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Influence of adsorbent characteristics on the performance of an adsorption heat storage cycle

 
: Schmidt, F.P.; Luther, J.; Glandt, E.D.

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Industrial and Engineering Chemistry Research 42 (2003), Nr.20, S.4910-4918
ISSN: 0888-5885
Englisch
Zeitschriftenaufsatz
Fraunhofer ISE ()
Energieeffiziente und solare Kühlung

Abstract
The increasing importance of heat transformation applications of adsorption (refrigeration, heat pumping, and heat storage) creates a demand for adsorbents optimized in new ways. The figures of merit in these applications are different from those that guide most adsorbent design processes today. A quantity to be optimized is the total sorptive heat stored over a cycle period rather than selectivity or total adsorption capacity. This optimization requires a detailed understanding of the link between cycle thermodynamics and microscopic adsorbent characteristics. We show that a simple statistical Langmuir model of adsorption is sufficient to analyze some of the key relationships. The influence of energetic heterogeneity on cycle performance is analyzed in a model system in relation to the energy and entropy change upon adsorption. For a homogeneous system of monoenergetic adsorption sites, it is shown that for each value of the adsorbed state entropy there is an optimal adsorbent-adsorbate interaction energy. Further, the largest possible entropy change upon adsorption is generally desired. When the model is extended to energetically heterogeneous adsorbents, it is shown that in many but not all cases heterogeneity is deleterious.

: http://publica.fraunhofer.de/dokumente/N-32725.html