Phenomena of Liquid Nitrogen Flashing under Rapid Depressurizations

Abstract

Flashing Experiment of liquid nitrogen in a pressure vessel was conducted under rapid depressurization rate. Observations of the explosive boiling behavior caused by quick opening of a electro-magnetic valve were undertaken by using a video camera. Pressure and temperature changes in the vessel were measured. Depressurization rates in these experiments fell in the range from 0.01 to 4.0MPa/s. Experimental results showed that the initial temperature distributions and depressurization rates have more intrinsic influence on these flashing phenomena. Relationship between pressure undershoot and depressurization rate was obtained. The rate of pressure recovery was found to increase with the rate of depressurization, which also resulted in the increase of the increment of pressure recovery. The empirical equation proposed by Alamgir and Lienhard was applied to predicted the recovery pressure of the flashing of liquid nitrogen. To obtain more precise prediction of the pressure recovery, another factor such as an orifice diameter that affects the discharge condition of the recovery pressure.