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

[William.Logie at solarenergy.ch]

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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