Details:HeatConductivityMoistureDependent - Versionsgeschichte

Barbara: /* Heat Conductivity, Moisture-dependent */

2009-03-27T11:32:51Z

Heat Conductivity, Moisture-dependent

← Nächstältere Version		Version vom 27. März 2009, 13:32 Uhr
Zeile 18:		Zeile 18:
	<TABLE>		<TABLE>
	<TR><TD COLSPAN="3">λ(w) = λ<small>o</small>·(1 + b·w/ρ<small>s</small>)</TD></TR>		<TR><TD COLSPAN="3">λ(w) = λ<small>o</small>·(1 + b·w/ρ<small>s</small>)</TD></TR>
	<TR><TD>~~<FONT FACE="SYMBOL">l</FONT>~~(w)</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of moist material</TD></TR>		<TR><TD>λ(w)</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of moist material</TD></TR>
	<TR><TD>~~<FONT FACE="SYMBOL">l</FONT>~~<small>o</small></TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of dry material</TD></TR>		<TR><TD>λ<small>o</small></TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of dry material</TD></TR>
	<TR><TD>~~<FONT FACE="SYMBOL">r</FONT>~~<small>~~ ~~s</small></TD><TD ALIGN="RIGHT">[kg/m³]:</TD><TD>bulk density of dry material</TD></TR>		<TR><TD>ρ<small>s</small></TD><TD ALIGN="RIGHT">[kg/m³]:</TD><TD>bulk density of dry material</TD></TR>
	<TR><TD>b</TD><TD ALIGN="RIGHT">[%/m-%]:</TD><TD>moisture-induced heat conductivity supplement</TD></TR>		<TR><TD>b</TD><TD ALIGN="RIGHT">[%/m-%]:</TD><TD>moisture-induced heat conductivity supplement</TD></TR>
	</TABLE>		</TABLE>
Zeile 35:		Zeile 35:

	<TABLE>		<TABLE>
	<TR ALIGN="CENTER"><TD>Material</TD><TD>Bulk Density</TD><TD>~~<FONT FACE="SYMBOL">l</FONT>~~</TD><TD>b</TD></TR>		<TR ALIGN="CENTER"><TD>Material</TD><TD>Bulk Density</TD><TD>λ</TD><TD>b</TD></TR>
	<TR ALIGN="CENTER"><TD> </TD><TD>[kg/m³]<BR> </TD><TD>[W/mK]<BR> </TD><TD>[%/M.-%]<BR> </TD></TR>		<TR ALIGN="CENTER"><TD> </TD><TD>[kg/m³]<BR> </TD><TD>[W/mK]<BR> </TD><TD>[%/M.-%]<BR> </TD></TR>

Zeile 91:		Zeile 91:
	don't depend very sensitively on the precise values of the heat		don't depend very sensitively on the precise values of the heat
	conductivities, so the difference may be generally negligible		conductivities, so the difference may be generally negligible
	unless you are specifically interested in heat flows.		unless you are specifically interested in <I>heat</I> flows.
	</P>		</P>

Barbara: /* Heat Conductivity, Moisture-dependent */

2009-03-27T11:29:48Z

Heat Conductivity, Moisture-dependent

← Nächstältere Version		Version vom 27. März 2009, 13:29 Uhr
Zeile 17:		Zeile 17:

	<TABLE>		<TABLE>
	<TR><TD COLSPAN="3">~~<FONT FACE="SYMBOL">l</FONT>~~(w) = <~~FONT FACE="SYMBOL"~~>l</~~FONT~~>o·(1 + b·w/~~<FONT FACE="SYMBOL">r</FONT>~~<small>~~ ~~s</small>)</TD></TR>		<TR><TD COLSPAN="3">λ(w) = λ<small>o</small>·(1 + b·w/ρ<small>s</small>)</TD></TR>
	<TR><TD><FONT FACE="SYMBOL">l</FONT>(w)</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of moist material</TD></TR>		<TR><TD><FONT FACE="SYMBOL">l</FONT>(w)</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of moist material</TD></TR>
	<TR><TD><FONT FACE="SYMBOL">l</FONT><small>o</small></TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of dry material</TD></TR>		<TR><TD><FONT FACE="SYMBOL">l</FONT><small>o</small></TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of dry material</TD></TR>

Len am 30. September 2008 um 19:04 Uhr

2008-09-30T19:04:35Z

← Nächstältere Version		Version vom 30. September 2008, 21:04 Uhr
Zeile 93:		Zeile 93:
	unless you are specifically interested in heat flows.		unless you are specifically interested in heat flows.
	</P>		</P>

	~~<HR>~~
	~~<TABLE width="100%"><TR>~~
	~~<TD width="40%" align="left"><A HREF="LiquidTransportCoefficients.htm">Previous topic: Liquid Transport Coefficients</A></TD>~~
	~~<TD align="center">Topic 16</TD>~~
	~~<TD width="40%" align="right"><A HREF="DiffusionResistanceFactorMoistureDependent.htm">Next topic: Diffusion Resistance Factor, Moisture-dependent</A></TD>~~
	~~</TR></TABLE>~~

AntretterF: Die Seite wurde neu angelegt: = Heat Conductivity, Moisture-dependent =
The heat conductivity of the dry material is a basic material parameter and thus indi...

2008-03-11T17:02:11Z

Die Seite wurde neu angelegt: = Heat Conductivity, Moisture-dependent = The heat conductivity of the dry material is a basic material parameter and thus indi...

Neue Seite

= Heat Conductivity, Moisture-dependent =

The [[Details:BasicMaterialData|heat conductivity of the
dry material]] is a basic material parameter and thus indispensable.
If, in addition, the dependence of the heat conductivity on the
moisture content must be taken into account, WUFI can optionally
employ a table with the relevant data. WUFI interpolates linearly
between table entries.


If a simple linear dependence of the heat conductivity on the
moisture content is sufficient, a two-line table may be
generated by entering the moisture-induced heat conductivity
supplement. The linear interpolation in this table is then
equivalent to evaluating the formula


<TABLE>
<TR><TD COLSPAN="3">l(w) = lo·(1 + b·w/r s)</TD></TR>
<TR><TD>l(w)</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of moist material</TD></TR>
<TR><TD>lo</TD><TD ALIGN="RIGHT">[W/mK]:</TD><TD>heat conductivity of dry material</TD></TR>
<TR><TD>r s</TD><TD ALIGN="RIGHT">[kg/m³]:</TD><TD>bulk density of dry material</TD></TR>
<TR><TD>b</TD><TD ALIGN="RIGHT">[%/m-%]:</TD><TD>moisture-induced heat conductivity supplement</TD></TR>
</TABLE>


The supplement b gives the fractional increase [in %] of the heat
conductivity per mass-% moisture. Its value depends on the material;
in hygroscopic materials, however, it is largely independent of
their bulk density.


Examples:


<TABLE>
<TR ALIGN="CENTER"><TD>Material</TD><TD>Bulk Density</TD><TD>l</TD><TD>b</TD></TR>
<TR ALIGN="CENTER"><TD> </TD><TD>[kg/m³]  </TD><TD>[W/mK]  </TD><TD>[%/M.-%]  </TD></TR>

<TR ALIGN="CENTER"><TD>cellular concrete</TD><TD>400-800</TD><TD>0.09-0.19</TD><TD>4</TD></TR>

<TR ALIGN="CENTER"><TD>lime silica brick</TD><TD>1800</TD><TD>0.7</TD><TD>8</TD></TR>

<TR ALIGN="CENTER"><TD>expanded clay concrete, pumice concrete</TD><TD>1400-1800</TD><TD>0.5-1.0</TD><TD>4</TD></TR>

<TR ALIGN="CENTER"><TD>light-weight concrete with EPS aggregate</TD><TD>300-900</TD><TD>0.07-0.28</TD><TD>3</TD></TR>

<TR ALIGN="CENTER"><TD>normal concrete</TD><TD>2300</TD><TD>1.3-1.5</TD><TD>8</TD></TR>

<TR ALIGN="CENTER"><TD>wood</TD><TD>400-700</TD><TD>0.08-0.15</TD><TD>1.5</TD></TR>
</TABLE>


In organic insulation materials, there is in general no linear
relationship between the heat conductivity and the moisture content.


In this context, 'heat conductivity of moist materials' means
exclusively the influence of stationary water on heat transport.
Water vapor diffusion with phase change (evaporation and condensation
of water) also contributes to heat transport, but this is allowed
for by separate terms in the transport equations. However, since
in the standard measurement techniques this effect of water vapor
diffusion is usually included, results of measurements in
the plate apparatus for permeable materials (e.g. mineral wool)
have to be regarded with caution.


During the calculation WUFI performs iterations where it samples
small regions of the tabulated curve. Very sharp bends in the curve
may throw the iteration off and thus impede its convergence. In
such a case, the curve should be smoothed by inserting additional
points. A large number of entries may slow the search in the
table, however.


Please note that design values, such as the data given in
German Standard DIN 4108, may already contain the contribution
of a typical water content and, if so, are not strictly dry values. 
If you want to perform the calculation with a constant (i.e. not
moisture-dependent) heat conductivity (for example because you have
no detailed data on the moisture-dependence), you may use these
design values to allow for moisture content at least in a crude
approximation. However, if you explicitly use a table of
moisture-dependent heat conductivities, you should make sure that
the value for moisture content = 0 is really the dry value.


On the other hand, hygrothermal simulations (in particular the
resulting moisture contents and distributions) usually
don't depend very sensitively on the precise values of the heat
conductivities, so the difference may be generally negligible
unless you are specifically interested in heat flows.


<HR>
<TABLE width="100%"><TR>
<TD width="40%" align="left"><A HREF="LiquidTransportCoefficients.htm">Previous topic: Liquid Transport Coefficients</A></TD>
<TD align="center">Topic 16</TD>
<TD width="40%" align="right"><A HREF="DiffusionResistanceFactorMoistureDependent.htm">Next topic: Diffusion Resistance Factor, Moisture-dependent</A></TD>
</TR></TABLE>

Details:HeatConductivityMoistureDependent - Versionsgeschichte

Barbara: /* Heat Conductivity, Moisture-dependent */

Barbara: /* Heat Conductivity, Moisture-dependent */

Len am 30. September 2008 um 19:04 Uhr

AntretterF: Die Seite wurde neu angelegt: = Heat Conductivity, Moisture-dependent = The heat conductivity of the dry material is a basic material parameter and thus indi...

AntretterF: Die Seite wurde neu angelegt: = Heat Conductivity, Moisture-dependent =
The heat conductivity of the dry material is a basic material parameter and thus indi...