Numerical Design of a Reactor for an Ammonia-SrCl2 Thermochemical Storage System
Abstract
This work presents the numerical modelling of a reactor-heat exchanger combined unit using transient simulation in 2D using COMSOL, for a thermochemical storage system using ammonia-SrCl2 system. Here, absorption and desorption between SrCl2·NH3 and SrCl2·8NH3 are considered. The reactor is designed to store 0.5 kWh heat, for the stoichiometric amounts of 1.1 kg of SrCl2·NH3 that will form 1.8 kg of SrCl2·8NH3 using 0.74 kg of NH3 in gaseous-state. The reaction pressure is 8 bar, while the temperatures are 82 ℃ for desorption, and 79 ℃ for absorption. This is a packed-bed reactor in a cylindrical geometry, inside which SrCl2·8NH3 is embedded into 2.2 l of an Al mesh (10 pores per inch), for better heat transfer. To exchange the reaction heat, a stainless-steel helical coil heat exchanger is sandwiched within the Al mesh with salt, inside the reactor. The total volume of the reactor is 3 l, and with COMSOL modeling, the optimal dimensioning of the cylindrical reactor with the optimal positioning of the heat exchanger within the Al mesh-salt component is determined.