Experimental investigation of an absorption refrigerator working with ionic liquid and ethanol.

Electrically-driven vapor compression or thermally-driven ammonia water absorption refrigeration systems are commonly used for cooling below 0°C. Due to the non-negligible vapor pressure of water, usually a rectification during regeneration is required for the ammonia water system. Ionic liquids (IL) present an alternative to conventional working pairs. Ionic liquids are versatile absorbents since they extend the use of natural refrigerants other than ammonia in thermally driven absorption technology. Furthermore, room temperature ionic liquids do not crystallize at ambient temperature even at high ionic liquid mass fractions just like water in ammonia water chillers. In addition, they exhibit a nearly zero vapor pressure allowing for regeneration without rectification.
In the present paper, the first experimental results of a single stage absorption refrigerator using ethanol as the refrigerant and the ionic liquid [EMIM][DEP] as the absorbent are presented. For 10°C and 30°C as external evaporator and absorber inlet temperatures the experimental thermal efficiency (COP) ranges from 0.4 to 0.62 and the refrigeration power from 0.7 to 1.9kW for varying driving temperatures from 66°C to 110°C. The simulated thermal efficiency is rather high with 0.75. This discrepancy to the experiment most likely is due to a thermal loss in the experiment.