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<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 :<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></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.<o:p></o:p></span></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.<o:p></o:p></span></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 !<o:p></o:p></span></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…<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></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 ?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Kind regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-family:"Verdana","sans-serif";
color:black">Vincent PARTENAY<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";
color:black">Energies Renouvelables - Département ESE</span><span style="font-size:12.0pt;font-family:"Times New Roman","serif";color:#1F497D"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-family:"Verdana","sans-serif";
color:#0000A1">Centre Scientifique et Technique du Bâtiment<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";
color:black">290 Route des Lucioles BP 209 – F 06904 Sophia Antipolis Cedex<o:p></o:p></span></p>
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