Effective thermal conductivity modeling of consolidated sorption composites containing graphite flakes

Thermal conductivity of CaCl2-silica gel composites adsorbent, which is generally used in water-based adsorption cooling systems, can be enhanced by adding natural flakes graphite and consolidating the mixture with a binder. In this study, a bound conduction model with a unit cell approach is employed to predict the effective thermal conductivity of consolidated composite. The model takes the volume fraction, flake size and orientation of the graphite flakes as input, and calculates the effective thermal conductivity of the consolidated mixture. To validate the model result with experimental data, consolidated adsorbents with 0-20 wt% graphite flakes were prepared and their thermal conductivity was measured by Transient Plane Source (TPS) method. The results show that the addition of graphite flakes into consolidated adsorbent increases thermal conductivity from 0.13 to 0.57 W·m−1·K−1 when tested at 2% RH and 35 °C. The predictions of the model at steady-state condition qualitatively agreed with the experimental data.