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Re: [TRNSYS-users] Heat exchanger UA value

If you don't have measured data to tune the model against, use a value of 1.0 for both.  From years of calibrating the model against real data, I would also suggest a value between 0.4 and 0.6 for the Rayleigh multiplier and a value of 0.25 for the Rayleigh exponent.

Jeff Thornton (Author of Type534)

Sent from my iPhone

On Mar 27, 2015, at 6:21 PM, Martin Berov <martber88@gmail.com> wrote:

Dear David,

Thank you for the suggestion. I'll use Type 534 - coiled, but can you suggest me which are usually used values for the "geometry factor for natural convection" and "geometry exponent for natural convection".

Best Regards
Martin

On Fri, Mar 27, 2015 at 10:45 PM, David BRADLEY <d.bradley@tess-inc.com> wrote:
Martin,
  I would highly recommend that if at all possible you use Type534 from the TESS Storage Tank library in place of Type60. Type534 has an internal heat exchanger model that is far more robust than the one built in to Type60.
Kind regards,
 David



On 3/27/2015 3:11 PM, Martin Berov wrote:
Dear TRNSYS users,

I'm trying to analyse the influence of the heat exchanger  area on the solar fraction and collector efficiency.

I'm using storage tank Type 60c  with internal HX. Although I change the area and the length(keeping the outside diameter constant) I always get same results for the monthly solar fraction and efficiency - like there is no influence.

What could be the reason for this?   

Best regards
Martin


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***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
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