In most commercial machines, absorption enhancement has been done by adding small amounts various kinds of surfactants, thereby reducing the surface tension of the absorbent solution and generating Marangoni convection near the solution surface during the refrigerant vapor absorption process. This paper clarifies the most effective conditions of surfactant addition for absorption enhancement in the process of refrigerant vapor absorption into a vertical falling absorbent film. H2O/LiBr and n-octanol were used as the refrigerant/absorbent combination and the additive. Experiments were carried out by using the LiBr aqueous solution with and without n-octanol dissolution. Moreover, n-octanol vapor was supplied to the absorber in order to clarify the effect of additive on the absorption enhancement. The results of these experiments reveal that the presence of dropwise n-octanol in the surface of the absorbent falling film contributed greatly to the generation of violent and irregular Marangoni convection.
