Stationary thin film microgroove-based sorber reactor for sorption heat transformers: Surface modification, sorption dynamics, and crystallization

The present study proposes a new type of sorber bed, a stationary thin film microgroove-based absorber for oscillatory waste-heat-driven sorption heat transformers, which operate on a temperature swing sorption process. Although this study focuses on sorption heat transformers, the present sorber bed can be used for other temperature swing sorption applications such as carbon capture, atmospheric water harvesting, and desalination. As a proof of concept for this idea, a microgrooved aluminum substrate is fabricated. The substrate is coated with Al2O3/TiO2 layers using plasma enhanced atomic layer deposition and magnetron sputtering physical vapor deposition to enhance wetting and confine the solution within the microgrooves. Contact angle and capillary rise measurements are performed for three different salts: LiBr, LiCl, and CaCl2, demonstrating the microgrooves' wettability. A custom-built gravimetric large pressure jump setup is used to experimentally measure the water uptake of the sorbent. It is shown that a specific cooling power of up to seven times that of experimental data available in the literature can be obtained. The effect of crystallization on the sorption dynamic for the three mentioned salts is also investigated. It is shown that the present sorber bed demonstrates the capability to handle crystallization.