Experimental investigation of ionic liquid emim EtSO4 as solvent in a single-effect cycle with adiabatic absorption and desorption.

Thermally driven chillers and heat pumps usually run with a working pair composed of refrigerant and solvent. Yet, commonly used working pairs show limitations with regard to operating conditions, i.e. external temperature levels and temperature lift. The performance of chillers operating with aqueous lithium bromide solution as solvent is limited due to salt crystallisation at high mass fractions and low temperatures as well as to the limited thermal stability of the used corrosion inhibitors. Due to the properties of the refrigerant chillers running with ammonia/water exhibit an increased complexity concerning mechanical design and operating safety. During the last years ionic liquids (organic, liquid salts with melting points below 100°C and negligible vapour pressure) were proposed as promising substitute for solvents used in absorption chillers. Within this work a complete lab-scale absorption chiller has been constructed, in order to evaluate the suitability of ionic liquids as solvent. In order to overcome limitations due to insufficient wetting of falling film heat exchangers only spray components were installed within this chiller. Heat transfer is carried out by external heat exchangers, followed by exchange of refrigerant vapour in an adiabatic spray process. The first results using a working pair consisting of water and 1-ethyl-3-methylimidazolium ethylsulfate are presented. It is shown that this ionic liquid is a suitable working fluid for a thermally driven chiller, however it exibits severe limitations concerning external temperatures and capacity.