<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style id="owaParaStyle">P {
MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px
}
</style>
</head>
<body fPStyle="1" ocsi="0">
<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">
<p>Leen,</p>
<p> </p>
<p>This depends on whether or not the wind is blowing... or not. ASHRAE used to have tabluated values (still in some textbooks) of R = .17 Btu/ft2-hr-F for winter (15 mph wind) and .25 Btu/ft2-hr-F for summer (7 mph wind). Otherwise, for a vertical surface
it would be .68 for free convection, probably less for a tilted surface, .9 if horizontal heat flow down.
</p>
<p> </p>
<p>Also, radiation can be significant if the surface is facing a cloudless sky. I think Kreider's solar textbook has a equation for sky temperature...which is somewhat complicated by cloud cover, etc.</p>
<p> </p>
<p>Jeff</p>
<div>
<p> </p>
<div><font color="#0000ff" size="2" face="Tahoma">8=! 8=) :=) 8=) ;=) 8=) 8=( 8=) 8=() 8=) 8=| 8=) :=') 8=)8=?<br>
<br>
Jeff S. Haberl, Ph.D.,P.E., FASHRAE..............jhaberl@tamu.edu<br>
<br>
Professor............................................................Office Ph: 979-845-6507<br>
<br>
Department of Architecture.............................Lab Ph:979-845-6065<br>
<br>
Energy Systems Laboratory.............................FAX: 979-862-2457<br>
<br>
Texas A&M University.....................................77843-3581<br>
<br>
College Station, Texas, USA, 77843..................URL:www.esl.tamu.edu<br>
<br>
8=/ 8=) :=) 8=) ;=) 8=) 8=() 8=) :=) 8=) 8=! 8=) 8=? 8=)8=0<br>
</font></div>
</div>
<div style="FONT-FAMILY: Times New Roman; COLOR: #000000; FONT-SIZE: 16px">
<hr tabindex="-1">
<div style="DIRECTION: ltr" id="divRpF52504"><font color="#000000" size="2" face="Tahoma"><b>From:</b> bldg-sim-bounces@lists.onebuilding.org [bldg-sim-bounces@lists.onebuilding.org] on behalf of leen peeters [l.f.r.peeters@gmail.com]<br>
<b>Sent:</b> Saturday, February 11, 2012 1:59 PM<br>
<b>To:</b> bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> [Bldg-sim] exterior convection coefficient for tilted roof<br>
</font><br>
</div>
<div></div>
<div>
<div>Dear,</div>
<div> </div>
<div>can anyone point me to some reference values for exterior convection coefficients for tilted surfaces like a roof?</div>
<div> </div>
<div>Thanks</div>
<div> </div>
<div>Leen</div>
</div>
</div>
</div>
</body>
</html>