Ammonium carbamate-based heat exchanger reactor as an endothermic heat sink for thermal management

We present our work on the investigation of a chemical reactor heat sink which used an endothermic reaction to absorb low-grade heat. Ammonium carbamate, which has an enthalpy of decomposition of ∼2 MJ/kg and decomposes over a wide range of temperatures, was used as the endothermic chemical. The objective of the effort was to develop the methods and apparatus required to demonstrate endothermic cooling. Ammonium carbamate (AC) particles were suspended in propylene glycol (PG) and pumped through a heat exchanger, where it chemically reacted and decomposed as it absorbed heat from a hot fluid. Two conditions involving the reactants (AC in PG) were studied: (1) elevated decomposition temperatures occurring at near-ambient pressures and (2) near-ambient decomposition temperatures occurring at low pressures. The influences of reactant pressure, relative reactant temperature, reactant residence time, AC particle size, and AC mass flow rate on the heat absorption rate were investigated. Reaction pressure, residence time, and temperature were found to be the dominant factors.