Abstract
Lithium bromide/water (LiBr/water) absorption systems are potential candidates for absorption heat pump water heating applications since they have been widely commercialized for cooling applications. One drawback to LiBr/water absorption water heater systems is that they are unable to operate at typical water heating temperatures due to solution crystallization hazards. Binary or ternary mixtures, serving as working fluids, were reported (Ally, 1988; Herold et al., 1991; Iyoki and Uemura, 1981; Yasuhide Nemoto et al., 2010; Zogg et al., 2005) to help improve the absorption performance or avoid crystallization of absorption heat pump systems. A recent development (De Lucas et al., 2007) investigated the use of a ternary mixture of aqueous mixture of lithium bromide and sodium formate (CHO2Na). The new working fluid composition maintains a ratio of LiBr/CHO2Na of 2 by weight. This new working fluid is a potential competitor to aqueous LiBr solution in absorption system due to higher water vapor absorption rates and lower generation temperature needed (De Lucas et al., 2004). There exists data on equilibrium performance and other physical properties of this new working fluid. However, there is no available data on crystallization behavior. Crystallization temperature is crucial for the design of absorption heat pump water heater in order to avoid crystallization hazards during operation. We have therefore conducted a systematic study to explore the crystallization temperature of LiBr/CHO2Na water solution and compared it against aqueous LiBr solutions. These results were then used to evaluate the feasibility of using the new working fluid in water heating applications showing limited potential.