What is falling film?

“The term \"film\" in ascending and descending film evaporation refers to the flow of the feed liquid along the walls of the heating tubes during operation, in a film-like pattern that provides the best heat transfer efficiency. Film-evaporator: The feed liquid enters from the bottom of the evaporator and, driven by secondary steam, flows upward along the tubes. Falling film evaporator: The feed liquid enters from the top of the evaporator and flows downward along the tube wall under the force of gravity. ”The above is from BoDou. We use falling film evaporation; we have never used rising film evaporation

Film-evaporation: The feed liquid enters from the bottom of the evaporator and, driven by secondary steam, flows upward along the tubes. For heat-sensitive materials: Falling film evaporation – in this process, the feed liquid enters from the top of the evaporator and flows downward along the tube walls under the effect of gravity.

Falling-film evaporators are used in the caustic soda production process; falling-film evaporators are employed for concentrating the solution from 32% to 50%, while rising-film evaporators are used for concentrating it from 50% to 99%.

Please refer to the book titled \"Q&A on the Production of Caustic Soda using Ion-Exchange Membranes\", the one with a blue cover; it provides detailed information on the subject

I’m not studying crafts; I don’t have that book. Do you have an electronic version?

Working principle: The raw material liquid is introduced into the upper tube sheet of the heat exchanger. Through a distributor, the material is distributed into each heat exchange tube, where it forms a uniform liquid film along the inner wall of these tubes. As this liquid film flows downward, it is heated by the steam in the shell side, resulting in boiling and evaporation as it moves downward. At the bottom of the heat exchange tube, the material turns into a concentrate and secondary steam. The concentrate falls into the lower tube bank, while the secondary steam enters the gas-liquid separator. Features: 1. High heat exchange efficiency; 2. Small footprint; 3. Short residence time of the material, reducing the risk of spoilage; 4. Suitable for materials with high viscosity. Application range: Falling film evaporators are suitable for material concentration and can evaporate materials with high viscosity; they are particularly appropriate for heat-sensitive materials, but not suitable for processing crystalline materials.

Thank you very much!

The last time I bought it was on the fourth floor (or maybe the fifth floor) of that bookstore on Wangfujing Street in Beijing; after taking the elevator up, turn left and it’s there

There are three types: rising-film evaporators, falling-film evaporators, and rising-falling film evaporators. All of them belong to the tubular film evaporators among single-pass evaporators. By \"film\" is meant that the liquid flows over the heat exchange surface in the form of a thin film, resulting in a large heat exchange area and high efficiency. Film-evaporator: Under the principle of thermal siphonage, the material is fed from below the evaporator; driven by an adequate amount of secondary steam, the liquid flows upward in a thin film form, thereby completing the process of evaporation and concentration. The secondary steam and the concentrated liquid enter the gas-liquid separator from above the evaporator. Not applicable to falling-film evaporators with high viscosity: The material enters the evaporator from above and, under the action of the liquid distribution head, is evenly distributed across the various heat exchange tubes. Under the force of gravity, the liquid flows from top to bottom, thereby undergoing evaporation and concentration. The secondary steam and concentrated liquid enter the gas-liquid separator from below the evaporator. Suitable for materials with high viscosity: The rising-film evaporator is essentially a combination of a rising-film evaporator and a falling-film evaporator; the material moves first upward and then downward, making it suitable for materials whose viscosity changes significantly with concentration