Mechanism Investigation On Heat Transfer Of Liquid-nitrogen Cooled Shroud

As an important investigation method of infrared stealth technology, it will gain theeffect of weakening the infrared radiation to use liquid-nitrogen cooled shroud, whichapplies the basic principle of heat transfer with phase change to cool target's surface to alow enough temperature. If the target is covered with a liquid-nitrogen cooled shroudwhose infrared radiation are similar to the space's, then the detection and interceptionrange can be reduced enough. Therefore, it is of importance to improve thecountermeasures of ballistic missiles.This paper not only establishes the energy transfer model of the liquid-nitrogen cooledshroud in the backgrounds of space, but also presents the flow and evaporation model ofliquid-nitrogen in the porous medium with variational section. The heat transfercharacteristics of the liquid-nitrogen cooled shroud are investigated theoretically andexperimentally. The heat and mass transfer processes of liquid-nitrogen cooled shroud areinvestigated when its surface is refrigerated in midcourse phase and in laboratory. Somemajor factors that influence the wastage of liquid-nitrogen are calculated and discussedwhen the liquid-nitrogen cooled shroud is in midcourse phase. In addition, the flow andevaporation processes of liquid-nitrogen are analyzed in detail, as well as the changingprocesses of the liquid-nitrogen cooled shroud's surface temperature. The infraredcharacterizations of liquid-nitrogen cooled shroud are calculated. Finally the surfacetemperature distribution and the flux changing of liquid-nitrogen cooled shroud are testedwhen its surface is refrigerated in laboratory. Comparison between numerical results andexperimental data proves that the proposed model describes the flow and evaporationprocesses of liquid-nitrogen in the porous medium.