A falling film evaporator is a type of heat exchanger used to concentrate liquids by evaporating their solvent, typically water. In this system, a thin film of liquid flows down vertical tubes, where it is heated. The heat causes the solvent to evaporate, leaving behind a more concentrated solution. This process is efficient because the thin film allows for a large surface area for heat transfer, reducing the energy required for evaporation. Falling film evaporators are commonly used in industries such as food processing, pharmaceuticals, and chemical manufacturing to concentrate products like fruit juices and syrups.