Snowtech equipments offers rising film evaporators. The evaporator operates on thermo-siphon principle. Feed enters from the bottom of the calandria. As the liquid rises up the external heat of system or other heat source preheats and then vaporizes the feed. The vapour or steam generated during boiling helps the liquid and vapour to flow upwards and as more and more vapours are formed it presses the liquid into a thin film on the internal surface of the tube in a form annular ring. This film rises and simultaneously upward motion of vapour and liquid gives turbulence in the liquid enhancing the heat transfer coefficient. The vapours and liquid formed in the calandria enter into centrifugal cum mist separator, where the vapour rises through the top and is condensed. The concentrate falls from the bottom. The evaporator operates at a temperature difference of exceeding 10-12°c. Residence time in these units is in few minutes for single pass operation. Reticulation loop can be provided to provide adequate wetting of tube to prevent dry spots. Multi-effect evaporators can be provided for steam economy or better wetting rates.
