Heat transfer enhancement by additive in vertical falling film absorption of H2O/LiBr

The enhancement effects of additive on vertical falling film of water into aqueous lithium bromide (LiBr) were studied by an experimental method. Based on the Navier–Stokes equations of falling film absorption, a new dimensionless parameter, surface renewal number Rn, was introduced, and a semi-empirical equation of enhancement factor of additive was obtained. It was shown that the absorption Marangoni number Ma, the surface Marangoni number MaA, and the surface renewal number Rn enhance the heat transfer of absorption, however the adsorption number Π and the Reynolds number Re weaken the heat transfer of absorption. It was proved that the semi-empirical equation agreed well with the experimental results by introduction of the parameters related to surface tension characters presented by the authors into the equation.