Extended Frequency Response Analysis for Loading and Temperature Dependent Heat and Mass Transfer Evaluation in Adsorbent Coatings

The combination of heat and mass transfer (HMT) phenomena and sorption equilibria are governing the adsorption dynamics. Their thorough understanding is crucial for the improvement of power density on appliance level. HMT phenomena are often difficult to distinguish, especially regarding the dependency on loading and temperature, i.e. the thermodynamic state of the adsorbent. In this contribution a frequency response (FR) analysis extended by manometrical equilibrium measurements is presented as a novel method for measuring both, adsorption equilibrium and HMT, in a single measurement for the example of an aluminium fumarate coating with water as refrigerant. This includes the direct measurement of the adsorption equilibrium derivatives for adsorption enthalpy evaluation. The thermal conductivity of the samples was identified as about 0.07 W/(m K), and the LDF time constant between 0.1 and 3 1/s at 40 °C with a U-shaped loading dependency and an Arrhenius-type temperature dependency. The heat transfer coefficient h for the contact between coating and support was identified to ≥ 4×10³ W/(m2K). The method is validated by comparing a measured large temperature jump experiment to the results from a non-linear simulation informed solely by these parameters obtained from the new FR-based method.