Measurement Of Contact Angle And Its Effect On Gas-liquid Mass Transfer

Packings are wildly used in the equipments for gas-liquid mass transfer processes such as distillation, absorption, etc., the wettability of the liquid on the packing surface is very important for the mass transfer efficiency. In general, the wettability is effected by the species and interfacial properties of the packings, the property of the system, operating conditions and special phenomenon in mass transfer (such as Marangoni effect).The researches on these effects are useful for investing the influence of the wettability, and play an important role on developing new packings and enhancing gas-liquid mass transfer.In this paper, an experimental device to measure contact angles directly under the vapor-liquid equilibrium conditions is set for measuring the contact angles on the interface of copper, aluminum, stainless steel 304 and stainless steel 316L and its modified stainless steel under different concentrations of ethanol - water system, and acetone - water system. The results show that the contact angle of the acetone - water system in the wettability of the metal materials is less than that of the ethanol - water system. In other word, the wettability of the acetone - water system is better than that of the ethanol - water system. Contact angles on the surfaces of the metal materials studied decrease with the increasing of the ethanol/acetone concentration in the ethanol– water/acetone - water system, and tend to vary gently at high concentration. The wettability of stainless steel named 316L is better than 304 lines, and best among all the metal materials measured; the modification of stainless steel surface has a great improvement on the wettability of the ethanol– water/acetone - water systems. The wettability of the modified stainless steel 304 is significantly better than 316L, which may be related to the hydrophilic membrane produced by chemical modification.The penetration model is used to calculate the mass transfer efficiency of membranous flow, droplet flow, and thread-like flow falling along a vertical wall film. The result shows that the mass transfer rates of film flow are much greater than that of droplet flow in the same concentration, and the mass transfer rates of thread-like flow are also larger than that of droplet flow. Minimum contact angle for film flow and maximum of droplet flow indicate mass transfer rate increasing with wettability.