Investigating ad/desorption kinetics of SAPO-34/graphite filled coatings by T-LTJ for energy-efficient sorption application

This study assesses the performance of coated heat exchangers in order to favor heat and mass transfer for adsorption-based thermal energy storage and conversion systems. The investigation focused on the kinetic behavior of a novel composite coating composed of a sulfonated polyether ether ketone (S-PEEK) matrix, SAPO-34 zeolite, and exfoliated graphite (EG) as a conductive filler, applied on aluminum heat exchangers. Using the Thermal Large Temperature Jump (T-LTJ) method, a comparative kinetic analysis of a coating with 90 wt% zeolite and 5 wt% graphite filler was performed against a baseline zeolite-only coating under real operating conditions. Results show that EG significantly enhances adsorption kinetics, reducing characteristic times by 21 %–31 % and increasing maximum specific power by 24 %–29 %. This improvement is attributed to enhanced heat transfer due to EG's thermal conductivity. Desorption kinetics showed marginal improvements, likely due to the inherent efficiency of the zeolite-only coating. The study confirms that even small amounts of EG effectively boost heat transfer and overall coating performance, especially during adsorption. This highlights the potential of EG for optimizing adsorbent coatings in adsorption heat transforming applications.