The lithium bromide-based absorption chiller has been around commercially since the late 1950s. It was introduced as a simple cooling system if there was already a source of steam available to concentrate diluted lithium bromide brine.
Under vacuum, water vapor flash boils at temperatures less than 100°C. The boiling action provides a mechanism whereby heat can be removed from a chilled-water loop, which circulates through the chiller and building areas to be cooled.
But as the water vapor accumulates inside the chiller, the vacuum is soon lost. Hence, lithium bromide brine at 58% to 62% concentrations is mixed with the water vapor to absorb it, thereby maintaining the essential vacuum. This absorption process can continue until the lithium bromide becomes too diluted with absorbed water vapor and its absorption properties are lost.