Homogeneous Condensation of Argon: An Experimental Study Using the Nozzle Flow of a Cryogenic Ludwieg Tube

Abstract

The homogeneous condensation of argon in helium was investigated in the supersonic nozzle expansion of a cryogenic Ludwieg tube operated at 77.4 K. The onset of condensation at the nozzle exit was observed by laser light scattering. The static pressure at the observation station was measured by a piezoelectric transducer. Argon condensation was found in the partial pressure range 0.6 torr ≤ p _Ar ≤ 57 torr at the corresponding temperatures 41 K ≤ T ≤ 62 K. Regarding the effect of the cooling rate on the onset of condensation, the adiabatic supercooling of ΔT _ad ∼ 10° C determined in the present experiments is in agreement with recently obtained results on argon condensation in the unsteady expansion waves of cryogenic shock tubes also operated at 77.4 K. The experiments do not, however, agree with previous studies showing substantially more supersaturation employing steady supersonic nozzle flow and free jet expansions starting at higher temperatures.