[TRNSYS-users] Low flow collector operation with immersed heat exchanger in Type60

[David BRADLEY]

William,
  I would be very careful in using the Type60 with an internal heat 
exchanger and low flow rates, particularly if you are anywhere close to 
laminar flow. I have run into some problems with its internal 
calculation of the heat exchanger UA as well. If possible, I would 
recommend that you use Type534 from the TESS Storage Libary. In my 
experience, the UA calculation for that tank model's internal heat 
exchanger is more robust.
Best,
  David


On 11/10/2011 04:32, William.Logie at solarenergy.ch wrote:
>
> Dear TRNSYS folk,
>
> I was wondering if anyone can shed some light on Type60, in particular 
> low flow operation of the immersed heat exchanger model (IHX). I'm 
> using the 16.01.0003 edition of TRNSYS and 2005-01-31 -- Mku version 
> of Type60.
>
> I've been happily simulating high-flows (>40kg/hr per m^2 collector 
> area) but run into non-convergence warnings (and infinite loops) with, 
> for example, a specific collector flow of 10kg/hr; storage volume 400 
> litres with 25 nodes and a simulation time step between 3 and 6 mins; 
> http://sel.me.wisc.edu/trnsys/mailinglist/archive2004/msg00640.html. I 
> have tried reducing the flow rate to a minute and even less but 
> non-convergence persists (for an annual simulation that doesn't abort 
> I get between 2 and 5 thousand warnings). Some exemplary energy 
> balances (measured with Type60) are as follows;
>
> 10kg/hr:
>
> Q_coll + Q_aux = 13934081.86 kJ
>
> Q_losses + Q_dhw = 13920759.15 kJ
>
> Q_coll + Q_aux -- Q_losses -- Q_dhw = Q_err = 13322.71 kJ
>
> 50kg/hr:
>
> Q_coll + Q_aux = 13961476.57 kJ
>
> Q_losses + Q_dhw = 13947209.16 kJ
>
> Q_coll + Q_aux -- Q_losses -- Q_dhw = Q_err = 14267.41 kJ
>
> Is this all within reason? If not, any tips?
>
> Kind regards,
>
> ------------------------------------------------------------------------
>
> *William Logie*
> Forschung / Research
>
> Institut für Solartechnik SPF: Adresse 
> <http://www.solarenergy.ch/spf.php?lang=de&fam=44&tab=3> / Website 
> <http://www.solarenergy.ch/spf.php?lang=de&fam=41&tab=1>
> Hochschule für Technik Rapperswil HSR
> Tel. +41 55 222 48 34
> Fax +41 55 222 48 44
>
> ------------------------------------------------------------------------
>
>
>
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> TRNSYS-users at cae.wisc.edu
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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
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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