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A novel adsorption module with fiber heat exchangers: Performance analysis based on driving temperature differences

: Wittstadt, U.; Füldner, G.; Laurenz, E.; Warlo, A.; Große, A.; Herrmann, R.; Schnabel, L.; Mittelbach, W.


Renewable energy 110 (2017), pp.154-161
ISSN: 0960-1481
Journal Article
Fraunhofer ISE ()
Thermische Anlagen und Gebäudetechnik; adsorption; adsorption chiller; heat exchanger; heat pump; Gebäudeenergietechnik; Materialien und Komponenten für Wärmetransformation

A main focus of recent R&D on adsorption modules for thermally driven heat pumps and chillers has been to enhance the volume specific power output while maintaining a reasonable coefficient of performance (COP).An adsorption module using a new type of heat exchanger based on aluminum sintered metal fiber structures brazed on flat fluid channels has been developed. The heat exchangers for adsorber/desorber and evaporator/condenser are identically constructed. The adsorption heat exchanger is coated with a silico-alumino phosphate (SAPO-34) by a partial support transformation direct crystallization (PST) [1]. Both components are placed in a vacuum tight housing using a valve-free configuration. Water is used as adsorptive. The experimental characterization of the module shows a high volume specific power (up to 82 W/litre module for cooling, 320 W/litre for heating). Although no heat is recovered between ad- and desorption cycle, a COP of almost 0.4 is reached for cooling and 1.4 for heating. Driving temperature differences are defined for the analysis of the heat exchanger performance. The evaporator/condenser shows extremely good performance with about 240 W/K specific evaporation power per litre of heat exchanger, while the adsorber is limiting the module performance.