Assessment of thermal conductivity in activated carbon adsorbents for liquid nitrogen-based cryo-adsorption vacuum pump applications.

Abstract

This paper presents a method for measuring the thermal conductivity of activated carbon adsorbents at liquid nitrogen (LN2) temperature for LN2-based cryo-adsorption vacuum pumps. This method is simple, versatile, and adaptable to various sample geometries of material under evaluation, including powders, spheres, granules, and pellets. This method can also be applied to assess similar materials with thermal conductivity in the range of 0.1-1.5 W/(m K). The thermal conductivity was evaluated by establishing a temperature gradient across the LN2-cooled sample using controlled heat inputs. The measurement accuracy was verified using glassy glycerol whose thermal conductivities at LN2 temperature had already been studied and reported in the literature. The thermal conductivities of activated carbon measured ranged from 0.14 to 0.25 W/(m K) across different sample types and conditions, including forms, packing density, and filler compositions. With an error margin established at 5%, the technique proves both effective and reliable for thermal conductivity measurements at LN2 temperature, offering promising applications in cryogenic engineering, insulation material development, and thermal management systems.