Thermal conductivity of AQSOA FAM-Z02 packed bed adsorbers in open and closed adsorption thermal energy storage systems

Abstract

In this study, the effective thermal conductivity (ETC) of uniformly-sized packed bed adsorber is modeled as a function of water uptake, number of adsorbent layers, particle size, bed porosity, temperature, contact pressure, and interstitial gas pressure. The model is validated against experimental data for 2 mm AQSOA FAM-Z02, measured by heat flow meter method (ASTM standard C518), and the maximum relative differences between the predicted values and the experimental data are 2% for ETC and 8% for total thermal conductivity. For 0.32 kg kgads−1 water uptake, at 30 °C, ETC of an open-system 2 mm FAM-Z02 SC-arranged packed bed adsorber is 2.2 times higher than the ETC of a closed-system (0.1031 W m−1 K−1 compared to 0.0474 W m−1 K−1). ETC charts are presented based on the equilibrium water uptake isotherms for 0.5 and 2 mm FAM-Z02 packed beds, which provides a detailed and clear picture of ETC of packed bed adsorbers for both open and closed thermal energy storage applications. For each packed bed storage volume, an optimum particle size can be predicted by the presented model, which ensures the highest packed bed total thermal conductivity.