Fouling
Heat-transfer surface fouling
Also known as HTS fouling, heat transfer fouling.
Heat-transfer surface fouling is the engineering term for tube fouling viewed from the thermodynamic-impact angle. A fouling layer adds a thermal-resistance term in series with the underlying tube wall and the inside/outside film coefficients, reducing the overall heat-transfer coefficient (U) for the tube.
Quantifying the effect
The added fouling resistance R_f is reported in m²·K/W (or h·ft²·°F/Btu in US units). Typical published values:
| Service | R_f (m²·K/W) |
|---|---|
| Clean steam-side | 0 |
| Clean coal-fired boiler gas-side | ~0.0005 |
| Fouled coal-fired economiser | 0.001–0.003 |
| Heavily-fouled biomass / WtE superheater | 0.005+ |
| Acid-dew-point-corroded air heater | severe + corrosion |
Doubling R_f roughly halves the useful heat-transfer coefficient for the surface, with proportional impact on heat rate.
Why sonic horns matter here
Sonic horns keep R_f close to its design value over the operating campaign by preventing the friable-to-bonded transition that drives R_f up. Plants commonly report 1–3% heat-rate improvement on retrofitting horns to a unit with established fouling drift.
Related terms
Related terms
- Tube foulingTube fouling is the umbrella term for deposit accumulation on the gas-side surfaces of boiler and heat-exchanger tubes. Reduces heat transfer, increases ΔP, accelerates corrosion.
- Fouling (general)Fouling is the accumulation of unwanted deposits on process-equipment surfaces. The general umbrella term covering slagging, scaling, coking, sintering and many other specific mechanisms.
- Heat rateHeat rate is the fuel energy required to produce one unit of electrical output, measured in BTU/kWh or kJ/kWh. Fouling on convective surfaces directly degrades heat rate.
- Sonic hornA sonic horn is a pneumatically-driven low-frequency sound emitter (typically 60–400 Hz at 140–180 dB SPL) used to dislodge particulate fouling from boilers, ESPs, baghouses and process vessels.