What is the difference between a climbing film evaporator and a falling film evaporator?

Climbing film evaporator and falling film evaporator are two common film evaporator, the main difference lies in the liquid flow mode, heat transfer efficiency, applicable materials and operating characteristics. The following is a detailed comparison:

Climbing film evaporator

• Liquid in the heating tube upward flow, heat boiling steam, steam driven liquid to form a thin film along the tube wall rise.
• Relying on the steam drag force and liquid boiling force to realize the climb.

Falling Film Evaporator

• Liquid enters from the top and flows downward by gravity, forming a thin film on the wall of the heated tube, and the evaporation process is completed in the descending process.
• It is necessary to ensure that the liquid evenly covers the tube wall through the distributor.

Climbing film evaporator

• Liquid at the bottom of the heating tube begins to boil, vapor bubbles push the liquid upward movement, the formation of ring flow or spray flow.
• Suitable for medium viscosity or easy to scale materials.

Falling film evaporator

• Liquid is evenly distributed through the top distributor, a thin film is formed under the effect of gravity, and the evaporation process is completed quickly.
• Suitable for heat-sensitive, high viscosity or easy foaming materials.

Climbing film evaporator

• Due to the mixed flow of steam and liquid, the heat transfer coefficient is high, but may cause efficiency fluctuation due to unstable flow.

Falling film evaporator

• Liquid film distribution uniform and short residence time, heat transfer efficiency is higher (especially for heat-sensitive materials), but need to accurately control the liquid distribution.

Climbing film evaporator

• Medium viscosity, easy to scale or contain a small amount of solid materials (such as some chemical intermediates).
• Not suitable for extremely viscous or heat-sensitive materials.

Falling film evaporator

• High viscosity, heat-sensitive (such as food, medicine, juice concentration), easy to foam or high boiling point materials.
• Better when low operating pressure is required.

Climbing film evaporator

• Wide range of operating pressure, but need to control the feed rate to avoid dry wall or clogging.
• Some tolerance to fouling.

Falling film evaporator

• Requires precise control of liquid distribution, otherwise prone to drywall or localized overheating.
• Usually operated under vacuum to reduce boiling point.

Climbing film evaporator: relatively simple structure, but cleaning may be more complicated (especially after scaling).

Falling film evaporator: distributor design is critical, high maintenance requirements, but easy to clean.

Climbing film evaporator: chemical industry, wastewater treatment, part of the food concentration.

Falling film evaporator: dairy products, pharmaceuticals, fruit juice concentration, seawater desalination.

Select Climbing film evaporator: material easy to scale, need medium evaporation intensity.

Select falling film evaporator: heat-sensitive, high viscosity, low temperature and fast evaporation.