HEAT AND MASS TRANSFER ENHANCEMENT BY ADDITIVES IN ABSORPTIONS OF H2O/LiBr AND NH3/H2O

摘要

The surface tensions of both aqueous LiBr and aqueous ammonia in the presence of additives were measured. The effects of additives on absorption of vapor into vertical falling aqueous LiBr film, absorption of vapor into aqueous LiBr in a static pool, and absorption of ammonia vapor bubble into NH3-H2O were studied by experimental methods, respectively. The experimental results showed that the heat and mass transfer performance was significantly enhanced with additives (2-EH, n-Octanol etc.) in the process of both the aqueous LiBr absorption and the ammonia bubble absorption. The enhancement mechanisms of additives on aqueous LiBr absorption has been concluded in that additives in the liquid phase is absorbed by aqueous LiBr on the liquid side of the liquid-vapor-interface, so is the vapor phase on the vapor side, which generates surface tension gradient, then causes Marangoni convection at the interface, and consequently results in the enhancement of the heat and mass transfer during the absorption process.