1D:Dialog MaterialData

Dialog: Material Data

In this subdialog you can enter, edit or view the material data for the highlighted layer.
Version notice: entering and editing material data is only available in WUFI Pro.

For a detailed discussion of the material data, please consult the reference: Material Data.

• "Layer/Material Name":

The name of the current material, as defined in the assembly. Use the drop-down list to switch between the materials of the current assembly without closing and reopening this dialog.
 

• "Basic Values"
  • "Bulk Density [kg/m³]",
  • "Porosity [m³/m³]",
  • "Specific Heat Capacity, Dry [J/kgK]",
  • "Thermal Conductivity Dry [W/mK]",
  • "Water Vapor Diffusion Resistance Factor [-]":
    

These basic material data are required as a minimum for a calculation.
 

• "Optional Parameters":
  

Some of the material data in the following section "Optional Data" are difficult to acquire, but WUFI offers means to approximate or generate them from standard data which can be collected more easily. These standard data are then "Optional Parameters" which may be required, depending on the settings in the "Optional Data" dialog.
 
The optional parameters are discussed in the respective topics of the following section:
 

• "Optional Data":
  

Enter the optional material data in these tables (if required).

 

The optional material data comprise the moisture storage function of the material, the liquid transport coefficients, the moisture-dependent thermal conductivity and the moisture-dependent vapor diffusion resistance factor.

 

The optional data are always entered in tables. However, you can have WUFI automatically create some of these tables by entering other related data from which the tables can be generated.

 

"Moisture Storage Function":

Enter the moisture storage function of the material, i.e. the moisture contents [kg/m³] which result from exposition to air with various relative humidities (0..1).
If detailed tabulated data are not available, but the moisture retention function of the material can be adequately described by an approximation function, you can check the option "Approximate" and enter

• the sorption moisture corresponding to 0.8 RH, w80 ("Reference Water Content [kg/m³]", nowadays determined according to German standard DIN 52620) and
  
• the "Free Water Saturation [kg/m³]" wf

in the additional table "Optional Parameters". WUFI then uses an analytical moisture storage function which passes through these two points and zero.

 

For non-hygroscopic materials, just leave the table of the moisture storage function empty. For numerical reasons, however, WUFI needs a defined moisture storage function; it then internally uses a default function which allows for the very low sorption moisture of non-hygroscopic materials.

 

"Liquid Transport Coefficient - Suction"

"Liquid Transport Coefficient - Redistribution":

Enter the liquid transport coefficients in this table - separately for suction and redistribution.

 

If the liquid transport coefficients for the material at hand are not known, you can have WUFI automatically generate a table by estimating the coefficients from the water absorption coefficient (A-value) which is known for most materials or at least easily measurable.

 

To this end, check the option "Generate" and enter the A-value in the additional table "Optional Parameters" (in [kg/m²√s]; the relevant German standard uses the non-SI units [kg/m²√h]. Division by 60 converts such values to SI). WUFI automatically generates a three-line table with the corresponding estimated liquid transport coefficients.

 

Please note that only a rough estimate is possible which proves successful in many cases, but which is not necessarily useful for all materials. Especially, there may be inaccuracies in the shape of the suction profiles. Generating is just meant to be some assistance; you should not blindly rely on it. Future WUFI versions are planned to offer more sophisticated methods.

 

Remarks on generating:

The estimate of the liquid transport coefficients from the A-value also uses the moisture contents w80 and wf. If the moisture storage function is being approximated from w80 and wf (see above), the two values are directly taken from these two entries; otherwise they are calculated from the corresponding table - by interpolation, if necessary.

 

If no moisture storage function has been defined as yet, generating is not possible - the table remains empty (but you can already enter the A-value).

 

If the moisture storage function is modified after generating, the generated table adapts automatically. Please note, therefore, that modification of a material property can also change another property as a side effect without this being immediately evident.

 

If you want to generate both the tables for suction and those for redistribution, both must of course be derived from the same A-value - the two tables therefore share this text box in the "optional Parameters". Note that here, too, a modification of the A-value intended to change one coefficient may entail changes in the other one (if you are generating only one of the tables and editing the other one by hand, the non-generated table is not affected by a modification of the water absorption factor, of course).

 

"Heat Conductivity, Moisture-dependent":

Enter the heat conductivity of the material as a function of its moisture content if you want to allow for this dependence.

 

If you are satisfied with a simple linear dependence of the heat conductivity on the moisture content, you can have WUFI automatically generate a two-line table by entering the moisture-induced heat conductivity supplement.

 

To this end, check the option "Generate" and enter the supplement in the additional table "Optional Parameters" (in [%/m-%]). WUFI automatically generates a two-line table with the heat conductivities resulting for the dry condition and the maximum water content. Heat conductivities for intermediate moisture contents are linearly interpolated during the calculation.

 

Remarks on Generating:

The evaluation of the heat conductivity for maximum water content also uses the basic material properties bulk density, porosity and heat conductivity dry. If these values are modified after generating, the generated table adapts automatically. Please note, therefore, that modification of a material property can also change another property as a side effect without this being immediately evident.

If the required basic material data have not all been defined as yet, generating is not possible - the table remains empty (but you can already enter the supplement).

 

• "Water Vapor Diffusion Resistance Factor, Moisture-dependent":

Enter the diffusion resistance factor of the material as a function of moisture content if you want to allow for this dependence.
 
General remarks on approximating and generating: For all optional material properties - except the diffusion resistance factor - WUFI is holding two tables in memory: one table created by hand (editable), and one generated table (non-editable). You can work on both tables in parallel; which of both is used for the calculation depends on whether the option "Approximate" or "Generate" is activated at the start of the calculation, or not.
 
By activating or deactivating the option, you can switch between the two kinds of tables. The unused table remains inactive in background.
 
You can use the "Copy" button to copy the generated table line by line to the editable table and work on it there by hand.
 

• "Color":

Select the color of the material for the graphical assembly display.
 

• "Typical Built-In Moisture [kg/m³]":

A typical application for WUFI is a calculation to determine the time it takes a newly-built wall to dry out. If a typical initial moisture content for the current material is known, you can enter it here. Assigning the initial moisture contents to the individual layers then only takes one click on a button in the "Initial Conditions" dialog.
 

• "Layer Thickn. [m]":

A quick way to edit the layer thickness without going back to the assembly editor.
 

• "Paste into Material Database":

Opens the "New Material" dialog of the material database which allows you to write the current material data to the material database for quick and easy use in other assemblies.