heat exchanger fouling 1

[johngerhart]

does anyone know a good literature source for modelling heat exchanger fouling and redesign . We would like to chracterize the type of fouling , cacl U on line and look at redsigning the exchanger to eliminate the issue

 

[TrevorP]

Fouling in heat exchangers is an extremely complex issue, as there are a large number of factors in play, and a large number of different types of fouling that can occur. I am not aware of any modelling techniques that exist. It is, however, possible to reduce fouling in heat exchangers which is dependent on the type of fouling that occurs. A good starting point is the book "Fouling Notebook: A Practical Guide to Minimising Fouling in Heat Exchangers" published by the UK's IChemE.

One general point that has proved to be reasonably effective is to keep the velocities high, and to keep the dirt factor low. High dirt factors in design can result in an inefficient design that encourages fouling, and so can become a self-fulfilling prophecy.

 

[EdStainless]

There are a number of EPRI papers that deal with calculating and estimating overall heat transfer. The favor a 'sum of the resistances' method that easily allows for seperate factors.

That said, in the real world I see a short list of problems that lead to most fouling.
1. Velocities too low. Pick the right material and run hard. If you are running water through stainless tubes make sure that you are over 10 ft/sec, and 15 wouldn't hurt.
2. Poor lay-up. Materials allowed to dry, settle and/or scale, in or on tubes when not in service.
3. Poor temperature uniformity. Usually a result of an oversized HX. The reactions at hot and cold spots are different and often lead to scaling or precipitation.
4. Lack of maintainace/filtration. I have seen more stuff in HX tubes. Various pieces of trash and debris from other parts of the operation.
Don't let me get started on corrosion.

There has also been some good work done on building modles to help you select the economically optimum cleaning sched. Most of this has been related to power generation, but it applies to process also. The heat and flow still cost you something.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[Montemayor]

johngerhart:

The best and greatest treatise on heat exchanger fouling and how to design for it was a classic article written by Charles Gilmour in the 1965 issue of Chemical Engineering Progress, (61) 7. In his article Charlie Gilmour clearly and expertly describes the many arcane and false ideas surrounding the concept of exchanger fouling, why it occurs, and how to avoid it. Charlie led his heat transfer division within Union Carbide during the "hay" days of the exploding petrochemical industry during the 1950's through the 1960's. He was, and is still regarded as one of (if not, THE) the outstanding world authorities on practical, industrial heat exchanger design and operation. I strongly recommend you (or any interested person) obtain a copy of this article and read it thoroughly. It contains a lot of surprises and revealing empirical and field knowldege that not only is true, but it works.

Charlie was the first expert engineer who frankly and clearly proved how most design and specification engineers were the main cause of fouling taking place within heat exchangers and how to remedy this. He proved it time-after-time at Union Carbide and his concepts were proven in all the exchangers I have designed, specified, and operated.

Nobody else - not even Donald Q. Kern - comes close to dealing with this subject as did Gilmour. He had to; he worked for a profit-oriented company that demanded the ultimate in efficient heat exchanger service.

I hope you can get a copy of this article and that it is of service to you too.


Art Montemayor
Spring, TX

 

[unclesyd]

There article mentioned by Montemeyer is a good one and can probably be obtained at the following website.

http://www.lindahall.org/

I have to concur about the design and specification for HX's being at the root of a lot of fouling problems.

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