Industrial & Engineering Chemistry Research, Vol.43, No.21, 6832-6835, 2004
A falling-film evaporator with film promoters
Falling-film evaporators have been used extensively in chemical processing plants due to their minimal fluid residence time and high heat transfer rates with low temperature differences. A cheaper alternative for achieving suitable liquid distribution and film stability was investigated here for solutions with low solids content and sufficiently low viscosity to allow for gravity-driven down-flow. The alternative consists of using a film promoter of thin stainless steel woven wire specified by mesh (opening number per linear inch), placed flush against the heating surface where the liquid film flows down. For very low liquid feed-flow rates per length of internal perimeter, such as 0.004 kg/(m(.)s), the fluid can be scattered over the entire vertical surface of the evaporator in a very thin film. The use of this film promoter leads to 3-fold higher evaporation rates.