Overall Heat Transfer Coefficients in Heat Exchangers
Representative values of the overall heat transfer coefficients in heat exchangers.
Note that the overall heat transfer coefficient ranges from about 10 W/m2· °C for gas-to-gas heat exchangers to about 10,000 W/m2· °C for heat exchangers that involve phase changes. This is very typical since gases have very low thermal conductivities, and phase-change processes involve very high heat transfer coefficients.
|Type of heat exchanger||U, W/m2 · °C*|
|Water-to-gasoline or kerosene||300–1000|
|Steam-to-light fuel oil||200–400|
|Steam-to-heavy fuel oil||50–200|
|Freon condenser (water cooled)||300–1000|
|Ammonia condenser (water cooled)||800–1400|
|Alcohol condensers (water cooled)||250–700|
|Water-to-air in finned tubes (water in tubes)||30–60†
|Steam-to-air in finned tubes (steam in tubes)||30–300†
* Multiply the listed values by 0.176 to convert them to Btu/h · ft2 · °F.
† Based on air-side surface area.
‡ Based on water- or steam-side surface area.