Thermal Conductivity of Polyurethane Foam at Liquid Hydrogen Temperature Region

Abstract

Hydrogen is a promising, clean energy source which never produces CO₂. Liquid hydrogen (LH₂) is considered one of the large scale hydrogen storage methods. LH₂ must be thermally insulated from the ambient temperature region and must be stored with minimum evaporation loss. It is difficult to apply the usual cryogenic thermal insulation technique for a large scale LH₂ storage tank with moderate construction cost. We have been studying applications of polyurethane foam (PUF) to the thermal insulation material of the LH₂ storage tank. In order to design the storage tank, thermal conductivity data at LH₂ temperature region is required, but unfortunately no thermal conductivity data of PUF is available. For the above reason, we have developed a test facility and have measured thermal conductivity of PUF. This test facility has some design features: (1) thermal conductivity is measured by the steady cylindrical method, (2) PUF is cooled by a GM-refrigerator, and (3) measurement can be done at any point between LH₂ and ambient temperature and under or over atmospheric pressure. Some samples which have different density have been measured, and characteristics of thermal conductivity for temperature and density have been examined.