Qualitative investigation of the flow behaviour during falling film evaporation of a dairy product

Falling film evaporation is an important technology in the dairy industry for producing powders. In this paper, flow details of liquid falling films have qualitatively been investigated using a pilot evaporator, and in particular using a high-speed camera. Variations with different dry solids contents, flow rates and driving temperature differences were investigated. The flow characteristics were seen to be considerably affected by all three variables. Two of the main observations were the formation of bubbles under evaporative conditions and that the flow, bubble formation and evaporative heat transfer coefficient was observed to be heat flux dependent.