Canadian Journal of Pure & Applied Sciences

Abstract: Experimental modeling has over the past three decades been used in analyzing simultaneous heat and mass transfer in thin-liquid falling-film absorption processes. However, numerical modeling applications in this area have been minimal due to complications arising from the presence of waves. An approach in numerical modeling is to consider waves as a second order effect, thereby making it a smooth falling-film. The objective of this paper was to develop a numerical model for the absorption process on a thin-liquid smooth falling-film using lithium bromide (LiBr) and lithium chloride (LiCl) solutions. The absorption process of a thin-liquid smooth falling-film was considered as a two-dimensional steady laminar flow within the film thickness to the absorber wall. The conservation equations were used to determine temperature and concentration distribution within the film-thickness using the finite difference technique. Existing data on LiBr and LiCl solutions in the literature were used to validate the developed model. Standard values of absorber wall length, film thickness, solution mass flow-rate, absorbent inlet concentration, inlet temperature, absorber wall temperature, conventional film Reynolds number and absorption design effectiveness were used for both LiBr and LiCl solutions. Data were analyzed using descriptive statistics and student’s t-test (p<0.05). The physical properties distribution for both LiBr and LiClsolutions were not significantly different from published results available in the literature(p<0.05). The nodal temperature distribution obtained within the film thickness both in the bulk and interface between the liquid and vapour regions were between 44.4 and 35.0oC while concentration was between 60.0 and 54.5% for LiBr-H2O. Similarly for LiCl-H2O, the model temperature distribution was between 35.0 and 30.0oC while the concentration was between 45.0 and 35.8%.A numerical model on a thin-liquid smooth falling film using LiBr and LiCl solutions was developed. Lithium bromide was also observed to have higher concentration values than lithium chloride thus suggesting a better working fluid combination especially in the absorption air-conditioning system.