Heat and mass transfer in non-isothermal absorption of gases in falling liquid films: Part I: Experimental determination of heat and mass transfer coefficients

Abstract

In non-isothermal absorption of steam in falling films of aqueous LiBr solutions local heat and mass transfer coefficients were determined independently of each other by measuring the film surface temperature with an infrared pyrometer. The experimentally determined mass transfer coefficients (Sherwood numbers) confirm well-known correlations, as well as the statements of the Levich-type description of falling film heat and mass transfer, that is, the damping of the turbulence not only near the wall but also in the vicinity of the film surface. So, the assumption that the bulk and the surface temperatures of the film are equal, owing to undamped eddy transport, is not correct. The experimentally determined heat transfer coefficients deviate from the experimental data of Blangetti, the latter determined in film condensation of 1-methoxy-2-propanol-water azeotrope (MWA). This discrepancy is due to the thermal entrance effects in the experiments of Blangetti and will be discussed in Part II.