Coefficient for convection to air for one single cable, three cables spaced and three cables trefoil are given in the book 'Kabel und Leitungen für Starkstrom' by L. Heinhold, 5th edition 1999. The book does not give values for 2 cables. It was assumed that the values are identical to 3 cables.
|2||1.000||3 cables spaced||equal for horizontal and vertical spacing|
|3||0.833||3 cables touching||equal for horizontal and vertical spacing|
|4||0.667||3 cables touching trefoil|