Optimal fluids for adsorptive cooling and heating

The search for optimal fluid/adsorbent working pairs in adsorption heat transformers is featured by trial and error method. In the last decades this approach has produced relevant progresses especially resulted in new advanced adsorption materials. On the refrigerant fluid side water, ammonia, methanol and ethanol still seem to be the only viable options. This work aims to explain the reason of that and the requirement that a refrigerant fluid must fulfil in order to be considered as promising for adsorptive cooling and heating. A thermodynamic framework is developed that merges the corresponding states principle with the characteristic curve of adsorption. Finally the framework is applied to assess the theoretical coefficient of performance of 258 fluids on 16 adsorption materials belonging to activated carbons, silica gels and zeolites, by avoiding in this way blind search strategy of the optimal working pair. Furthermore, the approach is used also to identify more generally the refrigerant thermodynamic properties for maximum performance. Fluid critical temperature is often the chief property enabling higher performance, although not always all the adsorption materials share the same sensitivity to the same thermodynamic properties.