Development of an absorption heat pump water heater using an aqueous ternary hydroxide working fluid

Abstract

A novel absorption cycle, with a significantly higher temperature lift than current technology, is under development. The cycle is based on an aqueous ternary hydroxide working fluid consisting of sodium, potassium and caesium hydroxide in the proportions 40:36:24 (NaOH:KOH:CsOH). The higher temperature lift is made possible by the unique properties of this solution. The ternary hydroxide blend is used to shift the crystallization curve to provide the high lift. High lift is needed in many applications and often cannot be achieved by conventional absorption systems. Water heating is one application where the high lift feature is necessary. Development efforts to date have included thermophysical property measurements on the ternary hydroxide system, heat and mass transfer measurements in absorption and vapour generation and cycle design calculations.