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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Claire,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Cory provided a good description of the best approach and made a good point that, for an early study, it will probably be best and very fast to use the “chilled
ceiling” panel mode in IES-VE ApacheHVAC---especially considering you’re modeling a hydronic ceiling slab, rather than an exposed floor.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">As you’re attempting to represent a massive hydronic concrete slab, you can enter an appropriate value for the mass of the slab in the “Weight of chilled panel
(excluding water)” parameter in the “chilled ceiling” type dialog. This will provide representation of thermal inertia (capacitance) suitable for a quick early study. It will also provide modeling of radiant exchange between other room surfaces and this massive
ceiling “panel”.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">You can quickly set up a generic “chilled ceiling” panel type with a suitably conservative maximum cooling capacity. For use in zones of different floor areas,
and thus differing cooling capacities, you can multiply the number of panels within the controller dialog as needed to represent realistic cooling capacities for each floor area. The cooling capacity will also be constrained during simulation by the flow rate
you set in the controller dialog and the moderate supply water temperature from the CHWL representing your ground water supply.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The main benefit of setting up the full hydronic slab model, as detailed in the ApacheHVAC user guide appendix on this, is that you can very accurately model
the effects of slab mass and u-value of the average path between the water in the hydronic tubes and the surface of the slab, response time, radiant exchanges with other surfaces in the zone, and direct-solar gains received by the floor slab surface if this
were exposed to the space above in any part of the building (may not be important in your case, if the cooled slab is only every exposed as a ceiling, and not a floor).
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">As the quick panel-based model will limit cooling capacity as a function of water flow rate and temperature, but does not have a way to actually model the limiting
effects of the tube spacing and depth within the concrete, it will be important to appropriately constrain the cooling capacity either by the flow rate control setting and/or the maximum capacity entered in the panel type dialog. There are numerous papers
published on the topic, and the CBE paper at the following link summarizes the conclusions from many of them including (on page 3) cooling capacity on the order of 77 W/m2 for chilled concrete slabs (excluding any contribution from ventilation systems) with
moderate SWT and surface temperature held more or less constant: <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><a href="http://escholarship.org/uc/item/3j52t8vz#page-3">http://escholarship.org/uc/item/3j52t8vz#page-3</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">That and the many publications it cites might give you a better idea of appropriate maximum cooling capacity of your particular hydronic slab design and water
temperature.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Cheers,<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Bldg-sim [mailto:bldg-sim-bounces@lists.onebuilding.org]
<b>On Behalf Of </b>Duggin, Cory<br>
<b>Sent:</b> Wednesday, June 10, 2015 10:37 AM<br>
<b>To:</b> Claire Das Bhaumik; bldg-sim@lists.onebuilding.org<br>
<b>Subject:</b> Re: [Bldg-sim] Modelling groundwater cooling via concrete slab<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I would use the chilled ceiling room units and connect them chilled water loop supplying the constant temperature, but set the chiller fuel code to none and
zero out any heat rejection energy such as cooling tower or condenser fans. System 9g would be a good start since it can be used for ventilation and has the room units already assigned. The only thing you won’t see is the thermal mass effects of the slab.
The chilled ceiling is really to model just a panel. For an early study, I wouldn’t go through the trouble of trying to get the slab right as it requires much more effort.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Cory Duggin, PE, LEED AP BD+C
<o:p></o:p></span></b></p>
<p class="MsoNormal"><i><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#333333">Associate/Energy Engineer<o:p></o:p></span></i></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#006363">TLC Engineering for Architecture
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<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#1F497D">615-346-1939<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Bldg-sim [<a href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>]
<b>On Behalf Of </b>Claire Das Bhaumik<br>
<b>Sent:</b> Wednesday, June 10, 2015 9:02 AM<br>
<b>To:</b> <a href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a><br>
<b>Subject:</b> [Bldg-sim] Modelling groundwater cooling via concrete slab<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">I'm looking for the most suitable approach for modelling groundwater cooling in a thermal model. It's proposed to have pipes embedded in a concrete ceiling with groundwater flowing through
them. The groundwater supply temp will be fixed at around 12degC. </span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><o:p> </o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Arial","sans-serif"">I'm using IES software but I expect the possible approaches would be similar with most packages.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><o:p> </o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Arial","sans-serif"">I could either use a simplified approach calculating the cooling capacity from the flow rate and temperature difference, or use a
detailed systems modelling approach. I want something fairly quick but reasonably accurate (don't we all?!) as it's a preliminary study.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><o:p> </o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Arial","sans-serif"">Thanks,</span><o:p></o:p></p>
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<o:p></o:p></p>
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<p><b><span style="color:#262626">Dr Claire Das Bhaumik CEng FCIBSE</span></b><o:p></o:p></p>
<p><b><span style="font-size:10.0pt;color:#365F91">Partner - Inkling LLP</span></b><o:p></o:p></p>
<p><b><span style="font-size:10.0pt;color:#1F497D"> </span></b><span style="font-size:9.0pt;color:#262626">e:
</span><a href="mailto:claire@inklingllp.com" target="_blank"><span style="font-size:9.0pt;color:#262626;text-decoration:none">claire@inklingllp.com</span></a><o:p></o:p></p>
<p><span style="font-size:9.0pt;color:#262626">t: 07950 282800</span><o:p></o:p></p>
<p><span style="font-size:9.0pt;color:#262626">w: <a href="http://www.inklingllp.com/" target="_blank">
<span style="color:#262626;text-decoration:none">www.inklingllp.com</span></a></span><o:p></o:p></p>
<p><span style="font-size:9.0pt;color:#365F91">Follow us on Twitter: @DasInkling</span><o:p></o:p></p>
<p><span style="font-size:9.0pt;color:#262626">Partnership No. OC367619</span><o:p></o:p></p>
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