Vapour Absorption Process in an Nh3/Lino3 Bubble Absorber Using an Optimized CFD Model

Abstract

The present study aims to assess the vapour bubble absorption into the ammonia/lithium nitrate (NH3/LiNO3) solution by using an optimized CFD model. A detailed methodology to build up the CFD model is presented, as well as its validation using experimental data. The operating conditions set corresponds to an absorption chiller driven by low-temperature heat sources such as solar energy in warm environments. Results evidenced that the Volume of Fluid and Mixture models are adequate to be used in the CFD model to predict the absorption process in the bubble absorber assessed depending on the mesh density refinement. Moreover, the heat transfer coefficient from the solution side and the absorption mass flux are the variables needed for reliable validation of the model. Finally, the absorbed flux estimated from the CFD model ranged between 3.2×10 -3 kg.m −2 .s −1 and 4.4×10 -3 kg.m −2 .s −1 , while the solution side heat transfer coefficient varied between 457 W.m −2 .K −1 and 786 W.m −2 .K −1 , under the conditions considered.