Theory

The solver's externalWallHeatFluxTemperature condition takes this $h$ as the convective coefficient between the outer surface and the ambient temperature, in series with the shell and insulation resistances (equation (1) of Thermal condition of a wall). Radiation is not included in it: the boundary condition adds radiation separately from the emissivity, so do not include a radiation share in this number unless the emissivity is set very low.

Equations

q_{conv} = \frac{T_w - T_a}{1/h + \sum_i t_i/k_i}

(1)

where	meaning	unit
$q_{conv}$	Convective part of the heat flux	W/m²
$h$	Outer convective coefficient (this setting)	W/(m² K)
$T_w, T_a$	Gas-side wall temperature and ambient temperature	K
$t_i, k_i$	Layer thicknesses and conductivities	m, W/(m K)

Default and rule

Default: 10 W/(m² K) in the box (environment 'Manual h' only)
Rule: 10 W/(m² K) in the box; required for this environment.
Source: The value is passed to the solver's externalWallHeatFluxTemperature condition unchanged.

Valid range > 0

Typical values

Natural convection in air about 3-10, forced convection in air about 10-100 W/(m² K).

Theory

Equations

Default and rule

Valid range > 0

Related 4