Development of new working fluid for air-cooled absorption chiller

Abstract

The increasing energy cost and environmental problems have made the heat-powered absorption chiller more attractive. Recently, much efforts have been made to develop an air-cooled absorption chiller because of the high equipment cost of the existing water-cooled absorption unit. The air-cooled operation of an absorption unit can be accomplished by the development of new working fluids which have a broad operation range. In order to find the new working fluid, several candidates of solutions containing different high boiling organic liquids were considered in terms of solubility. Two systems, lithium bromide + ethanol amine + water $(LiBr/H_2N(CH_2)_2OH$ mass ratio 3.5:1) and lithium bromide + lithium iodide + ethanol amine + water (LiBr/LiI mole ratio 4:1 and $(LiBr+LiI)/H_2N(CH_2)_2OH$ mole ratio 4:1) were selected, and Duhring charts were constructed through the measurements of solubility and vapor pressure. Thus the operation ranges of these two systems were found to be broadened. For more detailed cycle analysis, specific heats of the lithium bromide + ethanol amine + water $(LiBr/H_2N(CH_2)_2OH$ mass ratio 3.5:1) system were measured, then enthalpy - concentration chart was constructed. Through the cycle analysis, the absorption cycle using lithium bromide + ethanol amine + water $(LiBr/H_2N(CH_2)_2OH$ mass ratio 3.5:1) solution as a new working fluid was found to have high theoretical COP, low crystallization temperature, and high cooling capacity at an appropriate condition. Therefore, the air-cooled absorption chiller can be constructed successfully by using the lithium bromide + ethanol amine + water $(LiBr/H_2N(CH_2)_2OH$ mass ratio 3.5:1) solution as a new working fluid.