Modelling of the thermal radiation shields for cryogenic systems.

The paper presents models for different thermal radiation fields which are very important in all cryogenic systems. Although in literature exist models for calculate the net radiation between surfaces, the aim of paper is to present difficulties met when calculate the thermal radiation for particular surfaces. Moreover, in the paper it is shown that the radiation heat transferred between two surfaces at different temperatures depends by the emissivity coefficients of the surfaces, the geometrical configuration and the type of reflection. Analytical and experimental results regarding the thermal radiation influence in design of cryogenic systems, with application on Superconducting Magnetic Energy Storage System (SMES) and eXtreme High Vacuum (XHV) systems are also presented in the paper. The numerical results have been obtained by Finite Element Analysis (FEA) performed in COMSOL Multiphysics and ANSYS software. Based on the numerical simulation results, five types of floating radiation thermal shields were design and manufactured. These thermal shields were tested using a SUMITOMO RDK - 415D cryocooler, which with an adequate thermal shield has also been used as cryogenic pump in order to improve the level of vacuum within an extreme high vacuum test chamber.