Expendable High Energy Density Thermal Management Material: Ammonium Carbamate

摘要

Phase change materials have low specific energy storage capacities within the temperature range of 20-100℃. State-of-the-art phase change materials in this temperature range are usually paraffin waxes with energy densities on the order of a few 100 kilojoules per kilogram or ice slurries with energy densities of the same magnitude. However, for applications where system weight and size are limited, it is necessary to improve this energy density by at least an order of magnitude. The compound ammonium carbamate [NHJ][H_2NCOO~-], a solid formed from the reaction of ammonia and carbon dioxide, endothermically decomposes back to CO_2 and NH_3 hi the temperature range 20-100℃ with an enthalpy of decomposition of 2010 kj/kg. Various methods of using ammonium carbamate for thermal management of low-grade high-flux heat have been evaluated, and results are reported, including bare powder, thermally conductive carbon foams, thermally conductive metal foams, hydrocarbon-based slurries, and a slurry solution in ethylene glycol or propylene glycol. A slurry solution in glycol is a promising medium for enhancing heat and mass transfer for thermal management Small-scale system-level characterizations of ammonium carbamate in glycol have been performed, and results indicate that ammonium carbamate is indeed a promising material for thermal management of low-grade heat.