MLI Basics

The Multi-Layer Insulation (MLI) Shield (aka thermal radiation blanket) is very important in cryogenic systems. MLI shields insulate components from thermal energy transferred via light on rockets, satellites, and cryogenic experiments. The shield consists of 10s of alternating layers of polymer mesh and reflective mylar (metalized nylon) film. For a 2.5cm (1″) thick blanket at 1×10^-4 torr vacuum level, equivalent R values of ~1440 can be obtained (Technifab). Typical insulation of a building wall is in the equivalent R of 10-60 (Energy.gov). It’s no wonder engineers in the Linde Devision of Union Carbide named it “superinsulation” in the 1950s (McIntosh). To understand how … » More …

The helium compressor that drives a cryocooler has to effectively reject the heat it’s removing from the helium stream to prevent itself from overheating, and keep the cryocooler cooling efficiently. In most cases, this means running a heat exchanger with a cooled water loop to keep everything cool. This can be very effective when you’re running high purity, clean water through the heat exchanger, but dirty, rusty, or impure water can reduce performance and foul the heat exchanger tubes. In the lab, we use a cooling loop independent from the building water paired with a water filter to help keep water as clean as possible … » More …