Thermal conductivity of polyurethane foams from room temperature to 20 K

The thermal conductivity of the polyurethane (PU) foam in the temperature range between 300 and 20 K is investigated theoretically and experimentally for the development of liquid hydrogen storage tanks. An experimental set-up based on the JIS standard A1412 is built to measure the thermal conductivity of the foams under various temperature and pressure conditions. An analytical model, including the contributions from radiative heat transfer, is used to predict the thermal conductivity of the PU foams. The model is found to be able to accurately predict the thermal conductivity of the PU foams under normal and reduced pressures. The thermal conductivity of the PU foam can be reduced by as much as 70% by evacuating the gases in the foam cells. Radiative heat transfer is found to account for about 10-20% at room temperature. The thermal conductivity data below 90 K are available for the first time.