Heat pumps, cooling machines, heat storage
The subproject on thermally driven systems focus on the development of hydrothermal stable MOFs with a high water sorption capacity, and a polarity which fits the requirements of the application. Previous studies showed an enormous potential of MOFs for this application. Beside the necessary stability, another key issue is the coupled heat and mass transfer. Thus, direct and indirect coatings are essential to overcome these limitations.
As outcome of a comprehensive evaluation, various MOF candidates were identified. The evaluation was based on physical characteristics such as water sorption capacity, polarity, cycle stability, complexity of the synthesis, as well as cost estimation.
Through the "Direct-Crystallization" approach, which was developed at Fraunhofer ISE, the MOF is directly applied onto the surface of the heat exchanger structure, regardless of size and complexity. Beside, the thickness can be controlled by synthese time. In addition, a binder based coating was developed, which has already proven a high flexibility and versatility of the process for various geometries.
Both methods were used to coat a full scale heat exchangers, which can directly be applied into the application.