Heat Transport of Powder as the Subject of Cryogenic Insulation : 1st Report, Effective Thermal Conductivity at Atmospheric and Low Pressures

摘要

As thermal insulation powder usually contains numerous voids in each particle of the powder, the previous theoretical equations on its effective thermal conductivity do not agree with experiments if the equations are employed without modification. In the present study, the thermal conductivity of a particle is firstly estimated by a simple cell model, then the effective thermal conductivity of the powder is calculated on the assumption that the powder consists of particles with the above estimated thermal conductivity. On the other hand, the effective thermal conductivities of the powder of perlite and hollow glass microsphere are measured at low temperatures, and are compared with the calculated values. The result shows that at a given temperature and gas pressure the experimental values agree well with the calculated values.