To give a value for the specified temperature or specified flux or convective flux for the STL pipe walls, do we enter the values at the fluid’s pane or solid’s pane.
I don’t understand how do I input the value for the transfer coefficient for convective flux because the units are in /m, instead of W/m^2K. A lot of values use the latter units so how do I convert them to /m so that I can enter the values correctly.
Many thanks,
Nabil
Hi @Sheikh_Nabil, sorry for the delayed response
1) To give a value for the specified temperature or specified flux or convective flux for the STL pipe walls, do we enter the values at the fluid’s pane or solid’s pane?
The values in the fluid pane are used for solving the boundary equations for the fluid elements. The values in the solids pane are used for the solids elements. You should specify both. You can enter different values in each pane if needed.
2) I don’t understand how do I input the value for the transfer coefficient for convective flux because the units are in /m, instead of W/m^2K.
As the help text states (this is for the gas/fluid phase, similar holds for the solids), the coefficient Hw is
Gas phase heat transfer coefficient Hw in diffusion boundary condition: dTg/dn + Hw(Tg ‑ Tref) = C where n is the fluid‑to‑wall normal.
dT/dn has units of Kelvin per meter, and Tg - Tref has units of Kelvin, so Hw must have units of 1/m to make the units work out.
This formulation is different from the conventional heat transfer coefficient (h) which appears in Newton’s cooling law (q = h·ΔT) and has units of [W/(m²·K)].
The relationship between this Hw [1/m] and the conventional heat transfer coefficient h [W/(m²·K)] would involve the thermal conductivity k [W/(m·K)] of the fluid:
Hw = h/k
Hope this helps,
– Charles
