MODELLING OF BOILING IN DIFFUSION ABSORPTION REFRIGERATORS FOR CFD ANALYSES

The evaporation of binary mixtures is a complex transport phenomenon, including fluid flow, heat exchange, mass transfer and phase change in multi-component, multi-phase domain. The boiling and buoyancy of the vapor bubbles in the generators of absorption diffusion refrigerators (DAR) lead to the bubble pump effect, which is the main driving force of the absorption cycle. Computational fluid dynamics (CFD) is an advanced approaches to improve the efficiency of DAR’s components. Its implementation for the boiling process requires modelling of the thermodynamical processes of the binary mixtures, which is also open problem, especially at vertical generators with rectifier for separation of the saturated liquid and steam, and absorbent recirculation. This paper presents a conception for CFD simulation of binary mixture boiling in such generators, including a new be-temperature model of the saturation temperature. The models are tested based on an experimentally obtained diffusion absorption cycle of ammonia-water solution and its application is confirmed.