NoteDuring development of the IEC method, we identified an error in the publications used for the two methods by Anders and Chippendale. The error is considerable and giving optimistic results. We have corrected this in our implementation in deviation to the referenced publications.
Explanation: In the publications by Anders and Chippendale, the equation for heat transfer coefficient for forced convection uses a factor of 2, meaning only half the outer diameter of the duct is used as characteristic length.The publication by Chippendale refers to a publication by Anders from 1996, which was the basis for our implementation of Anders method. In the publication from 1996, Anders refers to his own publication D.2.8 'Rating of cables on riser' from Jicable 1995. In there, the factor 2 is used and it is stated the heat transfer coefficient can be calculated as described in Holman (1990) or Incropera and Dewitt (1990). We do not have the edition from 1990 but in the 6th edition from 2011 of the book 'Introduction to Heat Transfer' by F.P. Incropera and D.P. Dewitt, the equation 7.44 does not consider this factor of 2.
| $\frac{\mathrm{Nu}_{ext} k_{gas}}{L_d}$ | natural convection (no wind) |
| $\frac{\mathrm{Nu}_{ext} k_{gas}}{D_{do}}$ | forced convection due to wind >0.5 m/s |
| $\left({h_{nat}}^2+{h_{for}}^2\right)^{0.5}$ | natural and forced convection at low wind speed≤0.5 m/s |
| $\frac{k_{gas} c_{Nu,r}}{L_d} {\mathrm{Ra}_{ext}}^{n_{Nu,r}}$ | natural convection Chippendale, IEC 60287 |
| $\operatorname{max}\left(h_{nat}, h_{for}\right)$ | higher heat transfer coefficient from natural or forced convection (IEC 60287) |
