply port.

When configured for flight, there would be orifice plates to control the amount of helium which entered the heat exchanger.

The text below the flange at the 7:00 position reads "HE In".