Pipes - Insulated Heat Loss Diagrams

The heat loss diagrams below can be used to indicate the heat loss from insulated pipes at various temperature differences. The diagrams are based on

• metal pipes
• fiber glass insulation with thermal conductivity 0.036 W/(mK)
• outdoor condition with moderate wind 9 m/s

A safety factor of 10% is included.

• indoor location - reduce values with 10%
• mineral wool insulation - increase values with 6%
• rigid cellular polyurethane - reduce values by 30%
• Heat loss diagram (W/m)

Pipe Heat Loss - Insulation thickness 80 mm

• 1 W/m = 0.305 W/ft
• 1 ^oC = 1.8 ^oF

Example - Heat Loss from Insulated Pipe Line

100 m of steel pipe with nominal dimension 2 1/2 inches is insulated with 80 mm fiber glass insulation. The temperature of the fluid in the pipe is 90 ^oC and the ambient temperature outside the pipe is 10 ^oC.

From the diagram above - 80 mm fiber glass insulation, temperature difference 80 ^oC and pipe dimension 2 1/2" - the heat loss is approximately 20 W/m.

The heat loss from the whole pipe can be calculated as

(100 m) (20 W/m)

    = 2000 W

Pipe Heat Loss - Insulation thickness 50 mm

Pipe Heat Loss - Insulation thickness 40 mm

Pipe Heat Loss - Insulation thickness 30 mm

Pipe Heat Loss - Insulation thickness 25 mm

Pipe Heat Loss - Insulation thickness 20 mm

Pipe Heat Loss - Insulation thickness 10 mm