Vapour nucleation in a cryogenic-fluid-dissolved-nitrogen mixture during rapid depressurization

摘要

The behaviour of four cryogenic-fluid-dissolved-nitrogen mixtures inside a pressure vessel during rapid depressurization was investigated through experiment. The four fluids studied were CF_3I, FC-218 (C_3F_8), HFC-125, (C_2HF_5), and CF_3Br. Depressurization was achieved by discharging the liquid mixture through a solenoid valve at room temperature. Two initial total vessel pressures were used: (1) ca. 2.8 MPa and (2) ca. 4.2 MPa. Based on the experimental observations obtained by using a high-speed movie camera, the evolution of dissolved nitrogen was suggested for FC-218, HFC-125 and CF_3Br in the cases of initial total pressures of ca. 4.2 MPa. For initial vessel pressures of ca. 2.8 MPa, vapour nucleation was not observed for any of the four fluid-dissolved-nitrogen mixtures. No degassing was observed for CF_3I irrespective of the two initial total pressures. The predicted nucleation pressures based on the classical homogeneous nucleation theory for a binary-component mixture provided qualitative agreement with the observed vapour nucleation inside the vessel.