Adsorption-based low temperature refrigeration using water-ethylene glycol mixtures.

Adsorption chilling with the working fluid water is environmentally friendly, but limited to cooling temperatures above 0°C. To expand the operational range of adsorption chillers below the freezing point of water, experiments have been conducted adding ethylene glycol to the evaporator as anti-freezing agent. According to vapour liquid equilibrium data ethylene glycol should remain in the evaporator. Thus, only water should serve as refrigerant. Experiments with cold production at 0°C demonstrate that the adsorption process still works if ethylene glycol is used as anti-freezing agent in the evaporator. Furthermore, measured ethylene glycol concentrations in condenser and evaporator confirm that almost pure water is used as refrigerant. Increasing ethylene glycol concentrations in the evaporator decreases the heat flows. This decrease is caused by reduced heat transfer properties of the ethylene glycol-water mixture. Better heat transfer properties can be achieved by using different evaporator designs allowing low temperature refrigeration in adsorption chillers.