Comparison between numerical simulation and neutron radiography of ammonia sorption in SrCl2 for application in thermochemical storage system for waste heat recovery

Description

To support the transition to fossil-free society and economy, energy storage and particularly thermal energy storage has been identified as strategic technology. Large quantities of thermal energy – both per weight and price - can be stored reversibly in many salts upon exo-/endothermal ab-/desorption of ammonia. To achieve high efficiency of the ammonia-based heat storage system, particular attention must be taken in the realization of reactor design and heat exchanger, as well as salts behavior over ammonia cycling. Therefore, we adopted two approaches - theoretical and experimental. While a 3D numerical simulation was used to study heat and mass transfer in the thermochemical storage (TCS) system, neutron radiography and tomography was used as experimental imaging tool to follow in-situ the ammonia sorption and spatial behavior of the salts.
The neutron measurements were performed at the NECTAR instrument located at the FRMII neutron source (Munich-Germany). Data were collected on one stainless steel honeycomb structure representative of one basic heat exchanger element of our thermochemical storage prototype.
The images show that during desorption the heat provided is not evenly distributed presumably because of the relatively poor thermal conductivity of stainless steel. It is also found that the NH3 absorption is quiet homogeneous within the salt bed. The movement of the salt bed into each of the honeycomb cell is also probed. Indeed there is a large volume expansion of the salt upon NH3 absorption.
The results obtained illustrate the power of neutron imaging to study our system and validate our 3D model. Indeed, the results obtained from the simulation are in very good agreement with the experimental ones. This study will be used to further develop our prototype using our COMSOL model to identify the optimal bed thickness as well as the optimal value of the salt porosity that determines such opposing material properties as thermal conductivity and permeability of the bed.

Period	12 Mar 2019 → 14 Mar 2019
Event title	13th International Renewable Energy Storage Conference
Event type	Conference
Conference number	13
Location	Düsseldorf, GermanyShow on map
Degree of Recognition	International