<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
@font-face
{font-family:Verdana;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
color:black;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Preformatted Char";
margin:0cm;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";
color:black;}
span.EmailStyle17
{mso-style-type:personal;
font-family:"Calibri","sans-serif";
color:windowtext;}
span.HTMLPreformattedChar
{mso-style-name:"HTML Preformatted Char";
mso-style-priority:99;
mso-style-link:"HTML Preformatted";
font-family:Consolas;
color:black;}
span.EmailStyle20
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 70.85pt 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>If the energy (de)stored between the initial and final state cannot explain the differences, I think there is another possible cause: Type 4 can have quite large energy balance errors when the nodes are “flushed out” during one time step. <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Here is my understanding: <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>If you have 10 nodes and a total volume of 500 L, that means each node holds 50 L of water. Using 0.1 h time steps you cannot have a flowrate through the tank higher than 500 L/h, otherwise you will replace the entire volume of a node within a time step, and the equations used by Type 4 are not valid anymore. This would explain that it works again when you reduce the timestep (with 0.001 h you would need a flowrate of 50000 L/h to “flush” a node out).<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>To my knowledge this problem is specific to Type 4, i.e. it does not affect the Storage tanks in the TESS libraries (Type 534 etc.) – if you have access to them that may be a more practical solution than running 0.001 h timesteps…<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Michaël Kummert<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Polytechnique Montréal<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> trnsys-users-bounces@cae.wisc.edu [mailto:trnsys-users-bounces@cae.wisc.edu] <b>On Behalf Of </b>David BRADLEY<br><b>Sent:</b> Thursday, October 25, 2012 17:34<br><b>To:</b> PARTENAY Vincent<br><b>Cc:</b> trnsys-users@cae.wisc.edu<br><b>Subject:</b> Re: [TRNSYS-users] Type energy balance<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'>Vincent,<br> When you perform an energy balance on a tank, you need to take into account its change in temperature between the beginning and the end of the simulation (output 7 of your Type4). If the tank ends up hotter at the end of the simulation than it was at the beginning, it has stored some energy. If it ends up colder, then it has given up some energy. I would imagine that with 10 nodes, there is some stratification developing in the tank that is not modeled when you have a fully mixed tank (1 node)<br>Best,<br> David<br><br><o:p></o:p></p><div><p class=MsoNormal>On 10/25/2012 09:40, PARTENAY Vincent wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><p class=MsoNormal>Dear all,<o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><span lang=EN-US>Typ4a (Storage tank) allows to model a stratified tank with several temperature nodes. The problem I noticed is that the energy balance of both sides on the tank can vary depending on the chosen timestep :</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>In the attached file, a simplified example, the tank is coupled to an energy production and energy consumption model (very simple in an equation). Thermal losses of the tank is set to zero.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>When I run a simulation with one node (1m height for 0.5m3) for the tank and a timestep of 0.1hr, I get the same energy on both side (see plotter “”Power&NRJ”, Esource = 2659kWh and Eload = 2666kWh), slight difference maybe explained by initial charging period to setpoint temperature.</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>When I run it in the same conditions but with 10 nodes (each 0.1m), these two energy are different ! While I still have 2666kWh for Eload I have 3146kWh !</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>When I run it again reducing the timestep from 0.1hr to 0.001 hr, still with 10 nodes, I get 2666kWh, the energy balance is ok…</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>So, my question is : is it necessary to check before every bigger simulation (that can include lots of tank models) the energy balance of this model for one defined timestep and boundary conditions to the model or is there some rules to predefine adapted discretisation for one given timestep ?</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US>Kind regards,</span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><span lang=EN-US> </span><o:p></o:p></p><p class=MsoNormal><b><span style='font-family:"Verdana","sans-serif"'>Vincent PARTENAY</span></b><o:p></o:p></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Verdana","sans-serif"'>Energies Renouvelables - Département ESE</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt'> </span><o:p></o:p></p><p class=MsoNormal><b><span style='font-family:"Verdana","sans-serif";color:#0000A1'>Centre Scientifique et Technique du Bâtiment</span></b><o:p></o:p></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Verdana","sans-serif"'>290 Route des Lucioles BP 209 – F 06904 Sophia Antipolis Cedex</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Verdana","sans-serif"'>Tél : +33-(0)4-93-95-67-21</span><o:p></o:p></p><p class=MsoNormal><span style='font-size:8.0pt;font-family:"Verdana","sans-serif"'>Fax : +33-(0)4-93-95-64-31</span><o:p></o:p></p><p class=MsoNormal><b><span style='font-size:8.0pt;font-family:"Verdana","sans-serif";color:#008100'>Évitez d’imprimer vos emails inutilement. Respectez l’environnement</span></b><o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal> <o:p></o:p></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><br><br><br><o:p></o:p></span></p><pre>_______________________________________________<o:p></o:p></pre><pre>TRNSYS-users mailing list<o:p></o:p></pre><pre><a href="mailto:TRNSYS-users@cae.wisc.edu">TRNSYS-users@cae.wisc.edu</a><o:p></o:p></pre><pre><a href="https://mailman.cae.wisc.edu/listinfo/trnsys-users">https://mailman.cae.wisc.edu/listinfo/trnsys-users</a><o:p></o:p></pre></blockquote><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><br><br><o:p></o:p></span></p><pre>-- <o:p></o:p></pre><pre>***************************<o:p></o:p></pre><pre>David BRADLEY<o:p></o:p></pre><pre>Principal<o:p></o:p></pre><pre>Thermal Energy Systems Specialists, LLC<o:p></o:p></pre><pre>22 North Carroll Street - suite 370<o:p></o:p></pre><pre>Madison, WI 53703 USA<o:p></o:p></pre><pre><o:p> </o:p></pre><pre>P:+1.608.274.2577<o:p></o:p></pre><pre>F:+1.608.278.1475<o:p></o:p></pre><pre><a href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a><o:p></o:p></pre><pre><o:p> </o:p></pre><pre><a href="http://www.tess-inc.com">http://www.tess-inc.com</a><o:p></o:p></pre><pre><a href="http://www.trnsys.com">http://www.trnsys.com</a><o:p></o:p></pre></div></body></html>