A Compact, Passive, Cryogenic Cooling Unit for Shipboard Environments

The Navy has stated a need for a backup cryogenic cooling method for shipboard superconducting systems. The cooling method must be as compact as practical and should operate without consumables even if power is lost for an extended period. Ideally, the backup cooling method should take advantage of the energy associated with a phase change. One known compound has a solid-to-liquid phase transition within the temperature range of interest (at 77 K) and remains a liquid up to and above room temperature. The compound presents no unusual hazards and is commercially available. Despite its apparent promise, the compound has not been previously explored for use in cryogenic applications. Sierra Lobo proposes to develop a backup Cryogenic Cooling Unit (CCU) using the compound. In the CCU, the energy storage medium is completely enclosed, does not need replenishment, and is storable at atmospheric pressure at room temperature. While power is available, helium gas is cooled to cryogenic temperatures by a dedicated cryocooler and circulated through tubes embedded in the energy storage medium. When power is lost, valves switch the flow through the heat exchanger from the dedicated cryocooler to the superconducting equipment"s cooling loop to deliver cooling power.