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