[TRNSYS-users] Question related to EAHE type 460

[jeannieboef]

Good point about the turbulant flow, David. Glad to see someone still  
knows how to use there Fluid and Heat Transfer mechanics knowledge.

Sent from my iPhone

On 25.06.2012, at 21:45, David BRADLEY <d.bradley at tess-inc.com> wrote:

> 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 t 
>> ranssolar, 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 n 
>> ot have a answare, maybe you have this information, also, i make s 
>> ome probes share the result the total energy (latent and sensible) 
>>  with             a psychometric entalphy difference by the same f 
>> low mass             rate, the result are the same in the most par 
>> ts, but for some ones show some differences, do you know the reaso 
>> n of this?.
>>
>> Thanks
>>
>> Camilo Arias
>>
>>
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>
> -- 
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> David BRADLEY
> Principal
> Thermal Energy Systems Specialists, LLC
> 22 North Carroll Street - suite 370
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>
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