Benchmarking metal-organic framework coatings from Large-Temperature-Jump experiments: Learning from trade-offs in mean powers versus characteristic times

Adsorption chillers can substitute the electric energy demand of conventional compression chillers with lowtemperature heat. The efficiency and power density of adsorption chillers depend on their adsorbent and refrigerant, which form the working pair. Novel working pairs are therefore actively developed and characterized in dynamic small-scale experiments using a characteristic time constant. However, this evaluation by only few characteristic time constants, does not resolve the trade-off between efficiency and power density of adsorption chillers and novel materials are challenging to compare due to varying size, shape, and density. To fill these gaps, we investigate the trade-off between efficiency and power density by quantifying all characteristic time constants and transferring them to specific mean powers. We perform Large-Temperature-Jump experiments with water as the refrigerant on the two metal–organic frameworks CAU-10-H and aluminum fumarate for a chilling/recooling/regeneration temperature triple of 10/30/80 °C. We compare the metal–organic frameworks’ specific mean powers to the commercially available RD type silica gels Siogel and SG123. Siogel performed best in terms of area-specific mean powers with a maximum value of 3.2 kW/m2. For low time constants up to 20 % relative loading, corresponding to high power density but lower efficiency, Siogel also provided the highest volumespecific mean power at 8.1 MW/m3. CAU-10-H had the highest mass- and volume-specific mean powers at 19.0-19.9 kW/kg and 7.2-8.6 MW/m3 for characteristic time constants of 35 % relative loading and higher. Aluminum fumarate and SG123 showed low specific mean powers for all chosen characteristic time constants. The results show that studying specific mean powers is a useful tool to benchmark adsorption working pairs as they would perform in an adsorption chiller, regardless of mass, shape, or density.