Experimental study of moisture uptake of polyurethane foam subjected to a heat sink below 30K

• Published in: Cryogenics (Guildford) 2014-01, Vol.59, p.1-6
• Main Authors: Zhang, X.B., Chen, J.Y., Gan, Z.H., Qiu, L.M., Zhang, K.H., Yang, R.P., Ma, X.J., Liu, Z.H.
• Format: Article
• Language: English
• Subjects: Insulation; Liquid hydrogen; Moisture uptake; Polyurethane foam
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/j.cryogenics.2013.12.002

•An apparatus for moisture uptake of foam at cryogenic temperature was built.•Cryocoolers are used to cool one side of specimen to liquid hydrogen temperature.•Added weight due to moisture uptake at 78K and 26K is almost same in 9h period.•In-between butt-joint has no effects on moisture uptake at 78K or 26K in 9h period. Rigid closed-cell foam is widely used to thermally insulate liquid hydrogen and oxygen tanks of space launch vehicles due to its lightweight, mechanical strength and thermal-insulating performance. Up to now, little information is available on the intrusion of moisture into the foam that subjects one side to liquid hydrogen temperatures and the other side to room temperatures and high relative humidity. A novel cryogenic moisture uptake apparatus has been designed and fabricated to measure the moisture uptake into the polyurethane foam. For safety and convenience, two identical single-stage pulse tube cryocoolers instead of liquid hydrogen are used to cool one side of the foam specimen to the lowest temperature of 26K. Total of eight specimens in three groups, according to whether there is a butt-joint or weathering period, are tested respectively for both 5h and 9h. The additional weight due to moisture uptake of the foam for the 26K cases is compared to previous measurements at 79K. The results are instructive for the applications of foam to the insulation of liquid hydrogen tanks in space launch vehicles.