Form factor

The form factor F was introduced by J. Vermeer in the paper: 'A simple formula for the calculation of the convective heat transfer between conductor and sheath in compressed gas insulated (CGI) cables', 1983 as published in Elektra 87.

A different form factor - for single- and three-core GIL - was introduced by K. Itaka, T. Araki, and T. Hara in the paper: 'Heat Transfer Characteristics of Gas Spacer Cables', 1978.

Symbol
$F_{form}$
Formulae
$\frac{D_{c} \left(- \frac{D_{c}}{D_{comp}} + 1\right)^{2.167}}{\ln{\left(\frac{D_{comp}}{D_{c}} \right)}}$Vermeer1983
$\frac{D_{c}^{0.75}}{\left(\left(\frac{D_{c}}{D_{comp}}\right)^{0.6} + 1\right)^{1.25} \left(\ln{\left(\frac{D_{comp}}{D_{c}} \right)} + 2.2\right)}$Itaka1978, single-core
$\frac{1.0 D_{c}^{0.75}}{\left(\left(\frac{D_{c}}{D_{comp}}\right)^{0.6} + 0.415243646538506\right)^{1.25} \left(\ln{\left(\frac{0.416666666666667 D_{comp}}{D_{c}} \right)} + 2.2\right)}$Itaka1978, three-core
Related
$D_{c}$