Thermal insulations based on vacuum and radiation shields were developed in the late sixties and demonstrated high performance in the order of k=10-3 [W/m K]. However, variable conductance insulation can be achieved by using different gases and pressures instead of vacuum. Low value of effective thermal conductivity is also achieved by using a low thermal conductivity interstitial gas and keeping tiny gaps between the radiation shields. The tiny gaps creates small mean free path for the interstitial gas molecules. Therefore high value of Knudsen number is obtained which limit the gas conduction in the gap and prevent convection. A large range of effective thermal conductivities could be achieved by using gases like helium and xenon, which have high thermal conductivity value and low thermal conductivity value, respectively at different pressures. Such versatile insulation array can be used for a variety of application and for thermal management of different systems. In this study the effective thermal conductivity of such insulation array was investigated, with Helium and Xenon gases, in order to demonstrate a large range of thermal conductivities by the same insulation array. A parametric study for the number of foils, working pressure and gap size was performed.
