EuroSun 2012 - Membrane Pervaporation for advanced Absorber and Desorber Design in compact Lithiumbromide Absorption chillers

摘要

The worldwide growing demand for air conditioning (AC) requires the use of thermally driven cooling processes in order to avoid further grid overloads and to save primary energy. As an alternative to electrically driven compression cycles for AC thermally actuated systems can be used to supply cold for buildings, powered by solarthermal energy, district heating, waste heat from decentral cogeneration plants or industrial processes. To open the market of residential buildings to small scale absorption chillers, a reduction of unit size and costs is required. At Fraunhofer UMSICHT a new absorption chiller based on the Lithiumbromide/Water process is under development, using membrane pervaporation technology and a compact stack design in order to enhance the performance and reduce the unit volume. From the experimental lab scale investigation the vapor sorption capacity of the pervaporation process is in the range of 1 to 2 kW/m~2 of membrane area. The membrane process can operated both in absorption and desorption mode, by just setting the respective external water temperatures. A possible design concept for both absorber and desorber with flat sheet membranes is presented.