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Experimental setup for determining ammonia-salt adsorption and desorption behavior under typical heat pump conditions: a description of the setup and experimental results
Gepubliceerd door: Publicatie datum:
ECN Efficiency & Infrastructure 11-3-2011
ECN publicatienummer: Publicatie type:
ECN-M--11-030 Conferentiebijdrage
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Heat-driven heat pumps based on the principle of chemisorption have been researched worldwide. Such research typically focuses either on fundamental materials properties such as sorption isotherms, thermal conductivity and heat of sorption, or on the development and performance of complete systems. Also at ECN the research shows this typical pattern with publications on the fundamental thermodynamic properties on ammonia reactions of lithium chloride and magnesium chloride (Bevers et al., 2006; Bevers et al., 2007) together with results on complete systems (Haije et al., 2007; van der Pal et al., 2009). However, when trying to connect the material properties to the system’s performance, for example by using model calculations, various uncertainties on heat exchanger/sorption reactor level remain. These uncertainties, such as reaction kinetics, heat and mass transfer limitations for given specific geometries and conditions but also effects due to repeated sorption, pose a considerable problem for further development, improvement and scaling up of the system. In order to get a better understanding of the performance of the sorption reactor/heat exchanger design and sorbent bed loading, an experimental setup has been developed. This setup allows measuring the performance of various ammonia-sorbent reactions with various sorption reactor/heat exchanger designs under well-controlled and well-monitored process conditions similar to the heat pump conditions. This setup measures the ammonia uptake and release under well-controlled conditions with temperatures that can be varied from ambient temperature up to 200oC and ammonia pressures that can be varied between 0.02 to 2 MPa. These conditions can be set independently and repeated at regular time-intervals. Besides mass-flow meters, pressure and temperature sensors, the setup also contains an endoscope to observe the macroscopic structural changes in the material during uptake and release of ammonia. After initial testing, the setup is now ready for the first experiments on different heat exchanger designs and sorbent materials. The paper includes a description of the setup and the first experimental results.

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