Abstract: A falling-film evaporator is provided with improved means for uniformly supplying liquid to the heating tubes thereof. The means includes an arrangement whereby a substantially constant-level head of liquid is formed upon the upper tube sheet above which the heating tubes project so that the vapor can pass directly into the open ends of these tubes, the liquid being introduced into lateral openings of constant cross section for each of the tubes below the level of liquid standing on the upper tube sheet. An annular gap surrounding the array of tubes projecting upwardly from the upper tube sheet serves to feed the liquid phase to the standing liquid upon the tube sheet and the substance to be evaporated is introduced into a chamber above the upper tube sheet and is expanded therein to the pressure of the vaporator. The vapor phase passes through the open upper ends of the tubes.

Abstract: A method of concentrating or evaporating water from water-containing liquids in a falling-stream or falling-film evaporator through which the liquid is caused to pass downwardly through ribbed tubes which are heated externally. The material to be evaporated is distributed uniformly to the evaporator tubes and driving steam is simultaneously introduced into the latter at a velocity so controlled with respect to the pressure that turbulence develops at the inlet to the tubes. The mixture of the material to be evaporated and drive steam is caused to rotate about the longitudinal axis of the evaporator tubes as the mixture traverses same and the concentrated product is separated from the steam and product vapors at the outlet end of the tubes.

Abstract: Heat exchange is improved in natural-circulation and flowthrough evaporators in which the liquid to be evaporated is admitted to heating tubes and evaporators therein as the fluid rises in the tubes. According to the invention the liquid is preheated under a higher hydrostatic pressure than at the inlet to the heating tubes by treatment with direct steam, preferably in a steam-jacketed siphon tube forming a downcomer from a separator removing concentrate from the vapors emerging from the evaporator.