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

The behaviour of four cryogenic-fluid-dissolved-nitrogen mixtures inside a pressure vessel during rapid depressurization was investigated through expe riment. The four fluids studied were CF3I, FC-218 (C3F8), HFC-125 (C2HF5), and CF3Br. Depressurization was achieved by discharging the liquid mixture through a solenoid valve at room temperature. Two initial total vessel pres sures were used: (1) ca. 2.8 MPa and (2) ca. 4.2 MPa. Based on the experime ntal observations obtained by using a highspeed movie camera, the evolution of dissolved nitrogen was suggested for FC-218, HFC-125 and CF3Br in the c ases of initial total pressures of ca. 4.2 MPa. For initial vessel pressure s of ca. 2.8 MPa, vapour nucleation plas not observed for any of the four f luid-dissolved-nitrogen mixtures. No degassing was observed for CF3I irresp ective of the two initial total pressures. The predicted nucleation pressur es based on the classical homogeneous nucleation theory for a binary-compon ent mixture provided qualitative agreement with the observed vapour nucleat ion inside the vessel.