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<DIV id=idOWAReplyText74319 dir=ltr>
<DIV dir=ltr><FONT face=Arial color=#000000 size=2>When I was with Virginia
Tech. We built a model of a double skin facade similar to the <FONT
face="Times New Roman" size=3>Commerze Bank in Frankfurt window on a test cell
and made field measurements. The air circulation due to temperature difference
was not a big factor. </FONT></FONT></DIV>
<DIV dir=ltr>Dr. H. Abaza</DIV></DIV>
<DIV dir=ltr><BR>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> bldg-sim@gard.com on behalf of Gaurav
Mehta<BR><B>Sent:</B> Thu 1/12/2006 8:53 AM<BR><B>To:</B>
bldg-sim@gard.com<BR><B>Subject:</B> [bldg-sim] Insect screens on restricting
flow<BR></FONT><BR></DIV>
<DIV>
<DIV><FONT face="Book Antiqua">
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman">Ian,</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P><FONT face="Times New Roman">
<DIV dir=ltr><FONT face=Arial size=2>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"></FONT></FONT><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman">You
raised a very good point. Here are some of the things that I would like to
share and I would appreciate some input myself:</FONT></P></DIV>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman">1. You wrote:</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">[I'm concerned about insect screens
affecting the buoyancy driven airflow for a double skin façade.]</SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman">Dr.
Karl Gertis (director of the Fraunhofer Institute of Building Physics in
Stuttgart, Germany) provides a critical review of double-skin façades in one of
his article and cites some problems in the literature regarding research related
to Glass Double Facade e.g. “<I>window insect screens cannot be used with
natural ventilation because the airflow is too weak to overcome the pressure
loss over the air filter.</I>”<I></I></FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman">For
more information about the article please go to the following link:</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><A
href="http://gaia.lbl.gov/hpbf/perfor_c.htm">http://gaia.lbl.gov/hpbf/perfor_c.htm</A></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman">2. You wrote:</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">[I was wondering if anyone new of
some papers that have covered the airflow properties of insect screens or can
give me some information off hand.]</SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman"
size=3> Jun Tanimoto,
Jun and Kimura, Ken-ichi (1997), <I>Simulation study on an air flow window
system with an integrated roll screen</I>, </FONT><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Energy and Buildings
26(3):
317-325.</SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman">There are a few sources that also deal with the effect of
insect screen on airflow but they are specific to <U>wind driven</U> natural
ventilation. </FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt 0.5in; TEXT-INDENT: -0.5in"><FONT
face="Times New Roman"><SPAN> </SPAN></FONT><FONT
face="Times New Roman">Swami, M.V. and Chandra, S. (1988),<I> Correlations for
pressure distribution on buildings and calculation of natural ventilation
airflow</I>, ASHRAE Transactions, Vol. 94, Part 1, pp 243-266.</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt 0.5in; TEXT-INDENT: -0.5in"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman">This
paper provides a procedure for determining ventilation rates based on the
Vickery algorithm (1983), however, assumption inherent in this procedure is that
there is no stack effect.</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"> </SPAN><FONT
face="Times New Roman"> </FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt 0.5in; TEXT-INDENT: -0.5in"><FONT
face="Times New Roman"><SPAN>
</SPAN>Givoni, B. (1981), <I>Man, Climate and Architecture</I>, New York: Van
Nostrand Reinhold.</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN><FONT
face="Times New Roman">
</FONT></SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman">On
pp 304 Section 15.8 Givoni discusses the effect of fly-screens on ventilation.
He quotes van Straaten, the decrease in total airflow, caused by a 16 mesh, 30
gauge wire screen is about 60% and 50% when the wind speeds are respectively 1.5
and 2 mph and only about 25% when the wind speed is 10 mph.</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt 0.5in"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt 0.5in"><FONT
face="Times New Roman">Straateen, J. F. van, (1967), <I>Thermal performance of
buildings</I>, Elsevier Publishing Co Ltd</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman">3. You wrote:</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">[I'm also wondering how to
incorporate their effects on the flow by use of discharge coefficients and
pressure loss coefficients.]</SPAN></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </P><FONT
face="Times New Roman">
<P class=MsoNormal style="MARGIN: 0in 0in 0pt 0.5in"><FONT
face="Times New Roman">Andersen, Karl T. (1995), <I>Theoretical considerations
on natural ventilation by thermal buoyancy,</I> ASHRAE Trans. 1995, Vol.101,
Part 2, Paper number SD-95-14-1, 1103-1117</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman">For
abstract please visit the following link:</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><A
href="http://resourcecenter.ashrae.org/store/ashrae/newstore.cgi?itemid=17248&view=item&categoryid=452&categoryparent=452&page=1&loginid=1357156"><FONT
face="Times New Roman">http://resourcecenter.ashrae.org/store/ashrae/newstore.cgi?itemid=17248&view=item&categoryid=452&categoryparent=452&page=1&loginid=1357156</FONT></A></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT face="Times New Roman">In
the section ‘coefficients of interest’ the author discusses velocity,
contraction, discharge, and resistance coefficients and may provide insight into
the effect of insect screen on airflow, however, the author does not directly
relate it to the insect screen.</FONT></P></FONT>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman">There is a gap in the computation of natural ventilation
research especially in terms of discharge coefficients and pressure loss
coefficients as Ansyley (1999) and Linden (1999) point out that the computation
of natural ventilation lacks experimental data and borrows the discharge
coefficient and flow resistance of openings derived from data traditionally used
for fluid flow in pipes and resistance values traditionally used in computation
of mine ventilation. <SPAN> </SPAN></FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt; TEXT-INDENT: 0.5in"><FONT
face="Times New Roman">Ansyley R. (1999), <I>Unresolved Issues in Natural
Ventilation for Thermal </I></FONT><FONT face="Times New Roman"><I>Comfort,
</I>HybVent Forum’99</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt; TEXT-INDENT: 0.5in"><FONT
face="Times New Roman"></FONT> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt 0.5in"><FONT
face="Times New Roman">Linden, P.F, (1999), <I>Fluid Mechanics of Natural
Ventilation, </I>Annu. Rev. Fluid Mech. 1999. 31:201–38</FONT></P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"><I><FONT
face="Times New Roman"></FONT></I> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt">Best regards,</P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt">Gaurav Mehta</P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"> </P>
<P class=MsoNormal style="MARGIN: 0in 0in 0pt"> </P></FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial"><B>From:</B> <A
title=Ian.Doebber@arup.com href="mailto:Ian.Doebber@arup.com">Ian Doebber</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=bldg-sim@gard.com
href="mailto:bldg-sim@gard.com">bldg-sim@gard.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, January 11, 2006
15:28</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [bldg-sim] Insect screens on
restricting flow</DIV>
<DIV><BR></DIV>
<P><FONT face=Arial size=2>I'm concerned about insect screens affecting the
buoyancy driven airflow for a double skin façade. I was wondering if
anyone new of some papers that have covered the airflow properties of insect
screens or can give me some information off hand. I'm also wondering how
to incorporate their effects on the flow by use of discharge coefficients and
pressure loss coefficients. </FONT></P><BR>
<P><FONT face=Arial size=2>Thanks</FONT> </P>
<P><FONT face=Arial size=2>Ian Doebber</FONT> <BR><FONT face=Arial
size=2>Graduate Mechanical Engineer</FONT> <BR><FONT face=Arial
size=2>Arup</FONT> <BR><FONT face=Arial size=2>901 Market Street Suite 260 San
Francisco CA 94103</FONT> <BR><FONT face=Arial size=2>tel: 415-946-0292</FONT>
<BR><FONT face=Arial size=2>fax: 415-957-9096</FONT> <BR><FONT face=Arial
size=2>cell: 415-613-4314</FONT> <BR><A
href="mailto:ian.doebber@arup.com"><U><FONT face=Arial color=#0000ff
size=2>ian.doebber@arup.com</FONT></U></A> <BR><A
href="file://www.arup.com"><U><FONT face=Arial color=#0000ff
size=2>www.arup.com</FONT></U></A> </P><PRE>____________________________________________________________
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