Numerical Investigation on Heat-Transfer and Hydromechanical Performance Inside Contaminant-Insensitive Sublimators Under a Vacuum Environment for Spacecraft Applications

The contaminant-insensitive sublimator (CIS) is a novel water sublimator in development, which uses two porous substrates to separate the sublimation point from the pressure-control point and provide long-life effective cooling for spacecraft. Many essential studies need to be carried out in the field. To overcome the reliability issues such as ice breakthrough caused by large temperature or pressure differences, the CIS development unit model, the mathematical models of heat and mass transfer and the evaluation coefficient have been established. Numerical investigations have been implemented aiming at the impacts of physical properties of porous substrate, physical properties of working fluid, orifice layouts and orifice-structure parameters on the characteristics of flow field and temperature field. The numerical investigation shows some valuable conclusion, such as the temperature uniformity coefficient at the bottom surface of the large pore substrate is 0.997669 and the pressure uniformity coefficient at the same surface is 0.85361267. These numerical results can provide structure and data reference for the CIS design of lunar probe or spacesuit.

Electron-emission-induced cooling of boundary region in fusion devices

In this brief communication we have explored whether the electron emission from the boundary region surfaces (or from additional fine structured dust particles/droplets of some benign material put purposely in the area surrounding the surfaces) can act as an efficient cooling mechanism for boundary region surfaces/dust electrons and hence the lattice. In order to estimate the contribution of this cooling process a simple kinetic model based on charge flux balance and associated energetics has been established. Along with some additional sophistication like suitable choice of material and modification in the work function via surface coating, the estimates show that it is possible to keep the temperature of the plate/particles well within the critical limit, i.e. melting/sublimation point for the desired regime of incident heat flux.

Study of Processing Hllw by Super High Temperature Method. Part II*. Reducing Reactions and Formation of Complex Oxides in the Simplified Hllw

The reducing reactions of platinum metal oxides and the formation of the complex oxides were studied to estimate the process at high temperatures. Heat treatment of Re207 with TiN causes reduction up to the sublimation point of Re207 and exhibits the highest value of the recovery among the reducing agents used in the present study. Reducing reactions of the platinum metal oxides with the reducing agents lower the melting temperature. The simplified complex oxides contain the complex oxides of the representative elements of FP and the metallic elements of the reducing agents, which contribute to a decrease of melting temperature, neodymium zirconium oxides and neodymium barium oxide which may transform to the other phases during heating. Uranium may dissolve in the phases in which uranium is identified by EPMA but cannot detected by X-ray diffraction.