Name
The name of the material.
Width
The width of the layer.
Convection Coefficient
The heat transfer coefficient for convective heat transfer across the layer. If the gas layer is adjacent to a blind, the convection coefficient is automatically increased by a factor 4/3. Values of the Convection Coefficient may be calculated for gas cavities of various dimensions and orientations as follows:
1) Calculate the dimensionless quantity GrPr (the product of the Grashof and Prandtl numbers) using:
2) Calculate Calculate the dimensionless Nusselt number Nu using
Heat flow |
|
C |
n |
m |
Horizontal |
GrPr < 200000 |
0.197 |
1/4 |
-1/9 |
|
GrPr > 200000 |
0.073 |
1/3 |
-1/9 |
Up |
GrPr < 7000 |
0.059 |
2/5 |
0 |
|
7000 < GrPr < 320000 |
0.212 |
1/4 |
0 |
|
GrPr > 320000 |
0.061 |
1/3 |
0 |
Down |
|
1.0 |
0 |
0 |
3) If Nu is less than 1.0, set Nu = 1.0.
4) Calculate the heat transfer coefficient h (W/m2K) using
Vapour Diffusion Factor
The specific moisture diffusion resistance of the material (the ratio of the permeability of air (1.92e-10 kg/Ns ) to the permeability of the material).