Given: Thermal conductivity of PVC, λ1 = 0.17 W/K·m.
Thermal conductivity of the gas filling, λ2 = 0.034 W/K·m.
Problem: Calculate the two-dimensional thermal conductance L2D of the frame in accordance with ISO 10077-2:2012*.
(Reference thermal conductance L2D = 0.207 W/(m*K) )
Solution: Boundary conditions on the upper and bottom frame surfaces are thermal convection. The convection coefficient value is reciprocal to the surface resistance value Rs provided in the test case description:
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 distribution in the PVC shutter profile is shown below:
Two-dimensional thermal conductance L2D = Heat flux / Temperature difference = 4.139 / 20 = 0.207 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.