Visual documentation of transfer processes in horizontal-tube falling-film ammonia–water absorbers
Abstract Flow patterns in a horizontal-tube falling-film absorber operated as part of a complete ammonia–water absorption system are presented. A tube bank consisting of four columns of six 9.5 mm nominal outer diameter, 0.292 m long tubes was installed in an absorber shell that allowed heat and mass transfer measurements and optical access for flow visualization. High-speed, high-resolution videos were recorded over a wide range of operating conditions (desorber solution outlet concentrations of 15–40% at absorber pressures of 150, 345 and 500 kPa, over solution flow rates of 0.019–0.034 kg s−1). Image analyses indicated that the droplet mode was the dominant inter-tube flow mode for the range of the experiments. Droplet characteristics and flow regime transitions are strongly influenced by the solution flow rate. Variation in the solution concentration and the operating pressure also affect the flow characteristics such as film thickness, residence time and droplet spacing.