Thermal resistance of medium in the duct

Thermal resistance between cable and duct.

The equation for ducts with bentonite filling is based on the conduction shape factor of a cylinder surrounded by an eccentric cylinder of larger radius, refer to Table 5.4 in the book "A Heat Transfer Textbook" by John H. Lienhard IV and V (Phlogiston Press 2008) or to table 3.5 in the book "Heat Transfer - A Practical Approach" by Yunus A. Cengel (2014). It is assumed that the cables are in the duct so that it comes to contact.

$\frac{U_{d}}{D_{eq} \left(0.1 V_{d} + 0.1 Y_{d} \theta_{dm}\right) + 1}$default
$\frac{\rho_{d_{fill}} \operatorname{acosh}{\left(\frac{D_{eq}^{2} + Di_{d}^{2} - \left(- \frac{D_{eq}}{2} + \frac{Di_{d}}{2}\right)^{2}}{2 D_{eq} Di_{d}} \right)}}{2 \pi}$with bentonite filling
Used in
$\Delta \theta_{c}$
OHTC of pipe wall [W/(K.m$^2$)]
Heat Transfer - A Practical Approach by Yunus A. Cengel (2014) Table 3-5