Performance parameters of a compact cryogenic hydrogen test platform

Abstract A versatile test apparatus has been developed for material samples and components for tests in a LH2 environment without the need of an external LH2 supply. Applications range from mechanical material testing such as tensile testing and exposure tests to check for low temperature compatibility at 20 K, H2 compatibility and potential degradation or permeation effects. A limited LH2 quantity of typically 2–3 L is generated directly on site by simple condensation. Hydrogen is taken from an external reservoir (high pressure cylinders) and condensed by means of a two-stage cryocooler (110 W @ 80 K, 18 W @ 20 K). Pre-cooling is done by the 80 K stage, final cooling and liquefaction by the 20 K stage. A cylindrical pressure vessel with an inner diameter of d = 107 mm and a length of 990 mm is attached. It is designed for a working pressure of 0.1 MPa up to max. 2.1 MPa. The cryocooler and the pressure vessel (sample chamber) are installed in a common vacuum cryostat and are thermally coupled at the two temperature levels. At the 20 K flange, thermal coupling is achieved by a sophisticated thermosiphon arrangement. This contribution discusses the main performance parameters of this test platform using helium, including the cool-down and warm-up, as well as the maximum heat input in steady-state operation. The operating principle of the low-temperature thermosiphon is validated.