Chapter 1 - Basics

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 methodThermal conductance [W/K]Heat transfer coefficient [W/(m2K)]Condition
ConductionTC = (k A) / Lh = k / Lunidirectional conduction
(over length L, cross-section A)
ConvectionTC = A hch = hconvTypical value for laminar water flow:
hconv= 1000[W/(m2K)]
Radiationh1 = 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 = hcontactTypical value for dry contact at  moderate pressure:
hcontact= 100 – 1000[W/(m2K)]