Wrapped multilayer insulation for cryogenic piping

Abstract

Many cryogenic systems require thermal insulation on piping and tubing containing cryogenic fluids. The lowest heat leak is typically achieved with conventional multilayer insulation (MLI) wrapped around the tubing and contained in a vacuum. However, because of inherent insulation compression and its effect on conventional netting spacer MLI, MLI performance on piping and tubing is four to ten times worse than MLI on a cryogenic tank or flat surface. Wrapped Multilayer Insulation (WMLI) is a high performance multilayer insulation designed for cryogenic piping that uses an innovative discrete spacer technology to control layer spacing/density and reduce heat leak. This paper reports on the initial development of WMLI and its demonstration as a feasible technology. The WMLI design was estimated in thermal models to provide four times better thermal insulation than conventional MLI on cryogenic piping. A WMLI prototype was built and had a measured heat leak 37% of the heat leak of conventional MLI insulating tubing. Test results for WMLI are presented, and plans for continued development of this insulation are discussed.