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Re: [TRNSYS-users] Help with two parallel ground loop heat exchangers simulation (Borehole and Horizontal Loop)

<I got a problem during the simulation. When the heat pump is not in operation (also the fluid flow rate in both ground loop heat exchangers are 0), the outlet temperature of the borehole is same as the inlet temperature of the borehole. But the outlet temperature of the horizontal loop is lower than the inlet temperature when the fluid flow rate in the pipe is 0. I cannot understand why there exists a temperature difference of the horizontal loop when the system is not in operation.>

I'm not sure what you're doing wrong without taking a closer look, but neither the vertical nor horizontal ground heat exchanger models set the outlet temperature to the inlet temperature when there is no flow.  Both models calculate the fluid temperature in the pipes and report the temperature as it decays with time towards the local soil temperature.  To check this, run both models with a high inlet temperature (100 C) and vary the flow on and off each for 24 hours using a forcing function.  You'll notice neither model sets the flow to the inlet temperature and both models show a decay when the flow is off.

 

Jeff

 

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Jeff Thornton

President - TESS LLC

22 N. Carroll Street, Madison WI USA 53703

Office: (608) 274-2577  Fax: (608) 278-1475

www.tess-inc.com

E-Mail: thornton@tess-inc.com

 

On 08/15/2013 4:35 am, Su Huang wrote:

Dear All,

 

Results.jpg

 


 

I did one test with a simple GSHP system, in which one horizontal loop heat exchanger and vertical borehole heat exchanger connect in parallel with one water source heat pump.
I got a problem during the simulation. When the heat pump is not in operation (also the fluid flow rate in both ground loop heat exchangers are 0), the outlet temperature of the borehole is same as the inlet temperature of the borehole. But the outlet temperature of the horizontal loop is lower than the inlet temperature when the fluid flow rate in the pipe is 0. I cannot understand why there exists a temperature difference of the horizontal loop when the system is not in operation.
Much appreciated if anyone can help!
Many thanks! (Attached is the file).
Regards,
Su

 

 

Su Huang

 

Ph.D Candidate in Sustainable Buildings Research Centre

University of Wollongong  

Email: sh377@uowmail.edu.au