THERMAL-CONDUCTIVITY OF POLYURETHANE FOAMS FROM ROOM-TEMPERATURE TO 20 K

The thermal conductivity of the polyurethane (PU) foam in the temperat ure range between 300 and 20 K is investigated theoretically and exper imentally for the development of liquid hydrogen storage tanks. An exp erimental set-up based on the JIS standard A1412 is built to measure t he thermal conductivity of the foams under various temperature and pre ssure conditions. An analytical model, including the contributions fro m 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 pres sures. The thermal conductivity of the PU foam can be reduced by as mu ch as 70% by evacuating the gases in the foam cells. Radiative heat tr ansfer is found to account for about 10-20% at room temperature. The t hermal conductivity data below 90 K are available for the first time. (C) 1997 Elsevier Science Ltd.