[TRNSYS-users] Mass blance problem with flow diverter

David BRADLEY d.bradley at tess-inc.com
Wed Sep 19 12:12:52 PDT 2012


Santeri,
   Pumps in TRNSYS set the downstream flow rate according to their rated 
flow rate and the value of their current control signal. Apart from 
checking for mass balance problems, they ignore their inlet mass flow 
rate. When there are loops that have multiple pumped branches, you have 
to be particularly careful to make the flow splitting decisions based on 
the flow rate that is currently entering the flow diverter. I would 
recommend that you remove the connections from the diverter to the 
pumps. Then connect the outlet flow rate of every device in the loop to 
an online plotter and make sure that you understand the outlet flow at 
each component. Make sure that the mass balance is preserved. Next, 
reconnect the flow diverter to the pumps and see whether the mass 
balance is still preserved. If it is not, there may not be enough 
thermal capacitance in your loop. Controllers may be making decisions 
based on unconverged temperatures.
Best,
  David


On 9/19/2012 05:54, Santeri Siren wrote:
> Dear all,
>
> I have a problem with the mass balances of my system. In my proct a 
> flow diverter divides the waterflow into two separate pipes. .After 
> the flowdiverter both pipes go to their own pumps. The flow diverter 
> is controlled according to the ratio of mass flows produced by the 
> pumps. After the pumps comes heating loads. After that the waterflows 
> are connected in a flow mixer and the water is being heated in a 
> heatpump.
>
> The problem is that Trnsys gives mass balance warnings for both pumps. 
> When I check the mass flows of the pumps, they some times are even 
> larger than the rated flow of the pump.I think the problem has 
> something to do with the flow diverter...
>
> Can someone give me advice how to fix this problem and make the mass 
> flows balanced. I have attached a demonstrative picture of my project.
>
> best regards.
> Santeri Siren
>
>
> _______________________________________________
> TRNSYS-users mailing list
> TRNSYS-users at cae.wisc.edu
> https://mailman.cae.wisc.edu/listinfo/trnsys-users

-- 
***************************
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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