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Pseudo film coefficient of ambient fluid at ground level

When a pipe is fully buried, a term, the pseudo film coefficient, $h_{amb}$, is modeling the heat transfer by convection at the sea/soil interface.

Symbol
$h_{amb}$
Unit
W/(K.m$^2$)
Formulae
$\frac{D_{ext}}{D_{soil}} h_{ext}$Carslaw & Jaeger
$\frac{D_{ext}}{D_{ref}} h_{ext}$Morud & Simonsen / Ovuworie / OTC 23033
$\frac{\mathrm{Nu}_w k_w}{D_{soil}}$fully buried
Related
$D_{ext}$
Overall outer diameter of pipe [m]
$D_{ref}$
Reference diameter for determination of OHTC [m]
$D_{soil}$
Outer diameter of soil layer [m]
$h_{ext}$
External heat transfer coefficient [W/(K.m$^2$)]
$k_w$
Thermal conductivity of water [W/(m.K)]
$\mathrm{Nu}_w$
Nusselt number, surface to water
Used in
$\mathrm{Bi}_g$
Biot number of the ground
$e_{soil}$
Thickness of soil layer [m]
$U_{buried}$
OHTC of fully buried pipe [W/(K.m$^2$)]
$U_{ground}$
OHTC of part of pipe in contact with ground [W/(K.m$^2$)]