Consolidated adsorbent containing graphite flakes for heat-driven water sorption cooling systems

Thermally-driven sorption cooling systems can reduce the primary energy demand for air conditioning and refrigeration. The specific cooling performance (SCP) of an adsorption cooling system can be enhanced by increasing the heat transfer rate in a heat exchanger packed or coated with sorbent material. In this study, calcium chloride in a silica gel matrix was combined with a binder and graphite flakes to produce water absorbent consolidated composites. The characteristics of the composites were evaluated by porosimetry and transient plane source (TPS) thermal properties analysis. The addition of 20 wt% graphite flakes increased the thermal conductivity of the composite adsorbent from 0.57 W m−1 K−1 to 0.78 W m−1 K−1. Water sorption isotherms and vapor pressure swing durability tests were collected with a thermogravimetric vapor sorption analyser. Water uptake capacity of samples at a 1.2 kPa vapor pressure decreased from 0.32 g/g for CaCl2/silica gel to 0.15 g/g for silica gel/CaCl2 consolidated with 10 wt% graphite flakes and 13 wt% binder. Water sorption during vapor pressure durability test was consistent within 28.5 and 18 wt% across 150 cycles at 25 and 35 °C.