The demand for cooling devices has increased during the last years and this trend will continue. Adsorption-driven chillers (ADCs) using water as the working fluid and low temperature waste energy for regeneration are an environmentally friendly alternative to currently employed cooling devices and can concurrently help to dramatically decrease energy consumption. Due to the ideal water sorption behavior and proven lifetime stability of [Al(OH)(m-BDC)] ∙ x H O (m-BDC = 1,3-benzenedicarboxylate), also denoted CAU-10-H, a green very robust synthesis process under reflux, with high yields up to 95% is developed and scaled up to 12 kg-scale. Shaping of the adsorbent is demonstrated, which is important for an application. Thus monoliths and coatings of CAU-10-H are produced using a water-based binder. The composites are thoroughly characterized toward their mechanical stability and water sorption behavior. Finally a full-scale heat exchanger is coated and tested under ADC working conditions. Fast adsorption dynamic leads to a high power output and a good power density. A low regeneration temperature of only 70 °C is demonstrated, allowing the use of low temperature sources like waste heat and solar thermal collectors.
Metal-organic frameworks of general composition [M(OH)(O)(PDC)(Cl)(HO)] with M = Zr, Ce, Hf; PDC = 2,5-pyridinedicarboxylate and 0 ≤ x ≤ 2 were obtained under reflux using formic, nitric or acetic acid as an additive. Rietveld refinements carried out using a fixed occupancy of the linker molecules according to the results of thermogravimetric measurements confirmed that the MOFs crystallize in the UiO-66 type structure and demonstrate that the structural models describe the data well. Further characterization was carried out by NMR spectroscopy, thermogravimetric analysis, Zr K-edge EXAFS- and Ce L-edge XANES measurements. To highlight the influence of the additional nitrogen atom of the pyridine ring, luminescence and vapour sorption measurements were carried out. The hydrophilisation of the MOFs was shown by the adsorption of water at lower p/p (<0.2) values compared to the corresponding BDC-MOFs (0.3). For water and methanol stability cycling adsorption experiments were carried out to evaluate the MOFs as potential adsorbents in heat transformation applications.
Metal–organic frameworks represent
a class of microporous
adsorbents with high application potential for adsorption heat transformation.
Here, we present a functional, full-scale heat exchanger coated with
the microporous aluminum fumarate MOF Basolite A520 using a polysiloxane-based
binding agent. The function of the heat exchanger was evaluated resulting
in a gross cooling power of 2900 W (at the beginning of the adsorption
cycle) or, respectively an average cooling power of 690 W (up to a limit of 90% equilibrium
loading in 7 min) under the working conditions of a realistic adsorption
chiller of 90 °C – 30 °C – 18 °C
(temperature level of heat source, heat rejection/condenser, and evaporator).
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