How to define Shell and Tube Heat Exchanger dirt factor based on data sheet ?

[miftahazhar]

I have data sheet of shell and tube heat exchanger said that the dirt factor or fouling coefficient if 0 for both shell and tube.

I want use kern method to know the heat exchanger need to be cleaned or not (rating problem). In rating problem it must compare calculated dirt factor and allowable dirt factor. What is the allowable dirt factor ? is it based on the design (on my design is zero) or based on apropriate table ? In apropriate table it said that on my case, the dirt factor is 0,0005 (in british, sorry i didn't convert it to SI)

Thank you so much

 

[srfish]

The allowable dirt(fouling) factor can be found in TEMA (Tubular Exchanger Manufactures Association)

 

[MrBTU]

Miftahazhar,
Please tell us the fluids on shellside and tubeside. You can consult TEMA book to get recommended fouling factors to use based on this. Another approach is to design with a % clean. This is sometimes used by designers of surface condensers. An 85% clean for instance, would add 17.6% to the surface area required, to account for some fouling. Ultimately, adding a fouling factor of any kind has the affect of adding surface area to the heat exchanger and to allow for some operation with the surfaces in other than new and clean condition. The higher the fouling factor, the more surface area is added. This has the affect, in operation, of determining the interval required between cleanings. When the actual fouling exceeds the amount added in design, performance drops off and cleaning is required to restore heat exchanger to adequate operation. Of course, fouling factor can have a detrimental affect on performance if diameter and number of tubes are added in order to add the extra surface instead of length. As diameter is increased and more tubes are added, velocities decrease, bypass increases, and you end up with a less efficient heat exchanger. So a higher fouling does not always end up with a better heat exchanger. These are all variables that the designer must take into consideration.

 

[georgeverghese]

This is an error in the datasheet, so you should ask the plant owner or the owner's engineering contractor to correct this. A zero or close to zero fouling factor is only used in very clean services with compact heat exchangers such as all welded PHE, PCHE, brazed fin or spiral wound heat exchangers.