Fouling Factor

Fouling Factor

23 Jan 2019

The larger the fouling factor is, the worse the test work condition is. In the actual process, the water quality of the air-conditioning water is good, but after using for a period, the surface will have dirt. The best source is from existing operating facilities. When production data is available, it can be used to calculate the actual fouling factors for the system.  Together with the maintenance and cleaning history, this provides the best resource for selecting the fouling factors for a application.

The fouling factor of the chiller is F.F: 0.0001, which is often said to be one ten-thousandth of the fouling factor. This is a statement of the previous common engineering units in China, so the unit of 0.0001 is h.m2.c/kcal, which corresponds to the international unit 0.086m2.k/kw, and its corresponding unit is 0.0005h.ft2.F/Btu.

Ask the seniors about the fouling factor of some chillers. Our national standard is the water side fouling coefficient of 0.086m2 °C / KW, while the ARI standard is the evaporator: 0.0176m2 ° C / KW, the condenser 0.044m2 ° C / KW, which of the two standards is better? Is it good or small for the centrifuge? What is the reason?

Reason
The thermal resistance becomes about 0.06. If 0.086 manufacturers are used, the actual cooling capacity will be larger. If the cooling capacity is 0.044, the cooling capacity will be too small. In other words, the security performance of 0.086 is higher.

You should first understand that the definition of "national standard is the water side fouling factor 0.086m2°C/KW" and the definition of "ARI standard is evaporator: 0.0176m2°C/KW, condenser 0.044m2°C/KW”, and the difference between them (are not only for the numerical differences). Manufacturers use a small fouling factor to make their heat exchangers more competitive in the market.

If you use a large fouling factor and others choose small one, your heat exchanger will do a lot and the cost will go up. Would you say that it would be worthwhile? However, the water quality in actual use is difficult to control and it is easy to scale. The actual fouling rate is different for each application.

Below show some of these typical fouling factors:

Process Fluids

Fouling Resistance

 

(ft2-°F-hr/BTU)

Oils


         Fuel Oil #2

0.002

         Fuel Oil #6

0.005

         Transformer Oil

0.001

         Engine Lube Oil

0.001

Gases and Vapors


         Acid gas

0.002 - 0.003

         Ammonia vapor

0.001

         Chlorinated hydrocarbons vapors

0.001 - 0.0015

         Chlorine Vapor 

0.002

         CO2 vapor

0.001

         Compressed Air

0.001

         Hydrogen

0.0005

         Hydrogen (saturated with water)

0.002

         Light Hydrocarbon vapors (clean)

0.001

         Natural Gas

0.001 - 0.002

         Natural Gas Flue Gas

0.005

         Nitrogen

0.0005

         Polymerizable vapors (with inhibitor)

0.003 - 0.03

         Refrigerant Vapors (oil bearing)

0.002

         Solvent Vapor

0.001

         Stable Overhead Products

0.001

         Steam (non-oil bearing)

0.0005

         Steam (exhaust, oil bearing)

0.0015 - 0.002

Liquids


         Ammonia Liquid

0.001

         Ammonia Liquid (oil bearing)

0.003

         CO2 Liquid

0.001

         Chlorinated hydrocarbons liquid

0.001 - 0.002

         Chlorine Liquid

0.002

         DEG & TEG Solutions

0.002

         Ethylene Glycol Solutions

0.002

         Gasoline

0.002

         Heavy Fuel Oils

0.005 - 0.007

         Heavy Gas Oil

0.003 - 0.005

         Hydraulic Fluid

0.001

         Kerosene

0.002 - 0.003

         Light Gas Oil

0.002 - 0.003

         Light hydrocarbon liquid (clean)

0.001

         MEA & DEA Solutions

0.002

         Naphtha and Light Distillates

0.002 - 0.003

         Organic Heat Transfer Liquids

0.002

         Refrigerant Liquids

0.001

                                                       

Water

Fouling Resistance

Fouling Resistance

 

(ft2-°F-hr/BTU)

(ft2-°F-hr/BTU)

water temperature

 125°F or less

over 125°F

water velocity

3 ft/s or less

over 3 ft/s

3 ft/s or less

over 3 ft/s

Boiler Blowdown Water

0.002

0.002

0.002

0.002

Brackish Water

0.002

0.001

0.003

0.002

Condensate

0.0005

0.0005

0.0005

0.0005

Cooling Tower Water (treated)

0.001

0.001

0.002

0.002

Cooling Tower Water (untreated)

0.003

0.003

0.005

0.004

City or Well Water

0.001

0.001

0.002

0.002

River Water (minimum)

0.002

0.001

0.003

0.002

River Water (average)

0.003

0.002

0.004

0.003

River Water (muddy or silty)

0.003

0.002

0.004

0.003

Sea Water

0.0005

0.0005

0.001

0.001

Treated Boiler Feed Water

0.001

0.0005

0.001

0.001


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