Fouling and Reduced Heat Transfer in Heat Exchangers

The heat-transfer in a heat exchanger is reduced by fouling

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 the deposit (m2K/W)

Ud = thermal conductance of heat exchanger after fouling (W/m2K)

U = thermal conductance 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)

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