Thermophysical Properties and Heat and Mass Transfer of New Working Fluids in Plate Heat Exchangers for Absorption Refrigeration Systems

Ammonia/lithium nitrate and ammonia/(lithium nitrate + water) have been proposed as suitable working pairs for absorption refrigeration systems driven by low-temperature heat sources. The use of water in the absorbent of the ternary mixture reduces the viscosity of the binary mixture and increases the affinity between the refrigerant (ammonia) and the absorbent, which should have a positive effect on the absorption process. In this paper, a brief review on the thermodynamic and transport properties available in the open literature for NH3/LiNO3 and NH3/(LiNO3 + H2O) mixtures is presented, and the most significant results of an experimental characterization of absorption and desorption processes taking place in plate heat exchangers are discussed.