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<DIV><SPAN class=484325009-24112003><FONT face=Arial color=#0000ff size=2>I am
doing some modelling work on an earth coupled duct<SPAN
class=984405210-24112003> at the moment</SPAN>. I have used CFD (CFX 4) to model
the duct in 3D, including the concrete wall. It has shown that the duct surface
temperature does vary significantly along its length. This variation in the
driving temperature difference is more significant than variations in fluid
temperature would be in a hydronic system, as this temp. diff. is smaller. I
have also done some 2D finite volume calcs that include about 10m <SPAN
class=984405210-24112003>depth </SPAN>of soil. As it is a 2D model it has been
possible to run with weather data for multiple years. This has shown that the
temp. distribution does not reach steady-periodic conditions until several years
have past (about 10 years in my case). The long term rise/fall in temp
depends on the annual balance of heating/cooling loads. This characteristic is
well known in the geothermal heat pump community but it appears often neglected
in air coupled designs.</FONT></SPAN></DIV>
<DIV><SPAN class=484325009-24112003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=484325009-24112003><FONT face=Arial color=#0000ff size=2>I am
keen to hear of the experience of others. I can suggest another reference: F.
Al-Ajmi (2002). Potential cooling of the subsoil environment in dry desert
climate implicated by means of Earth-Air Heat exchanger in domestic dwellings.
PhD Thesis, Loughborough University (UK).</FONT></SPAN></DIV>
<DIV><SPAN class=484325009-24112003><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=484325009-24112003><FONT face=Arial color=#0000ff size=2>Simon
Rees,</FONT></SPAN></DIV>
<DIV><SPAN class=484325009-24112003><FONT face=Arial color=#0000ff size=2>De
Montfort University, UK.</FONT></SPAN></DIV></DIV>
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<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma size=2>-----Original Message-----<BR><B>From:</B> postman@gard.com
[mailto:postman@gard.com] <B>On Behalf Of </B>Hugues Boivin<BR><B>Sent:</B> 21
November 2003 18:11<BR><B>To:</B> BLDG-SIM@gard.com<BR><B>Subject:</B>
[BLDG-SIM] earth-air exchanger (earth channels)<BR><BR></FONT></DIV>
<DIV><FONT face=Arial size=2>Does anyone knows a simulation tool to evaluate
energy savings by earth-to-air exchanger (earth channels) ?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thank you.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Hugues Boivin</FONT></DIV>
<DIV><FONT face=Arial size=2>Mechanical Engineer</FONT></DIV>
<DIV><FONT face=Arial size=2>Laval University</FONT></DIV>
<DIV><FONT face=Arial size=2>GRAP (Groupe de recherche en ambiance
physique)</FONT></DIV><PRE>
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