2-DIMENSIONAL MODEL OF A SPACE STATION FREEDOM THERMAL-ENERGY STORAGECANISTER

The Solar Dynamic Power Module being developed for Space Station Freed om uses a eutectic mixture of LiF-CaF2 phase-change salt contained in toroidal canisters for thermal energy storage. This paper presents res ults from heat transfer analyses of the phase-change salt containment canister. A two-dimensional, axisymmetric finite difference computer p rogram which models the canister walls, salt, void, and heat engine wo rking fluid coolant was developed. Analyses included effects of conduc tion in canister walls and solid salt, conduction and free con vection in liquid salt, conduction and radiation across salt vapor-filled voi d regions, and forced convection in the heat engine working fluid. Voi d shape and location were prescribed based on engineering judgment. Th e salt phase-change process was modeled using the enthalpy method. Dis cussion of results focuses on the role of free convection in the liqui d salt on canister heat transfer performance. This role is shown to be important for interpreting the relationship between ground-based cani ster performance (in 1-g) and expected on-orbit performance (in micro- g). Attention is also focused on the influence of void heat transfer o n canister wall temperature distributions. The large thermal resistanc e of void regions is shown to accentaute canister hot spots and temper ature gradients.