Numerical Simulation On Phase-changed Refrigeration Of Cold Shield System

Ballistic missiles in flight will produce a strong thermal radiation, and infrared stealth technology is applied to eliminate and reduce this radiation to reach the purpose of stealth. The cold shield system in Infrared stealth technology uses the basic principle of refrigerant’s phase-changed refrigeration(liquefied nitrogen), cool the outside wall of cold shield, and finally reach the goal to reduce the infrared radiation. Cold shield system has become an important research direction of infrared stealth technology. Loading cold shield system on the outside of the target, the infrared radiation characteristics of the target is similar as much as possible to the space background. It can greatly shorten the distance detected by infrared detectors and also increase the difficulty of interception, which has a very important significance for improving the penetration ability of ballistic missiles.Since liquid nitrogen absorbs heat to form two phase flow of gas and liquid, the multiphase flow model of FLUENT software was used. A mixture model for multiphase flow was applied to the numerical simulation of phase-change cooling of liquid nitrogen, and through user defined function (UDF) the interphase transfer of mass and energy achieved. The three-dimensional model of cold shield system was established through appropriate simplification. Regarding the actual working conditions as boundary conditions, the solution set up and specific numerical simulation were carred out. According to the results of numerical simulation, the temperature distribution of cold shield wall, internal pressure distribution, velocity distribution, gas fraction distribution change were analyzed and summarized. That cold shielding system can meet the expected goal. The conclusions have certain reference value and instructional significance the for the optimization design of cold shield system. It also shows that FLUENT software can achieve the numerical simulation of phase change cooling for liquid nitrogen shield system.