Pros And Cons Of Forced Circulation Evaporator


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What is a forced circulation evaporator? What are the pros and cons of forced circulation evaporator? This are questions that most people ask in the internet and this articles will provide you with the useful answers and understanding you need.

a forced circulation evaporator showing all the connections

Forced circulation evaporators are a type of evaporation system that rely on both vapor and liquid to be present in order to work efficiently. And while they do allow for great improvements in efficiency there are many cons as well such as increased energy costs and maintenance expenses.

Forced circulation evaporators are mainly used in industrial production processes whereby the overall quality of the product is important and the time it takes to complete the process is also a crucial factor.

When compared to a batch or open tank type of evaporator forced circulation evaporators are much more efficient, but they are also more expensive to construct and they require a lot more maintenance work.

But while they may be complicated and expensive forced circulation evaporators do offer many advantages compared to other types of evaporation methods.

The high efficiency levels that can be achieved with forced circulation evaporator systems allow for the recovery of over 95% in energy which can help companies save costs on their electricity bills, just one of their many additional benefits.

This article will be discussing on what a forced circulation evaporator is and the pros and cons of forced circulation evaporator.

What Is A Forced Circulation Evaporator?

Evaporation is the process in which a liquid transforms into a vapor state. A vapor can be used to then be condensed into a liquid again, however the process of condensation creates pollutants such as water vapor and humidity that can affect any surrounding objects such as employees, machinery and even other tools.

This is where forced circulation evaporators come in.

This is the type of evaporation process that happens naturally however it can also be achieved via other methods such as heat and cold air. In order to create more efficient forced circulation evaporation systems, the liquid in question must be heated to increase the amount of vapor that is produced. But while this method may offer good results, it can be a very costly process to implement.

A forced circulation evaporator allows for the evaporation of liquids by using both vapor and liquid and only uses air pressure to move the fluids around.

A forced circulation evaporator is a device that is used for the evaporation of liquids in industrial processes such as food and chemical manufacturing.

Forced circulation evaporators function in different ways than their batch or open tank based counterparts. In forced circulation evaporators heat transfer occurs due to a combination of conduction, convection and heat radiation wherein all three mechanisms work together to ensure that everything is kept at optimal temperatures.

This kind of system is highly effective for high volume applications such as solvents, water based products, oil based products, cosmetics, pharmaceuticals, foodstuffs and other materials which are not vapor sensitive.

Forced circulation is achieved by various means, such as locating pumps outside of the evaporator. Forced circulation leads to high tubeside velocities (6-18 ft/s), and hence higher heat-transfer coefficients and smaller heating surfaces.

Positive circulation renders this unit relatively insensitive to variations in physical properties or lards, making it suitable for crystallizing solutions or slurries.

Forced circulation is a way to keep the liquid and vapor in contact with each other. The liquid is forced to flow over the surface of the evaporator, while also circulating inside via pumps.

a huge steel forced circulation evaporator

Without forced circulation, the liquid would tend to settle on one side, due to gravity effects. In an open-tank system, the water would sit on top of the outside surface of the tanks that are holding it.

This could lead to some problems such as higher energy usage and higher maintenance costs because it requires more fluid movement than other types of evaporation systems.

The most important thing about forced circulations evaporators is that they are able to distribute heat evenly across their large surface area.

The heating surface may be inside or outside of the evaporator; this is also true for the device that creates the forced circulation. The tubes can be horizontal or vertical. Boiling can take place, or be suppressed due to the hydrostatic head maintained above the top tubesheet.

In the latter case, the liquor is superheated and flashes into a liquid-vapor mixture. The type of vapor head used, ranging from a simple centrifugal separator to a crystallizing chamber, is selected on the basis of product characteristics.

An evaporator temperature should be above the boiling point of the product to be evaporated.

The vapor flow rate can be increased by applying a vacuum, which reduces the boiling point and causes more vapor to be produced.

Heat transfer is usually enhanced by using steam jets or tubes, which are connected to the evaporator surface through perforated plates or tubesheets. These vapor jets increase heat transfer from the surface of an evaporator because they increase fluid turbulence in direct contact with the heating medium.

Moving on to the next topic, let’s discuss on the pros and cons of a forced circulation evaporator.

Pros And Cons Of Forced Circulation Evaporator

Here, we will be looking into the pros and cons of forced circulation evaporator but firstly, we will discuss the pros of forced circulation evaporation and then later the cons of forced circulation evaporator.


Some of the advantages of forced circulation evaporation are as follows:

1. High Heat Transfer Coefficients

One of the biggest advantages of forced circulation evaporators is that they have higher heat transfer rates which can help to increase the speed of heating and reduce the total amount of time taken for evaporation; thus reducing energy costs and making this process more efficient.

Without forced circulation, evaporation could take days to complete and consequently energy consumption could be high. As more energy is required to carry out forced circulation, the bottom line is that it will even increase the amount of heat lost through conduction, convection and radiation.

But with forced circulation, the heating surface can be larger in size thus allowing for higher heat transfer rates which can lead to reduced energy usage and increased efficiency.

2. High Vapor and Liquid Viscosity

Fluid velocity is an extremely important factor in forced circulation evaporators. Forced circulation evaporators use vapor and liquid being mixed together inside the pipes of the system in order to increase vapor flow rates and reduce energy consumption.

The increased vapor speeds are achieved by using steam jets or tubes to provide a bubble-like flow that can produce a higher velocity than a direct flow would allow.

3. Reasonable Temperature Range

Forced circulation evaporators require a constant temperature range. This allows for a consistent evaporation process to take place, which helps the entire process to run more efficiently and effectively.

It is important that the temperature of a forced circulation evaporator remains relatively stable so that it can operate at an optimal level without losing heat and not allowing for ingredients to begin boiling due to rapid changes in temperatures.


Some of the disadvantages of forced circulation evaporator are as follows:

1. High Maintenance Cost

These types of forced circulation evaporators tend to require more maintenance than other types of evaporation devices because they need regular cleaning and chemicals such as nitric acid must be added to remove the grease deposits in them.

In order to clean forced circulation evaporators, high amounts of water need to be flushed into them; this is a common process which many people have found challenges when carrying out as it can lead to issues such as scaling which can cause damage to the system.

2. Costly Equipment

Forced circulation evaporators are often expensive. As these types of evaporation systems require a lot of equipment to work correctly, they can have an effect on your budget if you don’t have the necessary funds to put into them.

Due to the high maintenance cost, forced circulation evaporators can also be costly in terms of their operating costs. As this type of evaporation system needs more care and attention, it may need to be operated more frequently than other types as well.

3. The Hold-Up Time For Liquids Is High

This is one of the major disadvantages with forced circulation evaporators and it would be unrealistic to expect this issue to be eradicated.

Hold-up times can vary depending on how long the system has been used and how long it has been since the last time it was cleaned as well as the amount of water being used when cleaning it.

There is no set amount of time that a hold-up can take place, but it could range from a few hours to up to several days depending on conditions and what is stated in your contract for forced circulation evaporators.


In conclusion, forced circulation evaporators are an efficient method of evaporation. As they are more energy efficient than other types of evaporation processes, they can reduce energy usage and increase efficiency as well.

But as with all types of systems, there can be disadvantages that you need to take into account. This method for forced evaporation is mainly used for the production of products such as fragrances and flavorings which require long periods of evaporation and so the benefits behind using this type of system outweigh its disadvantages.

a forced circulation evaporator with different tubes and pipes connected together

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