Overall Heat Transfer Coefficients for some common Fluids and Heat Exchanger Surfaces

Average overall heat transmission coefficients for some common fluids and surface combinations as Water to Air, Water to Water, Air to Air, Steam to Water and more

The overall heat transfer coefficient can be used to calculate the total heat transfer through a wall or heat exchanger construction. The overall heat transfer coefficient depends on the fluids and their properties on both sides of the wall, and the properties of the wall and the transmission surface.

For practically still fluids - average values for the overall heat transmission coefficient through different combinations of fluids on both sides of the wall and type of wall - can be found in the table below:

FluidTransmission SurfaceFluidOverall Heat Transmission Coefficient
(Btu/ft2 hr oF)(W/m2 K)
Water Cast Iron Air or Gas 1.4 7.9
Water Mild Steel Air or Gas 2.0 11.3
Water Copper Air or Gas 2.3 13.1
Water Cast Iron Water 40 - 50 230 - 280
Water Mild Steel Water 60 - 70 340 - 400
Water Copper Water 60 - 80 340 - 455
Air Cast Iron Air 1.0 5.7
Air Mild Steel Air 1.4 7.9
Steam Cast Iron Air 2.0 11.3
Steam Mild Steel Air 2.5 14.2
Steam Copper Air 3.0 17
Steam Cast Iron Water 160 910
Steam Mild Steel Water 185 1050
Steam Copper Water 205 1160
Steam Stainless Steel Water 120 680
  • 1 Btu/ft2 hr oF = 5.678 W/m2 K = 4.882 kcal/h m2 oC - Unit Converter

Note that these coefficients are very rough. They depends on the fluid velocities, their viscosity, the condition of the heating surfaces, the size of the temperature differences and so on. For exact calculations - always check manufacturing data.

Related Topics

  • Steam and Condensate - Steam & condensate properties - capacities, pipe sizing, systems configuration and more
  • Heating - Heating systems - capacity and design of boilers, pipelines, heat exchangers, expansion systems and more
  • Thermodynamics - Thermodynamics of steam and condensate applications
  • Heat Loss and Insulation - Steam and condensate pipes - heat loss uninsulated and insulated pipes, insulation thickness and more
  • Thermodynamics - The effects of work, heat and energy on a system

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