Overview of thermal couplings

Here is a list of the types of thermal couplings discussed up to here. A thermal conductance is defined as total Watts per Kelvin temperature difference [W/K] over a thermal interface. The heat transfer coefficient [W/(m2K)] takes surface area into account.

Heat transfer method Thermal conductance [W/K] Heat transfer coefficient [W/(m2K)] Condition
Conduction TC = (k A) / L h = k / L unidirectional conduction
(over length L, cross-section A)
Convection TC = A hc h = hconv Typical value for laminar water flow:
hconv= 1000[W/(m2K)]
Radiation h1 = TC / A1
h2 = TC / A2
Linearized: Valid for small deviations from nominal temperature Tnom
Contacting surfaces

"dry" contact: TC = A hcontact


gap material: TX = A kfill / d
(gap height d, filler conductivity kfill)

h = hcontact Typical value for dry contact at  moderate pressure:
hcontact= 100 - 1000[W/(m2K)]