R one tech engineering has technical expertise in process and mechanical design of various application Falling Film Evaporators. Our capacity varies from 100 liters per hour 20000 liters per hour.
A falling film evaporator is an industrial device to concentrate solutions, especially with heat sensitive components. The evaporator is a special type of heat exchanger. The process fluid to be evaporated flows downwards by gravity as a continuous film. The fluid will create a film along the tube walls, progressing downwards (falling) - hence the name.
The fluid distributor has to be designed carefully in order to maintain an even liquid distribution for all tubes along which the solution falls. These distributors are usually called ferrules due to their concentric shape. In the majority of applications, the heating medium is placed on the outside of the tubes. High heat transfer coefficients are required in order to achieve equally balanced heat transfer resistances. Therefore, condensing steam is commonly used as a heating medium.
For internally evaporating fluids, separation between the liquid phase (the solution) and the gaseous phase takes place inside the tubes. In order to maintain conservation of mass as this process proceeds, the downward vapour velocity increases, increasing the shear force acting on the liquid film and therefore also the velocity of the solution. The result can be a high film velocity of a progressively thinner film resulting in increasingly turbulent flow. The combination of these effects allows very high heat transfer coefficients.
The heat transfer coefficient on the evaporating side of the tube is mostly determined by the hydrodynamic flow conditions of the film. Evaporation takes place at very low mean temperature differences between heating medium and process stream, therefore these devices are ideal for heat recovery in multi stage processes. A further advantage of the falling film evaporator is the very short residence time of the liquid and the absence of superheating of the same. Not considering the vapour separator, the residence time inside the tubes is measured in seconds, making it ideal for heat-sensitive products such as milk, fruit juice, pharmaceuticals, and many others.
Falling film evaporators are also characterised by very low pressure drops; therefore, they are often used in deep vacuum applications.
