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# Heat Exchangers - Fouling and Reduced Heat Transfer

During operation with liquids and gases a dirt film may build up on the heat exchanger surfaces . The deposit film is referred to as fouling

Increased thermal resistance caused by the deposit can normally only be obtained from tests or experience. The fouling factor can be determined as

Rd = 1 / Ud - 1 / U                            (1)

where

Rd = fouling factor - or unit thermal resistance of deposit (m2K/W)

Ud = overall heat transfer coefficient of heat exchanger after fouling (W/m2K)

U = overall heat transfer coefficient of clean heat exchanger (W/m2K)

(1) can also be expressed as:

Ud  = 1 / (Rd + 1 / U)

### 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)
• Seawater above 325 K : Rd = 0.0002 (m2K/W)
• Steam : Rd = 0.00009 (m2K/W)

## Related Topics

### • Thermodynamics

Work, heat and energy systems.

## Related Documents

### Conductive Heat Transfer

Conductive heat transfer takes place in a solid if there is a temperature gradient.

### Convective Heat Transfer

Heat transfer between a solid and a moving fluid is called convection. This is a short tutorial about convective heat transfer.

### Feed Water Treatment to Avoid Corrosion

Make-up water to steam boilers should be treated with oxygen scavengers to avoid serious corrosion problems.

### Heat Exchangers - Overall Heat Transfer Coefficients

Overall heat transfer coefficients in common heat exchanger designs - tubular, plate or spiral.

### Heat Transfer Coefficients in Heat Exchanger Surface Combinations

Average overall heat transmission coefficients for fluid and surface combinations like Water to Air, Water to Water, Air to Air, Steam to Water and more.

### Overall Heat Transfer Coefficients

Walls or heat exchangers - calculate overall heat transfer coefficients.

Heat transfer due to emission of electromagnetic waves is known as thermal radiation.

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