Intermittency of sustainable energy or waste heat availability calls for energy storage systems such as thermal batteries. Thermochemical batteries based on a reversible solid–gas (MgCl2–NH3) reactions and NH3 liquid–gas phase change are of specific interest since the kinetics of absorption are fast and the heat transfer rates for liquid–vapor phase change are high. Thus, a thermochemical battery based on reversible reaction between magnesium chloride and ammonia was studied. Two-dimensional experimental studies were conducted on a reactor in which temperature profiles within the solid matrix and pressure and flow rates of gas were obtained during discharging processes. A numerical model based on heat and mass transfer within the salt and salt–gas reactions was developed to simulate the NH3 absorption processes within the solid matrix, and the results were compared with experimental data to determine dominant heat and mass transfer processes within the salt. It is shown that for high permeability salt beds, the reactor uniformly adsorbs gaseous ammonia until the bed reaches the equilibrium temperature, then adsorbs gas near the cooled boundaries as the reaction front moves inward. In that mode, the heat transfer is the dominant factor in determining reaction rates.
Study of Heat and Mass Transfer in MgCl2/NH3 Thermochemical Batteries
Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received August 12, 2016; final manuscript received January 11, 2017; published online February 14, 2017. Assoc. Editor: Antonio J. Bula.
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Mofidi, S. A. H., and Udell, K. S. (February 14, 2017). "Study of Heat and Mass Transfer in MgCl2/NH3 Thermochemical Batteries." ASME. J. Energy Resour. Technol. May 2017; 139(3): 032005. https://doi.org/10.1115/1.4035750
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