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# Pipes and Cylinders - Conductive Heat Losses

## Conductive heat losses through cylinder or pipe walls.

### Uninsulated Cylinder or Pipe

Conductive heat loss through the wall of a cylinder or pipe can be expressed as

Q = 2 π L (ti - to) / [ln(r/ ri) / k]                              (1)

where

Q = heat transfer from cylinder or pipe (W, Btu/hr)

k = thermal conductivity of piping material (W/mK or W/m oC, Btu/(hr oF ft2/ft))

L = length of cylinder or pipe (m, ft)

π = pi = 3.14...

to = temperature outside pipe or cylinder (K or oC, oF)

ti = temperature inside pipe or cylinder (K or oC, oF)

ln = the natural logarithm

ro = cylinder or pipe outside radius (m, ft)

ri = cylinder or pipe inside radius (m, ft)

### Insulated Cylinder or Pipe

Conductive heat loss through an insulated cylinder or pipe can be expressed as

Q = 2 π L (ti - to) / [(ln(r/ ri) / k) + (ln(rs / ro) / ks)]                          (2)

where

rs = outside radius of insulation (m, ft)

ks = thermal conductivity of insulation material (W/mK or W/m oC, Btu/(hr oF ft2/ft))

Equation 2 with inside convective heat resistance can be expressed as

Q = 2 π L (ti - to) / [1 / (hc ri ) + (ln(r/ ri) / k) + (ln(rs / ro) / ks)]                          (3)

where

hc = convective heat transfer coefficient (W/m2K)

## Related Topics

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Calculate heat, work, temperature and energy. The thermodynamics of steam and condensate systems. Water and Ice properties.

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## Citation

• The Engineering ToolBox (2009). Pipes and Cylinders - Conductive Heat Losses. [online] Available at: https://www.engineeringtoolbox.com/conductive-heat-loss-cylinder-pipe-d_1487.html [Accessed Day Month Year].

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8.21.8

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