Thermal conductivity and contact resistance of mesoporous silica gel adsorbents bound with polyvinylpyrrolidone in contact with a metallic substrate for adsorption cooling system applications

Silica gel bound with polyvinylpyrrolidone (PVP) is a new composite adsorbent with promising uptake rate designed for adsorption cooling systems. In this study, the thermal conductivity of silica gel-PVP and its thermal contact resistance (TCR) with a metallic substrate are measured using the guarded-hot plate apparatus under vacuum pressure. This study sheds light on the importance of TCR at the interface between the adsorbent and substrate, which has been overlooked in most studies in the literature. The measurements show that the thermal conductivity of silica gel-PVP adsorbent is 0.26 W/m/K which is 78.6% higher than that of dry silica gel packed bed. Also, the analysis indicates that the TCR between the adsorbent and metallic substrate is between 1.29-3.80 K/W which is equivalent to 0.20-0.69 mm of adsorbent thickness. Finally, the results indicate that the ratio of total TCR between the adsorbent and metallic substrate is up to 26% of the adsorbent-metallic substrate bulk resistance.