Experimental study on the flash evaporation process of LiBrH2O solution in an absorption heat pump

• LiBr solution flashing performance in a generator is experimentally studied.
• Observation results reveal three types of flashing jets under different superheat.
• Three processes consist of the whole spraying flash phenomenon.
• The flashing rate is proportional to the superheat pressure in the first process.
• Mass transfer coefficients are about 2 × 10−4–7 × 10−4 m/s for the second stage.

Recently, more and more absorption heat pumps have been applied in district heating systems, especially with industrial waste heat used as the driving heat source. This type of heat pumps utilizes flashing as an alternative to generators. The performance of a LiBr solution-based flashing process in an absorption heat pump is discussed in this paper. Flashing experiments were conducted in an absorption heat and mass transfer test bench. Observation results highlighted various types of flashing jets, i.e. the non-shattering jets, partially shattering jets, and completely shattering jets. Experimental results also showed that the initial superheat pressure significantly influenced transitions of the flow regimes. The whole spraying flash phenomenon is divided into three processes, and the flashing performance in each process was discussed. The flashing rate was simplified to be proportional to the superheat pressure in the first stage. And the mass transfer coefficients for the second stage were calculated, which is about 2 × 10−4–7 × 10−4 m/s. It is hoped that these results will help predict the flashing results of LiBrH2O solutions in future research.