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Vertical ground heat exchanger

6 Posts
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Topic starter

Hi all

The GHP components by TESS have components where internal bore hole resistance can be inserted to the model from TRT testing. None of the 548b or 557b (old one) informs user about what the unit of the borehole thermal resistance should be while inserting. Can anybody let me know what unit 557/548 expects? In TRNSYS this resistance is referred to as The thermal resistance between the fluid in the pipes and the ground at the edge of the borehole wall per unit of borehole length (the fluid to ground thermal resistance).

Thanks in advance. 

2 Answers
0

Abir,

  The units are in h.m.K/kJ. Thank you for catching the omission. We will get the proformas fixed in the next version release.

kind regards,

 David

 

TM Abir Ahsan Topic starter 31/05/2023 10:29 pm

@davidbradley Thanks for your quick response David. Appreciate it.

JJLiu 01/06/2023 12:45 am
This post was modified 1 year ago 2 times by JJLiu

@davidbradley

Hi David,

 

I have a question about the Ground heat exchanger Type 557a in TRNSYS 18. How to set the parameters 36-38 if the number of preheating years is 0 in the simulation?

 

Parameter 36: Average air temperature - preheat years

 

Parameter 37: Amplitude of air temperature - preheat years

 

Parameter 38: Air temperature phase delay - preheat years

 

I have left the parameters related to preheating years (i.e. maximum/minimum preheat temperature, preheat phase delay) as default values.

Please correct me if it is not the proper setting.

 

Kind regards,

Jingjing

DavidBradley 13/06/2023 1:33 pm

@JJLiu
Hi Jingjing,
You can set the number of preheat years to zero in which case the other values don't matter.

In case it is useful in future, the yearly average air temperature is not too hard to find online for a given location. The amplitude in this case is the difference between the average annual temperature and the peak air temperature. The phase delay is the hardest one to find but it is almost always somewhere between 30 and 36 days for locations in the northern hemisphere. It is the number of days between January 1 and the day of the year on which the minimum temperature occurs.
kind regards,
David

0

@tm-abir-ahsan If you open the wizard for Type 548b (when you open the proforma, it's the magic wand icon in the lower left) and navigate to the Borehole Geometry tab, you'll see that the units of thermal resistance between the fluid and the borehole wall are K-h-m/kJ. Sometimes when there's a wizard for a particular proforma, the wizard can give a little more context than the proforma alone.

TM Abir Ahsan Topic starter 31/05/2023 10:55 pm

@a_weiss Thank you, I did not check that before.

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