Development of production system of cryogenic micro-slush particles using a two-fluid nozzle

Abstract

A production system for cryogenic fine micro-slush nitrogen particles is developed using a two-fluid atomization nozzle to apply micro-slush as a refrigerant for long-distance high temperature superconducting cables (HTS); a process that is expected to result in an extensive improvement in effective cooling performance for super-conducting systems. The principle of the micro-slush production nozzle and the performance of the nozzle investigated by Particle Image Velocimetry (PIV) measurement are herein presented. We mainly focus on the development of a new type of superadiabatic two-fluid ejector nozzle, which is capable of generating and atomizing solid nitrogen using liquid–gas impingement of a pressurized subcooled liquid nitrogen (LN 2) flow and by a low-temperature, high-speed gaseous helium (GHe) flow. In addition, we constructed a micro-slush particle production system using this new type of two-fluid nozzle and then investigated the effect of the mass flow rate of GHe on the characteristics of the micro-slush two-phase atomizing flow by PIV. The results of this research show that it is possible to produce fine micro-slush nitrogen particles using this newly developed two-fluid nozzle under high-speed atomizing flow conditions, and by applying the appropriate mass-flow rate of subcooled LN 2 and cryogenic GHe. Based on the optimized thermal flow conditions of cryogenic micro-slush particulate atomizing two-phase flow and the practical use of its multi-phase functionality, utilization in the development of a new type of superconducting cooling system is predicted.