Conductive heat loss through a cylinder or pipe wall can be expressed as
q = 2 π k (ti - to) / ln(ro / ri) (1)
where
q = heat transferred per unit time per unit length of cylinder or pipe (W/m, Btu/hr ft)
k = thermal conductivity of the material (W/m.K or W/m oC, Btu/(hr oF ft2/ft))
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)
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