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keff (SI unit: W/(m·K)) is the effective thermal conductivity (a scalar or a tensor if the thermal conductivity is anisotropic).
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δp (SI unit: s) is the vapor permeability.
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psat (SI unit: Pa) is the vapor saturation pressure.
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Q (SI unit: W/m3) is the heat source (or sink). Add one or several heat sources as separate physics features. See the Heat Source node, for example.
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This model input does not override the Reference temperature Tref set in the Physical Model section of the physics interface, and that is used to evaluate the reference enthalpy, and a reference density for incompressible nonisothermal flows.
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When Equivalent thermal conductivity is selected (the default), a value for the Effective thermal conductivity keff should be specified directly. The default Effective thermal conductivity is taken From material. For User defined, select Isotropic, Diagonal, Symmetric, or Full based on the characteristics of the thermal conductivity, and enter another value or expression. For Isotropic enter a scalar which will be used to define a diagonal tensor. For the other options, enter values or expressions into the editable fields of the tensor.
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When Dry material thermal conductivity is selected, the effective thermal conductivity is defined as a function of the solid matrix and moisture properties:
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w (SI unit: kg/m3) is the water content given by a moisture storage function.
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Vapor permeability (default) to define directly the vapor permeability δp. The default Vapor permeability is taken From material. For User defined, enter another value or expression.
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See Building Materials Database in the COMSOL Multiphysics Reference Manual for a description of materials containing the thermal and hygroscopic properties required by the Building Material node.
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The Building Material node is defined in the spatial frame. The material properties should be entered in the spatial frame, and the coupling with a moving frame interface is not supported. See Handling Frames in Heat Transfer for more details.
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When Surface-to-surface radiation is activated, the Opacity (Surface-to-Surface Radiation Interface) subnode is automatically added to the entire selection, with Opaque option selected. The domain selection can’t be edited. To set some part of the domain as transparent, add a new Opacity (Surface-to-Surface Radiation Interface) subnode from the context menu (right-click the parent node) or from the Physics toolbar, Attributes menu.
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