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<DIV>Even a 2 node model is not very good, because space temperatures vary in 3 space. The workaround in eQUEST is effectively a 2 node model, using the return plenum as the second node. You put a portion of the solar, lighting, equipment and people sensible gains into the return plenum. These fractions can be based upon CFD models or widely published rules of thumb. The next problem is keeping the psychrometrics correct at the same time as you keep the fan energy correct, since eQUEST doesn't have a 2-path supply air system. As you know, in dehumidifying climates, the most common way of putting air into the floor plenum at the right temperature while maintaining humidity control is to bypass some return (not mixed) air around the cooling coil, while continuing to operate that coil at a sufficiently low temperature to maintain required space dewpoint. Mixing the return air with the air off the coil doesn't raise the dew point temperature much, even though it raises the supply air dry bulb temperature from 52-53 DegF up to the desired 60-62 DegF level. The workaround for this is to use the correct coil temperature to maintain dewpoint, ignore the bypassed return, which is just being pumped around in a circle anyway, and to decrease the fan efficiency to take into account the fan energy required to pump that recirculated air around in a circle. The air system is then modelled as a CAV system, VAV system, or a VAV reheat system, or a fan powered terminal system, depending upon how the perimeter is handled. This two workarounds leave one last problem, which is the heat transfer acrros the floor slab between the return plenum and the supply plenum. You can take a stab at this with the duct conduction heat gain capability. This procedure is insufficiently precise to do anything more than put a swag on this effect. The best bet is to put in a duct heat transfer coefficient that would give a 3 to 4 DegF rise to the supply air temperaure at full volume, which is consistent with the magnitude of that heat transfer in a number of built projects. <BR></DIV>
<DIV>Having said all that, these workarounds are only good enough to do LEED qualifications or code compliance, not for design optimization. The only tool for doing design optimization is CFD, using models that simultaneously include the room, supply and return plenum and model heat transfer effects among these three.<BR><BR>-----Original Message----- <BR>From: Vaibhav Potnis <VAIPOTNIS@HOTMAIL.COM><BR>Sent: Aug 25, 2005 3:33 PM <BR>To: BLDG-SIM@gard.com <BR>Subject: [BLDG-SIM] Heat Stratification model in eQuest <BR><BR></DIV><ZZZHTML>
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<P>Suneel,</P>
<P>What purpose do you need to factor the stratification? If you need to check space temperatures, you should look at Eplus or CFD. If you just need to reduce the volume of conditioned air, you can use eQuest.</P>
<P>Thanks,<BR></P>
<DIV>
<P>Vaibhav Potnis <BR>Green Building Services</P>
<P>Contact - 503-715-6113<BR><A href="mailto:vaipotnis@hotmail.com">vaipotnis@hotmail.com</A></P>
<P><A href="http://www.greenbuildingservices.com">www.greenbuildingservices.com</A></P>
<P> </P></DIV>
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From: <I>"Joe Huang" <yjhuang@lbl.gov></I><BR>Reply-To: <I>yjhuang@lbl.gov</I><BR>To: <I><BLDG-SIM@gard.com></I><BR>Subject: <I>[BLDG-SIM] Heat Stratification model in eQuest</I><BR>Date: <I>Thu, 25 Aug 2005 11:44:03 -0700</I><BR><BR><ZZZMETA content="Microsoft SafeHTML" name="Generator">
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<DIV><FONT face=Arial size=2>Vikram, others,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>EnergyPlus models displacement ventilation or other underfloor systems with significant temperature stratification with a two-node room model developed by Paul Linden and others at UCSD, and Phil Haves at LBNL.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Joe</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>----- Original Message ----- </DIV>
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<DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A title=VSami@lasarchitect.com href="mailto:VSami@lasarchitect.com">Vikram Sami</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> Thursday, August 25, 2005 7:11 AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [BLDG-SIM] Heat Stratification model in eQuest</DIV>
<DIV><BR></DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2>Suneel,</FONT></SPAN></DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2>As far as I know, you cannot model stratification in eQUEST. There is a workaround with modelling underfloor systems (Dan Nall & Marlin Addison have done some work in this area - check the link here, or just google their names)</FONT></SPAN></DIV>
<DIV><SPAN class=978050414-25082005>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2><A href="http://www.doe2.com/Download/Docs/Addison-Nall_UnderfloorAirDistPaper_Rev1.pdf">http://www.doe2.com/Download/Docs/Addison-Nall_UnderfloorAirDistPaper_Rev1.pdf</A></FONT></SPAN></DIV></SPAN></DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2>I am not sure that this is what you are looking for though. If you are modelling only stratification, you probably want to use CFD.</FONT></SPAN></DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2>I am not familiar with Energy Plus, so I dont know if it does stratification modelling, but that might be an option thats cheaper than cfd.</FONT></SPAN></DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=978050414-25082005><FONT face=Arial color=#0000ff size=2><A href="http://www.doe2.com/Download/Docs/Addison-Nall_UnderfloorAirDistPaper_Rev1.pdf"></A></FONT></SPAN> </DIV>
<DIV><SPAN class=978050414-25082005></SPAN> </DIV>
<DIV><SPAN class=978050414-25082005></SPAN><FONT face=Garamond><STRONG>Vikram Sami,</STRONG> LEED AP</FONT><B></B> <BR><FONT face=Garamond>Direct Phone 404-253-1466 | Direct Fax 404-253-1366</FONT> </DIV>
<P><B><FONT face=Garamond color=#800000>L</FONT><FONT face=Garamond color=#800000 size=2>ORD</FONT><FONT face=Garamond color=#800000>, A</FONT><FONT face=Garamond color=#800000 size=2>ECK</FONT><FONT face=Garamond color=#800000> & S</FONT><FONT face=Garamond color=#800000 size=2>ARGENT</FONT><FONT face=Garamond color=#800000> A</FONT><FONT face=Garamond color=#800000 size=2>RCHITECTURE</FONT><BR></B><FONT face=Garamond size=2>Responsive Design</FONT> <FONT face=Symbol size=1>·<FONT face="Courier New"></FONT></FONT> <FONT face=Garamond size=2>Technological Expertise</FONT> <FONT face=Symbol size=1>·<FONT face="Courier New"></FONT></FONT> <FONT face=Garamond size=2>Exceptional Service</FONT> <BR><FONT face=Garamond color=#000000>www.lordaecksargent.com</FONT> </P>
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<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Tahoma size=2>-----Original Message-----<BR><B>From:</B> BLDG-SIM@gard.com [mailto:BLDG-SIM@gard.com]<B>On Behalf Of </B>Suneel Gupta<BR><B>Sent:</B> Thursday, August 25, 2005 8:17 AM<BR><B>To:</B> BLDG-SIM@gard.com<BR><B>Subject:</B> [BLDG-SIM] Heat Stratification model in eQuest<BR><BR></FONT></DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2>I am modeling energy use within an airplane hanger. </FONT></SPAN></DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2>Does anyone have any experience/recommendations on how to model the heat stratification within the building space using eQuest?</FONT></SPAN></DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2>Apologies if this is a repeat question.</FONT></SPAN></DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2>Thanks</FONT></SPAN></DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=208511212-25082005><FONT face=Arial size=2>Suneel Gupta</FONT></SPAN></DIV><PRE>==================
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