Given: Thermal conductivity of EPDM, λ1 = 0.25 W/K·m.
Thermal conductivity of insulation panel, λ2 = 0.035 W/K·m.
Thermal conductivity of soft wood λ3 = 0.13 W/K·m.
Thermal conductivity of aluminium λ4 = 160 W/K·m.
Problem: Calculate two-dimensional thermal conductance L2D in accordance with ISO 10077-2:2012*.
(Reference thermal conductance L2D = 0.408 W/(m*K) )
Solution: Air contact surface thermal resistance Rs is caused by convention mechanism of heat transfer (contrary to conductivity mechanism in case of two solid bodies in contact).
The convection coefficient value is reciprocal to the surface resistance value:
α20 = 1/0.13 W/(K·m2),
α0 = 1/0.04 W/(K·m2).
Thermal conductivities of air gaps are adjusted to include the convection and radiation heat transfers in real situation, and correlated with the actual temperatures on the gap contours according to the recommendation of ISO 10077-2:2012. Equivalent air gap conductivity calculations are automated in the accompanying Excel spreadsheet.
Results: Heat flux and temperature distribution in frame section profile:
Two-dimensional thermal conductance L2D = Heat flux / Temperature difference = 8.32 / 20 = 0.416 W/(m*K).
Difference between the calculated and reference values is less than 3%. This simulation accuracy complies with the requirements of ISO 10077-2:2012.