ABSTRACT
Supports in cold masses and storage volumes of cryogenic fluids are designed to meet the mechanical loading requirements to position the cold space at a desired location and to provide thermal isolation from the warm environment through the design of thermally isolating support structures, which is the subject of this chapter. Thermal insulation is the main means of thermal isolation, but supports contribute a significant portion of the total heat load. The optimal selection of materials used in construction of a support depends on the thermal conductivity and the mechanical strength of the materials. Supports come in many forms, including rigid, such as tension rods or support posts, or flexible such as chains, cables, or straps. The type of support depends on the application. Shipping supports may be designed to provide mechanical support only when the system is warm during transport. As such, they may rely on thermal contractions upon cooldown to disconnect the support thermally from a warm container when no mechanical support is required after installation. Other support posts may need to allow for thermal contractions upon cooldown or provide for sliding between the cold mass and the support to permit relative motion on cooldown. Any discussion regarding the design of structural supports for low-temperature applications should include a description of the typical mechanical loads as well as the thermal loads A brief introduction to the stresses that occur under simple mechanical loads from tension and compression, bending, and twisting is provided. Some support structures have provisions for heat stations along the support. One approach to thermally optimizing the temperatures and locations of the heat stations by minimizing the ideal refrigeration is explained. Several practical examples from the literature are provided for applications such as supports for MRI and accelerator magnets, pipe supports when multiple cryogenic fluid lines are enclosed in a single vacuum enclosure, and supports for storage vessels. Advanced support designs that use high-temperature superconductors to levitate a cold mass are also presented.
