Abstract
Slush nitrogen is a mixture of liquid and solid nitrogen. Fine solid particles are included and dispersed in the liquid phase. It enables the utilization of latent heat and make it possible to increase the quantity of refrigeration supply. Therefore, it is expected that it will be applied as a refrigerant for high-temperature super conductivity devices. This study deals with the pipe flow characteristics of slush nitrogen. The relationship between pressure loss and velocity is investigated experimentally. Flow velocity and mass solid fraction are made to be control parameters. As a result, on the condition that the solid proportion is less than 0.2, pressure loss in the pipe flow increases as the solid proportion increases. However, this increasing rate decreases with increasing flow velocity, and it is found that the pressure loss does not increase even if the solid proportion is increased under the condition of very high flow velocity. Furthermore, observation and classification of the flow pattern by visualization was carried out. The result of the visualization indicates that the flow pattern of the slush nitrogen can be classified into four patterns: uniform flow, layer flow, slide flow and separation flow. In addition, the relationship between the Reynolds number and tube friction coefficient was deduced and an empirical formula was derived.
