Adsorption Desalination and Cooling Systems: Advances in Design, Modeling and Performance

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Key findings

• Sztekler et al. new silica-based porous materials vs silica gel (water pair): metal-organic silica (MOS) nanocomposites had thermal properties similar to silica gel, diffusivity 0.17-0.25 mm2/s vs ~0.2 mm2/s for silica gel; highest water adsorption capacity AFSMo-Cu 33-35% vs ~25% for narrow-pore silica gel; pore size >5 nm recommended for water working pairs.
• Copper additive (15% mass fraction) blended into silica gel in a two-bed chiller (distilled water adsorbate) increased both COP and SCP vs plain silica gel; tested cycle times 100/200/300/600 s. Increasing cycle time raised COP; SCP rose then fell past an optimum. CNT additives most promising (smallest water-uptake penalty, shortest sorption time); Al addition gave significant time reduction; Cu doping caused mixture delamination in another study.
• Steam preheating of beds: using steam instead of water to preheat the silica gel-water chiller bed cut desorption time to ~30 s vs ~300 s with water, enabling smaller, more efficient devices (steam is an industrial by-product).
• Three-bed adsorption chiller with desalination (silica gel-water): COP increased 0.20 -> 0.58 and SCP increased 27 -> 160 W/kg as heating water temperature rose 57 -> 85 C; heating-water temperature strongly drives performance. Longer cycle time increases COP.
• Variable-mode air-cooled chiller (SAPO-34/water): four cooling modes (single-stage; mass recovery 25%/50%/75% of cycle). Optimum mode depends on recooling temperature: single-stage best at <35 C, short mass recovery at 35-44 C, medium mass recovery at >44 C.
• Exergy analysis (single-stage cycle): exergy destruction concentrated in desorber 49%, adsorber 27%, evaporator 13%, condenser 9%, expansion valve 2%; preheating ~35% and precooling ~58% of respective bed exergy destruction; destruction rises with mass-recovery time, most sensitive in the adsorbent beds.
• MOF MIL-160 for atmospheric water harvesting: specific water productivity 0.31-0.33 g_H2O/g_ads per cycle, high extracted/collected fractions (0.90-0.98 / 0.48-0.97) at 80 C regeneration with ambient condenser cooling; specific energy 3.5-6.8 kJ/g (acceptable with solar heat).
• AI/LSTM deep-learning model predicted vapor mass in fixed and fluidized adsorption beds with agreement >0.95; fluidized beds raise the bed-to-HX heat transfer coefficient, improving adsorption cooling/desalination performance.