Understanding Rising Film Evaporator Working Principle and Differences from Falling Film Evaporators

Even though evaporation is a natural process, you may want to do it manually using industrial equipment if you want the best results for labs and industries. In fact, because of how important evaporation is, you can find various types of evaporators out there. Out of all the options available out there, rising/falling film evaporators are some of the most common ones.

Because choosing the right evaporator is quite important for lab processes, chemical industries, food industries, and much more, we are here with a complete guide on the rising film evaporator working principle. You can even find details on rising and falling film evaporator uses down below in this guide to easily pick the best evaporators for you.

Working Principle of Rising Film Evaporators

If you are new to evaporators, you may have questions like what is a rising film evaporator? In that case, you should first understand the rising film evaporator working principle. Just per the name, a rising film evaporator involves a thin liquid film that rises up.

Taking a closer look, a liquid is evaporated by boiling it which creates vapor inside a heating tube. These vapors then create a pressure that makes the liquid rise up and is pushed against the tube pipes. And thus, a thin film is formed inside the tube pipes that rise up and separates the vapor and the liquid. Hence, the complete evaporator process is complete where you get a liquid and vapors separately.

Working Principle of Falling Film Evaporators

Opposite to a rising film evaporator, you will also come across falling film evaporators. And before checking their differences, you should first learn about the falling film evaporator working principle. While this type of evaporator also has a liquid film, it is based on gravity instead of pressure as discussed in the rising film evaporator working principle.

As for its exact working principle, a falling film evaporator uses gravity to make the liquid go down a heating tube. Inside this heating tube, the liquid forms a thin film on the wall that is then heated externally. And because this is a thin film, it easily evaporates into vapor. Once the vapors are created, they move inside the same tube increasing heat transfer due to turbulence. And at last, the liquid and vapors are separated.

Comparison between Rising Film and Falling Film Evaporators

Now that we have covered the rising film evaporator working principle and falling film evaporator working principle, you might have noticed that these are quite similar to each other. However, there is still a difference between these two. And if you want to better understand the rising film evaporator working principle, you should know the difference between these:

• Operation: While a rising film evaporator uses vapor pressure to move the liquid inside the heating tube, a falling film evaporator uses gravity to move the liquid inside the heating tube.

• Efficiency: Since you are not using extra heat to create vapor pressure, a falling film evaporator is more efficient than a rising film evaporator.

• Applications: Rising film evaporators have applications like food production, pharmaceuticals, thermal desalination, and more. On the other hand, falling film evaporators have applications like chemical industries, dairy industries, black liquor industries, and more.

• Advantages: Starting with rising film evaporators, you get advantages like low costs, higher heat transfer, better scalability, and suitable for high viscosity liquids. As for falling film evaporators, you get advantages like space saving design, energy efficiency, and better versatility. 

Applications of Falling Film Evaporators

While we have already covered the key applications of falling film evaporators up above, you may want to know more in detail. By checking the following applications of falling film evaporators, you will be able to easily pick the right one for your needs:

• Food production

• Pharmaceuticals

• Solvent recovery

• Polymer production

• Thermal desalination

• Pre-heaters

• Pre-concentrators

Applications of Rising Film Evaporators

To truly understand the rising film evaporator working principle, you should also know the key applications of rising film evaporators:

• Solution separation

• Chemical production

• Dairy industry

• Black liquor manufacturing

• Concentration and purification processes

Understanding the Advantages of Rising Film Evaporators in Industrial Processes

Even though there are also other types of evaporators like an agitated thin film evaporator (ATFE), rising film evaporators are still highly popular. This is due to the specific advantages of rising film evaporators in industrial processes that include the following: 

• Higher heat transfer

• Lower costs

• Efficient for high-viscosity liquids

• Easy to scale for large industries

• Suitable for high temperatures and high viscosity

Difference between Rising Film Evaporator and Falling Film Evaporator

Last but not least, you should also know the differences between rising film and falling film evaporators to completely understand the rising film evaporator working principle:

• Pressure vs gravity used in rising film and falling film evaporators

• Lower vs higher efficiency in rising film and falling film evaporators

• Lower costs vs higher costs in rising film and falling film evaporators

• Higher viscosity vs lower viscosity support in rising film and falling film evaporators