Adsorption cooling cycles for alternative adsorbent/adsorbate pairs working at partial vacuum and pressurized conditions

This article presents the performance analysis of both ideal single-stage and single-effect double-lift adsorption cooling cycles working at partially evacuated and pressurized conditions. Six specimens of adsorbents and refrigerant pairs, i.e., ACF (A-15)/ethanol, ACF (A-20)/ethanol, silica gel/water, Chemviron/R134a, Fluka/R134a and MaxsorbII/R134a have been investigated. The relationships between equilibrium pressures, adsorbent temperatures and equilibrium adsorption concentrations (Dühring diagram) are presented. Parametric analyses have been carried out with various regeneration (desorption) and evaporation temperatures. Theoretical analysis for adsorption cycles working in single-stage mode shows that ACF (A-20)/ethanol can achieve a specific cooling effect (SCE) of 344 kJ/kg_ads, which is followed by the silica gel/water pair with 217 kJ/kg_ads at a regeneration temperature of 85 °C. On the other hand, when the regeneration temperature is below 70 °C, single-effect double-lift cycle has a significant advantage over single-stage cycle, at which the SCE is higher due to the reduction in adsorption bed pressure in single-effect double-lift cycle.