raw · papers · ingested 2026-06-19
Adsorption Refrigeration Technologies
Source: https://doi.org/10.5772/intechopen.73167
Read from local Zotero full-text PDF (group 5183627 / Joule Heist).
Key findings
- Cycle and performance metrics: basic ARS uses the four-step cycle (pre-heating A–B, isobaric desorption B–C, pre-cooling C–D, isobaric adsorption D–A) shown on a Clapeyron (LnP vs −1/T) diagram. Performance defined by cooling capacity Q_eva, specific cooling capacity SCC = Q_eva/M_s (per kg adsorbent), and thermal COP = Q_evap/Q_heat. Typical thermal COPs of ARSs are ~0.6 (low); electrical COP can reach up to 10 vs 3–5 for conventional vapor-compression.
- Silica gel/water: pore diameter 2.0–3.5 nm, pore volume 0.3–0.4 cm³/g, specific surface 400–700 m²/g; regeneration temp typically 85 °C (down to 50 °C multi-stage), max not above 120 °C (silica gel destroyed). Adsorption heat 2500–2800 kJ/kg. Equilibrium uptake 0.35–0.4 kg/kg, but net instantaneous swing ≤0.1 kg water/kg silica gel.
- Zeolite/water: wide desorption range 70–250 °C (can be directly heated by engine exhaust); higher adsorption heat 3300–4200 kJ/kg → lower COPs.
- Activated carbon: surface area 800–1500 m²/g; low adsorption heat 1800–2000 kJ/kg (good for COP). AC-ammonia operates at high pressure (~1600 kPa at 40 °C condensing), suits ≥200 °C sources. AC-methanol uptake ~0.45 kg/kg_ads, regeneration ~100 °C (must stay <120 °C; decomposes to dimethyl ether >150 °C); ACF-methanol reaches 0.55 kg/kg but very low conductivity 0.0893 W/(m·K).
- Chemical adsorbents (metal chlorides): very high uptakes approaching 1 kg/kg_ads, desorption 40–80 °C; e.g. 1 mol CaCl₂ adsorbs 8 mol ammonia. Drawback: agglomeration/swelling instability — motivates composites (“Salt in Porous Matrix”/SWS).
- MOF-water: water uptakes far exceed silica gel/zeolite (~0.3 g/g). MIL-101Cr ~1 g/g; MIL-101@GO super-high 1.58 g_w/g_ads; aminated MIL-101Cr-NH₂ ~1.0 g/g at low regeneration; Al-fumarate regenerates as low as 60 °C with >0.5 g/g. CPO-27(Ni) gave SCP 440 W/kg at 130 °C desorption, 900 s cycle, vs 310 W/kg for SAPO-34. HKUST-1 water uptake +93.2% over silica gel RD-2060. MOF-ethanol: MIL-101Cr adsorbs up to 1.2 g_w/g_ads, stable over 20 cycles.
- Advanced cycles: heat-recovery cycle increases COP up to 25%; combined heat-and-mass recovery adds >10% more; zeolite-water thermal-wave two-bed cooler COP ≈ 1.0.
- Prototype chillers (Table 2): Freiburg hospital silica gel/water 70 kW (evacuated tube, 170 m²); SorTech two-bed silica gel/water 7.5 kW, system COP 0.55, 9 W electricity, epoxy-bonded silica gel pellets; SJTU silica gel/water 15 kW, system COP 0.35 / solar COP 0.15, regeneration 85 °C, 90 m² evacuated tube + 60 m² heat-pipe collectors.