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Dear Dr C.K.Lee and Jeff,
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<div>The external water circuit system is the same to supply the inlet and outlet water conditions of both vertical heat exchangers and horizontal loop heat exchangers. </div>
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<div>Attached is the result I did for two cases.</div>
<div>Case 1: borehole heat exchanger and horizontal loop heat exchanger connected in parallel</div>
<div>Case 2: Simply just horizontal loop heat exchanger</div>
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<div>In case 1: almost 3<sup>o</sup>C temperature difference between the inlet and outlet temperature from the horizontal loop heat exchanger when there was no flow.</div>
<div>In case 2: there was no temperature difference.</div>
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<div>I assume that there is something to do with the added borehole heat exchanger. But still struggling finding out the reason.</div>
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<div>Many thanks!</div>
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<div>Regards,</div>
<div>Su <br>
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<font color="#3366ff">Su Huang </font></font>
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<p dir="ltr" style="margin-right:0px"><font face="Arial" color="#3366ff" size="2">Ph.D Candidate in Sustainable Buildings Research Centre
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<p><font face="Arial" color="#3366ff" size="2">University of Wollongong </font></p>
<p><font face="Arial" size="2"><font color="#3366ff">Email: </font><font color="#3366ff"><a href="mailto:sh377@uowmail.edu.au">sh377@uowmail.edu.au</a></font></font></p>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> a8304506@graduate.hku.hk <a8304506@graduate.hku.hk><br>
<b>Sent:</b> Friday, 16 August 2013 10:28 AM<br>
<b>To:</b> thornton@tess-inc.com; TRNSYS users mailing list at the Solar Energy Lab, UW-Madison<br>
<b>Subject:</b> Re: [TRNSYS-users] Help with two parallel ground loop heat exchangers simulation (Borehole and Horizontal Loop)</font>
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<div class="PlainText">Hello.<br>
<br>
I think the problem can be interpreted in this way. As mentioned by Jeff, the<br>
outlet temperature is calculated in a specific way according to the ground heat<br>
exchanger model. However, the water circuit outside the ground heat exchanger<br>
tends to bring the outlet temperature back to the inlet temperature,<br>
particularly if you do not add any thermal mass in the external water circuit. <br>
In this sense, both the inlet and outlet temperatures decay at no flow amd they<br>
appear to be the same. Hence, I think the problem is in the horizontal loop<br>
system. Su, is the same external system used when employing the vertical and<br>
horizontal ground heat exchangers?<br>
<br>
Best Regards<br>
Chun Kwong LEE<br>
City University of Hong Kong<br>
<br>
Quoting Jeff Thornton <thornton@tess-inc.com>:<br>
<br>
> <br>
> <br>
> <I got a problem during the simulation. When the heat pump is not in<br>
> operation (also the fluid flow rate in both ground loop heat exchangers<br>
> are 0), the outlet temperature of the borehole is same as the inlet<br>
> temperature of the borehole. But the outlet temperature of the<br>
> horizontal loop is lower than the inlet temperature when the fluid flow<br>
> rate in the pipe is 0. I cannot understand why there exists a<br>
> temperature difference of the horizontal loop when the system is not in<br>
> operation.> <br>
> <br>
> I'm not sure what you're doing wrong without taking a<br>
> closer look, but neither the vertical nor horizontal ground heat<br>
> exchanger models set the outlet temperature to the inlet temperature<br>
> when there is no flow. Both models calculate the fluid temperature in<br>
> the pipes and report the temperature as it decays with time towards the<br>
> local soil temperature. To check this, run both models with a high inlet<br>
> temperature (100 C) and vary the flow on and off each for 24 hours using<br>
> a forcing function. You'll notice neither model sets the flow to the<br>
> inlet temperature and both models show a decay when the flow is off.<br>
> <br>
> <br>
> Jeff <br>
> <br>
> ---<br>
> <br>
> Jeff Thornton <br>
> <br>
> _President - TESS LLC_ <br>
> <br>
> _22 N. Carroll<br>
> Street, Madison WI USA 53703_ <br>
> <br>
> _Office: (608) 274-2577 Fax: (608)<br>
> 278-1475_ <br>
> <br>
> _www.tess-inc.com_ <br>
> <br>
> _E-Mail: thornton@tess-inc.com_ <br>
> <br>
> On<br>
> 08/15/2013 4:35 am, Su Huang wrote: <br>
> <br>
> > Dear All, <br>
> > <br>
> > Results.jpg <br>
> ><br>
> <br>
> > I did one test with a simple GSHP system, in which one horizontal<br>
> loop heat exchanger and vertical borehole heat exchanger connect in<br>
> parallel with one water source heat pump. <br>
> > I got a problem during the<br>
> simulation. When the heat pump is not in operation (also the fluid flow<br>
> rate in both ground loop heat exchangers are 0), the outlet temperature<br>
> of the borehole is same as the inlet temperature of the borehole. But<br>
> the outlet temperature of the horizontal loop is lower than the inlet<br>
> temperature when the fluid flow rate in the pipe is 0. I cannot<br>
> understand why there exists a temperature difference of the horizontal<br>
> loop when the system is not in operation. <br>
> > Much appreciated if anyone<br>
> can help! <br>
> > Many thanks! (Attached is the file). <br>
> > Regards, <br>
> > Su <br>
> ><br>
> <br>
> > -------------------------<br>
> > Su Huang <br>
> > <br>
> > Ph.D Candidate in<br>
> Sustainable Buildings Research Centre <br>
> > <br>
> > University of Wollongong <br>
> ><br>
> <br>
> > Email: sh377@uowmail.edu.au [1]<br>
> <br>
> <br>
> Links:<br>
> ------<br>
> [1]<br>
> <a href="mailto:sh377@uowmail.edu.au">mailto:sh377@uowmail.edu.au</a><br>
> <br>
<br>
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