Several variables contribute to fouling, including water pH, product viscosity, and the roughness of component surfaces, among many others. Together, the variables can be expressed as a fouling factor that numerically represents resistance to heat transfer — or thermal resistance — in your system.
How do you calculate fouling factor?
Typical Fouling Factors
- Alcohol vapors : Rd = 0.00009 (m2K/W)
- Boiler feed water, treated above 325 K : Rd = 0.0002 (m2K/W)
- Fuel oil : Rd = 0.0009 (m2K/W)
- Industrial air : Rd = 0.0004 (m2K/W)
- Quenching oil : Rd = 0.0007 (m2K/W)
- Refrigerating liquid : Rd = 0.0002 (m2K/W)
- Seawater below 325 K : Rd = 0.00009 (m2K/W)
What is a fouling factor?
The fouling factor represents the theoretical resistance to heat flow due to a build-up of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger, but they are often overstated by the end user in an attempt to minimize the frequency of cleaning.
Does fouling factor depend on temperature?
Fouling factors for corrosion fouling show a peak value as temperature increases; at low temperature, the corrosion rate increases with temperature but the corrosion requires the presence of dissolved oxygen and this dissolved oxygen content is reduced at higher temperatures due to the decreasing solubility of oxygen …
How do I reduce fouling?
The best way to avoid particulate fouling is to keep the cooling water clean and thereby prevent particles from entering the heat exchanger. However, in all cooling systems, and especially when using open cooling systems (with cooling towers), there will always be particles present in the cooling water.
How do you deal with fouling in heat exchangers?
Choosing stainless steel for your applications can help your heat exchanger resist fouling, maintain its optimal performance and last much longer. Using scraped-surface or corrugated-tube heat exchangers can also decrease fouling.
How do you reduce fouling factor in heat exchanger?
Which one is having the highest value of fouling factor?
Which one is having the highest value of fouling factor? Explanation: Fouling factor for engine exhaust is 0.002 while that of industrial liquids, fuel oil and turbine exhaust are 0.0002, 0.0010 and 0.0002 respectively.
What does fouling factor depend on?
Fouling factor (or dirt factor) definition It is also often referred to as the ‘dirt factor’. It normally depends on the process fluid or service on any side (shell or tube) of the heat exchanger. Fouling or dirt factor is used for calculation of the overall heat transfer coefficient of a heat exchanger.
How do you overcome fouling in heat exchangers?
How do you get rid of fouling in heat exchangers?
Mounting the heat exchanger vertically can also minimize the effect as gravity pulls any particles out of the heat exchanger away from the heat transfer surface even at low velocity levels. Deposition fouling is normally removed mechanically by brushing or scraping.
Can fouling factor be negative?
“Negative” fouling. This can occur when fouling rate is quantified by monitoring heat transfer. Relatively small amounts of deposit can improve heat transfer, relative to clean surface, and give an appearance of “negative” fouling rate and negative total fouling amount.
What are the factors that affect fouling?
Fouling Factors. Fouling is a function of the system and the equipment used. Parameters which influence the fouling rate in a system include: the type of fluid, the type of heat exchanger, the temperatures, the velocities and the materials of construction. The actual fouling rate is different for each application.
What is the fouling factor in a heat exchanger?
The fouling factor helps us add some additional detail, by representing the extra resistances that appear on the inside and outside of tubes after an exchanger has been operating awhile: the caked on products of fouling. There are different types of fouling, from crystalline scale to literal pieces of gunk.
What is the fouling factor for cooling water?
Fouling Factors for a variety of typical thermal applications. Home Up Back Cooling water Several fluids Refinery fluids TYPICAL FOULING FACTORS COOLING WATER – Fouling Factors in [m2K/W] Conditions cooling water < 50 ° C cooled fluid < 120 ° C cooling water > 50 ° C cooled fluid > 120 ° C
What units are used to calculate the fouling factor?
The fouling factor, Rf, as well as the deposition rate, d, and the removal rate, r, can be expressed in the units of thermal resistance as m2·K/W or in the units of the rate of thickness change as m/s or units of mass change as kg/ m2· s.
