To ensure minimal energy consumption, the interior of the pressure shell is thermally insulated. The drive system consists of a fan with variable inlet guide vanes for responsive Mach number control. The fan is powered by a 100-MW motor. The tunnel has two modes of cooling. In the variable temperature cryogenic mode, nitrogen is the test gas.
Liquid nitrogen is sprayed into the circuit.
The heat of vaporization and latent heat cools the tunnel structure while removing the fan heat. In this mode, the NTF tunnel provides full-scale flight Reynolds numbers without an increase in model size. In the ambient temperature air mode, air is the test gas. Water flows through the cooling coil to remove fan heat. NTF tunnel circuit arrangement.