A novel approach for modelling LiBr–H2O falling film absorption on cooled horizontal bundle of tubes

A two-dimensional numerical model is developed to describe the coupled heat and mass transfer phenomena for treating the two-dimensional water vapour absorption into an aqueous solution of LiBr, flowing over a bundle of smooth horizontal tubes. Unlike other studies, the partial differential equations describing the transport phenomena of the absorption process are solved using an efficient computational method. Emphasis is given in describing the electrolytic nature of the aqueous solution, introducing the effect of variable heat of absorption on the temperature field. The increase of solution mass flow rate results in the reduction of the solution temperature and concentration at the outlet of the tube bank. For solution mass flow rates higher than a certain value, the solution temperature and concentration remain unchanged. Thus, for given cooling water and solution inlet conditions, the maximum efficiency of the absorption process is directly related to a certain number of horizontal tubes.

► Two dimensional numerical model describing vapor absorption into LiBr solution. ► Intensive cooling, maximization of average heat flux on the first tube is observed. ► Concentration variation on first tube is minimized by reducing mass flux density. ► Increasing solution mass flow rate results in reduced T and X at tube bank exit.