Development and validation of an analytical formulation of the Nusselt and Sherwood numbers on a partially wetted absorber tube

With reference to a simplified analytical solution of the governing differential equation for falling film absorption, the corresponding formulation of the average Nusselt and Sherwood numbers obtained around a smooth horizontal tube is validated through a dedicated experimental investigation and data from previous literature. The assumption of a linear temperature profile together with the average interfacial mass fraction gradient and the hypotheses of small penetration for physical absorption are applied at the film interface to reach closed analytical expressions of average Nusselt and Sherwood numbers within falling film absorbers and generators. The inclusion of partial-wetting effects brings the results closer to the measurements and widens the applicability of these expressions.