HEAT AND MASS-TRANSFER IN FILM ABSORPTION WITH VARYING LIQUID-PHASE VOLUME

Analytical solutions to the problem for simultaneous heat and mass tra nsfer in film absorption under laminar flow, which take into account t he varying thickness of a film at its initial portion and at its porti on with a linear temperature profile, are obtained under the assumptio n of uniform cross-sectional velocity distribution. It is shown that t he equilibrium values of temperature and concentration remain constant at the initial film portion. The solution obtained for the film porti on with a linear temperature profile implies that the concentration at the film surface is greatly affected by the degree of supercooling of the mixture. The film thickness depends not only on the criteria typi cal for the Nusselt problem, but also on the Lewis number and the conc entration difference that characterizes the deviation of the inlet mix ture from the state of equilibrium (saturation). For the film portion with a linear temperature profile, an exact analytical solution for th e equilibrium concentration and temperature at the interface is obtain ed also for the problem with a constant film thickness. It is shown al so that the growth in thickness of the film in absorption is small for a lithium bromide-water solution-steam system under refrigerating-mac hine conditions.