[TRNSYS-users] Question related to EAHE type 460

[David BRADLEY]

Camilo,
   I am not familiar with the table that is mentioned. The documentation 
notes that values for Kair0 are typically between 7 and 11 kJ/h.K.m2 and 
Kair1 are between 14 and 18 (kJ/h.m2)/K/(m/s). What I have typically 
done is to use some basic heat transfer equations to calculate the 
Nusselt number for a few different flow rates through the ducts as a 
function of the Reynolds and Prandtl numbers. From the Nusselt number, 
you can then get the inside convection coefficient and fit the values to 
arrive at Kair0 and Kair1. I think my method over predicts the inside 
convection coefficient but I haven't found a better way to do it

  One critical thing about earth tubes is to keep the flow turbulent. 
Without knowing what kind of input changes you made in your simulation 
between the cases that do and do not show total energy differences 
across the earth duct it is hard to guess what might be happening.
Best,
  David


On 6/24/2012 01:38, Camilo Arias wrote:
> Hi, i´m working now with the type 460, in the FAQ file sended by 
> transsolar, said abaout a table to chose the Kair0 and Kair1 based in 
> the diameter of the tube, i write to trnsssolar but to now an not have 
> a answare, maybe you have this information, also, i make some probes 
> share the result the total energy (latent and sensible) with 
> a psychometric entalphy difference by the same flow mass rate, the 
> result are the same in the most parts, but for some ones show some 
> differences, do you know the reason of this?.
>
> Thanks
>
> Camilo Arias
>
>
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
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d.bradley at tess-inc.com

http://www.tess-inc.com
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