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Pipes and Cylinders - Conductive Heat Loss

Conductive heat losses through cylinder or pipe walls.

Cylinder or pipe - heat loss

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/moC, 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)

heat loss through pipe or cylinder wall

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/moC, 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)

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