Simulation of Pendant Droplets and Falling Films in Horizontal Tube Absorbers

Abstract

Recent literature suggests that the droplets that form in horizontal-tube, falling-film absorbers play a major role in the absorption process. The performance of such absorbers is critical to the performance of many absorption heat pump systems. The simulation of droplets of aqueous Lithium Bromide pendant from horizontal tubes was performed by numerically solving the equations of motion on a fixed three-dimensional (3D) grid. The so-called volume of fluid method was used to handle the interface between the liquid and vapor phase. Results are compared with simplified axisymmetric models and with high speed video taken during flow visualization experiments. The results show that simplified axisymmetric models do not satisfactorily represent the evolution of the droplets under horizontal tubes, and that the 3D numerical model appears to accurately match the important characteristics of droplet formation, detachment, and impact observed in the experiments.