raw · papers · ingested 2026-06-19
The cooling effect by adsorption-desorption cycles
Source: https://doi.org/10.1051/e3sconf/20171401052
Read from local Zotero full-text PDF (group 5183627 / Joule Heist).
Key findings
- Experimental test stand: activated carbon (coconut shell, ~170 g) / methanol pair in a steel-tube adsorber (60 mm dia, 2 mm wall, 270 mm long) with concentric 35 mm grid tube; thin-wall aluminium evaporator/reservoir 150 mL; two 900 W band heaters; fan cooling; evaporator filled with 100 cm^3 methanol; evacuated to -0.9 bar over 30 min.
- Measured cooling: single adsorption-desorption cycle (T_ad = 25 C) gave adsorber temperature rise 16.6 C and condenser drop of 10.4 C; double-cycle (T_ad = 28 C) gave condenser drops of 4.9 C and 4.7 C with adsorber rises of 13.7 C and 11.1 C. Lower adsorption start temperature gave greater cooling effect.
- Established operating timing for the rig: desorption time ~1 h at 120 C, cooling time 0.5 h, adsorption time 0.5 h; ~15 min to warm the generator/bed to 120 C desorption temperature.
- Cycle classification: intermittent vs continuous. Basic single-bed intermittent cycle (adsorber/regenerator + condenser + evaporator) is simplest and common in solar refrigerators but has very low COP (sometimes <0.1) due to large bed temperature fluctuation; continuous cycles use two or more beds running alternately.
- Advanced cycles quantified: heat recovery cycle can improve COP by ~25%; mass recovery improves low-temperature-driven performance by connecting hot and cold beds at switching; thermal wave cycle can supply ~80% of desorption heat from adsorption heat; Critoph’s convective thermal wave cycle reaches theoretical COP 0.9 (evap 9 C, cond 40 C, desorption 200 C). Cascade cycles (e.g. zeolite-water driving activated-carbon-methanol) bridge large temperature gradients.
- Typical adsorbents (activated carbon, zeolite, silica gel, CaCl2) paired with methanol, water, ammonia, hydrogen. ~15% of world electricity goes to refrigeration/air-conditioning, with AC ~45% of household/commercial building energy.
- Commercialization review: silica gel-water chillers (Nishiyodo, Mayekawa >70 kW zeolite-water, Macom, SorTech, InvenSor water-zeolite) and waste-heat/vehicle applications (fishing boats, automobiles, locomotive zeolite 13X-water, fuel-cell EV charcoal-methanol). Solar adsorption AC in Freiburg University Hospital (1999) and Shanghai Green Building (payback 5-8 yr, or ~2 yr if hot water used only for showers); several firms (SunMark, BLM, Zeopower, EG Solar, Solaref) failed to commercialize intermittent zeolite-water units.