Integrating novel materials into components can significantly improve the power density of heat pumps and make them much more efficient and environmentally friendly. Our R&D activities aim to optimize the thermophysical properties of materials and their functioning in the refrigerant circuit.
One example is our work on novel sorbents for thermal heat pumps and chillers. The sorbents typically used are zeolites, silica gels and activated carbons. Fraunhofer ISE researches not just these conventional materials, but also the new material class of metal-organic frameworks (MOFs). These highly crystalline hybrid materials are much more porous than any previously known material. Their modular structure offers a wide range of possibilities for synthesizing customized MOFs for individual applications. However, these new highperformance adsorbents place greater requirements on heat and mass transfer. To overcome these difficulties, we research ways to optimize the thermal coupling of the adsorbent to the heat exchanger while ensuring adequate accessibility for the refrigerant. We develop tailored solutions ranging from laboratory scale to complete heat exchangers for real-life applications.
Fraunhofer ISE has many years of experience in sorption technology and has already developed a number of application techniques (spraying, immersion, squeegee) that are ready for use in industrial mass production. Other R&D work is looking at compression heat pumps and refrigerant circuits, e.g. sorptive fuse elements for flammable refrigerants or coatings, which can be used to give air conditioning evaporators the desired surface properties.