A falling film apparatus comprising: (a) an outer shell enclosing an interior volume, (b) upper and lower tube sheets partitioning the interior volume into separate upper , middle and lower chambers, (c) one or more vertically oriented hollow tubes having open top and bottom ends, the hollow tubes each defining a fluid path from the upper chamber to the lower chamber , (d) for each at least one vertically oriented hollow tube , an associated tube insert located at the top end of the associated hollow tube, the tube insert comprising a hollow member having (i) an upper section residing above the upper tube sheet , (ii) a lower section extending into the associated hollow tube , (iii) one or more process fluid openings in the upper section for admitting a process fluid into the tube insert , (iv) an open bottom end for transferring a thin film of the process fluid from an interior surface of the tube insert onto an interior surface of the associated hollow tube ; and (v) one or more circumferential ribs residing on the interior surface of the tube insert below the one or more process fluid opening(s) ; (e) at least one process fluid inlet port for introducing a process liquid into the upper chamber and into contact with an upper surface of the upper tube sheet , (f) at least one process fluid outlet port for removing at least treated process fluid from the lower chamber ; (g) at least one heat exchange fluid inlet port for introducing a heat exchange fluid into the middle chamber ; and (h) at least one heat exchange fluid outlet port for removing the heat exchange fluid from the middle chamber . (a) an outer shell enclosing an interior volume, (b) upper and lower tube sheets partitioning the interior volume into separate upper , middle and lower chambers, (c) one or more vertically oriented hollow tubes having open top and bottom ends, the hollow tubes each defining a fluid path from the upper chamber to the lower chamber , (d) for each at least one vertically oriented hollow tube , an associated tube insert located at the top end of the associated hollow tube, the tube insert comprising a hollow member having (i) an upper section residing above the upper tube sheet , (ii) a lower section extending into the associated hollow tube , (iii) one or more process fluid openings in the upper section for admitting a process fluid into the tube insert , (iv) an open bottom end for transferring a thin film of the process fluid from an interior surface of the tube insert onto an interior surface of the associated hollow tube ; and (v) one or more circumferential ribs residing on the interior surface of the tube insert below the one or more process fluid opening(s) ; (e) at least one process fluid inlet port for introducing a process liquid into the upper chamber and into contact with an upper surface of the upper tube sheet , (f) at least one process fluid outlet port for removing at least treated process fluid from the lower chamber ; (g) at least one heat exchange fluid inlet port for introducing a heat exchange fluid into the middle chamber ; and (h) at least one heat exchange fluid outlet port for removing the heat exchange fluid from the middle chamber . <EOS>