Investigation of a New Heat-Pipe/Latent-Heat-Storage Receiver Element for Solar Dynamic Space Power Systems

A new latent heat storage technique for space applications developed by the DLR-ITT uses LiF as the storage medium in graphite capsules with internal capillary notches to accomodate the volume change upon melting. The receivers of solar dynamic power systems (SDPS) may contain a large number of heat pipes carrying annular such storage capsules for very effective heat transfer and thermal storage. The thermal behavior of one of these heat-pipe/latent-heat-storage elements was investigated theoretically and shall be verified experimentally, both in a geometrically and energetically 1:1 scale with respect to a 25 kW_e SDPS. This paper summarizes the most important theoretical predictions and describes the planned experiment. The theoretical results show that the required heat flows are essentially achievable but subject to variation with the state of charge of the heat storage units. The relevant temperatures vary in a similar manner.