[TRNSYS-users] Type 60c outlet temperature

[David BRADLEY]

Igor,
   It is a little worrisome that you get convergence problems at low 
flow rates. If you have used equations to set a minimum turndown ratio 
on a pump (essentially a minimum flow rate) then you can certainly run 
into some situations where your setpoints are not met. When doing this, 
however, it is important that you use similar equations in conjunction 
with your controller model so that the controller doesn't try to make 
the pump do something that it is unable to do (and thereby lead to 
convergence problems).
Kind regards,
  David


On 4/8/2014 13:37, Igor Seso wrote:
> Thank you David, exactly that was the problem,  I was recording 
> temperatures above 60 C when there was no flow through the valve - I 
> put a trigger printer recording only temp. when there is flow and the 
> temperatures values were exactly as the set mixing temp.
>
> I tried to put pipes between the collector the tank and the pump  to 
> get more realistic results regard outlet temperaturesas a result of 
> the increased thermal mass and it was ok - but the only disadvantage 
> is that the pump flow can not go under certain value (total volume of 
> fluid in pipes) it gives convergence problems...so it means that it is 
> not possible to test the influence of low flow on system efficiency etc..
>
> Regards,
> Barto
>
>
>
> On Tuesday, April 8, 2014 7:34 PM, David BRADLEY 
> <d.bradley at tess-inc.com> wrote:
> Barto,
>   It is not really possible to diagnose the problem without looking at 
> the project. I would recommend using an online plotter to look at all 
> of the temperatures and flow rates of all the flows going into and 
> coming out of the tank. If for some reason all of the temperatures in 
> the system are over 60C (including the temperature of the tempering 
> water) then Type953 would not be able to temper the outlet flow. It 
> could also be that you are seeing higher than 60C temperature at the 
> mixing valve when there is no flow through the valve.
>   If you are not able to sort out the problem using Type65 as a 
> debugging tool then you should send your project to your distributor 
> so that they can have a look at it.
> Kind regards,
>  David
>
>
>
> On 4/7/2014 08:16, Barto Pene wrote:
>> Hi ,
>>
>> I get some strange result i.e I can not find logic in it: I use tank 
>> Type 60c only heated by standard solar collector installation. I use 
>> the differential controller(monitoring temp.) to limit the tank top 
>> temperature to 60C and I'm also using tempering valve Type 953 with 
>> diverting and three-wat valves for controling the outlet temp. In the 
>> simulation I get temperatures at the outlet of the three-way valve 
>> (after mixing) higher than 60C (even 80-90C) how is it possible?
>>
>> When I model the HX in Type60c with glycol solution I get convergence 
>> problems and with water there is no problem...?
>>
>> Thank you
>>
>> Regards
>> Barto
>>
>>
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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  <mailto:d.bradley at tess-inc.com>
>
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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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