Dynamics of Liquid Nitrogen in a Closed Vessel in the Presence of Helium Pressurization Gas

In closed vessels with a cryogenic liquid, the heat gain from the environment leads to increase in the pressure in the vessel and self-heating of the liquid in the vessel. This problem is topical in storage and transportation of liquefied natural gas (LNG), for start-up refueling facilities of space rocket, and for a number of other applications of cryogenic liquids. A characteristic feature of these systems is the presence of significant temperature stratification in the upper layers of the cryogenic liquid volume. An experimental study was made of the dynamics of liquid nitrogen evaporation in a closed vessel under conditions of pressurization with helium gas up to a pressure of 0.35 MPa. The experiments were carried out in a cylindrical vessel with a height of 650 mm and an inner diameter of 213 mm at a filling of 82%. The study has shown that the stage of pressurization with helium intensifies the convective heat transfer between the interfacial surface and the vapor-gas medium in the upper part of the vessel. At the stage of subsequent heating of the liquid, two modes of heat transfer from the heat-generating walls of the vessel to the liquid are realized sequentially: with a high heat transfer coefficient at the first stage and with a significantly lower heat transfer rate at the second stage. As a result, at the stage of change of these heat transfer regimes, a sharp decrease in the intensity of liquid nitrogen evaporation is observed.