Study On The Preparation Mechanism And Characteristics Analysis Of Slush Nitrogen

High-temperature superconductor (HTS) that has zero resistance when being cooled below its critical temperature will have a wide range of applications, such as power transmission, under the advocacy of Energy Saving. Slush nitrogen contains small solid nitrogen particles suspending in liquid, leading to higher density, lower temperature and higher heat capacity than subcooled liquid nitrogen. It is considered as the more preferable coolant than subcooled liquid nitrogen for HTS devices. However, the researches concerning slush nitrogen are still insufficient, and sometimes need to refer to the literatures about slush hydrogen, which attracted much attention from the space propulsion technology. In this case, the preparation of slush nitrogen is chosen as our research object, and the main contents are as follows:1. Thermodynamic processes for slush production. The thermodynamic processes of vacuum pumping production method and helium cooling production method were analyzed, and their physical models and the corresponding differential equation were established and studied. Based on discussing the pros and cons of two methods, the vacuum pumping production method will be further focused on in the following sections.2. Numerical simulation of the vacuum pumping production method. The Volume-of-fluid (VOF) model incorporated with phase transition theory of gas-liquid and liquid-solid was developed and applied in the simulation. The simulation results give us a general understanding of vacuum pumping production method, and the inner temperature and pressure distribution, as well as the details of the vapor-liquid and liquid-solid phase transitions will be analyzed.3. Experimental study on the freeze-thaw method of slush nitrogen production. In the experimental study of freeze-thaw method, we focus on the visualization of solid nitrogen layer and the low-temperature measurement methods, including the level measurement by the photography and the volume fraction measurement by the capacitance-type densimeter. According to the observation and experimental data, the process the freeze-thaw production method was analyzed in details.