Study On The Flow And Heat Transfer Of Slush Nitrogen In Horizontal Pipe

As a mixture of liquid and solid with fine solid particles dispersing in liquid phase, slush is considered to have good fluidness at a low solid fraction. Slush hydrogen (temperature of 13.8K) and slush nitrogen (temperature of 63.2K) are the main cryogenic slurries attracting much attention recently. Compared with subcooled liquid nitrogen, slush nitrogen is expected to be an excellent coolant for high Tc superconducting devices thanks to the features of high density, low temperature and high heat capacity. The study on the flow and heat transfer characters of slush nitrogen is necessary for its potential applications.The research work on slush nitrogen started in the recent decade, which is much less than that on slush hydrogen since the latter attracted great attention from the aerospace impulse technology. The study on slush nitrogen, including theoretical and experimental work, is far from sufficient, especially in China the related study is still at the beginning and exploring stage in many aspects.In this case, we planned to make our efforts to work on this topic. The main research contents are as follows:1.Analysis of the simulation model for slush nitrogen flow. Due to the complexity of two-phase flow, it is important to adopt proper turbulence model and multiphase flow model. After an introduction of several common models, we analyze the applicability, accuracy, advantages and disadvantages of these models, in order to provide a reference to the following numerical simulation of slush nitrogen flow.2. Numerical simulation and analysis on the flow features of slush nitrogen flow in horizontal pipe with CFD software.The pressure drop of slush nitrogen flow is emphatically analyzed. The main influencing factors of pressure drop and their effects on pressure drop are discussed and analyzed.3.Laboratory-level slush nitrogen production. An experiment apparatus of slush nitrogen production is built up.The production of ice slurry and slush nitrogen has been successfully realized. The cooling condition of liquid nitrogen is focused on to analyze the features of the producing process of slush nitrogen. The cooling curves and the characters of slush nitrogen obtained under different pumping speeds are also compared.4.Numerical simulation on melting process of solid nitrogen particle. The heat transfer characters of slush nitrogen are analyzed with numerical simulation. The emphasis is devoted to the melting of solid nitrogen particles, resulting in a 2-dimensional variation map of particle diameter.