Thank you Abdul Kuddus for following.

https://www.sciencedirect.com/search?qs=fouling%20or%20scaling%20in%20heat%20exchangers&show=25&sortBy=relevance

The topic is sometimes dealt at main chemical engineering magazines; (e.g.):

R. Silvestrini, "Heat exchanger fouling and corrosion", Chem. Eng. Progr., 75(12) December 1979, 29-35.

L.J. Wachel, "Exchanger simulator: Guide to less fouling", Hydrocarbon Processing, 65(11) November 1986, 107-110.

All product manufacturers whose devices include heat exchangers will provide guidance on water quality and treatment to prevent fouling.

However, a lot of that guidance is not followed or at least not followed long term.

Makeup water quality can have a major impact on the chemical/biological treatment program and depending on where you are in the world, the water quality can fluctuate over the course of a year or less. The city of Phoenix Arizona has six different water sources throughout the year if I recall correctly.

There are numerous corporations whose entire business is equipment water quality and treatment. Should be easy enough to find. I'd start with cooling tower maintenance as it's the most challenging and also the highest risk from a public health perspective due to legionella concerns.

Trade associations like ASHRAE publish guidance on water treatment and quality.

Thank you Carlos Araujo Queiroz and Fred Betz for providing with answers. I wish I could get more analysis and discussion on Fouling and Scaling.

Md. Washim Akram, instead of sending so many files to download for my questions, can you please give your answer in writing?. This solves doubts and clarifications in the most effective way. I would like to mention that this is the platform to share the ideas and approaches.

With regards,

Unfortunately I can't provide a lot of guidance on water quality specifics as it is dependent on the application and the quality of the make up water for the process. Chemical treatment professionals need to test the water and determine what is right treatment protocol to keep various parameters such as silica, acidity, conductivity, hardness, etc. in the right ranges. Too high or too low for many parameters can degrade your system's performance or lifetime.

Sorry I can't be more specific than that.

Thank you Fred Betz for giving a useful answer.

Fouling or scaling in heat exchangers cannot be avoided since it depends on the types of fluids. If effective heat exchange has to take place, regular cleaning of tubes and maintanence has to be done. There are two methods, one is mechanical cleaning and the other is chemical cleaning. Chemical cleaning is best proven and effective method to remove scaling in heat exchanger after this is used for a period of time.

Scaling is a type of fouling caused by inorganic salts in the water circuit of the heat exchanger. It increases the pressure drop and insulates the heat transfer surface, thus preventing efficient heat transfer. ... The salts are therefore deposited on the warm surface when the cold water makes contact with it.

Thank you @Eman Ali Al-Khafaji for your answer.

Fouling or scaling in heat exchanger cannot be completely avoided but can be taken care to reduce. However, cleaning of a heat exchanger can be extended to a certain duration. The effective cleaning can be done by chemical cleaning, where the tubes are flushed, cleaned by water and later chemical treatment can be done which is slightly a cost affair.

Scaling in heat exchangers are common and the amount of this depends on the type of fluid used. Some may be subjected to high scaling and some may be low and hence based on the impurities, the fluid handles that much amount of scale formed. Scaling or fouling cannot be eliminated as a whole but can be reduced.

Scaling is quite common in heat exchanger. This cannot be completely removed or avoided but can be taken care by cleaning or going for scheduled maintenance. In order to reduce scaling a person can go for mechanical cleaning or chemical cleaning methods.

Fouling or scaling of heat exchangers cannot be reduced completely but can be cleaned on continous basis. The two methods are used for this purpose, one is mechanical cleaning by using wires, flushing by water, brushes etc. Chemical cleaning is done by cleaning with chemicals hence minimize fouling to certain extent.

Scaling on heat exchangers will be got by fluids used. Almost all the fluids are not free from impurities and hence scaling cannot be avoided completely. These can be removed by treatment either by mechanical or chemical means.

Fluid taken to flow inside or outside the tubes are not clean but contains certain impurities which cannot be removed. As the fluid flows over a certain period, this sticks on the wall and forms as a scale. The material of the scale will be a combination of certain elements. This can only be cleaned and reused.

Fouling and scaling in heat exchangers can be taken care by periodical cleaning and maintenance of the equipment. The periodic cleaning depends on the type of fluid used in a heat exchanger. Chemical cleaning method is found good, suitable and reliable in order to make work a heat exchanger for a longer duration.

In heat exchanger, fouling of exchanger surface results in lower overall heat transfer coefficient in operation than that calculated for clean surface. This is severe resulting in reduced effectiveness. Amount of fouling is given as fouling factor which is equivalent to thermal resistance of scale.

Scaling is formed on the heat exchanger surfaces either inside or outside i.e. (in core or in annulus) depending on the fluid flowing continuously in an heat exchanger. The scaling or fouling even the fluid cleaned and sent inside cannot be completely avoided and periodic cleaning and maintenance is required.

Fouling of heat exchanger takes place only due to the fluids flowing inside the core or annulus. This can also be said that, no fluid can be made crystal clean before going into equipment but can have maintanence or adopt cleaning methods after a certain period of time.

Fouling or scaling cannot be completely eliminated in a heat exchanger. The scale will be formed inside the tube and also outside the tube, if the fluid flows through annulus. Cleaning regularly and periodic maintanence of heat exchanger may help again to come back to initial stage.

Since the fluids used in heat exchanger are not free from impurities, fouling or scaling cannot be avoided and at the same time, cannot be ignored. This reduces overall heat transfer coefficient and hence decreases effectiveness of heat exchanger.

Fouling or scaling is very common in heat exchangers and cannot be avoided or eliminated. If scaling is not considered, then the deposits may block the tubes, leading to lower overall heat transfer coefficient which in turn weakens effectiveness. Hence, cleaning is the only solution to restore.

Fouling of heat exchanger is nothing but scale forming by the continous movement of fluid inside or outside a tube in a heat exchanger. This can be best cleaned by using chemical cleaning treatment which should be done periodically.

Managing Heat Exchanger Fouling To Reduce Risky Conditions

a lower heat transfer rate.

a higher outlet temperature on the hot side (and lower dT hot)

a lower outlet temperature on the cold side (and lower dT cold)

Thank you Nirmala S.V.S.G for your answer. But my question is how to reduce scaling. What you said in your answer is not related. Can. you please give a proper answer?

Following..

Thank you Abdul Kuddus for following.

Fouling or scaling in heat exchangers is very common. Even though, one cleans the fluid before entering into heat exchanger, dust particles and matter will be there. Hence, fouling can be removed at regular intervals as a part of maintainence activity by cleaning methods, namely mechanical and chemical.

As the fluid flows inside the tubes or outside the tubes in a heat exchanger, there is an every chance that scale is formed. This scaling consists of different types of elements, which cannot be removed by simple cleaning. Hence, in periodical maintanence, two methods are generally adopted for cleaning: one is mechanical cleaning and other is chemical cleaning.

This could take three main streams; material , working fluid, and operation. The working fluid helps in selecting HE material and internal surface conditions, proper additives to the fluid could be considered. Sometimes, operation could be controlled through pressure, temperature, and speed. These items could help in avoiding scale accumulation.

Thank you Elhadi Ibrahim Dekam for your answer.

Fouling or scaling in heat exchangers cannot be completely eliminated since it depends on the type of fluid used but can be periodically cleaned, maintained and put to use. One method is mechanical cleaning and other is chemical cleaning.

Fouling or scaling in heat exchangers depends on the type of fluid used. All fluids are not clean. Hence, lower heat transfer from one liquid to other liquid occurs. In order to make the heat exchanger perfect, two cleaning methods are adopted, one is mechanical cleaning and the other is chemical cleaning which is mostly used.

1. velocity

The main variable is the velocity of the fluid. In general the designer has freedom to set the velocity on both sides of the exchanger, it is usual to match its specification in terms of pressure drop, at minimum capital cost.

As the velocity is increased the overall heat transfer coefficient increases which means that for a given temperature difference, the heat transfer area (and hence the capital cost) is reduced. On the other hand as the velocity increases the pressure drop. The difficulty that arises however, in regard to fouling, is that the optimum velocity for acceptable pressure drop may not be the same as that required to minimise the incidence of fouling. For relatively low fouling conditions (e.g. clean organic liquids at low temperature) this approach may be satisfactory but not necessarily so, where heavy fouling is anticipated. For these situations the philosophy would be in general, to design for the highest velocity commensurate with the allowable pressure drop. It also has to be borne in mind that if the velocity is too high erosion of surfaces, particularly if droplets or particles are present in the fluid stream, may become a problem.

2. Temperature

In general raising the temperature can increase the rate of corrosion and the rate of chemical reactions and for inverse solubility salts, raising the temperature may initiate deposition. Although the temperatures required in the operation of a particular heat exchanger will be specified in the proposal, the designer has some limited control of the temperature at the solid/fluid interface through the choice of velocity. So, proposal is to minimise surface temperature in conjunction with the choice of fluid velocity.

3. Other

If at all possible, reduce the incidence of potential fouling by reducing the

concentration of foulant precursors.

Ensure that the residence time is as low as possible (residence time may be linked to chemical reaction).

Fouling process depend on the extent and nature of the surface roughness. Is possible select materials with smaller surface roughness.

Is it not all, but main consideration ...

Fouling or scaling in heat exchangers can be controlled by using clean fluids free from impurities. As fluids are not fully pure, there is a chance of fouling. This can be put under periodic maintanence and adopting mechanical and cleaning methods.